/*
 * Greybus driver for the Raw protocol
 *
 * Copyright 2015 Google Inc.
 * Copyright 2015 Linaro Ltd.
 *
 * Released under the GPLv2 only.
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sizes.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/idr.h>
#include <linux/uaccess.h>

#include "greybus.h"

struct gb_raw {
        struct gb_connection *connection;

        struct list_head list;
        int list_data;
        struct mutex list_lock;
        dev_t dev;
        struct cdev cdev;
        struct device *device;
};

struct raw_data {
        struct list_head entry;
        u32 len;
        u8 data[0];
};

static struct class *raw_class;
static int raw_major;
static const struct file_operations raw_fops;
static DEFINE_IDA(minors);

/* Number of minor devices this driver supports */
#define NUM_MINORS      256

/* Maximum size of any one send data buffer we support */
#define MAX_PACKET_SIZE (PAGE_SIZE * 2)

/*
 * Maximum size of the data in the receive buffer we allow before we start to
 * drop messages on the floor
 */
#define MAX_DATA_SIZE   (MAX_PACKET_SIZE * 8)

/*
 * Add the raw data message to the list of received messages.
 */
static int receive_data(struct gb_raw *raw, u32 len, u8 *data)
{
        struct raw_data *raw_data;
        struct device *dev = &raw->connection->bundle->dev;
        int retval = 0;

        if (len > MAX_PACKET_SIZE) {
                dev_err(dev, "Too big of a data packet, rejected\n");
                return -EINVAL;
        }

        mutex_lock(&raw->list_lock);
        if ((raw->list_data + len) > MAX_DATA_SIZE) {
                dev_err(dev, "Too much data in receive buffer, now dropping packets\n");
                retval = -EINVAL;
                goto exit;
        }

        raw_data = kmalloc(sizeof(*raw_data) + len, GFP_KERNEL);
        if (!raw_data) {
                retval = -ENOMEM;
                goto exit;
        }

        raw->list_data += len;
        raw_data->len = len;
        memcpy(&raw_data->data[0], data, len);

        list_add_tail(&raw_data->entry, &raw->list);
exit:
        mutex_unlock(&raw->list_lock);
        return retval;
}

static int gb_raw_request_handler(struct gb_operation *op)
{
        struct gb_connection *connection = op->connection;
        struct device *dev = &connection->bundle->dev;
        struct gb_raw *raw = greybus_get_drvdata(connection->bundle);
        struct gb_raw_send_request *receive;
        u32 len;

        if (op->type != GB_RAW_TYPE_SEND) {
                dev_err(dev, "unknown request type 0x%02x\n", op->type);
                return -EINVAL;
        }

        /* Verify size of payload */
        if (op->request->payload_size < sizeof(*receive)) {
                dev_err(dev, "raw receive request too small (%zu < %zu)\n",
                        op->request->payload_size, sizeof(*receive));
                return -EINVAL;
        }
        receive = op->request->payload;
        len = le32_to_cpu(receive->len);
        if (len != (int)(op->request->payload_size - sizeof(__le32))) {
                dev_err(dev, "raw receive request wrong size %d vs %d\n", len,
                        (int)(op->request->payload_size - sizeof(__le32)));
                return -EINVAL;
        }
        if (len == 0) {
                dev_err(dev, "raw receive request of 0 bytes?\n");
                return -EINVAL;
        }

        return receive_data(raw, len, receive->data);
}

static int gb_raw_send(struct gb_raw *raw, u32 len, const char __user *data)
{
        struct gb_connection *connection = raw->connection;
        struct gb_raw_send_request *request;
        int retval;

        request = kmalloc(len + sizeof(*request), GFP_KERNEL);
        if (!request)
                return -ENOMEM;

        if (copy_from_user(&request->data[0], data, len)) {
                kfree(request);
                return -EFAULT;
        }

        request->len = cpu_to_le32(len);

        retval = gb_operation_sync(connection, GB_RAW_TYPE_SEND,
                                   request, len + sizeof(*request),
                                   NULL, 0);

        kfree(request);
        return retval;
}

static int gb_raw_probe(struct gb_bundle *bundle,
                        const struct greybus_bundle_id *id)
{
        struct greybus_descriptor_cport *cport_desc;
        struct gb_connection *connection;
        struct gb_raw *raw;
        int retval;
        int minor;

        if (bundle->num_cports != 1)
                return -ENODEV;

        cport_desc = &bundle->cport_desc[0];
        if (cport_desc->protocol_id != GREYBUS_PROTOCOL_RAW)
                return -ENODEV;

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

        connection = gb_connection_create(bundle, le16_to_cpu(cport_desc->id),
                                          gb_raw_request_handler);
        if (IS_ERR(connection)) {
                retval = PTR_ERR(connection);
                goto error_free;
        }

        INIT_LIST_HEAD(&raw->list);
        mutex_init(&raw->list_lock);

        raw->connection = connection;
        greybus_set_drvdata(bundle, raw);

        minor = ida_simple_get(&minors, 0, 0, GFP_KERNEL);
        if (minor < 0) {
                retval = minor;
                goto error_connection_destroy;
        }

        raw->dev = MKDEV(raw_major, minor);
        cdev_init(&raw->cdev, &raw_fops);

        retval = gb_connection_enable(connection);
        if (retval)
                goto error_remove_ida;

        retval = cdev_add(&raw->cdev, raw->dev, 1);
        if (retval)
                goto error_connection_disable;

        raw->device = device_create(raw_class, &connection->bundle->dev,
                                    raw->dev, raw, "gb!raw%d", minor);
        if (IS_ERR(raw->device)) {
                retval = PTR_ERR(raw->device);
                goto error_del_cdev;
        }

        return 0;

error_del_cdev:
        cdev_del(&raw->cdev);

error_connection_disable:
        gb_connection_disable(connection);

error_remove_ida:
        ida_simple_remove(&minors, minor);

error_connection_destroy:
        gb_connection_destroy(connection);

error_free:
        kfree(raw);
        return retval;
}

static void gb_raw_disconnect(struct gb_bundle *bundle)
{
        struct gb_raw *raw = greybus_get_drvdata(bundle);
        struct gb_connection *connection = raw->connection;
        struct raw_data *raw_data;
        struct raw_data *temp;

        // FIXME - handle removing a connection when the char device node is open.
        device_destroy(raw_class, raw->dev);
        cdev_del(&raw->cdev);
        gb_connection_disable(connection);
        ida_simple_remove(&minors, MINOR(raw->dev));
        gb_connection_destroy(connection);

        mutex_lock(&raw->list_lock);
        list_for_each_entry_safe(raw_data, temp, &raw->list, entry) {
                list_del(&raw_data->entry);
                kfree(raw_data);
        }
        mutex_unlock(&raw->list_lock);

        kfree(raw);
}

/*
 * Character device node interfaces.
 *
 * Note, we are using read/write to only allow a single read/write per message.
 * This means for read(), you have to provide a big enough buffer for the full
 * message to be copied into.  If the buffer isn't big enough, the read() will
 * fail with -ENOSPC.
 */

static int raw_open(struct inode *inode, struct file *file)
{
        struct cdev *cdev = inode->i_cdev;
        struct gb_raw *raw = container_of(cdev, struct gb_raw, cdev);

        file->private_data = raw;
        return 0;
}

static ssize_t raw_write(struct file *file, const char __user *buf,
                         size_t count, loff_t *ppos)
{
        struct gb_raw *raw = file->private_data;
        int retval;

        if (!count)
                return 0;

        if (count > MAX_PACKET_SIZE)
                return -E2BIG;

        retval = gb_raw_send(raw, count, buf);
        if (retval)
                return retval;

        return count;
}

static ssize_t raw_read(struct file *file, char __user *buf, size_t count,
                        loff_t *ppos)
{
        struct gb_raw *raw = file->private_data;
        int retval = 0;
        struct raw_data *raw_data;

        mutex_lock(&raw->list_lock);
        if (list_empty(&raw->list))
                goto exit;

        raw_data = list_first_entry(&raw->list, struct raw_data, entry);
        if (raw_data->len > count) {
                retval = -ENOSPC;
                goto exit;
        }

        if (copy_to_user(buf, &raw_data->data[0], raw_data->len)) {
                retval = -EFAULT;
                goto exit;
        }

        list_del(&raw_data->entry);
        raw->list_data -= raw_data->len;
        retval = raw_data->len;
        kfree(raw_data);

exit:
        mutex_unlock(&raw->list_lock);
        return retval;
}

static const struct file_operations raw_fops = {
        .owner          = THIS_MODULE,
        .write          = raw_write,
        .read           = raw_read,
        .open           = raw_open,
        .llseek         = noop_llseek,
};

static const struct greybus_bundle_id gb_raw_id_table[] = {
        { GREYBUS_DEVICE_CLASS(GREYBUS_CLASS_RAW) },
        { }
};
MODULE_DEVICE_TABLE(greybus, gb_raw_id_table);

static struct greybus_driver gb_raw_driver = {
        .name           = "raw",
        .probe          = gb_raw_probe,
        .disconnect     = gb_raw_disconnect,
        .id_table       = gb_raw_id_table,
};

static int raw_init(void)
{
        dev_t dev;
        int retval;

        raw_class = class_create(THIS_MODULE, "gb_raw");
        if (IS_ERR(raw_class)) {
                retval = PTR_ERR(raw_class);
                goto error_class;
        }

        retval = alloc_chrdev_region(&dev, 0, NUM_MINORS, "gb_raw");
        if (retval < 0)
                goto error_chrdev;

        raw_major = MAJOR(dev);

        retval = greybus_register(&gb_raw_driver);
        if (retval)
                goto error_gb;

        return 0;

error_gb:
        unregister_chrdev_region(dev, NUM_MINORS);
error_chrdev:
        class_destroy(raw_class);
error_class:
        return retval;
}
module_init(raw_init);

static void __exit raw_exit(void)
{
        greybus_deregister(&gb_raw_driver);
        unregister_chrdev_region(MKDEV(raw_major, 0), NUM_MINORS);
        class_destroy(raw_class);
        ida_destroy(&minors);
}
module_exit(raw_exit);

MODULE_LICENSE("GPL v2");