// SPDX-License-Identifier: GPL-2.0+
/*
 * comedi/comedi_fops.c
 * comedi kernel module
 *
 * COMEDI - Linux Control and Measurement Device Interface
 * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include "comedi_compat32.h"

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched/signal.h>
#include <linux/fcntl.h>
#include <linux/delay.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/device.h>
#include <linux/fs.h>
#include "comedidev.h"
#include <linux/cdev.h>

#include <linux/io.h>
#include <linux/uaccess.h>

#include "comedi_internal.h"

/*
 * comedi_subdevice "runflags"
 * COMEDI_SRF_RT:               DEPRECATED: command is running real-time
 * COMEDI_SRF_ERROR:            indicates an COMEDI_CB_ERROR event has occurred
 *                              since the last command was started
 * COMEDI_SRF_RUNNING:          command is running
 * COMEDI_SRF_FREE_SPRIV:       free s->private on detach
 *
 * COMEDI_SRF_BUSY_MASK:        runflags that indicate the subdevice is "busy"
 */
#define COMEDI_SRF_RT           BIT(1)
#define COMEDI_SRF_ERROR        BIT(2)
#define COMEDI_SRF_RUNNING      BIT(27)
#define COMEDI_SRF_FREE_SPRIV   BIT(31)

#define COMEDI_SRF_BUSY_MASK    (COMEDI_SRF_ERROR | COMEDI_SRF_RUNNING)

/**
 * struct comedi_file - Per-file private data for COMEDI device
 * @dev: COMEDI device.
 * @read_subdev: Current "read" subdevice.
 * @write_subdev: Current "write" subdevice.
 * @last_detach_count: Last known detach count.
 * @last_attached: Last known attached/detached state.
 */
struct comedi_file {
        struct comedi_device *dev;
        struct comedi_subdevice *read_subdev;
        struct comedi_subdevice *write_subdev;
        unsigned int last_detach_count;
        unsigned int last_attached:1;
};

#define COMEDI_NUM_MINORS 0x100
#define COMEDI_NUM_SUBDEVICE_MINORS     \
        (COMEDI_NUM_MINORS - COMEDI_NUM_BOARD_MINORS)

static unsigned short comedi_num_legacy_minors;
module_param(comedi_num_legacy_minors, ushort, 0444);
MODULE_PARM_DESC(comedi_num_legacy_minors,
                 "number of comedi minor devices to reserve for non-auto-configured devices (default 0)"
                );

unsigned int comedi_default_buf_size_kb = CONFIG_COMEDI_DEFAULT_BUF_SIZE_KB;
module_param(comedi_default_buf_size_kb, uint, 0644);
MODULE_PARM_DESC(comedi_default_buf_size_kb,
                 "default asynchronous buffer size in KiB (default "
                 __MODULE_STRING(CONFIG_COMEDI_DEFAULT_BUF_SIZE_KB) ")");

unsigned int comedi_default_buf_maxsize_kb =
        CONFIG_COMEDI_DEFAULT_BUF_MAXSIZE_KB;
module_param(comedi_default_buf_maxsize_kb, uint, 0644);
MODULE_PARM_DESC(comedi_default_buf_maxsize_kb,
                 "default maximum size of asynchronous buffer in KiB (default "
                 __MODULE_STRING(CONFIG_COMEDI_DEFAULT_BUF_MAXSIZE_KB) ")");

static DEFINE_MUTEX(comedi_board_minor_table_lock);
static struct comedi_device
*comedi_board_minor_table[COMEDI_NUM_BOARD_MINORS];

static DEFINE_MUTEX(comedi_subdevice_minor_table_lock);
/* Note: indexed by minor - COMEDI_NUM_BOARD_MINORS. */
static struct comedi_subdevice
*comedi_subdevice_minor_table[COMEDI_NUM_SUBDEVICE_MINORS];

static struct class *comedi_class;
static struct cdev comedi_cdev;

static void comedi_device_init(struct comedi_device *dev)
{
        kref_init(&dev->refcount);
        spin_lock_init(&dev->spinlock);
        mutex_init(&dev->mutex);
        init_rwsem(&dev->attach_lock);
        dev->minor = -1;
}

static void comedi_dev_kref_release(struct kref *kref)
{
        struct comedi_device *dev =
                container_of(kref, struct comedi_device, refcount);

        mutex_destroy(&dev->mutex);
        put_device(dev->class_dev);
        kfree(dev);
}

/**
 * comedi_dev_put() - Release a use of a COMEDI device
 * @dev: COMEDI device.
 *
 * Must be called when a user of a COMEDI device is finished with it.
 * When the last user of the COMEDI device calls this function, the
 * COMEDI device is destroyed.
 *
 * Return: 1 if the COMEDI device is destroyed by this call or @dev is
 * NULL, otherwise return 0.  Callers must not assume the COMEDI
 * device is still valid if this function returns 0.
 */
int comedi_dev_put(struct comedi_device *dev)
{
        if (dev)
                return kref_put(&dev->refcount, comedi_dev_kref_release);
        return 1;
}
EXPORT_SYMBOL_GPL(comedi_dev_put);

static struct comedi_device *comedi_dev_get(struct comedi_device *dev)
{
        if (dev)
                kref_get(&dev->refcount);
        return dev;
}

static void comedi_device_cleanup(struct comedi_device *dev)
{
        struct module *driver_module = NULL;

        if (!dev)
                return;
        mutex_lock(&dev->mutex);
        if (dev->attached)
                driver_module = dev->driver->module;
        comedi_device_detach(dev);
        if (driver_module && dev->use_count)
                module_put(driver_module);
        mutex_unlock(&dev->mutex);
}

static bool comedi_clear_board_dev(struct comedi_device *dev)
{
        unsigned int i = dev->minor;
        bool cleared = false;

        lockdep_assert_held(&dev->mutex);
        mutex_lock(&comedi_board_minor_table_lock);
        if (dev == comedi_board_minor_table[i]) {
                comedi_board_minor_table[i] = NULL;
                cleared = true;
        }
        mutex_unlock(&comedi_board_minor_table_lock);
        return cleared;
}

static struct comedi_device *comedi_clear_board_minor(unsigned int minor)
{
        struct comedi_device *dev;

        mutex_lock(&comedi_board_minor_table_lock);
        dev = comedi_board_minor_table[minor];
        comedi_board_minor_table[minor] = NULL;
        mutex_unlock(&comedi_board_minor_table_lock);
        return dev;
}

static void comedi_free_board_dev(struct comedi_device *dev)
{
        if (dev) {
                comedi_device_cleanup(dev);
                if (dev->class_dev) {
                        device_destroy(comedi_class,
                                       MKDEV(COMEDI_MAJOR, dev->minor));
                }
                comedi_dev_put(dev);
        }
}

static struct comedi_subdevice *
comedi_subdevice_from_minor(const struct comedi_device *dev, unsigned int minor)
{
        struct comedi_subdevice *s;
        unsigned int i = minor - COMEDI_NUM_BOARD_MINORS;

        mutex_lock(&comedi_subdevice_minor_table_lock);
        s = comedi_subdevice_minor_table[i];
        if (s && s->device != dev)
                s = NULL;
        mutex_unlock(&comedi_subdevice_minor_table_lock);
        return s;
}

static struct comedi_device *comedi_dev_get_from_board_minor(unsigned int minor)
{
        struct comedi_device *dev;

        mutex_lock(&comedi_board_minor_table_lock);
        dev = comedi_dev_get(comedi_board_minor_table[minor]);
        mutex_unlock(&comedi_board_minor_table_lock);
        return dev;
}

static struct comedi_device *
comedi_dev_get_from_subdevice_minor(unsigned int minor)
{
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int i = minor - COMEDI_NUM_BOARD_MINORS;

        mutex_lock(&comedi_subdevice_minor_table_lock);
        s = comedi_subdevice_minor_table[i];
        dev = comedi_dev_get(s ? s->device : NULL);
        mutex_unlock(&comedi_subdevice_minor_table_lock);
        return dev;
}

/**
 * comedi_dev_get_from_minor() - Get COMEDI device by minor device number
 * @minor: Minor device number.
 *
 * Finds the COMEDI device associated with the minor device number, if any,
 * and increments its reference count.  The COMEDI device is prevented from
 * being freed until a matching call is made to comedi_dev_put().
 *
 * Return: A pointer to the COMEDI device if it exists, with its usage
 * reference incremented.  Return NULL if no COMEDI device exists with the
 * specified minor device number.
 */
struct comedi_device *comedi_dev_get_from_minor(unsigned int minor)
{
        if (minor < COMEDI_NUM_BOARD_MINORS)
                return comedi_dev_get_from_board_minor(minor);

        return comedi_dev_get_from_subdevice_minor(minor);
}
EXPORT_SYMBOL_GPL(comedi_dev_get_from_minor);

static struct comedi_subdevice *
comedi_read_subdevice(const struct comedi_device *dev, unsigned int minor)
{
        struct comedi_subdevice *s;

        lockdep_assert_held(&dev->mutex);
        if (minor >= COMEDI_NUM_BOARD_MINORS) {
                s = comedi_subdevice_from_minor(dev, minor);
                if (!s || (s->subdev_flags & SDF_CMD_READ))
                        return s;
        }
        return dev->read_subdev;
}

static struct comedi_subdevice *
comedi_write_subdevice(const struct comedi_device *dev, unsigned int minor)
{
        struct comedi_subdevice *s;

        lockdep_assert_held(&dev->mutex);
        if (minor >= COMEDI_NUM_BOARD_MINORS) {
                s = comedi_subdevice_from_minor(dev, minor);
                if (!s || (s->subdev_flags & SDF_CMD_WRITE))
                        return s;
        }
        return dev->write_subdev;
}

static void comedi_file_reset(struct file *file)
{
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;
        struct comedi_subdevice *s, *read_s, *write_s;
        unsigned int minor = iminor(file_inode(file));

        read_s = dev->read_subdev;
        write_s = dev->write_subdev;
        if (minor >= COMEDI_NUM_BOARD_MINORS) {
                s = comedi_subdevice_from_minor(dev, minor);
                if (!s || s->subdev_flags & SDF_CMD_READ)
                        read_s = s;
                if (!s || s->subdev_flags & SDF_CMD_WRITE)
                        write_s = s;
        }
        cfp->last_attached = dev->attached;
        cfp->last_detach_count = dev->detach_count;
        WRITE_ONCE(cfp->read_subdev, read_s);
        WRITE_ONCE(cfp->write_subdev, write_s);
}

static void comedi_file_check(struct file *file)
{
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;

        if (cfp->last_attached != dev->attached ||
            cfp->last_detach_count != dev->detach_count)
                comedi_file_reset(file);
}

static struct comedi_subdevice *comedi_file_read_subdevice(struct file *file)
{
        struct comedi_file *cfp = file->private_data;

        comedi_file_check(file);
        return READ_ONCE(cfp->read_subdev);
}

static struct comedi_subdevice *comedi_file_write_subdevice(struct file *file)
{
        struct comedi_file *cfp = file->private_data;

        comedi_file_check(file);
        return READ_ONCE(cfp->write_subdev);
}

static int resize_async_buffer(struct comedi_device *dev,
                               struct comedi_subdevice *s,
                               unsigned int new_size)
{
        struct comedi_async *async = s->async;
        int retval;

        lockdep_assert_held(&dev->mutex);

        if (new_size > async->max_bufsize)
                return -EPERM;

        if (s->busy) {
                dev_dbg(dev->class_dev,
                        "subdevice is busy, cannot resize buffer\n");
                return -EBUSY;
        }
        if (comedi_buf_is_mmapped(s)) {
                dev_dbg(dev->class_dev,
                        "subdevice is mmapped, cannot resize buffer\n");
                return -EBUSY;
        }

        /* make sure buffer is an integral number of pages (we round up) */
        new_size = (new_size + PAGE_SIZE - 1) & PAGE_MASK;

        retval = comedi_buf_alloc(dev, s, new_size);
        if (retval < 0)
                return retval;

        if (s->buf_change) {
                retval = s->buf_change(dev, s);
                if (retval < 0)
                        return retval;
        }

        dev_dbg(dev->class_dev, "subd %d buffer resized to %i bytes\n",
                s->index, async->prealloc_bufsz);
        return 0;
}

/* sysfs attribute files */

static ssize_t max_read_buffer_kb_show(struct device *csdev,
                                       struct device_attribute *attr, char *buf)
{
        unsigned int minor = MINOR(csdev->devt);
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int size = 0;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);
        s = comedi_read_subdevice(dev, minor);
        if (s && (s->subdev_flags & SDF_CMD_READ) && s->async)
                size = s->async->max_bufsize / 1024;
        mutex_unlock(&dev->mutex);

        comedi_dev_put(dev);
        return snprintf(buf, PAGE_SIZE, "%u\n", size);
}

static ssize_t max_read_buffer_kb_store(struct device *csdev,
                                        struct device_attribute *attr,
                                        const char *buf, size_t count)
{
        unsigned int minor = MINOR(csdev->devt);
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int size;
        int err;

        err = kstrtouint(buf, 10, &size);
        if (err)
                return err;
        if (size > (UINT_MAX / 1024))
                return -EINVAL;
        size *= 1024;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);
        s = comedi_read_subdevice(dev, minor);
        if (s && (s->subdev_flags & SDF_CMD_READ) && s->async)
                s->async->max_bufsize = size;
        else
                err = -EINVAL;
        mutex_unlock(&dev->mutex);

        comedi_dev_put(dev);
        return err ? err : count;
}
static DEVICE_ATTR_RW(max_read_buffer_kb);

static ssize_t read_buffer_kb_show(struct device *csdev,
                                   struct device_attribute *attr, char *buf)
{
        unsigned int minor = MINOR(csdev->devt);
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int size = 0;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);
        s = comedi_read_subdevice(dev, minor);
        if (s && (s->subdev_flags & SDF_CMD_READ) && s->async)
                size = s->async->prealloc_bufsz / 1024;
        mutex_unlock(&dev->mutex);

        comedi_dev_put(dev);
        return snprintf(buf, PAGE_SIZE, "%u\n", size);
}

static ssize_t read_buffer_kb_store(struct device *csdev,
                                    struct device_attribute *attr,
                                    const char *buf, size_t count)
{
        unsigned int minor = MINOR(csdev->devt);
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int size;
        int err;

        err = kstrtouint(buf, 10, &size);
        if (err)
                return err;
        if (size > (UINT_MAX / 1024))
                return -EINVAL;
        size *= 1024;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);
        s = comedi_read_subdevice(dev, minor);
        if (s && (s->subdev_flags & SDF_CMD_READ) && s->async)
                err = resize_async_buffer(dev, s, size);
        else
                err = -EINVAL;
        mutex_unlock(&dev->mutex);

        comedi_dev_put(dev);
        return err ? err : count;
}
static DEVICE_ATTR_RW(read_buffer_kb);

static ssize_t max_write_buffer_kb_show(struct device *csdev,
                                        struct device_attribute *attr,
                                        char *buf)
{
        unsigned int minor = MINOR(csdev->devt);
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int size = 0;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);
        s = comedi_write_subdevice(dev, minor);
        if (s && (s->subdev_flags & SDF_CMD_WRITE) && s->async)
                size = s->async->max_bufsize / 1024;
        mutex_unlock(&dev->mutex);

        comedi_dev_put(dev);
        return snprintf(buf, PAGE_SIZE, "%u\n", size);
}

static ssize_t max_write_buffer_kb_store(struct device *csdev,
                                         struct device_attribute *attr,
                                         const char *buf, size_t count)
{
        unsigned int minor = MINOR(csdev->devt);
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int size;
        int err;

        err = kstrtouint(buf, 10, &size);
        if (err)
                return err;
        if (size > (UINT_MAX / 1024))
                return -EINVAL;
        size *= 1024;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);
        s = comedi_write_subdevice(dev, minor);
        if (s && (s->subdev_flags & SDF_CMD_WRITE) && s->async)
                s->async->max_bufsize = size;
        else
                err = -EINVAL;
        mutex_unlock(&dev->mutex);

        comedi_dev_put(dev);
        return err ? err : count;
}
static DEVICE_ATTR_RW(max_write_buffer_kb);

static ssize_t write_buffer_kb_show(struct device *csdev,
                                    struct device_attribute *attr, char *buf)
{
        unsigned int minor = MINOR(csdev->devt);
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int size = 0;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);
        s = comedi_write_subdevice(dev, minor);
        if (s && (s->subdev_flags & SDF_CMD_WRITE) && s->async)
                size = s->async->prealloc_bufsz / 1024;
        mutex_unlock(&dev->mutex);

        comedi_dev_put(dev);
        return snprintf(buf, PAGE_SIZE, "%u\n", size);
}

static ssize_t write_buffer_kb_store(struct device *csdev,
                                     struct device_attribute *attr,
                                     const char *buf, size_t count)
{
        unsigned int minor = MINOR(csdev->devt);
        struct comedi_device *dev;
        struct comedi_subdevice *s;
        unsigned int size;
        int err;

        err = kstrtouint(buf, 10, &size);
        if (err)
                return err;
        if (size > (UINT_MAX / 1024))
                return -EINVAL;
        size *= 1024;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return -ENODEV;

        mutex_lock(&dev->mutex);
        s = comedi_write_subdevice(dev, minor);
        if (s && (s->subdev_flags & SDF_CMD_WRITE) && s->async)
                err = resize_async_buffer(dev, s, size);
        else
                err = -EINVAL;
        mutex_unlock(&dev->mutex);

        comedi_dev_put(dev);
        return err ? err : count;
}
static DEVICE_ATTR_RW(write_buffer_kb);

static struct attribute *comedi_dev_attrs[] = {
        &dev_attr_max_read_buffer_kb.attr,
        &dev_attr_read_buffer_kb.attr,
        &dev_attr_max_write_buffer_kb.attr,
        &dev_attr_write_buffer_kb.attr,
        NULL,
};
ATTRIBUTE_GROUPS(comedi_dev);

static void __comedi_clear_subdevice_runflags(struct comedi_subdevice *s,
                                              unsigned int bits)
{
        s->runflags &= ~bits;
}

static void __comedi_set_subdevice_runflags(struct comedi_subdevice *s,
                                            unsigned int bits)
{
        s->runflags |= bits;
}

static void comedi_update_subdevice_runflags(struct comedi_subdevice *s,
                                             unsigned int mask,
                                             unsigned int bits)
{
        unsigned long flags;

        spin_lock_irqsave(&s->spin_lock, flags);
        __comedi_clear_subdevice_runflags(s, mask);
        __comedi_set_subdevice_runflags(s, bits & mask);
        spin_unlock_irqrestore(&s->spin_lock, flags);
}

static unsigned int __comedi_get_subdevice_runflags(struct comedi_subdevice *s)
{
        return s->runflags;
}

static unsigned int comedi_get_subdevice_runflags(struct comedi_subdevice *s)
{
        unsigned long flags;
        unsigned int runflags;

        spin_lock_irqsave(&s->spin_lock, flags);
        runflags = __comedi_get_subdevice_runflags(s);
        spin_unlock_irqrestore(&s->spin_lock, flags);
        return runflags;
}

static bool comedi_is_runflags_running(unsigned int runflags)
{
        return runflags & COMEDI_SRF_RUNNING;
}

static bool comedi_is_runflags_in_error(unsigned int runflags)
{
        return runflags & COMEDI_SRF_ERROR;
}

/**
 * comedi_is_subdevice_running() - Check if async command running on subdevice
 * @s: COMEDI subdevice.
 *
 * Return: %true if an asynchronous COMEDI command is active on the
 * subdevice, else %false.
 */
bool comedi_is_subdevice_running(struct comedi_subdevice *s)
{
        unsigned int runflags = comedi_get_subdevice_runflags(s);

        return comedi_is_runflags_running(runflags);
}
EXPORT_SYMBOL_GPL(comedi_is_subdevice_running);

static bool __comedi_is_subdevice_running(struct comedi_subdevice *s)
{
        unsigned int runflags = __comedi_get_subdevice_runflags(s);

        return comedi_is_runflags_running(runflags);
}

bool comedi_can_auto_free_spriv(struct comedi_subdevice *s)
{
        unsigned int runflags = __comedi_get_subdevice_runflags(s);

        return runflags & COMEDI_SRF_FREE_SPRIV;
}

/**
 * comedi_set_spriv_auto_free() - Mark subdevice private data as freeable
 * @s: COMEDI subdevice.
 *
 * Mark the subdevice as having a pointer to private data that can be
 * automatically freed when the COMEDI device is detached from the low-level
 * driver.
 */
void comedi_set_spriv_auto_free(struct comedi_subdevice *s)
{
        __comedi_set_subdevice_runflags(s, COMEDI_SRF_FREE_SPRIV);
}
EXPORT_SYMBOL_GPL(comedi_set_spriv_auto_free);

/**
 * comedi_alloc_spriv - Allocate memory for the subdevice private data
 * @s: COMEDI subdevice.
 * @size: Size of the memory to allocate.
 *
 * Allocate memory for the subdevice private data and point @s->private
 * to it.  The memory will be freed automatically when the COMEDI device
 * is detached from the low-level driver.
 *
 * Return: A pointer to the allocated memory @s->private on success.
 * Return NULL on failure.
 */
void *comedi_alloc_spriv(struct comedi_subdevice *s, size_t size)
{
        s->private = kzalloc(size, GFP_KERNEL);
        if (s->private)
                comedi_set_spriv_auto_free(s);
        return s->private;
}
EXPORT_SYMBOL_GPL(comedi_alloc_spriv);

/*
 * This function restores a subdevice to an idle state.
 */
static void do_become_nonbusy(struct comedi_device *dev,
                              struct comedi_subdevice *s)
{
        struct comedi_async *async = s->async;

        lockdep_assert_held(&dev->mutex);
        comedi_update_subdevice_runflags(s, COMEDI_SRF_RUNNING, 0);
        if (async) {
                comedi_buf_reset(s);
                async->inttrig = NULL;
                kfree(async->cmd.chanlist);
                async->cmd.chanlist = NULL;
                s->busy = NULL;
                wake_up_interruptible_all(&async->wait_head);
        } else {
                dev_err(dev->class_dev,
                        "BUG: (?) %s called with async=NULL\n", __func__);
                s->busy = NULL;
        }
}

static int do_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
{
        int ret = 0;

        lockdep_assert_held(&dev->mutex);
        if (comedi_is_subdevice_running(s) && s->cancel)
                ret = s->cancel(dev, s);

        do_become_nonbusy(dev, s);

        return ret;
}

void comedi_device_cancel_all(struct comedi_device *dev)
{
        struct comedi_subdevice *s;
        int i;

        lockdep_assert_held(&dev->mutex);
        if (!dev->attached)
                return;

        for (i = 0; i < dev->n_subdevices; i++) {
                s = &dev->subdevices[i];
                if (s->async)
                        do_cancel(dev, s);
        }
}

static int is_device_busy(struct comedi_device *dev)
{
        struct comedi_subdevice *s;
        int i;

        lockdep_assert_held(&dev->mutex);
        if (!dev->attached)
                return 0;

        for (i = 0; i < dev->n_subdevices; i++) {
                s = &dev->subdevices[i];
                if (s->busy)
                        return 1;
                if (s->async && comedi_buf_is_mmapped(s))
                        return 1;
        }

        return 0;
}

/*
 * COMEDI_DEVCONFIG ioctl
 * attaches (and configures) or detaches a legacy device
 *
 * arg:
 *      pointer to comedi_devconfig structure (NULL if detaching)
 *
 * reads:
 *      comedi_devconfig structure (if attaching)
 *
 * writes:
 *      nothing
 */
static int do_devconfig_ioctl(struct comedi_device *dev,
                              struct comedi_devconfig __user *arg)
{
        struct comedi_devconfig it;

        lockdep_assert_held(&dev->mutex);
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        if (!arg) {
                if (is_device_busy(dev))
                        return -EBUSY;
                if (dev->attached) {
                        struct module *driver_module = dev->driver->module;

                        comedi_device_detach(dev);
                        module_put(driver_module);
                }
                return 0;
        }

        if (copy_from_user(&it, arg, sizeof(it)))
                return -EFAULT;

        it.board_name[COMEDI_NAMELEN - 1] = 0;

        if (it.options[COMEDI_DEVCONF_AUX_DATA_LENGTH]) {
                dev_warn(dev->class_dev,
                         "comedi_config --init_data is deprecated\n");
                return -EINVAL;
        }

        if (dev->minor >= comedi_num_legacy_minors)
                /* don't re-use dynamically allocated comedi devices */
                return -EBUSY;

        /* This increments the driver module count on success. */
        return comedi_device_attach(dev, &it);
}

/*
 * COMEDI_BUFCONFIG ioctl
 * buffer configuration
 *
 * arg:
 *      pointer to comedi_bufconfig structure
 *
 * reads:
 *      comedi_bufconfig structure
 *
 * writes:
 *      modified comedi_bufconfig structure
 */
static int do_bufconfig_ioctl(struct comedi_device *dev,
                              struct comedi_bufconfig __user *arg)
{
        struct comedi_bufconfig bc;
        struct comedi_async *async;
        struct comedi_subdevice *s;
        int retval = 0;

        lockdep_assert_held(&dev->mutex);
        if (copy_from_user(&bc, arg, sizeof(bc)))
                return -EFAULT;

        if (bc.subdevice >= dev->n_subdevices)
                return -EINVAL;

        s = &dev->subdevices[bc.subdevice];
        async = s->async;

        if (!async) {
                dev_dbg(dev->class_dev,
                        "subdevice does not have async capability\n");
                bc.size = 0;
                bc.maximum_size = 0;
                goto copyback;
        }

        if (bc.maximum_size) {
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;

                async->max_bufsize = bc.maximum_size;
        }

        if (bc.size) {
                retval = resize_async_buffer(dev, s, bc.size);
                if (retval < 0)
                        return retval;
        }

        bc.size = async->prealloc_bufsz;
        bc.maximum_size = async->max_bufsize;

copyback:
        if (copy_to_user(arg, &bc, sizeof(bc)))
                return -EFAULT;

        return 0;
}

/*
 * COMEDI_DEVINFO ioctl
 * device info
 *
 * arg:
 *      pointer to comedi_devinfo structure
 *
 * reads:
 *      nothing
 *
 * writes:
 *      comedi_devinfo structure
 */
static int do_devinfo_ioctl(struct comedi_device *dev,
                            struct comedi_devinfo __user *arg,
                            struct file *file)
{
        struct comedi_subdevice *s;
        struct comedi_devinfo devinfo;

        lockdep_assert_held(&dev->mutex);
        memset(&devinfo, 0, sizeof(devinfo));

        /* fill devinfo structure */
        devinfo.version_code = COMEDI_VERSION_CODE;
        devinfo.n_subdevs = dev->n_subdevices;
        strlcpy(devinfo.driver_name, dev->driver->driver_name, COMEDI_NAMELEN);
        strlcpy(devinfo.board_name, dev->board_name, COMEDI_NAMELEN);

        s = comedi_file_read_subdevice(file);
        if (s)
                devinfo.read_subdevice = s->index;
        else
                devinfo.read_subdevice = -1;

        s = comedi_file_write_subdevice(file);
        if (s)
                devinfo.write_subdevice = s->index;
        else
                devinfo.write_subdevice = -1;

        if (copy_to_user(arg, &devinfo, sizeof(devinfo)))
                return -EFAULT;

        return 0;
}

/*
 * COMEDI_SUBDINFO ioctl
 * subdevices info
 *
 * arg:
 *      pointer to array of comedi_subdinfo structures
 *
 * reads:
 *      nothing
 *
 * writes:
 *      array of comedi_subdinfo structures
 */
static int do_subdinfo_ioctl(struct comedi_device *dev,
                             struct comedi_subdinfo __user *arg, void *file)
{
        int ret, i;
        struct comedi_subdinfo *tmp, *us;
        struct comedi_subdevice *s;

        lockdep_assert_held(&dev->mutex);
        tmp = kcalloc(dev->n_subdevices, sizeof(*tmp), GFP_KERNEL);
        if (!tmp)
                return -ENOMEM;

        /* fill subdinfo structs */
        for (i = 0; i < dev->n_subdevices; i++) {
                s = &dev->subdevices[i];
                us = tmp + i;

                us->type = s->type;
                us->n_chan = s->n_chan;
                us->subd_flags = s->subdev_flags;
                if (comedi_is_subdevice_running(s))
                        us->subd_flags |= SDF_RUNNING;
#define TIMER_nanosec 5         /* backwards compatibility */
                us->timer_type = TIMER_nanosec;
                us->len_chanlist = s->len_chanlist;
                us->maxdata = s->maxdata;
                if (s->range_table) {

                        us->range_type =
                            (i << 24) | (0 << 16) | (s->range_table->length);
                } else {
                        us->range_type = 0;     /* XXX */
                }

                if (s->busy)
                        us->subd_flags |= SDF_BUSY;
                if (s->busy == file)
                        us->subd_flags |= SDF_BUSY_OWNER;
                if (s->lock)
                        us->subd_flags |= SDF_LOCKED;
                if (s->lock == file)
                        us->subd_flags |= SDF_LOCK_OWNER;
                if (!s->maxdata && s->maxdata_list)
                        us->subd_flags |= SDF_MAXDATA;
                if (s->range_table_list)
                        us->subd_flags |= SDF_RANGETYPE;
                if (s->do_cmd)
                        us->subd_flags |= SDF_CMD;

                if (s->insn_bits != &insn_inval)
                        us->insn_bits_support = COMEDI_SUPPORTED;
                else
                        us->insn_bits_support = COMEDI_UNSUPPORTED;
        }

        ret = copy_to_user(arg, tmp, dev->n_subdevices * sizeof(*tmp));

        kfree(tmp);

        return ret ? -EFAULT : 0;
}

/*
 * COMEDI_CHANINFO ioctl
 * subdevice channel info
 *
 * arg:
 *      pointer to comedi_chaninfo structure
 *
 * reads:
 *      comedi_chaninfo structure
 *
 * writes:
 *      array of maxdata values to chaninfo->maxdata_list if requested
 *      array of range table lengths to chaninfo->range_table_list if requested
 */
static int do_chaninfo_ioctl(struct comedi_device *dev,
                             struct comedi_chaninfo __user *arg)
{
        struct comedi_subdevice *s;
        struct comedi_chaninfo it;

        lockdep_assert_held(&dev->mutex);
        if (copy_from_user(&it, arg, sizeof(it)))
                return -EFAULT;

        if (it.subdev >= dev->n_subdevices)
                return -EINVAL;
        s = &dev->subdevices[it.subdev];

        if (it.maxdata_list) {
                if (s->maxdata || !s->maxdata_list)
                        return -EINVAL;
                if (copy_to_user(it.maxdata_list, s->maxdata_list,
                                 s->n_chan * sizeof(unsigned int)))
                        return -EFAULT;
        }

        if (it.flaglist)
                return -EINVAL; /* flaglist not supported */

        if (it.rangelist) {
                int i;

                if (!s->range_table_list)
                        return -EINVAL;
                for (i = 0; i < s->n_chan; i++) {
                        int x;

                        x = (dev->minor << 28) | (it.subdev << 24) | (i << 16) |
                            (s->range_table_list[i]->length);
                        if (put_user(x, it.rangelist + i))
                                return -EFAULT;
                }
        }

        return 0;
}

/*
 * COMEDI_BUFINFO ioctl
 * buffer information
 *
 * arg:
 *      pointer to comedi_bufinfo structure
 *
 * reads:
 *      comedi_bufinfo structure
 *
 * writes:
 *      modified comedi_bufinfo structure
 */
static int do_bufinfo_ioctl(struct comedi_device *dev,
                            struct comedi_bufinfo __user *arg, void *file)
{
        struct comedi_bufinfo bi;
        struct comedi_subdevice *s;
        struct comedi_async *async;
        unsigned int runflags;
        int retval = 0;
        bool become_nonbusy = false;

        lockdep_assert_held(&dev->mutex);
        if (copy_from_user(&bi, arg, sizeof(bi)))
                return -EFAULT;

        if (bi.subdevice >= dev->n_subdevices)
                return -EINVAL;

        s = &dev->subdevices[bi.subdevice];

        async = s->async;

        if (!async || s->busy != file)
                return -EINVAL;

        runflags = comedi_get_subdevice_runflags(s);
        if (!(async->cmd.flags & CMDF_WRITE)) {
                /* command was set up in "read" direction */
                if (bi.bytes_read) {
                        comedi_buf_read_alloc(s, bi.bytes_read);
                        bi.bytes_read = comedi_buf_read_free(s, bi.bytes_read);
                }
                /*
                 * If nothing left to read, and command has stopped, and
                 * {"read" position not updated or command stopped normally},
                 * then become non-busy.
                 */
                if (comedi_buf_read_n_available(s) == 0 &&
                    !comedi_is_runflags_running(runflags) &&
                    (bi.bytes_read == 0 ||
                     !comedi_is_runflags_in_error(runflags))) {
                        become_nonbusy = true;
                        if (comedi_is_runflags_in_error(runflags))
                                retval = -EPIPE;
                }
                bi.bytes_written = 0;
        } else {
                /* command was set up in "write" direction */
                if (!comedi_is_runflags_running(runflags)) {
                        bi.bytes_written = 0;
                        become_nonbusy = true;
                        if (comedi_is_runflags_in_error(runflags))
                                retval = -EPIPE;
                } else if (bi.bytes_written) {
                        comedi_buf_write_alloc(s, bi.bytes_written);
                        bi.bytes_written =
                            comedi_buf_write_free(s, bi.bytes_written);
                }
                bi.bytes_read = 0;
        }

        bi.buf_write_count = async->buf_write_count;
        bi.buf_write_ptr = async->buf_write_ptr;
        bi.buf_read_count = async->buf_read_count;
        bi.buf_read_ptr = async->buf_read_ptr;

        if (become_nonbusy)
                do_become_nonbusy(dev, s);

        if (retval)
                return retval;

        if (copy_to_user(arg, &bi, sizeof(bi)))
                return -EFAULT;

        return 0;
}

static int check_insn_config_length(struct comedi_insn *insn,
                                    unsigned int *data)
{
        if (insn->n < 1)
                return -EINVAL;

        switch (data[0]) {
        case INSN_CONFIG_DIO_OUTPUT:
        case INSN_CONFIG_DIO_INPUT:
        case INSN_CONFIG_DISARM:
        case INSN_CONFIG_RESET:
                if (insn->n == 1)
                        return 0;
                break;
        case INSN_CONFIG_ARM:
        case INSN_CONFIG_DIO_QUERY:
        case INSN_CONFIG_BLOCK_SIZE:
        case INSN_CONFIG_FILTER:
        case INSN_CONFIG_SERIAL_CLOCK:
        case INSN_CONFIG_BIDIRECTIONAL_DATA:
        case INSN_CONFIG_ALT_SOURCE:
        case INSN_CONFIG_SET_COUNTER_MODE:
        case INSN_CONFIG_8254_READ_STATUS:
        case INSN_CONFIG_SET_ROUTING:
        case INSN_CONFIG_GET_ROUTING:
        case INSN_CONFIG_GET_PWM_STATUS:
        case INSN_CONFIG_PWM_SET_PERIOD:
        case INSN_CONFIG_PWM_GET_PERIOD:
                if (insn->n == 2)
                        return 0;
                break;
        case INSN_CONFIG_SET_GATE_SRC:
        case INSN_CONFIG_GET_GATE_SRC:
        case INSN_CONFIG_SET_CLOCK_SRC:
        case INSN_CONFIG_GET_CLOCK_SRC:
        case INSN_CONFIG_SET_OTHER_SRC:
        case INSN_CONFIG_GET_COUNTER_STATUS:
        case INSN_CONFIG_PWM_SET_H_BRIDGE:
        case INSN_CONFIG_PWM_GET_H_BRIDGE:
        case INSN_CONFIG_GET_HARDWARE_BUFFER_SIZE:
                if (insn->n == 3)
                        return 0;
                break;
        case INSN_CONFIG_PWM_OUTPUT:
        case INSN_CONFIG_ANALOG_TRIG:
        case INSN_CONFIG_TIMER_1:
                if (insn->n == 5)
                        return 0;
                break;
        case INSN_CONFIG_DIGITAL_TRIG:
                if (insn->n == 6)
                        return 0;
                break;
        case INSN_CONFIG_GET_CMD_TIMING_CONSTRAINTS:
                if (insn->n >= 4)
                        return 0;
                break;
                /*
                 * by default we allow the insn since we don't have checks for
                 * all possible cases yet
                 */
        default:
                pr_warn("No check for data length of config insn id %i is implemented\n",
                        data[0]);
                pr_warn("Add a check to %s in %s\n", __func__, __FILE__);
                pr_warn("Assuming n=%i is correct\n", insn->n);
                return 0;
        }
        return -EINVAL;
}

static int check_insn_device_config_length(struct comedi_insn *insn,
                                           unsigned int *data)
{
        if (insn->n < 1)
                return -EINVAL;

        switch (data[0]) {
        case INSN_DEVICE_CONFIG_TEST_ROUTE:
        case INSN_DEVICE_CONFIG_CONNECT_ROUTE:
        case INSN_DEVICE_CONFIG_DISCONNECT_ROUTE:
                if (insn->n == 3)
                        return 0;
                break;
        case INSN_DEVICE_CONFIG_GET_ROUTES:
                /*
                 * Big enough for config_id and the length of the userland
                 * memory buffer.  Additional length should be in factors of 2
                 * to communicate any returned route pairs (source,destination).
                 */
                if (insn->n >= 2)
                        return 0;
                break;
        }
        return -EINVAL;
}

/**
 * get_valid_routes() - Calls low-level driver get_valid_routes function to
 *                      either return a count of valid routes to user, or copy
 *                      of list of all valid device routes to buffer in
 *                      userspace.
 * @dev: comedi device pointer
 * @data: data from user insn call.  The length of the data must be >= 2.
 *        data[0] must contain the INSN_DEVICE_CONFIG config_id.
 *        data[1](input) contains the number of _pairs_ for which memory is
 *                allotted from the user.  If the user specifies '0', then only
 *                the number of pairs available is returned.
 *        data[1](output) returns either the number of pairs available (if none
 *                where requested) or the number of _pairs_ that are copied back
 *                to the user.
 *        data[2::2] returns each (source, destination) pair.
 *
 * Return: -EINVAL if low-level driver does not allocate and return routes as
 *         expected.  Returns 0 otherwise.
 */
static int get_valid_routes(struct comedi_device *dev, unsigned int *data)
{
        lockdep_assert_held(&dev->mutex);
        data[1] = dev->get_valid_routes(dev, data[1], data + 2);
        return 0;
}

static int parse_insn(struct comedi_device *dev, struct comedi_insn *insn,
                      unsigned int *data, void *file)
{
        struct comedi_subdevice *s;
        int ret = 0;
        int i;

        lockdep_assert_held(&dev->mutex);
        if (insn->insn & INSN_MASK_SPECIAL) {
                /* a non-subdevice instruction */

                switch (insn->insn) {
                case INSN_GTOD:
                        {
                                struct timespec64 tv;

                                if (insn->n != 2) {
                                        ret = -EINVAL;
                                        break;
                                }

                                ktime_get_real_ts64(&tv);
                                /* unsigned data safe until 2106 */
                                data[0] = (unsigned int)tv.tv_sec;
                                data[1] = tv.tv_nsec / NSEC_PER_USEC;
                                ret = 2;

                                break;
                        }
                case INSN_WAIT:
                        if (insn->n != 1 || data[0] >= 100000) {
                                ret = -EINVAL;
                                break;
                        }
                        udelay(data[0] / 1000);
                        ret = 1;
                        break;
                case INSN_INTTRIG:
                        if (insn->n != 1) {
                                ret = -EINVAL;
                                break;
                        }
                        if (insn->subdev >= dev->n_subdevices) {
                                dev_dbg(dev->class_dev,
                                        "%d not usable subdevice\n",
                                        insn->subdev);
                                ret = -EINVAL;
                                break;
                        }
                        s = &dev->subdevices[insn->subdev];
                        if (!s->async) {
                                dev_dbg(dev->class_dev, "no async\n");
                                ret = -EINVAL;
                                break;
                        }
                        if (!s->async->inttrig) {
                                dev_dbg(dev->class_dev, "no inttrig\n");
                                ret = -EAGAIN;
                                break;
                        }
                        ret = s->async->inttrig(dev, s, data[0]);
                        if (ret >= 0)
                                ret = 1;
                        break;
                case INSN_DEVICE_CONFIG:
                        ret = check_insn_device_config_length(insn, data);
                        if (ret)
                                break;

                        if (data[0] == INSN_DEVICE_CONFIG_GET_ROUTES) {
                                /*
                                 * data[1] should be the number of _pairs_ that
                                 * the memory can hold.
                                 */
                                data[1] = (insn->n - 2) / 2;
                                ret = get_valid_routes(dev, data);
                                break;
                        }

                        /* other global device config instructions. */
                        ret = dev->insn_device_config(dev, insn, data);
                        break;
                default:
                        dev_dbg(dev->class_dev, "invalid insn\n");
                        ret = -EINVAL;
                        break;
                }
        } else {
                /* a subdevice instruction */
                unsigned int maxdata;

                if (insn->subdev >= dev->n_subdevices) {
                        dev_dbg(dev->class_dev, "subdevice %d out of range\n",
                                insn->subdev);
                        ret = -EINVAL;
                        goto out;
                }
                s = &dev->subdevices[insn->subdev];

                if (s->type == COMEDI_SUBD_UNUSED) {
                        dev_dbg(dev->class_dev, "%d not usable subdevice\n",
                                insn->subdev);
                        ret = -EIO;
                        goto out;
                }

                /* are we locked? (ioctl lock) */
                if (s->lock && s->lock != file) {
                        dev_dbg(dev->class_dev, "device locked\n");
                        ret = -EACCES;
                        goto out;
                }

                ret = comedi_check_chanlist(s, 1, &insn->chanspec);
                if (ret < 0) {
                        ret = -EINVAL;
                        dev_dbg(dev->class_dev, "bad chanspec\n");
                        goto out;
                }

                if (s->busy) {
                        ret = -EBUSY;
                        goto out;
                }
                /* This looks arbitrary.  It is. */
                s->busy = parse_insn;
                switch (insn->insn) {
                case INSN_READ:
                        ret = s->insn_read(dev, s, insn, data);
                        if (ret == -ETIMEDOUT) {
                                dev_dbg(dev->class_dev,
                                        "subdevice %d read instruction timed out\n",
                                        s->index);
                        }
                        break;
                case INSN_WRITE:
                        maxdata = s->maxdata_list
                            ? s->maxdata_list[CR_CHAN(insn->chanspec)]
                            : s->maxdata;
                        for (i = 0; i < insn->n; ++i) {
                                if (data[i] > maxdata) {
                                        ret = -EINVAL;
                                        dev_dbg(dev->class_dev,
                                                "bad data value(s)\n");
                                        break;
                                }
                        }
                        if (ret == 0) {
                                ret = s->insn_write(dev, s, insn, data);
                                if (ret == -ETIMEDOUT) {
                                        dev_dbg(dev->class_dev,
                                                "subdevice %d write instruction timed out\n",
                                                s->index);
                                }
                        }
                        break;
                case INSN_BITS:
                        if (insn->n != 2) {
                                ret = -EINVAL;
                        } else {
                                /*
                                 * Most drivers ignore the base channel in
                                 * insn->chanspec.  Fix this here if
                                 * the subdevice has <= 32 channels.
                                 */
                                unsigned int orig_mask = data[0];
                                unsigned int shift = 0;

                                if (s->n_chan <= 32) {
                                        shift = CR_CHAN(insn->chanspec);
                                        if (shift > 0) {
                                                insn->chanspec = 0;
                                                data[0] <<= shift;
                                                data[1] <<= shift;
                                        }
                                }
                                ret = s->insn_bits(dev, s, insn, data);
                                data[0] = orig_mask;
                                if (shift > 0)
                                        data[1] >>= shift;
                        }
                        break;
                case INSN_CONFIG:
                        ret = check_insn_config_length(insn, data);
                        if (ret)
                                break;
                        ret = s->insn_config(dev, s, insn, data);
                        break;
                default:
                        ret = -EINVAL;
                        break;
                }

                s->busy = NULL;
        }

out:
        return ret;
}

/*
 * COMEDI_INSNLIST ioctl
 * synchronous instruction list
 *
 * arg:
 *      pointer to comedi_insnlist structure
 *
 * reads:
 *      comedi_insnlist structure
 *      array of comedi_insn structures from insnlist->insns pointer
 *      data (for writes) from insns[].data pointers
 *
 * writes:
 *      data (for reads) to insns[].data pointers
 */
/* arbitrary limits */
#define MIN_SAMPLES 16
#define MAX_SAMPLES 65536
static int do_insnlist_ioctl(struct comedi_device *dev,
                             struct comedi_insnlist __user *arg, void *file)
{
        struct comedi_insnlist insnlist;
        struct comedi_insn *insns = NULL;
        unsigned int *data = NULL;
        unsigned int max_n_data_required = MIN_SAMPLES;
        int i = 0;
        int ret = 0;

        lockdep_assert_held(&dev->mutex);
        if (copy_from_user(&insnlist, arg, sizeof(insnlist)))
                return -EFAULT;

        insns = kcalloc(insnlist.n_insns, sizeof(*insns), GFP_KERNEL);
        if (!insns) {
                ret = -ENOMEM;
                goto error;
        }

        if (copy_from_user(insns, insnlist.insns,
                           sizeof(*insns) * insnlist.n_insns)) {
                dev_dbg(dev->class_dev, "copy_from_user failed\n");
                ret = -EFAULT;
                goto error;
        }

        /* Determine maximum memory needed for all instructions. */
        for (i = 0; i < insnlist.n_insns; ++i) {
                if (insns[i].n > MAX_SAMPLES) {
                        dev_dbg(dev->class_dev,
                                "number of samples too large\n");
                        ret = -EINVAL;
                        goto error;
                }
                max_n_data_required = max(max_n_data_required, insns[i].n);
        }

        /* Allocate scratch space for all instruction data. */
        data = kmalloc_array(max_n_data_required, sizeof(unsigned int),
                             GFP_KERNEL);
        if (!data) {
                ret = -ENOMEM;
                goto error;
        }

        for (i = 0; i < insnlist.n_insns; ++i) {
                if (insns[i].insn & INSN_MASK_WRITE) {
                        if (copy_from_user(data, insns[i].data,
                                           insns[i].n * sizeof(unsigned int))) {
                                dev_dbg(dev->class_dev,
                                        "copy_from_user failed\n");
                                ret = -EFAULT;
                                goto error;
                        }
                }
                ret = parse_insn(dev, insns + i, data, file);
                if (ret < 0)
                        goto error;
                if (insns[i].insn & INSN_MASK_READ) {
                        if (copy_to_user(insns[i].data, data,
                                         insns[i].n * sizeof(unsigned int))) {
                                dev_dbg(dev->class_dev,
                                        "copy_to_user failed\n");
                                ret = -EFAULT;
                                goto error;
                        }
                }
                if (need_resched())
                        schedule();
        }

error:
        kfree(insns);
        kfree(data);

        if (ret < 0)
                return ret;
        return i;
}

/*
 * COMEDI_INSN ioctl
 * synchronous instruction
 *
 * arg:
 *      pointer to comedi_insn structure
 *
 * reads:
 *      comedi_insn structure
 *      data (for writes) from insn->data pointer
 *
 * writes:
 *      data (for reads) to insn->data pointer
 */
static int do_insn_ioctl(struct comedi_device *dev,
                         struct comedi_insn __user *arg, void *file)
{
        struct comedi_insn insn;
        unsigned int *data = NULL;
        unsigned int n_data = MIN_SAMPLES;
        int ret = 0;

        lockdep_assert_held(&dev->mutex);
        if (copy_from_user(&insn, arg, sizeof(insn)))
                return -EFAULT;

        n_data = max(n_data, insn.n);

        /* This is where the behavior of insn and insnlist deviate. */
        if (insn.n > MAX_SAMPLES) {
                insn.n = MAX_SAMPLES;
                n_data = MAX_SAMPLES;
        }

        data = kmalloc_array(n_data, sizeof(unsigned int), GFP_KERNEL);
        if (!data) {
                ret = -ENOMEM;
                goto error;
        }

        if (insn.insn & INSN_MASK_WRITE) {
                if (copy_from_user(data,
                                   insn.data,
                                   insn.n * sizeof(unsigned int))) {
                        ret = -EFAULT;
                        goto error;
                }
        }
        ret = parse_insn(dev, &insn, data, file);
        if (ret < 0)
                goto error;
        if (insn.insn & INSN_MASK_READ) {
                if (copy_to_user(insn.data,
                                 data,
                                 insn.n * sizeof(unsigned int))) {
                        ret = -EFAULT;
                        goto error;
                }
        }
        ret = insn.n;

error:
        kfree(data);

        return ret;
}

static int __comedi_get_user_cmd(struct comedi_device *dev,
                                 struct comedi_cmd __user *arg,
                                 struct comedi_cmd *cmd)
{
        struct comedi_subdevice *s;

        lockdep_assert_held(&dev->mutex);
        if (copy_from_user(cmd, arg, sizeof(*cmd))) {
                dev_dbg(dev->class_dev, "bad cmd address\n");
                return -EFAULT;
        }

        if (cmd->subdev >= dev->n_subdevices) {
                dev_dbg(dev->class_dev, "%d no such subdevice\n", cmd->subdev);
                return -ENODEV;
        }

        s = &dev->subdevices[cmd->subdev];

        if (s->type == COMEDI_SUBD_UNUSED) {
                dev_dbg(dev->class_dev, "%d not valid subdevice\n",
                        cmd->subdev);
                return -EIO;
        }

        if (!s->do_cmd || !s->do_cmdtest || !s->async) {
                dev_dbg(dev->class_dev,
                        "subdevice %d does not support commands\n",
                        cmd->subdev);
                return -EIO;
        }

        /* make sure channel/gain list isn't too long */
        if (cmd->chanlist_len > s->len_chanlist) {
                dev_dbg(dev->class_dev, "channel/gain list too long %d > %d\n",
                        cmd->chanlist_len, s->len_chanlist);
                return -EINVAL;
        }

        /*
         * Set the CMDF_WRITE flag to the correct state if the subdevice
         * supports only "read" commands or only "write" commands.
         */
        switch (s->subdev_flags & (SDF_CMD_READ | SDF_CMD_WRITE)) {
        case SDF_CMD_READ:
                cmd->flags &= ~CMDF_WRITE;
                break;
        case SDF_CMD_WRITE:
                cmd->flags |= CMDF_WRITE;
                break;
        default:
                break;
        }

        return 0;
}

static int __comedi_get_user_chanlist(struct comedi_device *dev,
                                      struct comedi_subdevice *s,
                                      unsigned int __user *user_chanlist,
                                      struct comedi_cmd *cmd)
{
        unsigned int *chanlist;
        int ret;

        lockdep_assert_held(&dev->mutex);
        cmd->chanlist = NULL;
        chanlist = memdup_user(user_chanlist,
                               cmd->chanlist_len * sizeof(unsigned int));
        if (IS_ERR(chanlist))
                return PTR_ERR(chanlist);

        /* make sure each element in channel/gain list is valid */
        ret = comedi_check_chanlist(s, cmd->chanlist_len, chanlist);
        if (ret < 0) {
                kfree(chanlist);
                return ret;
        }

        cmd->chanlist = chanlist;

        return 0;
}

/*
 * COMEDI_CMD ioctl
 * asynchronous acquisition command set-up
 *
 * arg:
 *      pointer to comedi_cmd structure
 *
 * reads:
 *      comedi_cmd structure
 *      channel/range list from cmd->chanlist pointer
 *
 * writes:
 *      possibly modified comedi_cmd structure (when -EAGAIN returned)
 */
static int do_cmd_ioctl(struct comedi_device *dev,
                        struct comedi_cmd __user *arg, void *file)
{
        struct comedi_cmd cmd;
        struct comedi_subdevice *s;
        struct comedi_async *async;
        unsigned int __user *user_chanlist;
        int ret;

        lockdep_assert_held(&dev->mutex);

        /* get the user's cmd and do some simple validation */
        ret = __comedi_get_user_cmd(dev, arg, &cmd);
        if (ret)
                return ret;

        /* save user's chanlist pointer so it can be restored later */
        user_chanlist = (unsigned int __user *)cmd.chanlist;

        s = &dev->subdevices[cmd.subdev];
        async = s->async;

        /* are we locked? (ioctl lock) */
        if (s->lock && s->lock != file) {
                dev_dbg(dev->class_dev, "subdevice locked\n");
                return -EACCES;
        }

        /* are we busy? */
        if (s->busy) {
                dev_dbg(dev->class_dev, "subdevice busy\n");
                return -EBUSY;
        }

        /* make sure channel/gain list isn't too short */
        if (cmd.chanlist_len < 1) {
                dev_dbg(dev->class_dev, "channel/gain list too short %u < 1\n",
                        cmd.chanlist_len);
                return -EINVAL;
        }

        async->cmd = cmd;
        async->cmd.data = NULL;

        /* load channel/gain list */
        ret = __comedi_get_user_chanlist(dev, s, user_chanlist, &async->cmd);
        if (ret)
                goto cleanup;

        ret = s->do_cmdtest(dev, s, &async->cmd);

        if (async->cmd.flags & CMDF_BOGUS || ret) {
                dev_dbg(dev->class_dev, "test returned %d\n", ret);
                cmd = async->cmd;
                /* restore chanlist pointer before copying back */
                cmd.chanlist = (unsigned int __force *)user_chanlist;
                cmd.data = NULL;
                if (copy_to_user(arg, &cmd, sizeof(cmd))) {
                        dev_dbg(dev->class_dev, "fault writing cmd\n");
                        ret = -EFAULT;
                        goto cleanup;
                }
                ret = -EAGAIN;
                goto cleanup;
        }

        if (!async->prealloc_bufsz) {
                ret = -ENOMEM;
                dev_dbg(dev->class_dev, "no buffer (?)\n");
                goto cleanup;
        }

        comedi_buf_reset(s);

        async->cb_mask = COMEDI_CB_BLOCK | COMEDI_CB_CANCEL_MASK;
        if (async->cmd.flags & CMDF_WAKE_EOS)
                async->cb_mask |= COMEDI_CB_EOS;

        comedi_update_subdevice_runflags(s, COMEDI_SRF_BUSY_MASK,
                                         COMEDI_SRF_RUNNING);

        /*
         * Set s->busy _after_ setting COMEDI_SRF_RUNNING flag to avoid
         * race with comedi_read() or comedi_write().
         */
        s->busy = file;
        ret = s->do_cmd(dev, s);
        if (ret == 0)
                return 0;

cleanup:
        do_become_nonbusy(dev, s);

        return ret;
}

/*
 * COMEDI_CMDTEST ioctl
 * asynchronous acquisition command testing
 *
 * arg:
 *      pointer to comedi_cmd structure
 *
 * reads:
 *      comedi_cmd structure
 *      channel/range list from cmd->chanlist pointer
 *
 * writes:
 *      possibly modified comedi_cmd structure
 */
static int do_cmdtest_ioctl(struct comedi_device *dev,
                            struct comedi_cmd __user *arg, void *file)
{
        struct comedi_cmd cmd;
        struct comedi_subdevice *s;
        unsigned int __user *user_chanlist;
        int ret;

        lockdep_assert_held(&dev->mutex);

        /* get the user's cmd and do some simple validation */
        ret = __comedi_get_user_cmd(dev, arg, &cmd);
        if (ret)
                return ret;

        /* save user's chanlist pointer so it can be restored later */
        user_chanlist = (unsigned int __user *)cmd.chanlist;

        s = &dev->subdevices[cmd.subdev];

        /* user_chanlist can be NULL for COMEDI_CMDTEST ioctl */
        if (user_chanlist) {
                /* load channel/gain list */
                ret = __comedi_get_user_chanlist(dev, s, user_chanlist, &cmd);
                if (ret)
                        return ret;
        }

        ret = s->do_cmdtest(dev, s, &cmd);

        kfree(cmd.chanlist);    /* free kernel copy of user chanlist */

        /* restore chanlist pointer before copying back */
        cmd.chanlist = (unsigned int __force *)user_chanlist;

        if (copy_to_user(arg, &cmd, sizeof(cmd))) {
                dev_dbg(dev->class_dev, "bad cmd address\n");
                ret = -EFAULT;
        }

        return ret;
}

/*
 * COMEDI_LOCK ioctl
 * lock subdevice
 *
 * arg:
 *      subdevice number
 *
 * reads:
 *      nothing
 *
 * writes:
 *      nothing
 */
static int do_lock_ioctl(struct comedi_device *dev, unsigned long arg,
                         void *file)
{
        int ret = 0;
        unsigned long flags;
        struct comedi_subdevice *s;

        lockdep_assert_held(&dev->mutex);
        if (arg >= dev->n_subdevices)
                return -EINVAL;
        s = &dev->subdevices[arg];

        spin_lock_irqsave(&s->spin_lock, flags);
        if (s->busy || s->lock)
                ret = -EBUSY;
        else
                s->lock = file;
        spin_unlock_irqrestore(&s->spin_lock, flags);

        return ret;
}

/*
 * COMEDI_UNLOCK ioctl
 * unlock subdevice
 *
 * arg:
 *      subdevice number
 *
 * reads:
 *      nothing
 *
 * writes:
 *      nothing
 */
static int do_unlock_ioctl(struct comedi_device *dev, unsigned long arg,
                           void *file)
{
        struct comedi_subdevice *s;

        lockdep_assert_held(&dev->mutex);
        if (arg >= dev->n_subdevices)
                return -EINVAL;
        s = &dev->subdevices[arg];

        if (s->busy)
                return -EBUSY;

        if (s->lock && s->lock != file)
                return -EACCES;

        if (s->lock == file)
                s->lock = NULL;

        return 0;
}

/*
 * COMEDI_CANCEL ioctl
 * cancel asynchronous acquisition
 *
 * arg:
 *      subdevice number
 *
 * reads:
 *      nothing

 *
 * writes:
 *      nothing
 */
static int do_cancel_ioctl(struct comedi_device *dev, unsigned long arg,
                           void *file)
{
        struct comedi_subdevice *s;

        lockdep_assert_held(&dev->mutex);
        if (arg >= dev->n_subdevices)
                return -EINVAL;
        s = &dev->subdevices[arg];
        if (!s->async)
                return -EINVAL;

        if (!s->busy)
                return 0;

        if (s->busy != file)
                return -EBUSY;

        return do_cancel(dev, s);
}

/*
 * COMEDI_POLL ioctl
 * instructs driver to synchronize buffers
 *
 * arg:
 *      subdevice number
 *
 * reads:
 *      nothing
 *
 * writes:
 *      nothing
 */
static int do_poll_ioctl(struct comedi_device *dev, unsigned long arg,
                         void *file)
{
        struct comedi_subdevice *s;

        lockdep_assert_held(&dev->mutex);
        if (arg >= dev->n_subdevices)
                return -EINVAL;
        s = &dev->subdevices[arg];

        if (!s->busy)
                return 0;

        if (s->busy != file)
                return -EBUSY;

        if (s->poll)
                return s->poll(dev, s);

        return -EINVAL;
}

/*
 * COMEDI_SETRSUBD ioctl
 * sets the current "read" subdevice on a per-file basis
 *
 * arg:
 *      subdevice number
 *
 * reads:
 *      nothing
 *
 * writes:
 *      nothing
 */
static int do_setrsubd_ioctl(struct comedi_device *dev, unsigned long arg,
                             struct file *file)
{
        struct comedi_file *cfp = file->private_data;
        struct comedi_subdevice *s_old, *s_new;

        lockdep_assert_held(&dev->mutex);
        if (arg >= dev->n_subdevices)
                return -EINVAL;

        s_new = &dev->subdevices[arg];
        s_old = comedi_file_read_subdevice(file);
        if (s_old == s_new)
                return 0;       /* no change */

        if (!(s_new->subdev_flags & SDF_CMD_READ))
                return -EINVAL;

        /*
         * Check the file isn't still busy handling a "read" command on the
         * old subdevice (if any).
         */
        if (s_old && s_old->busy == file && s_old->async &&
            !(s_old->async->cmd.flags & CMDF_WRITE))
                return -EBUSY;

        WRITE_ONCE(cfp->read_subdev, s_new);
        return 0;
}

/*
 * COMEDI_SETWSUBD ioctl
 * sets the current "write" subdevice on a per-file basis
 *
 * arg:
 *      subdevice number
 *
 * reads:
 *      nothing
 *
 * writes:
 *      nothing
 */
static int do_setwsubd_ioctl(struct comedi_device *dev, unsigned long arg,
                             struct file *file)
{
        struct comedi_file *cfp = file->private_data;
        struct comedi_subdevice *s_old, *s_new;

        lockdep_assert_held(&dev->mutex);
        if (arg >= dev->n_subdevices)
                return -EINVAL;

        s_new = &dev->subdevices[arg];
        s_old = comedi_file_write_subdevice(file);
        if (s_old == s_new)
                return 0;       /* no change */

        if (!(s_new->subdev_flags & SDF_CMD_WRITE))
                return -EINVAL;

        /*
         * Check the file isn't still busy handling a "write" command on the
         * old subdevice (if any).
         */
        if (s_old && s_old->busy == file && s_old->async &&
            (s_old->async->cmd.flags & CMDF_WRITE))
                return -EBUSY;

        WRITE_ONCE(cfp->write_subdev, s_new);
        return 0;
}

static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
                                  unsigned long arg)
{
        unsigned int minor = iminor(file_inode(file));
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;
        int rc;

        mutex_lock(&dev->mutex);

        /*
         * Device config is special, because it must work on
         * an unconfigured device.
         */
        if (cmd == COMEDI_DEVCONFIG) {
                if (minor >= COMEDI_NUM_BOARD_MINORS) {
                        /* Device config not appropriate on non-board minors. */
                        rc = -ENOTTY;
                        goto done;
                }
                rc = do_devconfig_ioctl(dev,
                                        (struct comedi_devconfig __user *)arg);
                if (rc == 0) {
                        if (arg == 0 &&
                            dev->minor >= comedi_num_legacy_minors) {
                                /*
                                 * Successfully unconfigured a dynamically
                                 * allocated device.  Try and remove it.
                                 */
                                if (comedi_clear_board_dev(dev)) {
                                        mutex_unlock(&dev->mutex);
                                        comedi_free_board_dev(dev);
                                        return rc;
                                }
                        }
                }
                goto done;
        }

        if (!dev->attached) {
                dev_dbg(dev->class_dev, "no driver attached\n");
                rc = -ENODEV;
                goto done;
        }

        switch (cmd) {
        case COMEDI_BUFCONFIG:
                rc = do_bufconfig_ioctl(dev,
                                        (struct comedi_bufconfig __user *)arg);
                break;
        case COMEDI_DEVINFO:
                rc = do_devinfo_ioctl(dev, (struct comedi_devinfo __user *)arg,
                                      file);
                break;
        case COMEDI_SUBDINFO:
                rc = do_subdinfo_ioctl(dev,
                                       (struct comedi_subdinfo __user *)arg,
                                       file);
                break;
        case COMEDI_CHANINFO:
                rc = do_chaninfo_ioctl(dev, (void __user *)arg);
                break;
        case COMEDI_RANGEINFO:
                rc = do_rangeinfo_ioctl(dev, (void __user *)arg);
                break;
        case COMEDI_BUFINFO:
                rc = do_bufinfo_ioctl(dev,
                                      (struct comedi_bufinfo __user *)arg,
                                      file);
                break;
        case COMEDI_LOCK:
                rc = do_lock_ioctl(dev, arg, file);
                break;
        case COMEDI_UNLOCK:
                rc = do_unlock_ioctl(dev, arg, file);
                break;
        case COMEDI_CANCEL:
                rc = do_cancel_ioctl(dev, arg, file);
                break;
        case COMEDI_CMD:
                rc = do_cmd_ioctl(dev, (struct comedi_cmd __user *)arg, file);
                break;
        case COMEDI_CMDTEST:
                rc = do_cmdtest_ioctl(dev, (struct comedi_cmd __user *)arg,
                                      file);
                break;
        case COMEDI_INSNLIST:
                rc = do_insnlist_ioctl(dev,
                                       (struct comedi_insnlist __user *)arg,
                                       file);
                break;
        case COMEDI_INSN:
                rc = do_insn_ioctl(dev, (struct comedi_insn __user *)arg,
                                   file);
                break;
        case COMEDI_POLL:
                rc = do_poll_ioctl(dev, arg, file);
                break;
        case COMEDI_SETRSUBD:
                rc = do_setrsubd_ioctl(dev, arg, file);
                break;
        case COMEDI_SETWSUBD:
                rc = do_setwsubd_ioctl(dev, arg, file);
                break;
        default:
                rc = -ENOTTY;
                break;
        }

done:
        mutex_unlock(&dev->mutex);
        return rc;
}

static void comedi_vm_open(struct vm_area_struct *area)
{
        struct comedi_buf_map *bm;

        bm = area->vm_private_data;
        comedi_buf_map_get(bm);
}

static void comedi_vm_close(struct vm_area_struct *area)
{
        struct comedi_buf_map *bm;

        bm = area->vm_private_data;
        comedi_buf_map_put(bm);
}

static int comedi_vm_access(struct vm_area_struct *vma, unsigned long addr,
                            void *buf, int len, int write)
{
        struct comedi_buf_map *bm = vma->vm_private_data;
        unsigned long offset =
            addr - vma->vm_start + (vma->vm_pgoff << PAGE_SHIFT);

        if (len < 0)
                return -EINVAL;
        if (len > vma->vm_end - addr)
                len = vma->vm_end - addr;
        return comedi_buf_map_access(bm, offset, buf, len, write);
}

static const struct vm_operations_struct comedi_vm_ops = {
        .open = comedi_vm_open,
        .close = comedi_vm_close,
        .access = comedi_vm_access,
};

static int comedi_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;
        struct comedi_subdevice *s;
        struct comedi_async *async;
        struct comedi_buf_map *bm = NULL;
        struct comedi_buf_page *buf;
        unsigned long start = vma->vm_start;
        unsigned long size;
        int n_pages;
        int i;
        int retval = 0;

        /*
         * 'trylock' avoids circular dependency with current->mm->mmap_sem
         * and down-reading &dev->attach_lock should normally succeed without
         * contention unless the device is in the process of being attached
         * or detached.
         */
        if (!down_read_trylock(&dev->attach_lock))
                return -EAGAIN;

        if (!dev->attached) {
                dev_dbg(dev->class_dev, "no driver attached\n");
                retval = -ENODEV;
                goto done;
        }

        if (vma->vm_flags & VM_WRITE)
                s = comedi_file_write_subdevice(file);
        else
                s = comedi_file_read_subdevice(file);
        if (!s) {
                retval = -EINVAL;
                goto done;
        }

        async = s->async;
        if (!async) {
                retval = -EINVAL;
                goto done;
        }

        if (vma->vm_pgoff != 0) {
                dev_dbg(dev->class_dev, "mmap() offset must be 0.\n");
                retval = -EINVAL;
                goto done;
        }

        size = vma->vm_end - vma->vm_start;
        if (size > async->prealloc_bufsz) {
                retval = -EFAULT;
                goto done;
        }
        if (offset_in_page(size)) {
                retval = -EFAULT;
                goto done;
        }

        n_pages = vma_pages(vma);

        /* get reference to current buf map (if any) */
        bm = comedi_buf_map_from_subdev_get(s);
        if (!bm || n_pages > bm->n_pages) {
                retval = -EINVAL;
                goto done;
        }
        if (bm->dma_dir != DMA_NONE) {
                /*
                 * DMA buffer was allocated as a single block.
                 * Address is in page_list[0].
                 */
                buf = &bm->page_list[0];
                retval = dma_mmap_coherent(bm->dma_hw_dev, vma, buf->virt_addr,
                                           buf->dma_addr, n_pages * PAGE_SIZE);
        } else {
                for (i = 0; i < n_pages; ++i) {
                        unsigned long pfn;

                        buf = &bm->page_list[i];
                        pfn = page_to_pfn(virt_to_page(buf->virt_addr));
                        retval = remap_pfn_range(vma, start, pfn, PAGE_SIZE,
                                                 PAGE_SHARED);
                        if (retval)
                                break;

                        start += PAGE_SIZE;
                }
        }

        if (retval == 0) {
                vma->vm_ops = &comedi_vm_ops;
                vma->vm_private_data = bm;

                vma->vm_ops->open(vma);
        }

done:
        up_read(&dev->attach_lock);
        comedi_buf_map_put(bm); /* put reference to buf map - okay if NULL */
        return retval;
}

static __poll_t comedi_poll(struct file *file, poll_table *wait)
{
        __poll_t mask = 0;
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;
        struct comedi_subdevice *s, *s_read;

        down_read(&dev->attach_lock);

        if (!dev->attached) {
                dev_dbg(dev->class_dev, "no driver attached\n");
                goto done;
        }

        s = comedi_file_read_subdevice(file);
        s_read = s;
        if (s && s->async) {
                poll_wait(file, &s->async->wait_head, wait);
                if (s->busy != file || !comedi_is_subdevice_running(s) ||
                    (s->async->cmd.flags & CMDF_WRITE) ||
                    comedi_buf_read_n_available(s) > 0)
                        mask |= EPOLLIN | EPOLLRDNORM;
        }

        s = comedi_file_write_subdevice(file);
        if (s && s->async) {
                unsigned int bps = comedi_bytes_per_sample(s);

                if (s != s_read)
                        poll_wait(file, &s->async->wait_head, wait);
                if (s->busy != file || !comedi_is_subdevice_running(s) ||
                    !(s->async->cmd.flags & CMDF_WRITE) ||
                    comedi_buf_write_n_available(s) >= bps)
                        mask |= EPOLLOUT | EPOLLWRNORM;
        }

done:
        up_read(&dev->attach_lock);
        return mask;
}

static ssize_t comedi_write(struct file *file, const char __user *buf,
                            size_t nbytes, loff_t *offset)
{
        struct comedi_subdevice *s;
        struct comedi_async *async;
        unsigned int n, m;
        ssize_t count = 0;
        int retval = 0;
        DECLARE_WAITQUEUE(wait, current);
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;
        bool become_nonbusy = false;
        bool attach_locked;
        unsigned int old_detach_count;

        /* Protect against device detachment during operation. */
        down_read(&dev->attach_lock);
        attach_locked = true;
        old_detach_count = dev->detach_count;

        if (!dev->attached) {
                dev_dbg(dev->class_dev, "no driver attached\n");
                retval = -ENODEV;
                goto out;
        }

        s = comedi_file_write_subdevice(file);
        if (!s || !s->async) {
                retval = -EIO;
                goto out;
        }

        async = s->async;
        if (s->busy != file || !(async->cmd.flags & CMDF_WRITE)) {
                retval = -EINVAL;
                goto out;
        }

        add_wait_queue(&async->wait_head, &wait);
        while (count == 0 && !retval) {
                unsigned int runflags;
                unsigned int wp, n1, n2;

                set_current_state(TASK_INTERRUPTIBLE);

                runflags = comedi_get_subdevice_runflags(s);
                if (!comedi_is_runflags_running(runflags)) {
                        if (comedi_is_runflags_in_error(runflags))
                                retval = -EPIPE;
                        if (retval || nbytes)
                                become_nonbusy = true;
                        break;
                }
                if (nbytes == 0)
                        break;

                /* Allocate all free buffer space. */
                comedi_buf_write_alloc(s, async->prealloc_bufsz);
                m = comedi_buf_write_n_allocated(s);
                n = min_t(size_t, m, nbytes);

                if (n == 0) {
                        if (file->f_flags & O_NONBLOCK) {
                                retval = -EAGAIN;
                                break;
                        }
                        schedule();
                        if (signal_pending(current)) {
                                retval = -ERESTARTSYS;
                                break;
                        }
                        if (s->busy != file ||
                            !(async->cmd.flags & CMDF_WRITE)) {
                                retval = -EINVAL;
                                break;
                        }
                        continue;
                }

                set_current_state(TASK_RUNNING);
                wp = async->buf_write_ptr;
                n1 = min(n, async->prealloc_bufsz - wp);
                n2 = n - n1;
                m = copy_from_user(async->prealloc_buf + wp, buf, n1);
                if (m)
                        m += n2;
                else if (n2)
                        m = copy_from_user(async->prealloc_buf, buf + n1, n2);
                if (m) {
                        n -= m;
                        retval = -EFAULT;
                }
                comedi_buf_write_free(s, n);

                count += n;
                nbytes -= n;

                buf += n;
        }
        remove_wait_queue(&async->wait_head, &wait);
        set_current_state(TASK_RUNNING);
        if (become_nonbusy && count == 0) {
                struct comedi_subdevice *new_s;

                /*
                 * To avoid deadlock, cannot acquire dev->mutex
                 * while dev->attach_lock is held.
                 */
                up_read(&dev->attach_lock);
                attach_locked = false;
                mutex_lock(&dev->mutex);
                /*
                 * Check device hasn't become detached behind our back.
                 * Checking dev->detach_count is unchanged ought to be
                 * sufficient (unless there have been 2**32 detaches in the
                 * meantime!), but check the subdevice pointer as well just in
                 * case.
                 *
                 * Also check the subdevice is still in a suitable state to
                 * become non-busy in case it changed behind our back.
                 */
                new_s = comedi_file_write_subdevice(file);
                if (dev->attached && old_detach_count == dev->detach_count &&
                    s == new_s && new_s->async == async && s->busy == file &&
                    (async->cmd.flags & CMDF_WRITE) &&
                    !comedi_is_subdevice_running(s))
                        do_become_nonbusy(dev, s);
                mutex_unlock(&dev->mutex);
        }
out:
        if (attach_locked)
                up_read(&dev->attach_lock);

        return count ? count : retval;
}

static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
                           loff_t *offset)
{
        struct comedi_subdevice *s;
        struct comedi_async *async;
        unsigned int n, m;
        ssize_t count = 0;
        int retval = 0;
        DECLARE_WAITQUEUE(wait, current);
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;
        unsigned int old_detach_count;
        bool become_nonbusy = false;
        bool attach_locked;

        /* Protect against device detachment during operation. */
        down_read(&dev->attach_lock);
        attach_locked = true;
        old_detach_count = dev->detach_count;

        if (!dev->attached) {
                dev_dbg(dev->class_dev, "no driver attached\n");
                retval = -ENODEV;
                goto out;
        }

        s = comedi_file_read_subdevice(file);
        if (!s || !s->async) {
                retval = -EIO;
                goto out;
        }

        async = s->async;
        if (s->busy != file || (async->cmd.flags & CMDF_WRITE)) {
                retval = -EINVAL;
                goto out;
        }

        add_wait_queue(&async->wait_head, &wait);
        while (count == 0 && !retval) {
                unsigned int rp, n1, n2;

                set_current_state(TASK_INTERRUPTIBLE);

                m = comedi_buf_read_n_available(s);
                n = min_t(size_t, m, nbytes);

                if (n == 0) {
                        unsigned int runflags =
                                     comedi_get_subdevice_runflags(s);

                        if (!comedi_is_runflags_running(runflags)) {
                                if (comedi_is_runflags_in_error(runflags))
                                        retval = -EPIPE;
                                if (retval || nbytes)
                                        become_nonbusy = true;
                                break;
                        }
                        if (nbytes == 0)
                                break;
                        if (file->f_flags & O_NONBLOCK) {
                                retval = -EAGAIN;
                                break;
                        }
                        schedule();
                        if (signal_pending(current)) {
                                retval = -ERESTARTSYS;
                                break;
                        }
                        if (s->busy != file ||
                            (async->cmd.flags & CMDF_WRITE)) {
                                retval = -EINVAL;
                                break;
                        }
                        continue;
                }

                set_current_state(TASK_RUNNING);
                rp = async->buf_read_ptr;
                n1 = min(n, async->prealloc_bufsz - rp);
                n2 = n - n1;
                m = copy_to_user(buf, async->prealloc_buf + rp, n1);
                if (m)
                        m += n2;
                else if (n2)
                        m = copy_to_user(buf + n1, async->prealloc_buf, n2);
                if (m) {
                        n -= m;
                        retval = -EFAULT;
                }

                comedi_buf_read_alloc(s, n);
                comedi_buf_read_free(s, n);

                count += n;
                nbytes -= n;

                buf += n;
        }
        remove_wait_queue(&async->wait_head, &wait);
        set_current_state(TASK_RUNNING);
        if (become_nonbusy && count == 0) {
                struct comedi_subdevice *new_s;

                /*
                 * To avoid deadlock, cannot acquire dev->mutex
                 * while dev->attach_lock is held.
                 */
                up_read(&dev->attach_lock);
                attach_locked = false;
                mutex_lock(&dev->mutex);
                /*
                 * Check device hasn't become detached behind our back.
                 * Checking dev->detach_count is unchanged ought to be
                 * sufficient (unless there have been 2**32 detaches in the
                 * meantime!), but check the subdevice pointer as well just in
                 * case.
                 *
                 * Also check the subdevice is still in a suitable state to
                 * become non-busy in case it changed behind our back.
                 */
                new_s = comedi_file_read_subdevice(file);
                if (dev->attached && old_detach_count == dev->detach_count &&
                    s == new_s && new_s->async == async && s->busy == file &&
                    !(async->cmd.flags & CMDF_WRITE) &&
                    !comedi_is_subdevice_running(s) &&
                    comedi_buf_read_n_available(s) == 0)
                        do_become_nonbusy(dev, s);
                mutex_unlock(&dev->mutex);
        }
out:
        if (attach_locked)
                up_read(&dev->attach_lock);

        return count ? count : retval;
}

static int comedi_open(struct inode *inode, struct file *file)
{
        const unsigned int minor = iminor(inode);
        struct comedi_file *cfp;
        struct comedi_device *dev = comedi_dev_get_from_minor(minor);
        int rc;

        if (!dev) {
                pr_debug("invalid minor number\n");
                return -ENODEV;
        }

        cfp = kzalloc(sizeof(*cfp), GFP_KERNEL);
        if (!cfp)
                return -ENOMEM;

        cfp->dev = dev;

        mutex_lock(&dev->mutex);
        if (!dev->attached && !capable(CAP_SYS_ADMIN)) {
                dev_dbg(dev->class_dev, "not attached and not CAP_SYS_ADMIN\n");
                rc = -ENODEV;
                goto out;
        }
        if (dev->attached && dev->use_count == 0) {
                if (!try_module_get(dev->driver->module)) {
                        rc = -ENXIO;
                        goto out;
                }
                if (dev->open) {
                        rc = dev->open(dev);
                        if (rc < 0) {
                                module_put(dev->driver->module);
                                goto out;
                        }
                }
        }

        dev->use_count++;
        file->private_data = cfp;
        comedi_file_reset(file);
        rc = 0;

out:
        mutex_unlock(&dev->mutex);
        if (rc) {
                comedi_dev_put(dev);
                kfree(cfp);
        }
        return rc;
}

static int comedi_fasync(int fd, struct file *file, int on)
{
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;

        return fasync_helper(fd, file, on, &dev->async_queue);
}

static int comedi_close(struct inode *inode, struct file *file)
{
        struct comedi_file *cfp = file->private_data;
        struct comedi_device *dev = cfp->dev;
        struct comedi_subdevice *s = NULL;
        int i;

        mutex_lock(&dev->mutex);

        if (dev->subdevices) {
                for (i = 0; i < dev->n_subdevices; i++) {
                        s = &dev->subdevices[i];

                        if (s->busy == file)
                                do_cancel(dev, s);
                        if (s->lock == file)
                                s->lock = NULL;
                }
        }
        if (dev->attached && dev->use_count == 1) {
                if (dev->close)
                        dev->close(dev);
                module_put(dev->driver->module);
        }

        dev->use_count--;

        mutex_unlock(&dev->mutex);
        comedi_dev_put(dev);
        kfree(cfp);

        return 0;
}

static const struct file_operations comedi_fops = {
        .owner = THIS_MODULE,
        .unlocked_ioctl = comedi_unlocked_ioctl,
        .compat_ioctl = comedi_compat_ioctl,
        .open = comedi_open,
        .release = comedi_close,
        .read = comedi_read,
        .write = comedi_write,
        .mmap = comedi_mmap,
        .poll = comedi_poll,
        .fasync = comedi_fasync,
        .llseek = noop_llseek,
};

/**
 * comedi_event() - Handle events for asynchronous COMEDI command
 * @dev: COMEDI device.
 * @s: COMEDI subdevice.
 * Context: in_interrupt() (usually), @s->spin_lock spin-lock not held.
 *
 * If an asynchronous COMEDI command is active on the subdevice, process
 * any %COMEDI_CB_... event flags that have been set, usually by an
 * interrupt handler.  These may change the run state of the asynchronous
 * command, wake a task, and/or send a %SIGIO signal.
 */
void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s)
{
        struct comedi_async *async = s->async;
        unsigned int events;
        int si_code = 0;
        unsigned long flags;

        spin_lock_irqsave(&s->spin_lock, flags);

        events = async->events;
        async->events = 0;
        if (!__comedi_is_subdevice_running(s)) {
                spin_unlock_irqrestore(&s->spin_lock, flags);
                return;
        }

        if (events & COMEDI_CB_CANCEL_MASK)
                __comedi_clear_subdevice_runflags(s, COMEDI_SRF_RUNNING);

        /*
         * Remember if an error event has occurred, so an error can be
         * returned the next time the user does a read() or write().
         */
        if (events & COMEDI_CB_ERROR_MASK)
                __comedi_set_subdevice_runflags(s, COMEDI_SRF_ERROR);

        if (async->cb_mask & events) {
                wake_up_interruptible(&async->wait_head);
                si_code = async->cmd.flags & CMDF_WRITE ? POLL_OUT : POLL_IN;
        }

        spin_unlock_irqrestore(&s->spin_lock, flags);

        if (si_code)
                kill_fasync(&dev->async_queue, SIGIO, si_code);
}
EXPORT_SYMBOL_GPL(comedi_event);

/* Note: the ->mutex is pre-locked on successful return */
struct comedi_device *comedi_alloc_board_minor(struct device *hardware_device)
{
        struct comedi_device *dev;
        struct device *csdev;
        unsigned int i;

        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev)
                return ERR_PTR(-ENOMEM);
        comedi_device_init(dev);
        comedi_set_hw_dev(dev, hardware_device);
        mutex_lock(&dev->mutex);
        mutex_lock(&comedi_board_minor_table_lock);
        for (i = hardware_device ? comedi_num_legacy_minors : 0;
             i < COMEDI_NUM_BOARD_MINORS; ++i) {
                if (!comedi_board_minor_table[i]) {
                        comedi_board_minor_table[i] = dev;
                        break;
                }
        }
        mutex_unlock(&comedi_board_minor_table_lock);
        if (i == COMEDI_NUM_BOARD_MINORS) {
                mutex_unlock(&dev->mutex);
                comedi_device_cleanup(dev);
                comedi_dev_put(dev);
                dev_err(hardware_device,
                        "ran out of minor numbers for board device files\n");
                return ERR_PTR(-EBUSY);
        }
        dev->minor = i;
        csdev = device_create(comedi_class, hardware_device,
                              MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i", i);
        if (!IS_ERR(csdev))
                dev->class_dev = get_device(csdev);

        /* Note: dev->mutex needs to be unlocked by the caller. */
        return dev;
}

void comedi_release_hardware_device(struct device *hardware_device)
{
        int minor;
        struct comedi_device *dev;

        for (minor = comedi_num_legacy_minors; minor < COMEDI_NUM_BOARD_MINORS;
             minor++) {
                mutex_lock(&comedi_board_minor_table_lock);
                dev = comedi_board_minor_table[minor];
                if (dev && dev->hw_dev == hardware_device) {
                        comedi_board_minor_table[minor] = NULL;
                        mutex_unlock(&comedi_board_minor_table_lock);
                        comedi_free_board_dev(dev);
                        break;
                }
                mutex_unlock(&comedi_board_minor_table_lock);
        }
}

int comedi_alloc_subdevice_minor(struct comedi_subdevice *s)
{
        struct comedi_device *dev = s->device;
        struct device *csdev;
        unsigned int i;

        mutex_lock(&comedi_subdevice_minor_table_lock);
        for (i = 0; i < COMEDI_NUM_SUBDEVICE_MINORS; ++i) {
                if (!comedi_subdevice_minor_table[i]) {
                        comedi_subdevice_minor_table[i] = s;
                        break;
                }
        }
        mutex_unlock(&comedi_subdevice_minor_table_lock);
        if (i == COMEDI_NUM_SUBDEVICE_MINORS) {
                dev_err(dev->class_dev,
                        "ran out of minor numbers for subdevice files\n");
                return -EBUSY;
        }
        i += COMEDI_NUM_BOARD_MINORS;
        s->minor = i;
        csdev = device_create(comedi_class, dev->class_dev,
                              MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i_subd%i",
                              dev->minor, s->index);
        if (!IS_ERR(csdev))
                s->class_dev = csdev;

        return 0;
}

void comedi_free_subdevice_minor(struct comedi_subdevice *s)
{
        unsigned int i;

        if (!s)
                return;
        if (s->minor < COMEDI_NUM_BOARD_MINORS ||
            s->minor >= COMEDI_NUM_MINORS)
                return;

        i = s->minor - COMEDI_NUM_BOARD_MINORS;
        mutex_lock(&comedi_subdevice_minor_table_lock);
        if (s == comedi_subdevice_minor_table[i])
                comedi_subdevice_minor_table[i] = NULL;
        mutex_unlock(&comedi_subdevice_minor_table_lock);
        if (s->class_dev) {
                device_destroy(comedi_class, MKDEV(COMEDI_MAJOR, s->minor));
                s->class_dev = NULL;
        }
}

static void comedi_cleanup_board_minors(void)
{
        struct comedi_device *dev;
        unsigned int i;

        for (i = 0; i < COMEDI_NUM_BOARD_MINORS; i++) {
                dev = comedi_clear_board_minor(i);
                comedi_free_board_dev(dev);
        }
}

static int __init comedi_init(void)
{
        int i;
        int retval;

        pr_info("version " COMEDI_RELEASE " - http://www.comedi.org\n");

        if (comedi_num_legacy_minors > COMEDI_NUM_BOARD_MINORS) {

                pr_err("invalid value for module parameter \"comedi_num_legacy_minors\".  Valid values are 0 through %i.\n",
                       COMEDI_NUM_BOARD_MINORS);
                return -EINVAL;
        }

        retval = register_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
                                        COMEDI_NUM_MINORS, "comedi");
        if (retval)
                return retval;

        cdev_init(&comedi_cdev, &comedi_fops);
        comedi_cdev.owner = THIS_MODULE;

        retval = kobject_set_name(&comedi_cdev.kobj, "comedi");
        if (retval)
                goto out_unregister_chrdev_region;

        retval = cdev_add(&comedi_cdev, MKDEV(COMEDI_MAJOR, 0),
                          COMEDI_NUM_MINORS);
        if (retval)
                goto out_unregister_chrdev_region;

        comedi_class = class_create(THIS_MODULE, "comedi");
        if (IS_ERR(comedi_class)) {
                retval = PTR_ERR(comedi_class);
                pr_err("failed to create class\n");
                goto out_cdev_del;
        }

        comedi_class->dev_groups = comedi_dev_groups;

        /* create devices files for legacy/manual use */
        for (i = 0; i < comedi_num_legacy_minors; i++) {
                struct comedi_device *dev;

                dev = comedi_alloc_board_minor(NULL);
                if (IS_ERR(dev)) {
                        retval = PTR_ERR(dev);
                        goto out_cleanup_board_minors;
                }
                /* comedi_alloc_board_minor() locked the mutex */
                lockdep_assert_held(&dev->mutex);
                mutex_unlock(&dev->mutex);
        }

        /* XXX requires /proc interface */
        comedi_proc_init();

        return 0;

out_cleanup_board_minors:
        comedi_cleanup_board_minors();
        class_destroy(comedi_class);
out_cdev_del:
        cdev_del(&comedi_cdev);
out_unregister_chrdev_region:
        unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0), COMEDI_NUM_MINORS);
        return retval;
}
module_init(comedi_init);

static void __exit comedi_cleanup(void)
{
        comedi_cleanup_board_minors();
        class_destroy(comedi_class);
        cdev_del(&comedi_cdev);
        unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0), COMEDI_NUM_MINORS);

        comedi_proc_cleanup();
}
module_exit(comedi_cleanup);

MODULE_AUTHOR("http://www.comedi.org");
MODULE_DESCRIPTION("Comedi core module");
MODULE_LICENSE("GPL");