/*
 * 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/irq.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 "../hid-ids.h"
#include "i2c-hid.h"

/* quirks to control the device */
#define I2C_HID_QUIRK_SET_PWR_WAKEUP_DEV        BIT(0)
#define I2C_HID_QUIRK_NO_IRQ_AFTER_RESET        BIT(1)
#define I2C_HID_QUIRK_BOGUS_IRQ                 BIT(4)
#define I2C_HID_QUIRK_RESET_ON_RESUME           BIT(5)
#define I2C_HID_QUIRK_BAD_INPUT_SIZE            BIT(6)
#define I2C_HID_QUIRK_NO_WAKEUP_AFTER_RESET     BIT(7)


/* flags */
#define I2C_HID_STARTED         0
#define I2C_HID_RESET_PENDING   1
#define I2C_HID_READ_PENDING    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) };
static const struct i2c_hid_cmd hid_no_cmd =            { .length = 0 };

/*
 * 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) };
 */

/* 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 */
        u8                      *inbuf;         /* Input buffer */
        u8                      *rawbuf;        /* Raw Input buffer */
        u8                      *cmdbuf;        /* Command buffer */
        u8                      *argsbuf;       /* Command arguments buffer */

        unsigned long           flags;          /* device flags */
        unsigned long           quirks;         /* Various quirks */

        wait_queue_head_t       wait;           /* For waiting the interrupt */

        bool                    irq_wake_enabled;
        struct mutex            reset_lock;

        struct i2chid_ops       *ops;
};

static const struct i2c_hid_quirks {
        __u16 idVendor;
        __u16 idProduct;
        __u32 quirks;
} i2c_hid_quirks[] = {
        { USB_VENDOR_ID_WEIDA, HID_ANY_ID,
                I2C_HID_QUIRK_SET_PWR_WAKEUP_DEV },
        { I2C_VENDOR_ID_HANTICK, I2C_PRODUCT_ID_HANTICK_5288,
                I2C_HID_QUIRK_NO_IRQ_AFTER_RESET },
        { I2C_VENDOR_ID_ITE, I2C_DEVICE_ID_ITE_VOYO_WINPAD_A15,
                I2C_HID_QUIRK_NO_IRQ_AFTER_RESET },
        { I2C_VENDOR_ID_RAYDIUM, I2C_PRODUCT_ID_RAYDIUM_3118,
                I2C_HID_QUIRK_NO_IRQ_AFTER_RESET },
        { USB_VENDOR_ID_ALPS_JP, HID_ANY_ID,
                 I2C_HID_QUIRK_RESET_ON_RESUME },
        { I2C_VENDOR_ID_SYNAPTICS, I2C_PRODUCT_ID_SYNAPTICS_SYNA2393,
                 I2C_HID_QUIRK_RESET_ON_RESUME },
        { USB_VENDOR_ID_ITE, I2C_DEVICE_ID_ITE_LENOVO_LEGION_Y720,
                I2C_HID_QUIRK_BAD_INPUT_SIZE },
        /*
         * Sending the wakeup after reset actually break ELAN touchscreen controller
         */
        { USB_VENDOR_ID_ELAN, HID_ANY_ID,
                 I2C_HID_QUIRK_NO_WAKEUP_AFTER_RESET |
                 I2C_HID_QUIRK_BOGUS_IRQ },
        { 0, 0 }
};

/*
 * i2c_hid_lookup_quirk: return any quirks associated with a I2C HID device
 * @idVendor: the 16-bit vendor ID
 * @idProduct: the 16-bit product ID
 *
 * Returns: a u32 quirks value.
 */
static u32 i2c_hid_lookup_quirk(const u16 idVendor, const u16 idProduct)
{
        u32 quirks = 0;
        int n;

        for (n = 0; i2c_hid_quirks[n].idVendor; n++)
                if (i2c_hid_quirks[n].idVendor == idVendor &&
                    (i2c_hid_quirks[n].idProduct == (__u16)HID_ANY_ID ||
                     i2c_hid_quirks[n].idProduct == idProduct))
                        quirks = i2c_hid_quirks[n].quirks;

        return quirks;
}

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 && (ihid->quirks & I2C_HID_QUIRK_NO_IRQ_AFTER_RESET)) {
                msleep(100);
        } else 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;
}

/**
 * i2c_hid_set_or_send_report: forward an incoming report to the device
 * @client: the i2c_client of the device
 * @reportType: 0x03 for HID_FEATURE_REPORT ; 0x02 for HID_OUTPUT_REPORT
 * @reportID: the report ID
 * @buf: the actual data to transfer, without the report ID
 * @data_len: size of buf
 * @use_data: true: use SET_REPORT HID command, false: send plain OUTPUT report
 */
static int i2c_hid_set_or_send_report(struct i2c_client *client, u8 reportType,
                u8 reportID, unsigned char *buf, size_t data_len, bool use_data)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        u8 *args = ihid->argsbuf;
        const struct i2c_hid_cmd *hidcmd;
        int ret;
        u16 dataRegister = le16_to_cpu(ihid->hdesc.wDataRegister);
        u16 outputRegister = le16_to_cpu(ihid->hdesc.wOutputRegister);
        u16 maxOutputLength = le16_to_cpu(ihid->hdesc.wMaxOutputLength);
        u16 size;
        int args_len;
        int index = 0;

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

        if (data_len > ihid->bufsize)
                return -EINVAL;

        size =          2                       /* size */ +
                        (reportID ? 1 : 0)      /* reportID */ +
                        data_len                /* buf */;
        args_len =      (reportID >= 0x0F ? 1 : 0) /* optional third byte */ +
                        2                       /* dataRegister */ +
                        size                    /* args */;

        if (!use_data && maxOutputLength == 0)
                return -ENOSYS;

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

        /*
         * use the data register for feature reports or if the device does not
         * support the output register
         */
        if (use_data) {
                args[index++] = dataRegister & 0xFF;
                args[index++] = dataRegister >> 8;
                hidcmd = &hid_set_report_cmd;
        } else {
                args[index++] = outputRegister & 0xFF;
                args[index++] = outputRegister >> 8;
                hidcmd = &hid_no_cmd;
        }

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

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

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

        ret = __i2c_hid_command(client, hidcmd, 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__);

        /*
         * Some devices require to send a command to wakeup before power on.
         * The call will get a return value (EREMOTEIO) but device will be
         * triggered and activated. After that, it goes like a normal device.
         */
        if (power_state == I2C_HID_PWR_ON &&
            ihid->quirks & I2C_HID_QUIRK_SET_PWR_WAKEUP_DEV) {
                ret = i2c_hid_command(client, &hid_set_power_cmd, NULL, 0);

                /* Device was already activated */
                if (!ret)
                        goto set_pwr_exit;
        }

        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");

set_pwr_exit:

        /*
         * The HID over I2C specification states that if a DEVICE needs time
         * after the PWR_ON request, it should utilise CLOCK stretching.
         * However, it has been observered that the Windows driver provides a
         * 1ms sleep between the PWR_ON and RESET requests.
         * According to Goodix Windows even waits 60 ms after (other?)
         * PWR_ON requests. Testing has confirmed that several devices
         * will not work properly without a delay after a PWR_ON request.
         */
        if (!ret && power_state == I2C_HID_PWR_ON)
                msleep(60);

        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__);

        /*
         * This prevents sending feature reports while the device is
         * being reset. Otherwise we may lose the reset complete
         * interrupt.
         */
        mutex_lock(&ihid->reset_lock);

        ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
        if (ret)
                goto out_unlock;

        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);
                goto out_unlock;
        }

        /* At least some SIS devices need this after reset */
        if (!(ihid->quirks & I2C_HID_QUIRK_NO_WAKEUP_AFTER_RESET))
                ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);

out_unlock:
        mutex_unlock(&ihid->reset_lock);
        return ret;
}

static void i2c_hid_get_input(struct i2c_hid *ihid)
{
        int ret;
        u32 ret_size;
        int size = le16_to_cpu(ihid->hdesc.wMaxInputLength);

        if (size > ihid->bufsize)
                size = ihid->bufsize;

        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 (ihid->quirks & I2C_HID_QUIRK_BOGUS_IRQ && ret_size == 0xffff) {
                dev_warn_once(&ihid->client->dev, "%s: IRQ triggered but "
                              "there's no data\n", __func__);
                return;
        }

        if ((ret_size > size) || (ret_size < 2)) {
                if (ihid->quirks & I2C_HID_QUIRK_BAD_INPUT_SIZE) {
                        ihid->inbuf[0] = size & 0xff;
                        ihid->inbuf[1] = size >> 8;
                        ret_size = size;
                } else {
                        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;
}

/*
 * 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->rawbuf);
        kfree(ihid->argsbuf);
        kfree(ihid->cmdbuf);
        ihid->inbuf = NULL;
        ihid->rawbuf = 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) + /* ReportID */
                       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->rawbuf = 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->rawbuf || !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->rawbuf, ask_count);

        if (ret < 0)
                return ret;

        ret_count = ihid->rawbuf[0] | (ihid->rawbuf[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->rawbuf + 2, count);

        return count;
}

static int i2c_hid_output_raw_report(struct hid_device *hid, __u8 *buf,
                size_t count, unsigned char report_type, bool use_data)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        int report_id = buf[0];
        int ret;

        if (report_type == HID_INPUT_REPORT)
                return -EINVAL;

        mutex_lock(&ihid->reset_lock);

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

        ret = i2c_hid_set_or_send_report(client,
                                report_type == HID_FEATURE_REPORT ? 0x03 : 0x02,
                                report_id, buf, count, use_data);

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

        mutex_unlock(&ihid->reset_lock);

        return ret;
}

static int i2c_hid_output_report(struct hid_device *hid, __u8 *buf,
                size_t count)
{
        return i2c_hid_output_raw_report(hid, buf, count, HID_OUTPUT_REPORT,
                        false);
}

static int i2c_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
                               __u8 *buf, size_t len, unsigned char rtype,
                               int reqtype)
{
        switch (reqtype) {
        case HID_REQ_GET_REPORT:
                return i2c_hid_get_raw_report(hid, reportnum, buf, len, rtype);
        case HID_REQ_SET_REPORT:
                if (buf[0] != reportnum)
                        return -EINVAL;
                return i2c_hid_output_raw_report(hid, buf, len, rtype, true);
        default:
                return -EIO;
        }
}

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;
        char *use_override;

        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;

        use_override = i2c_hid_get_dmi_hid_report_desc_override(client->name,
                                                                &rsize);

        if (use_override) {
                rdesc = use_override;
                i2c_hid_dbg(ihid, "Using a HID report descriptor override\n");
        } else {
                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);
        if (!use_override)
                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) {
                disable_irq(client->irq);
                i2c_hid_free_buffers(ihid);

                ret = i2c_hid_alloc_buffers(ihid, bufsize);
                enable_irq(client->irq);

                if (ret)
                        return ret;
        }

        return 0;
}

static void i2c_hid_stop(struct hid_device *hid)
{
        hid->claimed = 0;
}

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

        set_bit(I2C_HID_STARTED, &ihid->flags);
        return 0;
}

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

        clear_bit(I2C_HID_STARTED, &ihid->flags);
}

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,
        .output_report = i2c_hid_output_report,
        .raw_request = i2c_hid_raw_request,
};
EXPORT_SYMBOL_GPL(i2c_hid_ll_driver);

static int i2c_hid_init_irq(struct i2c_client *client)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        unsigned long irqflags = 0;
        int ret;

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

        if (!irq_get_trigger_type(client->irq))
                irqflags = IRQF_TRIGGER_LOW;

        ret = request_threaded_irq(client->irq, NULL, i2c_hid_irq,
                                   irqflags | 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;

        /* i2c hid fetch using a fixed descriptor size (30 bytes) */
        if (i2c_hid_get_dmi_i2c_hid_desc_override(client->name)) {
                i2c_hid_dbg(ihid, "Using a HID descriptor override\n");
                ihid->hdesc =
                        *i2c_hid_get_dmi_i2c_hid_desc_override(client->name);
        } else {
                i2c_hid_dbg(ihid, "Fetching the HID descriptor\n");
                ret = i2c_hid_command(client, &hid_descr_cmd,
                                      ihid->hdesc_buffer,
                                      sizeof(struct i2c_hid_desc));
                if (ret) {
                        dev_err(&client->dev, "hid_descr_cmd failed\n");
                        return -ENODEV;
                }
        }

        /* Validate the length of HID descriptor, the 4 first bytes:
         * bytes 0-1 -> length
         * bytes 2-3 -> bcdVersion (has to be 1.00) */
        /* 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;
        }

        /* Descriptor length should be 30 bytes as per the specification */
        dsize = le16_to_cpu(hdesc->wHIDDescLength);
        if (dsize != sizeof(struct i2c_hid_desc)) {
                dev_err(&client->dev, "weird size of HID descriptor (%u)\n",
                        dsize);
                return -ENODEV;
        }
        i2c_hid_dbg(ihid, "HID Descriptor: %*ph\n", dsize, ihid->hdesc_buffer);
        return 0;
}

static int i2c_hid_core_power_up(struct i2c_hid *ihid)
{
        if (!ihid->ops->power_up)
                return 0;

        return ihid->ops->power_up(ihid->ops);
}

static void i2c_hid_core_power_down(struct i2c_hid *ihid)
{
        if (!ihid->ops->power_down)
                return;

        ihid->ops->power_down(ihid->ops);
}

static void i2c_hid_core_shutdown_tail(struct i2c_hid *ihid)
{
        if (!ihid->ops->shutdown_tail)
                return;

        ihid->ops->shutdown_tail(ihid->ops);
}

int i2c_hid_core_probe(struct i2c_client *client, struct i2chid_ops *ops,
                       u16 hid_descriptor_address)
{
        int ret;
        struct i2c_hid *ihid;
        struct hid_device *hid;

        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;
        }

        if (client->irq < 0) {
                if (client->irq != -EPROBE_DEFER)
                        dev_err(&client->dev,
                                "HID over i2c doesn't have a valid IRQ\n");
                return client->irq;
        }

        ihid = devm_kzalloc(&client->dev, sizeof(*ihid), GFP_KERNEL);
        if (!ihid)
                return -ENOMEM;

        ihid->ops = ops;

        ret = i2c_hid_core_power_up(ihid);
        if (ret)
                return ret;

        i2c_set_clientdata(client, ihid);

        ihid->client = client;

        ihid->wHIDDescRegister = cpu_to_le16(hid_descriptor_address);

        init_waitqueue_head(&ihid->wait);
        mutex_init(&ihid->reset_lock);

        /* 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_powered;

        device_enable_async_suspend(&client->dev);

        /* Make sure there is something at this address */
        ret = i2c_smbus_read_byte(client);
        if (ret < 0) {
                dev_dbg(&client->dev, "nothing at this address: %d\n", ret);
                ret = -ENXIO;
                goto err_powered;
        }

        ret = i2c_hid_fetch_hid_descriptor(ihid);
        if (ret < 0) {
                dev_err(&client->dev,
                        "Failed to fetch the HID Descriptor\n");
                goto err_powered;
        }

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

        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->dev.parent = &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 %04X:%04X",
                 client->name, (u16)hid->vendor, (u16)hid->product);

        strlcpy(hid->phys, dev_name(&client->dev), sizeof(hid->phys));

        ihid->quirks = i2c_hid_lookup_quirk(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_powered:
        i2c_hid_core_power_down(ihid);
        i2c_hid_free_buffers(ihid);
        return ret;
}
EXPORT_SYMBOL_GPL(i2c_hid_core_probe);

int i2c_hid_core_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);

        i2c_hid_core_power_down(ihid);

        return 0;
}
EXPORT_SYMBOL_GPL(i2c_hid_core_remove);

void i2c_hid_core_shutdown(struct i2c_client *client)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);

        i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
        free_irq(client->irq, ihid);

        i2c_hid_core_shutdown_tail(ihid);
}
EXPORT_SYMBOL_GPL(i2c_hid_core_shutdown);

#ifdef CONFIG_PM_SLEEP
static int i2c_hid_core_suspend(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        struct hid_device *hid = ihid->hid;
        int ret;
        int wake_status;

        if (hid->driver && hid->driver->suspend) {
                ret = hid->driver->suspend(hid, PMSG_SUSPEND);
                if (ret < 0)
                        return ret;
        }

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

        disable_irq(client->irq);

        if (device_may_wakeup(&client->dev)) {
                wake_status = enable_irq_wake(client->irq);
                if (!wake_status)
                        ihid->irq_wake_enabled = true;
                else
                        hid_warn(hid, "Failed to enable irq wake: %d\n",
                                wake_status);
        } else {
                i2c_hid_core_power_down(ihid);
        }

        return 0;
}

static int i2c_hid_core_resume(struct device *dev)
{
        int ret;
        struct i2c_client *client = to_i2c_client(dev);
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        struct hid_device *hid = ihid->hid;
        int wake_status;

        if (!device_may_wakeup(&client->dev)) {
                i2c_hid_core_power_up(ihid);
        } else if (ihid->irq_wake_enabled) {
                wake_status = disable_irq_wake(client->irq);
                if (!wake_status)
                        ihid->irq_wake_enabled = false;
                else
                        hid_warn(hid, "Failed to disable irq wake: %d\n",
                                wake_status);
        }

        enable_irq(client->irq);

        /* Instead of resetting device, simply powers the device on. This
         * solves "incomplete reports" on Raydium devices 2386:3118 and
         * 2386:4B33 and fixes various SIS touchscreens no longer sending
         * data after a suspend/resume.
         *
         * However some ALPS touchpads generate IRQ storm without reset, so
         * let's still reset them here.
         */
        if (ihid->quirks & I2C_HID_QUIRK_RESET_ON_RESUME)
                ret = i2c_hid_hwreset(client);
        else
                ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);

        if (ret)
                return ret;

        if (hid->driver && hid->driver->reset_resume) {
                ret = hid->driver->reset_resume(hid);
                return ret;
        }

        return 0;
}
#endif

const struct dev_pm_ops i2c_hid_core_pm = {
        SET_SYSTEM_SLEEP_PM_OPS(i2c_hid_core_suspend, i2c_hid_core_resume)
};
EXPORT_SYMBOL_GPL(i2c_hid_core_pm);

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