// SPDX-License-Identifier: GPL-2.0
/*
 * Driver for Meywa-Denki & KAYAC YUREX
 *
 * Copyright (C) 2010 Tomoki Sekiyama (tomoki.sekiyama@gmail.com)
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kref.h>
#include <linux/mutex.h>
#include <linux/uaccess.h>
#include <linux/usb.h>
#include <linux/hid.h>

#define DRIVER_AUTHOR "Tomoki Sekiyama"
#define DRIVER_DESC "Driver for Meywa-Denki & KAYAC YUREX"

#define YUREX_VENDOR_ID         0x0c45
#define YUREX_PRODUCT_ID        0x1010

#define CMD_ACK         '!'
#define CMD_ANIMATE     'A'
#define CMD_COUNT       'C'
#define CMD_LED         'L'
#define CMD_READ        'R'
#define CMD_SET         'S'
#define CMD_VERSION     'V'
#define CMD_EOF         0x0d
#define CMD_PADDING     0xff

#define YUREX_BUF_SIZE          8
#define YUREX_WRITE_TIMEOUT     (HZ*2)

/* table of devices that work with this driver */
static struct usb_device_id yurex_table[] = {
        { USB_DEVICE(YUREX_VENDOR_ID, YUREX_PRODUCT_ID) },
        { }                                     /* Terminating entry */
};
MODULE_DEVICE_TABLE(usb, yurex_table);

#ifdef CONFIG_USB_DYNAMIC_MINORS
#define YUREX_MINOR_BASE        0
#else
#define YUREX_MINOR_BASE        192
#endif

/* Structure to hold all of our device specific stuff */
struct usb_yurex {
        struct usb_device       *udev;
        struct usb_interface    *interface;
        __u8                    int_in_endpointAddr;
        struct urb              *urb;           /* URB for interrupt in */
        unsigned char           *int_buffer;    /* buffer for intterupt in */
        struct urb              *cntl_urb;      /* URB for control msg */
        struct usb_ctrlrequest  *cntl_req;      /* req for control msg */
        unsigned char           *cntl_buffer;   /* buffer for control msg */

        struct kref             kref;
        struct mutex            io_mutex;
        unsigned long           disconnected:1;
        struct fasync_struct    *async_queue;
        wait_queue_head_t       waitq;

        spinlock_t              lock;
        __s64                   bbu;            /* BBU from device */
};
#define to_yurex_dev(d) container_of(d, struct usb_yurex, kref)

static struct usb_driver yurex_driver;
static const struct file_operations yurex_fops;


static void yurex_control_callback(struct urb *urb)
{
        struct usb_yurex *dev = urb->context;
        int status = urb->status;

        if (status) {
                dev_err(&urb->dev->dev, "%s - control failed: %d\n",
                        __func__, status);
                wake_up_interruptible(&dev->waitq);
                return;
        }
        /* on success, sender woken up by CMD_ACK int in, or timeout */
}

static void yurex_delete(struct kref *kref)
{
        struct usb_yurex *dev = to_yurex_dev(kref);

        dev_dbg(&dev->interface->dev, "%s\n", __func__);

        if (dev->cntl_urb) {
                usb_kill_urb(dev->cntl_urb);
                kfree(dev->cntl_req);
                usb_free_coherent(dev->udev, YUREX_BUF_SIZE,
                                dev->cntl_buffer, dev->cntl_urb->transfer_dma);
                usb_free_urb(dev->cntl_urb);
        }
        if (dev->urb) {
                usb_kill_urb(dev->urb);
                usb_free_coherent(dev->udev, YUREX_BUF_SIZE,
                                dev->int_buffer, dev->urb->transfer_dma);
                usb_free_urb(dev->urb);
        }
        usb_put_intf(dev->interface);
        usb_put_dev(dev->udev);
        kfree(dev);
}

/*
 * usb class driver info in order to get a minor number from the usb core,
 * and to have the device registered with the driver core
 */
static struct usb_class_driver yurex_class = {
        .name =         "yurex%d",
        .fops =         &yurex_fops,
        .minor_base =   YUREX_MINOR_BASE,
};

static void yurex_interrupt(struct urb *urb)
{
        struct usb_yurex *dev = urb->context;
        unsigned char *buf = dev->int_buffer;
        int status = urb->status;
        unsigned long flags;
        int retval, i;

        switch (status) {
        case 0: /*success*/
                break;
        /* The device is terminated or messed up, give up */
        case -EOVERFLOW:
                dev_err(&dev->interface->dev,
                        "%s - overflow with length %d, actual length is %d\n",
                        __func__, YUREX_BUF_SIZE, dev->urb->actual_length);
                return;
        case -ECONNRESET:
        case -ENOENT:
        case -ESHUTDOWN:
        case -EILSEQ:
        case -EPROTO:
        case -ETIME:
                return;
        default:
                dev_err(&dev->interface->dev,
                        "%s - unknown status received: %d\n", __func__, status);
                return;
        }

        /* handle received message */
        switch (buf[0]) {
        case CMD_COUNT:
        case CMD_READ:
                if (buf[6] == CMD_EOF) {
                        spin_lock_irqsave(&dev->lock, flags);
                        dev->bbu = 0;
                        for (i = 1; i < 6; i++) {
                                dev->bbu += buf[i];
                                if (i != 5)
                                        dev->bbu <<= 8;
                        }
                        dev_dbg(&dev->interface->dev, "%s count: %lld\n",
                                __func__, dev->bbu);
                        spin_unlock_irqrestore(&dev->lock, flags);

                        kill_fasync(&dev->async_queue, SIGIO, POLL_IN);
                }
                else
                        dev_dbg(&dev->interface->dev,
                                "data format error - no EOF\n");
                break;
        case CMD_ACK:
                dev_dbg(&dev->interface->dev, "%s ack: %c\n",
                        __func__, buf[1]);
                wake_up_interruptible(&dev->waitq);
                break;
        }

        retval = usb_submit_urb(dev->urb, GFP_ATOMIC);
        if (retval) {
                dev_err(&dev->interface->dev, "%s - usb_submit_urb failed: %d\n",
                        __func__, retval);
        }
}

static int yurex_probe(struct usb_interface *interface, const struct usb_device_id *id)
{
        struct usb_yurex *dev;
        struct usb_host_interface *iface_desc;
        struct usb_endpoint_descriptor *endpoint;
        int retval = -ENOMEM;
        DEFINE_WAIT(wait);
        int res;

        /* allocate memory for our device state and initialize it */
        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev)
                goto error;
        kref_init(&dev->kref);
        mutex_init(&dev->io_mutex);
        spin_lock_init(&dev->lock);
        init_waitqueue_head(&dev->waitq);

        dev->udev = usb_get_dev(interface_to_usbdev(interface));
        dev->interface = usb_get_intf(interface);

        /* set up the endpoint information */
        iface_desc = interface->cur_altsetting;
        res = usb_find_int_in_endpoint(iface_desc, &endpoint);
        if (res) {
                dev_err(&interface->dev, "Could not find endpoints\n");
                retval = res;
                goto error;
        }

        dev->int_in_endpointAddr = endpoint->bEndpointAddress;

        /* allocate control URB */
        dev->cntl_urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!dev->cntl_urb)
                goto error;

        /* allocate buffer for control req */
        dev->cntl_req = kmalloc(YUREX_BUF_SIZE, GFP_KERNEL);
        if (!dev->cntl_req)
                goto error;

        /* allocate buffer for control msg */
        dev->cntl_buffer = usb_alloc_coherent(dev->udev, YUREX_BUF_SIZE,
                                              GFP_KERNEL,
                                              &dev->cntl_urb->transfer_dma);
        if (!dev->cntl_buffer) {
                dev_err(&interface->dev, "Could not allocate cntl_buffer\n");
                goto error;
        }

        /* configure control URB */
        dev->cntl_req->bRequestType = USB_DIR_OUT | USB_TYPE_CLASS |
                                      USB_RECIP_INTERFACE;
        dev->cntl_req->bRequest = HID_REQ_SET_REPORT;
        dev->cntl_req->wValue   = cpu_to_le16((HID_OUTPUT_REPORT + 1) << 8);
        dev->cntl_req->wIndex   = cpu_to_le16(iface_desc->desc.bInterfaceNumber);
        dev->cntl_req->wLength  = cpu_to_le16(YUREX_BUF_SIZE);

        usb_fill_control_urb(dev->cntl_urb, dev->udev,
                             usb_sndctrlpipe(dev->udev, 0),
                             (void *)dev->cntl_req, dev->cntl_buffer,
                             YUREX_BUF_SIZE, yurex_control_callback, dev);
        dev->cntl_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;


        /* allocate interrupt URB */
        dev->urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!dev->urb)
                goto error;

        /* allocate buffer for interrupt in */
        dev->int_buffer = usb_alloc_coherent(dev->udev, YUREX_BUF_SIZE,
                                        GFP_KERNEL, &dev->urb->transfer_dma);
        if (!dev->int_buffer) {
                dev_err(&interface->dev, "Could not allocate int_buffer\n");
                goto error;
        }

        /* configure interrupt URB */
        usb_fill_int_urb(dev->urb, dev->udev,
                         usb_rcvintpipe(dev->udev, dev->int_in_endpointAddr),
                         dev->int_buffer, YUREX_BUF_SIZE, yurex_interrupt,
                         dev, 1);
        dev->urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
        if (usb_submit_urb(dev->urb, GFP_KERNEL)) {
                retval = -EIO;
                dev_err(&interface->dev, "Could not submitting URB\n");
                goto error;
        }

        /* save our data pointer in this interface device */
        usb_set_intfdata(interface, dev);
        dev->bbu = -1;

        /* we can register the device now, as it is ready */
        retval = usb_register_dev(interface, &yurex_class);
        if (retval) {
                dev_err(&interface->dev,
                        "Not able to get a minor for this device.\n");
                usb_set_intfdata(interface, NULL);
                goto error;
        }

        dev_info(&interface->dev,
                 "USB YUREX device now attached to Yurex #%d\n",
                 interface->minor);

        return 0;

error:
        if (dev)
                /* this frees allocated memory */
                kref_put(&dev->kref, yurex_delete);
        return retval;
}

static void yurex_disconnect(struct usb_interface *interface)
{
        struct usb_yurex *dev;
        int minor = interface->minor;

        dev = usb_get_intfdata(interface);
        usb_set_intfdata(interface, NULL);

        /* give back our minor */
        usb_deregister_dev(interface, &yurex_class);

        /* prevent more I/O from starting */
        usb_poison_urb(dev->urb);
        usb_poison_urb(dev->cntl_urb);
        mutex_lock(&dev->io_mutex);
        dev->disconnected = 1;
        mutex_unlock(&dev->io_mutex);

        /* wakeup waiters */
        kill_fasync(&dev->async_queue, SIGIO, POLL_IN);
        wake_up_interruptible(&dev->waitq);

        /* decrement our usage count */
        kref_put(&dev->kref, yurex_delete);

        dev_info(&interface->dev, "USB YUREX #%d now disconnected\n", minor);
}

static struct usb_driver yurex_driver = {
        .name =         "yurex",
        .probe =        yurex_probe,
        .disconnect =   yurex_disconnect,
        .id_table =     yurex_table,
};


static int yurex_fasync(int fd, struct file *file, int on)
{
        struct usb_yurex *dev;

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

static int yurex_open(struct inode *inode, struct file *file)
{
        struct usb_yurex *dev;
        struct usb_interface *interface;
        int subminor;
        int retval = 0;

        subminor = iminor(inode);

        interface = usb_find_interface(&yurex_driver, subminor);
        if (!interface) {
                printk(KERN_ERR "%s - error, can't find device for minor %d",
                       __func__, subminor);
                retval = -ENODEV;
                goto exit;
        }

        dev = usb_get_intfdata(interface);
        if (!dev) {
                retval = -ENODEV;
                goto exit;
        }

        /* increment our usage count for the device */
        kref_get(&dev->kref);

        /* save our object in the file's private structure */
        mutex_lock(&dev->io_mutex);
        file->private_data = dev;
        mutex_unlock(&dev->io_mutex);

exit:
        return retval;
}

static int yurex_release(struct inode *inode, struct file *file)
{
        struct usb_yurex *dev;

        dev = file->private_data;
        if (dev == NULL)
                return -ENODEV;

        /* decrement the count on our device */
        kref_put(&dev->kref, yurex_delete);
        return 0;
}

static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
                          loff_t *ppos)
{
        struct usb_yurex *dev;
        int len = 0;
        char in_buffer[20];
        unsigned long flags;

        dev = file->private_data;

        mutex_lock(&dev->io_mutex);
        if (dev->disconnected) {                /* already disconnected */
                mutex_unlock(&dev->io_mutex);
                return -ENODEV;
        }

        spin_lock_irqsave(&dev->lock, flags);
        len = snprintf(in_buffer, 20, "%lld\n", dev->bbu);
        spin_unlock_irqrestore(&dev->lock, flags);
        mutex_unlock(&dev->io_mutex);

        if (WARN_ON_ONCE(len >= sizeof(in_buffer)))
                return -EIO;

        return simple_read_from_buffer(buffer, count, ppos, in_buffer, len);
}

static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
                           size_t count, loff_t *ppos)
{
        struct usb_yurex *dev;
        int i, set = 0, retval = 0;
        char buffer[16 + 1];
        char *data = buffer;
        unsigned long long c, c2 = 0;
        signed long timeout = 0;
        DEFINE_WAIT(wait);

        count = min(sizeof(buffer) - 1, count);
        dev = file->private_data;

        /* verify that we actually have some data to write */
        if (count == 0)
                goto error;

        mutex_lock(&dev->io_mutex);
        if (dev->disconnected) {                /* already disconnected */
                mutex_unlock(&dev->io_mutex);
                retval = -ENODEV;
                goto error;
        }

        if (copy_from_user(buffer, user_buffer, count)) {
                mutex_unlock(&dev->io_mutex);
                retval = -EFAULT;
                goto error;
        }
        buffer[count] = 0;
        memset(dev->cntl_buffer, CMD_PADDING, YUREX_BUF_SIZE);

        switch (buffer[0]) {
        case CMD_ANIMATE:
        case CMD_LED:
                dev->cntl_buffer[0] = buffer[0];
                dev->cntl_buffer[1] = buffer[1];
                dev->cntl_buffer[2] = CMD_EOF;
                break;
        case CMD_READ:
        case CMD_VERSION:
                dev->cntl_buffer[0] = buffer[0];
                dev->cntl_buffer[1] = 0x00;
                dev->cntl_buffer[2] = CMD_EOF;
                break;
        case CMD_SET:
                data++;
                fallthrough;
        case '0' ... '9':
                set = 1;
                c = c2 = simple_strtoull(data, NULL, 0);
                dev->cntl_buffer[0] = CMD_SET;
                for (i = 1; i < 6; i++) {
                        dev->cntl_buffer[i] = (c>>32) & 0xff;
                        c <<= 8;
                }
                buffer[6] = CMD_EOF;
                break;
        default:
                mutex_unlock(&dev->io_mutex);
                return -EINVAL;
        }

        /* send the data as the control msg */
        prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
        dev_dbg(&dev->interface->dev, "%s - submit %c\n", __func__,
                dev->cntl_buffer[0]);
        retval = usb_submit_urb(dev->cntl_urb, GFP_ATOMIC);
        if (retval >= 0)
                timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
        finish_wait(&dev->waitq, &wait);

        /* make sure URB is idle after timeout or (spurious) CMD_ACK */
        usb_kill_urb(dev->cntl_urb);

        mutex_unlock(&dev->io_mutex);

        if (retval < 0) {
                dev_err(&dev->interface->dev,
                        "%s - failed to send bulk msg, error %d\n",
                        __func__, retval);
                goto error;
        }
        if (set && timeout)
                dev->bbu = c2;
        return timeout ? count : -EIO;

error:
        return retval;
}

static const struct file_operations yurex_fops = {
        .owner =        THIS_MODULE,
        .read =         yurex_read,
        .write =        yurex_write,
        .open =         yurex_open,
        .release =      yurex_release,
        .fasync =       yurex_fasync,
        .llseek =       default_llseek,
};

module_usb_driver(yurex_driver);

MODULE_LICENSE("GPL");