/*
 * HID over I2C protocol implementation
 *
 * Copyright (c) 2012 Benjamin Tissoires <benjamin.tissoires@gmail.com>
 * Copyright (c) 2012 Ecole Nationale de l'Aviation Civile, France
 * Copyright (c) 2012 Red Hat, Inc
 *
 * This code is partly based on "USB HID support for Linux":
 *
 *  Copyright (c) 1999 Andreas Gal
 *  Copyright (c) 2000-2005 Vojtech Pavlik <vojtech@suse.cz>
 *  Copyright (c) 2005 Michael Haboustak <mike-@cinci.rr.com> for Concept2, Inc
 *  Copyright (c) 2007-2008 Oliver Neukum
 *  Copyright (c) 2006-2010 Jiri Kosina
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file COPYING in the main directory of this archive for
 * more details.
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/input.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/pm.h>
#include <linux/device.h>
#include <linux/wait.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/hid.h>
#include <linux/mutex.h>
#include <linux/acpi.h>

#include <linux/i2c/i2c-hid.h>

/* flags */
#define I2C_HID_STARTED         (1 << 0)
#define I2C_HID_RESET_PENDING   (1 << 1)
#define I2C_HID_READ_PENDING    (1 << 2)

#define I2C_HID_PWR_ON          0x00
#define I2C_HID_PWR_SLEEP       0x01

/* debug option */
static bool debug;
module_param(debug, bool, 0444);
MODULE_PARM_DESC(debug, "print a lot of debug information");

#define i2c_hid_dbg(ihid, fmt, arg...)                                    \
do {                                                                      \
        if (debug)                                                        \
                dev_printk(KERN_DEBUG, &(ihid)->client->dev, fmt, ##arg); \
} while (0)

struct i2c_hid_desc {
        __le16 wHIDDescLength;
        __le16 bcdVersion;
        __le16 wReportDescLength;
        __le16 wReportDescRegister;
        __le16 wInputRegister;
        __le16 wMaxInputLength;
        __le16 wOutputRegister;
        __le16 wMaxOutputLength;
        __le16 wCommandRegister;
        __le16 wDataRegister;
        __le16 wVendorID;
        __le16 wProductID;
        __le16 wVersionID;
        __le32 reserved;
} __packed;

struct i2c_hid_cmd {
        unsigned int registerIndex;
        __u8 opcode;
        unsigned int length;
        bool wait;
};

union command {
        u8 data[0];
        struct cmd {
                __le16 reg;
                __u8 reportTypeID;
                __u8 opcode;
        } __packed c;
};

#define I2C_HID_CMD(opcode_) \
        .opcode = opcode_, .length = 4, \
        .registerIndex = offsetof(struct i2c_hid_desc, wCommandRegister)

/* fetch HID descriptor */
static const struct i2c_hid_cmd hid_descr_cmd = { .length = 2 };
/* fetch report descriptors */
static const struct i2c_hid_cmd hid_report_descr_cmd = {
                .registerIndex = offsetof(struct i2c_hid_desc,
                        wReportDescRegister),
                .opcode = 0x00,
                .length = 2 };
/* commands */
static const struct i2c_hid_cmd hid_reset_cmd =         { I2C_HID_CMD(0x01),
                                                          .wait = true };
static const struct i2c_hid_cmd hid_get_report_cmd =    { I2C_HID_CMD(0x02) };
static const struct i2c_hid_cmd hid_set_report_cmd =    { I2C_HID_CMD(0x03) };
static const struct i2c_hid_cmd hid_set_power_cmd =     { I2C_HID_CMD(0x08) };

/*
 * These definitions are not used here, but are defined by the spec.
 * Keeping them here for documentation purposes.
 *
 * static const struct i2c_hid_cmd hid_get_idle_cmd = { I2C_HID_CMD(0x04) };
 * static const struct i2c_hid_cmd hid_set_idle_cmd = { I2C_HID_CMD(0x05) };
 * static const struct i2c_hid_cmd hid_get_protocol_cmd = { I2C_HID_CMD(0x06) };
 * static const struct i2c_hid_cmd hid_set_protocol_cmd = { I2C_HID_CMD(0x07) };
 */

static DEFINE_MUTEX(i2c_hid_open_mut);

/* The main device structure */
struct i2c_hid {
        struct i2c_client       *client;        /* i2c client */
        struct hid_device       *hid;   /* pointer to corresponding HID dev */
        union {
                __u8 hdesc_buffer[sizeof(struct i2c_hid_desc)];
                struct i2c_hid_desc hdesc;      /* the HID Descriptor */
        };
        __le16                  wHIDDescRegister; /* location of the i2c
                                                   * register of the HID
                                                   * descriptor. */
        unsigned int            bufsize;        /* i2c buffer size */
        char                    *inbuf;         /* Input buffer */
        char                    *cmdbuf;        /* Command buffer */
        char                    *argsbuf;       /* Command arguments buffer */

        unsigned long           flags;          /* device flags */

        wait_queue_head_t       wait;           /* For waiting the interrupt */

        struct i2c_hid_platform_data pdata;
};

static int __i2c_hid_command(struct i2c_client *client,
                const struct i2c_hid_cmd *command, u8 reportID,
                u8 reportType, u8 *args, int args_len,
                unsigned char *buf_recv, int data_len)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        union command *cmd = (union command *)ihid->cmdbuf;
        int ret;
        struct i2c_msg msg[2];
        int msg_num = 1;

        int length = command->length;
        bool wait = command->wait;
        unsigned int registerIndex = command->registerIndex;

        /* special case for hid_descr_cmd */
        if (command == &hid_descr_cmd) {
                cmd->c.reg = ihid->wHIDDescRegister;
        } else {
                cmd->data[0] = ihid->hdesc_buffer[registerIndex];
                cmd->data[1] = ihid->hdesc_buffer[registerIndex + 1];
        }

        if (length > 2) {
                cmd->c.opcode = command->opcode;
                cmd->c.reportTypeID = reportID | reportType << 4;
        }

        memcpy(cmd->data + length, args, args_len);
        length += args_len;

        i2c_hid_dbg(ihid, "%s: cmd=%*ph\n", __func__, length, cmd->data);

        msg[0].addr = client->addr;
        msg[0].flags = client->flags & I2C_M_TEN;
        msg[0].len = length;
        msg[0].buf = cmd->data;
        if (data_len > 0) {
                msg[1].addr = client->addr;
                msg[1].flags = client->flags & I2C_M_TEN;
                msg[1].flags |= I2C_M_RD;
                msg[1].len = data_len;
                msg[1].buf = buf_recv;
                msg_num = 2;
                set_bit(I2C_HID_READ_PENDING, &ihid->flags);
        }

        if (wait)
                set_bit(I2C_HID_RESET_PENDING, &ihid->flags);

        ret = i2c_transfer(client->adapter, msg, msg_num);

        if (data_len > 0)
                clear_bit(I2C_HID_READ_PENDING, &ihid->flags);

        if (ret != msg_num)
                return ret < 0 ? ret : -EIO;

        ret = 0;

        if (wait) {
                i2c_hid_dbg(ihid, "%s: waiting...\n", __func__);
                if (!wait_event_timeout(ihid->wait,
                                !test_bit(I2C_HID_RESET_PENDING, &ihid->flags),
                                msecs_to_jiffies(5000)))
                        ret = -ENODATA;
                i2c_hid_dbg(ihid, "%s: finished.\n", __func__);
        }

        return ret;
}

static int i2c_hid_command(struct i2c_client *client,
                const struct i2c_hid_cmd *command,
                unsigned char *buf_recv, int data_len)
{
        return __i2c_hid_command(client, command, 0, 0, NULL, 0,
                                buf_recv, data_len);
}

static int i2c_hid_get_report(struct i2c_client *client, u8 reportType,
                u8 reportID, unsigned char *buf_recv, int data_len)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        u8 args[3];
        int ret;
        int args_len = 0;
        u16 readRegister = le16_to_cpu(ihid->hdesc.wDataRegister);

        i2c_hid_dbg(ihid, "%s\n", __func__);

        if (reportID >= 0x0F) {
                args[args_len++] = reportID;
                reportID = 0x0F;
        }

        args[args_len++] = readRegister & 0xFF;
        args[args_len++] = readRegister >> 8;

        ret = __i2c_hid_command(client, &hid_get_report_cmd, reportID,
                reportType, args, args_len, buf_recv, data_len);
        if (ret) {
                dev_err(&client->dev,
                        "failed to retrieve report from device.\n");
                return ret;
        }

        return 0;
}

static int i2c_hid_set_report(struct i2c_client *client, u8 reportType,
                u8 reportID, unsigned char *buf, size_t data_len)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        u8 *args = ihid->argsbuf;
        int ret;
        u16 dataRegister = le16_to_cpu(ihid->hdesc.wDataRegister);

        /* hidraw already checked that data_len < HID_MAX_BUFFER_SIZE */
        u16 size =      2                       /* size */ +
                        (reportID ? 1 : 0)      /* reportID */ +
                        data_len                /* buf */;
        int args_len =  (reportID >= 0x0F ? 1 : 0) /* optional third byte */ +
                        2                       /* dataRegister */ +
                        size                    /* args */;
        int index = 0;

        i2c_hid_dbg(ihid, "%s\n", __func__);

        if (reportID >= 0x0F) {
                args[index++] = reportID;
                reportID = 0x0F;
        }

        args[index++] = dataRegister & 0xFF;
        args[index++] = dataRegister >> 8;

        args[index++] = size & 0xFF;
        args[index++] = size >> 8;

        if (reportID)
                args[index++] = reportID;

        memcpy(&args[index], buf, data_len);

        ret = __i2c_hid_command(client, &hid_set_report_cmd, reportID,
                reportType, args, args_len, NULL, 0);
        if (ret) {
                dev_err(&client->dev, "failed to set a report to device.\n");
                return ret;
        }

        return data_len;
}

static int i2c_hid_set_power(struct i2c_client *client, int power_state)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        int ret;

        i2c_hid_dbg(ihid, "%s\n", __func__);

        ret = __i2c_hid_command(client, &hid_set_power_cmd, power_state,
                0, NULL, 0, NULL, 0);
        if (ret)
                dev_err(&client->dev, "failed to change power setting.\n");

        return ret;
}

static int i2c_hid_hwreset(struct i2c_client *client)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        int ret;

        i2c_hid_dbg(ihid, "%s\n", __func__);

        ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
        if (ret)
                return ret;

        i2c_hid_dbg(ihid, "resetting...\n");

        ret = i2c_hid_command(client, &hid_reset_cmd, NULL, 0);
        if (ret) {
                dev_err(&client->dev, "failed to reset device.\n");
                i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
                return ret;
        }

        return 0;
}

static void i2c_hid_get_input(struct i2c_hid *ihid)
{
        int ret, ret_size;
        int size = le16_to_cpu(ihid->hdesc.wMaxInputLength);

        ret = i2c_master_recv(ihid->client, ihid->inbuf, size);
        if (ret != size) {
                if (ret < 0)
                        return;

                dev_err(&ihid->client->dev, "%s: got %d data instead of %d\n",
                        __func__, ret, size);
                return;
        }

        ret_size = ihid->inbuf[0] | ihid->inbuf[1] << 8;

        if (!ret_size) {
                /* host or device initiated RESET completed */
                if (test_and_clear_bit(I2C_HID_RESET_PENDING, &ihid->flags))
                        wake_up(&ihid->wait);
                return;
        }

        if (ret_size > size) {
                dev_err(&ihid->client->dev, "%s: incomplete report (%d/%d)\n",
                        __func__, size, ret_size);
                return;
        }

        i2c_hid_dbg(ihid, "input: %*ph\n", ret_size, ihid->inbuf);

        if (test_bit(I2C_HID_STARTED, &ihid->flags))
                hid_input_report(ihid->hid, HID_INPUT_REPORT, ihid->inbuf + 2,
                                ret_size - 2, 1);

        return;
}

static irqreturn_t i2c_hid_irq(int irq, void *dev_id)
{
        struct i2c_hid *ihid = dev_id;

        if (test_bit(I2C_HID_READ_PENDING, &ihid->flags))
                return IRQ_HANDLED;

        i2c_hid_get_input(ihid);

        return IRQ_HANDLED;
}

static int i2c_hid_get_report_length(struct hid_report *report)
{
        return ((report->size - 1) >> 3) + 1 +
                report->device->report_enum[report->type].numbered + 2;
}

static void i2c_hid_init_report(struct hid_report *report, u8 *buffer,
        size_t bufsize)
{
        struct hid_device *hid = report->device;
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        unsigned int size, ret_size;

        size = i2c_hid_get_report_length(report);
        if (i2c_hid_get_report(client,
                        report->type == HID_FEATURE_REPORT ? 0x03 : 0x01,
                        report->id, buffer, size))
                return;

        i2c_hid_dbg(ihid, "report (len=%d): %*ph\n", size, size, ihid->inbuf);

        ret_size = buffer[0] | (buffer[1] << 8);

        if (ret_size != size) {
                dev_err(&client->dev, "error in %s size:%d / ret_size:%d\n",
                        __func__, size, ret_size);
                return;
        }

        /* hid->driver_lock is held as we are in probe function,
         * we just need to setup the input fields, so using
         * hid_report_raw_event is safe. */
        hid_report_raw_event(hid, report->type, buffer + 2, size - 2, 1);
}

/*
 * Initialize all reports
 */
static void i2c_hid_init_reports(struct hid_device *hid)
{
        struct hid_report *report;
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        u8 *inbuf = kzalloc(ihid->bufsize, GFP_KERNEL);

        if (!inbuf) {
                dev_err(&client->dev, "can not retrieve initial reports\n");
                return;
        }

        list_for_each_entry(report,
                &hid->report_enum[HID_INPUT_REPORT].report_list, list)
                i2c_hid_init_report(report, inbuf, ihid->bufsize);

        list_for_each_entry(report,
                &hid->report_enum[HID_FEATURE_REPORT].report_list, list)
                i2c_hid_init_report(report, inbuf, ihid->bufsize);

        kfree(inbuf);
}

/*
 * Traverse the supplied list of reports and find the longest
 */
static void i2c_hid_find_max_report(struct hid_device *hid, unsigned int type,
                unsigned int *max)
{
        struct hid_report *report;
        unsigned int size;

        /* We should not rely on wMaxInputLength, as some devices may set it to
         * a wrong length. */
        list_for_each_entry(report, &hid->report_enum[type].report_list, list) {
                size = i2c_hid_get_report_length(report);
                if (*max < size)
                        *max = size;
        }
}

static void i2c_hid_free_buffers(struct i2c_hid *ihid)
{
        kfree(ihid->inbuf);
        kfree(ihid->argsbuf);
        kfree(ihid->cmdbuf);
        ihid->inbuf = NULL;
        ihid->cmdbuf = NULL;
        ihid->argsbuf = NULL;
        ihid->bufsize = 0;
}

static int i2c_hid_alloc_buffers(struct i2c_hid *ihid, size_t report_size)
{
        /* the worst case is computed from the set_report command with a
         * reportID > 15 and the maximum report length */
        int args_len = sizeof(__u8) + /* optional ReportID byte */
                       sizeof(__u16) + /* data register */
                       sizeof(__u16) + /* size of the report */
                       report_size; /* report */

        ihid->inbuf = kzalloc(report_size, GFP_KERNEL);
        ihid->argsbuf = kzalloc(args_len, GFP_KERNEL);
        ihid->cmdbuf = kzalloc(sizeof(union command) + args_len, GFP_KERNEL);

        if (!ihid->inbuf || !ihid->argsbuf || !ihid->cmdbuf) {
                i2c_hid_free_buffers(ihid);
                return -ENOMEM;
        }

        ihid->bufsize = report_size;

        return 0;
}

static int i2c_hid_get_raw_report(struct hid_device *hid,
                unsigned char report_number, __u8 *buf, size_t count,
                unsigned char report_type)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        size_t ret_count, ask_count;
        int ret;

        if (report_type == HID_OUTPUT_REPORT)
                return -EINVAL;

        /* +2 bytes to include the size of the reply in the query buffer */
        ask_count = min(count + 2, (size_t)ihid->bufsize);

        ret = i2c_hid_get_report(client,
                        report_type == HID_FEATURE_REPORT ? 0x03 : 0x01,
                        report_number, ihid->inbuf, ask_count);

        if (ret < 0)
                return ret;

        ret_count = ihid->inbuf[0] | (ihid->inbuf[1] << 8);

        if (ret_count <= 2)
                return 0;

        ret_count = min(ret_count, ask_count);

        /* The query buffer contains the size, dropping it in the reply */
        count = min(count, ret_count - 2);
        memcpy(buf, ihid->inbuf + 2, count);

        return count;
}

static int i2c_hid_output_raw_report(struct hid_device *hid, __u8 *buf,
                size_t count, unsigned char report_type)
{
        struct i2c_client *client = hid->driver_data;
        int report_id = buf[0];
        int ret;

        if (report_type == HID_INPUT_REPORT)
                return -EINVAL;

        if (report_id) {
                buf++;
                count--;
        }

        ret = i2c_hid_set_report(client,
                                report_type == HID_FEATURE_REPORT ? 0x03 : 0x02,
                                report_id, buf, count);

        if (report_id && ret >= 0)
                ret++; /* add report_id to the number of transfered bytes */

        return ret;
}

static int i2c_hid_parse(struct hid_device *hid)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        struct i2c_hid_desc *hdesc = &ihid->hdesc;
        unsigned int rsize;
        char *rdesc;
        int ret;
        int tries = 3;

        i2c_hid_dbg(ihid, "entering %s\n", __func__);

        rsize = le16_to_cpu(hdesc->wReportDescLength);
        if (!rsize || rsize > HID_MAX_DESCRIPTOR_SIZE) {
                dbg_hid("weird size of report descriptor (%u)\n", rsize);
                return -EINVAL;
        }

        do {
                ret = i2c_hid_hwreset(client);
                if (ret)
                        msleep(1000);
        } while (tries-- > 0 && ret);

        if (ret)
                return ret;

        rdesc = kzalloc(rsize, GFP_KERNEL);

        if (!rdesc) {
                dbg_hid("couldn't allocate rdesc memory\n");
                return -ENOMEM;
        }

        i2c_hid_dbg(ihid, "asking HID report descriptor\n");

        ret = i2c_hid_command(client, &hid_report_descr_cmd, rdesc, rsize);
        if (ret) {
                hid_err(hid, "reading report descriptor failed\n");
                kfree(rdesc);
                return -EIO;
        }

        i2c_hid_dbg(ihid, "Report Descriptor: %*ph\n", rsize, rdesc);

        ret = hid_parse_report(hid, rdesc, rsize);
        kfree(rdesc);
        if (ret) {
                dbg_hid("parsing report descriptor failed\n");
                return ret;
        }

        return 0;
}

static int i2c_hid_start(struct hid_device *hid)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        int ret;
        unsigned int bufsize = HID_MIN_BUFFER_SIZE;

        i2c_hid_find_max_report(hid, HID_INPUT_REPORT, &bufsize);
        i2c_hid_find_max_report(hid, HID_OUTPUT_REPORT, &bufsize);
        i2c_hid_find_max_report(hid, HID_FEATURE_REPORT, &bufsize);

        if (bufsize > ihid->bufsize) {
                i2c_hid_free_buffers(ihid);

                ret = i2c_hid_alloc_buffers(ihid, bufsize);

                if (ret)
                        return ret;
        }

        if (!(hid->quirks & HID_QUIRK_NO_INIT_REPORTS))
                i2c_hid_init_reports(hid);

        return 0;
}

static void i2c_hid_stop(struct hid_device *hid)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);

        hid->claimed = 0;

        i2c_hid_free_buffers(ihid);
}

static int i2c_hid_open(struct hid_device *hid)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        int ret = 0;

        mutex_lock(&i2c_hid_open_mut);
        if (!hid->open++) {
                ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
                if (ret) {
                        hid->open--;
                        goto done;
                }
                set_bit(I2C_HID_STARTED, &ihid->flags);
        }
done:
        mutex_unlock(&i2c_hid_open_mut);
        return ret;
}

static void i2c_hid_close(struct hid_device *hid)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);

        /* protecting hid->open to make sure we don't restart
         * data acquistion due to a resumption we no longer
         * care about
         */
        mutex_lock(&i2c_hid_open_mut);
        if (!--hid->open) {
                clear_bit(I2C_HID_STARTED, &ihid->flags);

                /* Save some power */
                i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
        }
        mutex_unlock(&i2c_hid_open_mut);
}

static int i2c_hid_power(struct hid_device *hid, int lvl)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        int ret = 0;

        i2c_hid_dbg(ihid, "%s lvl:%d\n", __func__, lvl);

        switch (lvl) {
        case PM_HINT_FULLON:
                ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
                break;
        case PM_HINT_NORMAL:
                ret = i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
                break;
        }
        return ret;
}

static int i2c_hid_hidinput_input_event(struct input_dev *dev,
                unsigned int type, unsigned int code, int value)
{
        struct hid_device *hid = input_get_drvdata(dev);
        struct hid_field *field;
        int offset;

        if (type == EV_FF)
                return input_ff_event(dev, type, code, value);

        if (type != EV_LED)
                return -1;

        offset = hidinput_find_field(hid, type, code, &field);

        if (offset == -1) {
                hid_warn(dev, "event field not found\n");
                return -1;
        }

        return hid_set_field(field, offset, value);
}

static struct hid_ll_driver i2c_hid_ll_driver = {
        .parse = i2c_hid_parse,
        .start = i2c_hid_start,
        .stop = i2c_hid_stop,
        .open = i2c_hid_open,
        .close = i2c_hid_close,
        .power = i2c_hid_power,
        .hidinput_input_event = i2c_hid_hidinput_input_event,
};

static int i2c_hid_init_irq(struct i2c_client *client)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        int ret;

        dev_dbg(&client->dev, "Requesting IRQ: %d\n", client->irq);

        ret = request_threaded_irq(client->irq, NULL, i2c_hid_irq,
                        IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
                        client->name, ihid);
        if (ret < 0) {
                dev_warn(&client->dev,
                        "Could not register for %s interrupt, irq = %d,"
                        " ret = %d\n",
                        client->name, client->irq, ret);

                return ret;
        }

        return 0;
}

static int i2c_hid_fetch_hid_descriptor(struct i2c_hid *ihid)
{
        struct i2c_client *client = ihid->client;
        struct i2c_hid_desc *hdesc = &ihid->hdesc;
        unsigned int dsize;
        int ret;

        /* Fetch the length of HID description, retrieve the 4 first bytes:
         * bytes 0-1 -> length
         * bytes 2-3 -> bcdVersion (has to be 1.00) */
        ret = i2c_hid_command(client, &hid_descr_cmd, ihid->hdesc_buffer, 4);

        i2c_hid_dbg(ihid, "%s, ihid->hdesc_buffer: %*ph\n",
                        __func__, 4, ihid->hdesc_buffer);

        if (ret) {
                dev_err(&client->dev,
                        "unable to fetch the size of HID descriptor (ret=%d)\n",
                        ret);
                return -ENODEV;
        }

        dsize = le16_to_cpu(hdesc->wHIDDescLength);
        /*
         * the size of the HID descriptor should at least contain
         * its size and the bcdVersion (4 bytes), and should not be greater
         * than sizeof(struct i2c_hid_desc) as we directly fill this struct
         * through i2c_hid_command.
         */
        if (dsize < 4 || dsize > sizeof(struct i2c_hid_desc)) {
                dev_err(&client->dev, "weird size of HID descriptor (%u)\n",
                        dsize);
                return -ENODEV;
        }

        /* check bcdVersion == 1.0 */
        if (le16_to_cpu(hdesc->bcdVersion) != 0x0100) {
                dev_err(&client->dev,
                        "unexpected HID descriptor bcdVersion (0x%04hx)\n",
                        le16_to_cpu(hdesc->bcdVersion));
                return -ENODEV;
        }

        i2c_hid_dbg(ihid, "Fetching the HID descriptor\n");

        ret = i2c_hid_command(client, &hid_descr_cmd, ihid->hdesc_buffer,
                                dsize);
        if (ret) {
                dev_err(&client->dev, "hid_descr_cmd Fail\n");
                return -ENODEV;
        }

        i2c_hid_dbg(ihid, "HID Descriptor: %*ph\n", dsize, ihid->hdesc_buffer);

        return 0;
}

#ifdef CONFIG_ACPI
static int i2c_hid_acpi_pdata(struct i2c_client *client,
                struct i2c_hid_platform_data *pdata)
{
        static u8 i2c_hid_guid[] = {
                0xF7, 0xF6, 0xDF, 0x3C, 0x67, 0x42, 0x55, 0x45,
                0xAD, 0x05, 0xB3, 0x0A, 0x3D, 0x89, 0x38, 0xDE,
        };
        struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
        union acpi_object params[4], *obj;
        struct acpi_object_list input;
        struct acpi_device *adev;
        acpi_handle handle;

        handle = ACPI_HANDLE(&client->dev);
        if (!handle || acpi_bus_get_device(handle, &adev))
                return -ENODEV;

        input.count = ARRAY_SIZE(params);
        input.pointer = params;

        params[0].type = ACPI_TYPE_BUFFER;
        params[0].buffer.length = sizeof(i2c_hid_guid);
        params[0].buffer.pointer = i2c_hid_guid;
        params[1].type = ACPI_TYPE_INTEGER;
        params[1].integer.value = 1;
        params[2].type = ACPI_TYPE_INTEGER;
        params[2].integer.value = 1; /* HID function */
        params[3].type = ACPI_TYPE_INTEGER;
        params[3].integer.value = 0;

        if (ACPI_FAILURE(acpi_evaluate_object(handle, "_DSM", &input, &buf))) {
                dev_err(&client->dev, "device _DSM execution failed\n");
                return -ENODEV;
        }

        obj = (union acpi_object *)buf.pointer;
        if (obj->type != ACPI_TYPE_INTEGER) {
                dev_err(&client->dev, "device _DSM returned invalid type: %d\n",
                        obj->type);
                kfree(buf.pointer);
                return -EINVAL;
        }

        pdata->hid_descriptor_address = obj->integer.value;

        kfree(buf.pointer);
        return 0;
}

static const struct acpi_device_id i2c_hid_acpi_match[] = {
        {"ACPI0C50", 0 },
        {"PNP0C50", 0 },
        { },
};
MODULE_DEVICE_TABLE(acpi, i2c_hid_acpi_match);
#else
static inline int i2c_hid_acpi_pdata(struct i2c_client *client,
                struct i2c_hid_platform_data *pdata)
{
        return -ENODEV;
}
#endif

static int i2c_hid_probe(struct i2c_client *client,
                         const struct i2c_device_id *dev_id)
{
        int ret;
        struct i2c_hid *ihid;
        struct hid_device *hid;
        __u16 hidRegister;
        struct i2c_hid_platform_data *platform_data = client->dev.platform_data;

        dbg_hid("HID probe called for i2c 0x%02x\n", client->addr);

        if (!client->irq) {
                dev_err(&client->dev,
                        "HID over i2c has not been provided an Int IRQ\n");
                return -EINVAL;
        }

        ihid = kzalloc(sizeof(struct i2c_hid), GFP_KERNEL);
        if (!ihid)
                return -ENOMEM;

        if (!platform_data) {
                ret = i2c_hid_acpi_pdata(client, &ihid->pdata);
                if (ret) {
                        dev_err(&client->dev,
                                "HID register address not provided\n");
                        goto err;
                }
        } else {
                ihid->pdata = *platform_data;
        }

        i2c_set_clientdata(client, ihid);

        ihid->client = client;

        hidRegister = ihid->pdata.hid_descriptor_address;
        ihid->wHIDDescRegister = cpu_to_le16(hidRegister);

        init_waitqueue_head(&ihid->wait);

        /* we need to allocate the command buffer without knowing the maximum
         * size of the reports. Let's use HID_MIN_BUFFER_SIZE, then we do the
         * real computation later. */
        ret = i2c_hid_alloc_buffers(ihid, HID_MIN_BUFFER_SIZE);
        if (ret < 0)
                goto err;

        ret = i2c_hid_fetch_hid_descriptor(ihid);
        if (ret < 0)
                goto err;

        ret = i2c_hid_init_irq(client);
        if (ret < 0)
                goto err;

        hid = hid_allocate_device();
        if (IS_ERR(hid)) {
                ret = PTR_ERR(hid);
                goto err_irq;
        }

        ihid->hid = hid;

        hid->driver_data = client;
        hid->ll_driver = &i2c_hid_ll_driver;
        hid->hid_get_raw_report = i2c_hid_get_raw_report;
        hid->hid_output_raw_report = i2c_hid_output_raw_report;
        hid->dev.parent = &client->dev;
        ACPI_HANDLE_SET(&hid->dev, ACPI_HANDLE(&client->dev));
        hid->bus = BUS_I2C;
        hid->version = le16_to_cpu(ihid->hdesc.bcdVersion);
        hid->vendor = le16_to_cpu(ihid->hdesc.wVendorID);
        hid->product = le16_to_cpu(ihid->hdesc.wProductID);

        snprintf(hid->name, sizeof(hid->name), "%s %04hX:%04hX",
                 client->name, hid->vendor, hid->product);

        ret = hid_add_device(hid);
        if (ret) {
                if (ret != -ENODEV)
                        hid_err(client, "can't add hid device: %d\n", ret);
                goto err_mem_free;
        }

        return 0;

err_mem_free:
        hid_destroy_device(hid);

err_irq:
        free_irq(client->irq, ihid);

err:
        i2c_hid_free_buffers(ihid);
        kfree(ihid);
        return ret;
}

static int i2c_hid_remove(struct i2c_client *client)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        struct hid_device *hid;

        hid = ihid->hid;
        hid_destroy_device(hid);

        free_irq(client->irq, ihid);

        if (ihid->bufsize)

                i2c_hid_free_buffers(ihid);

        kfree(ihid);

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int i2c_hid_suspend(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);

        if (device_may_wakeup(&client->dev))
                enable_irq_wake(client->irq);

        /* Save some power */
        i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);

        return 0;
}

static int i2c_hid_resume(struct device *dev)
{
        int ret;
        struct i2c_client *client = to_i2c_client(dev);

        ret = i2c_hid_hwreset(client);
        if (ret)
                return ret;

        if (device_may_wakeup(&client->dev))
                disable_irq_wake(client->irq);

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(i2c_hid_pm, i2c_hid_suspend, i2c_hid_resume);

static const struct i2c_device_id i2c_hid_id_table[] = {
        { "hid", 0 },
        { },
};
MODULE_DEVICE_TABLE(i2c, i2c_hid_id_table);


static struct i2c_driver i2c_hid_driver = {
        .driver = {
                .name   = "i2c_hid",
                .owner  = THIS_MODULE,
                .pm     = &i2c_hid_pm,
                .acpi_match_table = ACPI_PTR(i2c_hid_acpi_match),
        },

        .probe          = i2c_hid_probe,
        .remove         = i2c_hid_remove,

        .id_table       = i2c_hid_id_table,
};

module_i2c_driver(i2c_hid_driver);

MODULE_DESCRIPTION("HID over I2C core driver");
MODULE_AUTHOR("Benjamin Tissoires <benjamin.tissoires@gmail.com>");
MODULE_LICENSE("GPL");