/*
 * 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/pm_wakeirq.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/unaligned.h>

#include <drm/drm_panel.h>

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

/* quirks to control the device */
#define I2C_HID_QUIRK_NO_IRQ_AFTER_RESET        BIT(0)
#define I2C_HID_QUIRK_BOGUS_IRQ                 BIT(1)
#define I2C_HID_QUIRK_RESET_ON_RESUME           BIT(2)
#define I2C_HID_QUIRK_BAD_INPUT_SIZE            BIT(3)
#define I2C_HID_QUIRK_NO_WAKEUP_AFTER_RESET     BIT(4)
#define I2C_HID_QUIRK_NO_SLEEP_ON_SUSPEND       BIT(5)
#define I2C_HID_QUIRK_DELAY_WAKEUP_AFTER_RESUME BIT(6)
#define I2C_HID_QUIRK_RE_POWER_ON               BIT(7)

/* Command opcodes */
#define I2C_HID_OPCODE_RESET                    0x01
#define I2C_HID_OPCODE_GET_REPORT               0x02
#define I2C_HID_OPCODE_SET_REPORT               0x03
#define I2C_HID_OPCODE_GET_IDLE                 0x04
#define I2C_HID_OPCODE_SET_IDLE                 0x05
#define I2C_HID_OPCODE_GET_PROTOCOL             0x06
#define I2C_HID_OPCODE_SET_PROTOCOL             0x07
#define I2C_HID_OPCODE_SET_POWER                0x08

/* flags */
#define I2C_HID_STARTED         0
#define I2C_HID_RESET_PENDING   1

#define I2C_HID_PWR_ON          0x00
#define I2C_HID_PWR_SLEEP       0x01

#define i2c_hid_dbg(ihid, ...) dev_dbg(&(ihid)->client->dev, __VA_ARGS__)

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;

/* The main device structure */
struct i2c_hid {
        struct i2c_client       *client;        /* i2c client */
        struct hid_device       *hid;   /* pointer to corresponding HID dev */
        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 */

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

        wait_queue_head_t       wait;           /* For waiting the interrupt */

        struct mutex            cmd_lock;       /* protects cmdbuf and rawbuf */
        struct mutex            reset_lock;

        struct i2chid_ops       *ops;
        struct drm_panel_follower panel_follower;
        struct work_struct      panel_follower_work;
        bool                    is_panel_follower;
        bool                    panel_follower_work_finished;
};

static const struct i2c_hid_quirks {
        __u16 idVendor;
        __u16 idProduct;
        __u32 quirks;
} i2c_hid_quirks[] = {
        { 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 },
        { I2C_VENDOR_ID_CIRQUE, I2C_PRODUCT_ID_CIRQUE_1063,
                I2C_HID_QUIRK_NO_SLEEP_ON_SUSPEND },
        /*
         * Without additional power on command, at least some QTEC devices send garbage
         */
        { I2C_VENDOR_ID_QTEC, HID_ANY_ID,
                I2C_HID_QUIRK_RE_POWER_ON },
        /*
         * 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 },
        { I2C_VENDOR_ID_GOODIX, I2C_DEVICE_ID_GOODIX_0D42,
                 I2C_HID_QUIRK_DELAY_WAKEUP_AFTER_RESUME },
        { 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_probe_address(struct i2c_hid *ihid)
{
        int ret;

        /*
         * Some STM-based devices need 400µs after a rising clock edge to wake
         * from deep sleep, in which case the first read will fail. Try after a
         * short sleep to see if the device came alive on the bus. Certain
         * Weida Tech devices also need this.
         */
        ret = i2c_smbus_read_byte(ihid->client);
        if (ret < 0) {
                usleep_range(400, 500);
                ret = i2c_smbus_read_byte(ihid->client);
        }
        return ret < 0 ? ret : 0;
}

static int i2c_hid_xfer(struct i2c_hid *ihid,
                        u8 *send_buf, int send_len, u8 *recv_buf, int recv_len)
{
        struct i2c_client *client = ihid->client;
        struct i2c_msg msgs[2] = { 0 };
        int n = 0;
        int ret;

        if (send_len) {
                i2c_hid_dbg(ihid, "%s: cmd=%*ph\n",
                            __func__, send_len, send_buf);

                msgs[n].addr = client->addr;
                msgs[n].flags = (client->flags & I2C_M_TEN) | I2C_M_DMA_SAFE;
                msgs[n].len = send_len;
                msgs[n].buf = send_buf;
                n++;
        }

        if (recv_len) {
                msgs[n].addr = client->addr;
                msgs[n].flags = (client->flags & I2C_M_TEN) |
                                I2C_M_RD | I2C_M_DMA_SAFE;
                msgs[n].len = recv_len;
                msgs[n].buf = recv_buf;
                n++;
        }

        ret = i2c_transfer(client->adapter, msgs, n);

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

        return 0;
}

static int i2c_hid_read_register(struct i2c_hid *ihid, __le16 reg,
                                 void *buf, size_t len)
{
        guard(mutex)(&ihid->cmd_lock);

        *(__le16 *)ihid->cmdbuf = reg;

        return i2c_hid_xfer(ihid, ihid->cmdbuf, sizeof(__le16), buf, len);
}

static size_t i2c_hid_encode_command(u8 *buf, u8 opcode,
                                     int report_type, int report_id)
{
        size_t length = 0;

        if (report_id < 0x0F) {
                buf[length++] = report_type << 4 | report_id;
                buf[length++] = opcode;
        } else {
                buf[length++] = report_type << 4 | 0x0F;
                buf[length++] = opcode;
                buf[length++] = report_id;
        }

        return length;
}

static int i2c_hid_get_report(struct i2c_hid *ihid,
                              u8 report_type, u8 report_id,
                              u8 *recv_buf, size_t recv_len)
{
        size_t length = 0;
        size_t ret_count;
        int error;

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

        guard(mutex)(&ihid->cmd_lock);

        /* Command register goes first */
        *(__le16 *)ihid->cmdbuf = ihid->hdesc.wCommandRegister;
        length += sizeof(__le16);
        /* Next is GET_REPORT command */
        length += i2c_hid_encode_command(ihid->cmdbuf + length,
                                         I2C_HID_OPCODE_GET_REPORT,
                                         report_type, report_id);
        /*
         * Device will send report data through data register. Because
         * command can be either 2 or 3 bytes destination for the data
         * register may be not aligned.
         */
        put_unaligned_le16(le16_to_cpu(ihid->hdesc.wDataRegister),
                           ihid->cmdbuf + length);
        length += sizeof(__le16);

        /*
         * In addition to report data device will supply data length
         * in the first 2 bytes of the response, so adjust .
         */
        recv_len = min(recv_len, ihid->bufsize - sizeof(__le16));
        error = i2c_hid_xfer(ihid, ihid->cmdbuf, length,
                             ihid->rawbuf, recv_len + sizeof(__le16));
        if (error) {
                dev_err(&ihid->client->dev,
                        "failed to get a report from device: %d\n", error);
                return error;
        }

        /* The buffer is sufficiently aligned */
        ret_count = le16_to_cpup((__le16 *)ihid->rawbuf);

        /* Check for empty report response */
        if (ret_count <= sizeof(__le16))
                return 0;

        recv_len = min(recv_len, ret_count - sizeof(__le16));
        memcpy(recv_buf, ihid->rawbuf + sizeof(__le16), recv_len);

        if (report_id && recv_len != 0 && recv_buf[0] != report_id) {
                dev_err(&ihid->client->dev,
                        "device returned incorrect report (%d vs %d expected)\n",
                        recv_buf[0], report_id);
                return -EINVAL;
        }

        return recv_len;
}

static size_t i2c_hid_format_report(u8 *buf, int report_id,
                                    const u8 *data, size_t size)
{
        size_t length = sizeof(__le16); /* reserve space to store size */

        if (report_id)
                buf[length++] = report_id;

        memcpy(buf + length, data, size);
        length += size;

        /* Store overall size in the beginning of the buffer */
        put_unaligned_le16(length, buf);

        return length;
}

/**
 * i2c_hid_set_or_send_report: forward an incoming report to the device
 * @ihid: the i2c hid device
 * @report_type: 0x03 for HID_FEATURE_REPORT ; 0x02 for HID_OUTPUT_REPORT
 * @report_id: the report ID
 * @buf: the actual data to transfer, without the report ID
 * @data_len: size of buf
 * @do_set: true: use SET_REPORT HID command, false: send plain OUTPUT report
 */
static int i2c_hid_set_or_send_report(struct i2c_hid *ihid,
                                      u8 report_type, u8 report_id,
                                      const u8 *buf, size_t data_len,
                                      bool do_set)
{
        size_t length = 0;
        int error;

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

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

        if (!do_set && le16_to_cpu(ihid->hdesc.wMaxOutputLength) == 0)
                return -ENOSYS;

        guard(mutex)(&ihid->cmd_lock);

        if (do_set) {
                /* Command register goes first */
                *(__le16 *)ihid->cmdbuf = ihid->hdesc.wCommandRegister;
                length += sizeof(__le16);
                /* Next is SET_REPORT command */
                length += i2c_hid_encode_command(ihid->cmdbuf + length,
                                                 I2C_HID_OPCODE_SET_REPORT,
                                                 report_type, report_id);
                /*
                 * Report data will go into the data register. Because
                 * command can be either 2 or 3 bytes destination for
                 * the data register may be not aligned.
                */
                put_unaligned_le16(le16_to_cpu(ihid->hdesc.wDataRegister),
                                   ihid->cmdbuf + length);
                length += sizeof(__le16);
        } else {
                /*
                 * With simple "send report" all data goes into the output
                 * register.
                 */
                *(__le16 *)ihid->cmdbuf = ihid->hdesc.wOutputRegister;
                length += sizeof(__le16);
        }

        length += i2c_hid_format_report(ihid->cmdbuf + length,
                                        report_id, buf, data_len);

        error = i2c_hid_xfer(ihid, ihid->cmdbuf, length, NULL, 0);
        if (error) {
                dev_err(&ihid->client->dev,
                        "failed to set a report to device: %d\n", error);
                return error;
        }

        return data_len;
}

static int i2c_hid_set_power_command(struct i2c_hid *ihid, int power_state)
{
        size_t length;

        guard(mutex)(&ihid->cmd_lock);

        /* SET_POWER uses command register */
        *(__le16 *)ihid->cmdbuf = ihid->hdesc.wCommandRegister;
        length = sizeof(__le16);

        /* Now the command itself */
        length += i2c_hid_encode_command(ihid->cmdbuf + length,
                                         I2C_HID_OPCODE_SET_POWER,
                                         0, power_state);

        return i2c_hid_xfer(ihid, ihid->cmdbuf, length, NULL, 0);
}

static int i2c_hid_set_power(struct i2c_hid *ihid, int power_state)
{
        int ret;

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

        /*
         * Some STM-based devices need 400µs after a rising clock edge to wake
         * from deep sleep, in which case the first request will fail due to
         * the address not being acknowledged. Try after a short sleep to see
         * if the device came alive on the bus. Certain Weida Tech devices also
         * need this.
         */
        ret = i2c_hid_set_power_command(ihid, power_state);
        if (ret && power_state == I2C_HID_PWR_ON) {
                usleep_range(400, 500);
                ret = i2c_hid_set_power_command(ihid, I2C_HID_PWR_ON);
        }

        if (ret)
                dev_err(&ihid->client->dev,
                        "failed to change power setting.\n");

        /*
         * 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_start_hwreset(struct i2c_hid *ihid)
{
        size_t length = 0;
        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.
         */
        lockdep_assert_held(&ihid->reset_lock);

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

        scoped_guard(mutex, &ihid->cmd_lock) {
                /* Prepare reset command. Command register goes first. */
                *(__le16 *)ihid->cmdbuf = ihid->hdesc.wCommandRegister;
                length += sizeof(__le16);
                /* Next is RESET command itself */
                length += i2c_hid_encode_command(ihid->cmdbuf + length,
                                                 I2C_HID_OPCODE_RESET, 0, 0);

                set_bit(I2C_HID_RESET_PENDING, &ihid->flags);

                ret = i2c_hid_xfer(ihid, ihid->cmdbuf, length, NULL, 0);
                if (ret) {
                        dev_err(&ihid->client->dev,
                                "failed to reset device: %d\n", ret);
                        break;
                }

                return 0;
        }

        /* Clean up if sending reset command failed */
        clear_bit(I2C_HID_RESET_PENDING, &ihid->flags);
        i2c_hid_set_power(ihid, I2C_HID_PWR_SLEEP);
        return ret;
}

static int i2c_hid_finish_hwreset(struct i2c_hid *ihid)
{
        int ret = 0;

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

        if (ihid->quirks & I2C_HID_QUIRK_NO_IRQ_AFTER_RESET) {
                msleep(100);
                clear_bit(I2C_HID_RESET_PENDING, &ihid->flags);
        } else if (!wait_event_timeout(ihid->wait,
                                       !test_bit(I2C_HID_RESET_PENDING, &ihid->flags),
                                       msecs_to_jiffies(1000))) {
                dev_warn(&ihid->client->dev, "device did not ack reset within 1000 ms\n");
                clear_bit(I2C_HID_RESET_PENDING, &ihid->flags);
        }
        i2c_hid_dbg(ihid, "%s: finished.\n", __func__);

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

        return ret;
}

static void i2c_hid_get_input(struct i2c_hid *ihid)
{
        u16 size = le16_to_cpu(ihid->hdesc.wMaxInputLength);
        u16 ret_size;
        int ret;

        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;
        }

        /* Receiving buffer is properly aligned */
        ret_size = le16_to_cpup((__le16 *)ihid->inbuf);
        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 < sizeof(__le16)) {
                if (ihid->quirks & I2C_HID_QUIRK_BAD_INPUT_SIZE) {
                        *(__le16 *)ihid->inbuf = cpu_to_le16(size);
                        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)) {
                if (ihid->hid->group != HID_GROUP_RMI)
                        pm_wakeup_event(&ihid->client->dev, 0);

                hid_input_report(ihid->hid, HID_INPUT_REPORT,
                                ihid->inbuf + sizeof(__le16),
                                ret_size - sizeof(__le16), 1);
        }

        return;
}

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

        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->cmdbuf);
        ihid->inbuf = NULL;
        ihid->rawbuf = NULL;
        ihid->cmdbuf = 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 cmd_len = sizeof(__le16) +  /* command register */
                      sizeof(u8) +      /* encoded report type/ID */
                      sizeof(u8) +      /* opcode */
                      sizeof(u8) +      /* optional 3rd byte report ID */
                      sizeof(__le16) +  /* data register */
                      sizeof(__le16) +  /* report data size */
                      sizeof(u8) +      /* report ID if numbered report */
                      report_size;

        ihid->inbuf = kzalloc(report_size, GFP_KERNEL);
        ihid->rawbuf = kzalloc(report_size, GFP_KERNEL);
        ihid->cmdbuf = kzalloc(cmd_len, GFP_KERNEL);

        if (!ihid->inbuf || !ihid->rawbuf || !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,
                                  u8 report_type, u8 report_id,
                                  u8 *buf, size_t count)
{
        struct i2c_client *client = hid->driver_data;
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        int ret_count;

        if (report_type == HID_OUTPUT_REPORT)
                return -EINVAL;

        /*
         * In case of unnumbered reports the response from the device will
         * not have the report ID that the upper layers expect, so we need
         * to stash it the buffer ourselves and adjust the data size.
         */
        if (!report_id) {
                buf[0] = 0;
                buf++;
                count--;
        }

        ret_count = i2c_hid_get_report(ihid,
                        report_type == HID_FEATURE_REPORT ? 0x03 : 0x01,
                        report_id, buf, count);

        if (ret_count > 0 && !report_id)
                ret_count++;

        return ret_count;
}

static int i2c_hid_output_raw_report(struct hid_device *hid, u8 report_type,
                                     const u8 *buf, size_t count, bool do_set)
{
        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);

        /*
         * Note that both numbered and unnumbered reports passed here
         * are supposed to have report ID stored in the 1st byte of the
         * buffer, so we strip it off unconditionally before passing payload
         * to i2c_hid_set_or_send_report which takes care of encoding
         * everything properly.
         */
        ret = i2c_hid_set_or_send_report(ihid,
                                report_type == HID_FEATURE_REPORT ? 0x03 : 0x02,
                                report_id, buf + 1, count - 1, do_set);

        if (ret >= 0)
                ret++; /* add report_id to the number of transferred 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, HID_OUTPUT_REPORT, buf, count,
                                         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, rtype, reportnum, buf, len);
        case HID_REQ_SET_REPORT:
                if (buf[0] != reportnum)
                        return -EINVAL;
                return i2c_hid_output_raw_report(hid, rtype, buf, len, 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;
        char *rdesc = NULL, *use_override = NULL;
        unsigned int rsize;
        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;
        }

        mutex_lock(&ihid->reset_lock);
        do {
                ret = i2c_hid_start_hwreset(ihid);
                if (ret == 0)
                        ret = i2c_hid_finish_hwreset(ihid);
                else
                        msleep(1000);
        } while (tries-- > 0 && ret);
        mutex_unlock(&ihid->reset_lock);

        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)
                        return -ENOMEM;

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

                ret = i2c_hid_read_register(ihid,
                                            ihid->hdesc.wReportDescRegister,
                                            rdesc, rsize);
                if (ret) {
                        hid_err(hid, "reading report descriptor failed\n");
                        goto out;
                }
        }

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

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

out:
        if (!use_override)
                kfree(rdesc);

        return ret;
}

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);
}

static const 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,
};

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

        i2c_hid_dbg(ihid, "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 | IRQF_NO_AUTOEN,
                                   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 error;

        /* 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");
                error = i2c_hid_read_register(ihid,
                                              ihid->wHIDDescRegister,
                                              &ihid->hdesc,
                                              sizeof(ihid->hdesc));
                if (error) {
                        dev_err(&ihid->client->dev,
                                "failed to fetch HID descriptor: %d\n",
                                error);
                        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(&ihid->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(&ihid->client->dev,
                        "weird size of HID descriptor (%u)\n", dsize);
                return -ENODEV;
        }
        i2c_hid_dbg(ihid, "HID Descriptor: %*ph\n", dsize, &ihid->hdesc);
        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);
}

static void i2c_hid_core_restore_sequence(struct i2c_hid *ihid)
{
        if (!ihid->ops->restore_sequence)
                return;

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

static int i2c_hid_core_suspend(struct i2c_hid *ihid, bool force_poweroff)
{
        struct i2c_client *client = ihid->client;
        struct hid_device *hid = ihid->hid;
        int ret;

        ret = hid_driver_suspend(hid, PMSG_SUSPEND);
        if (ret < 0)
                return ret;

        /* Save some power */
        if (!(ihid->quirks & I2C_HID_QUIRK_NO_SLEEP_ON_SUSPEND))
                i2c_hid_set_power(ihid, I2C_HID_PWR_SLEEP);

        disable_irq(client->irq);

        if (force_poweroff || !device_may_wakeup(&client->dev))
                i2c_hid_core_power_down(ihid);

        return 0;
}

static int i2c_hid_core_resume(struct i2c_hid *ihid)
{
        struct i2c_client *client = ihid->client;
        struct hid_device *hid = ihid->hid;
        int ret;

        if (!device_may_wakeup(&client->dev))
                i2c_hid_core_power_up(ihid);

        enable_irq(client->irq);

        /* On Goodix 27c6:0d42 wait extra time before device wakeup.
         * It's not clear why but if we send wakeup too early, the device will
         * never trigger input interrupts.
         */
        if (ihid->quirks & I2C_HID_QUIRK_DELAY_WAKEUP_AFTER_RESUME)
                msleep(1500);

        /* 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) {
                mutex_lock(&ihid->reset_lock);
                ret = i2c_hid_start_hwreset(ihid);
                if (ret == 0)
                        ret = i2c_hid_finish_hwreset(ihid);
                mutex_unlock(&ihid->reset_lock);
        } else {
                ret = i2c_hid_set_power(ihid, I2C_HID_PWR_ON);
        }

        if (ret)
                return ret;

        return hid_driver_reset_resume(hid);
}

/*
 * Check that the device exists and parse the HID descriptor.
 */
static int __i2c_hid_core_probe(struct i2c_hid *ihid)
{
        struct i2c_client *client = ihid->client;
        struct hid_device *hid = ihid->hid;
        int ret;

        ret = i2c_hid_probe_address(ihid);
        if (ret < 0) {
                i2c_hid_dbg(ihid, "nothing at this address: %d\n", ret);
                return -ENXIO;
        }

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

        hid->version = le16_to_cpu(ihid->hdesc.bcdVersion);
        hid->vendor = le16_to_cpu(ihid->hdesc.wVendorID);
        hid->product = le16_to_cpu(ihid->hdesc.wProductID);

        hid->initial_quirks |= i2c_hid_get_dmi_quirks(hid->vendor,
                                                      hid->product);

        snprintf(hid->name, sizeof(hid->name), "%s %04X:%04X",
                 client->name, (u16)hid->vendor, (u16)hid->product);
        strscpy(hid->phys, dev_name(&client->dev), sizeof(hid->phys));

        ihid->quirks = i2c_hid_lookup_quirk(hid->vendor, hid->product);

        return 0;
}

static int i2c_hid_core_register_hid(struct i2c_hid *ihid)
{
        struct i2c_client *client = ihid->client;
        struct hid_device *hid = ihid->hid;
        int ret;

        enable_irq(client->irq);

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

        /* At least some QTEC devices need this after initialization */
        if (ihid->quirks & I2C_HID_QUIRK_RE_POWER_ON)
                ret = i2c_hid_set_power(ihid, I2C_HID_PWR_ON);

        return ret;
}

static int i2c_hid_core_probe_panel_follower(struct i2c_hid *ihid)
{
        int ret;

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

        ret = __i2c_hid_core_probe(ihid);
        if (ret)
                goto err_power_down;

        ret = i2c_hid_core_register_hid(ihid);
        if (ret)
                goto err_power_down;

        return 0;

err_power_down:
        i2c_hid_core_power_down(ihid);

        return ret;
}

static void ihid_core_panel_follower_work(struct work_struct *work)
{
        struct i2c_hid *ihid = container_of(work, struct i2c_hid,
                                            panel_follower_work);
        struct hid_device *hid = ihid->hid;
        int ret;

        /*
         * hid->version is set on the first power up. If it's still zero then
         * this is the first power on so we should perform initial power up
         * steps.
         */
        if (!hid->version)
                ret = i2c_hid_core_probe_panel_follower(ihid);
        else
                ret = i2c_hid_core_resume(ihid);

        if (ret)
                dev_warn(&ihid->client->dev, "Power on failed: %d\n", ret);
        else
                WRITE_ONCE(ihid->panel_follower_work_finished, true);

        /*
         * The work APIs provide a number of memory ordering guarantees
         * including one that says that memory writes before schedule_work()
         * are always visible to the work function, but they don't appear to
         * guarantee that a write that happened in the work is visible after
         * cancel_work_sync(). We'll add a write memory barrier here to match
         * with i2c_hid_core_panel_unpreparing() to ensure that our write to
         * panel_follower_work_finished is visible there.
         */
        smp_wmb();
}

static int i2c_hid_core_panel_follower_resume(struct drm_panel_follower *follower)
{
        struct i2c_hid *ihid = container_of(follower, struct i2c_hid, panel_follower);

        /*
         * Powering on a touchscreen can be a slow process. Queue the work to
         * the system workqueue so we don't block the panel's power up.
         */
        WRITE_ONCE(ihid->panel_follower_work_finished, false);
        schedule_work(&ihid->panel_follower_work);

        return 0;
}

static int i2c_hid_core_panel_follower_suspend(struct drm_panel_follower *follower)
{
        struct i2c_hid *ihid = container_of(follower, struct i2c_hid, panel_follower);

        cancel_work_sync(&ihid->panel_follower_work);

        /* Match with ihid_core_panel_follower_work() */
        smp_rmb();
        if (!READ_ONCE(ihid->panel_follower_work_finished))
                return 0;

        return i2c_hid_core_suspend(ihid, true);
}

static const struct drm_panel_follower_funcs
                                i2c_hid_core_panel_follower_prepare_funcs = {
        .panel_prepared = i2c_hid_core_panel_follower_resume,
        .panel_unpreparing = i2c_hid_core_panel_follower_suspend,
};

static const struct drm_panel_follower_funcs
                                i2c_hid_core_panel_follower_enable_funcs = {
        .panel_enabled = i2c_hid_core_panel_follower_resume,
        .panel_disabling = i2c_hid_core_panel_follower_suspend,
};

static int i2c_hid_core_register_panel_follower(struct i2c_hid *ihid)
{
        struct device *dev = &ihid->client->dev;
        int ret;

        if (ihid->hid->initial_quirks & HID_QUIRK_POWER_ON_AFTER_BACKLIGHT)
                ihid->panel_follower.funcs = &i2c_hid_core_panel_follower_enable_funcs;
        else
                ihid->panel_follower.funcs = &i2c_hid_core_panel_follower_prepare_funcs;

        /*
         * If we're not in control of our own power up/power down then we can't
         * do the logic to manage wakeups. Give a warning if a user thought
         * that was possible then force the capability off.
         */
        if (device_can_wakeup(dev)) {
                dev_warn(dev, "Can't wakeup if following panel\n");
                device_set_wakeup_capable(dev, false);
        }

        ret = drm_panel_add_follower(dev, &ihid->panel_follower);
        if (ret)
                return ret;

        return 0;
}

int i2c_hid_core_probe(struct i2c_client *client, struct i2chid_ops *ops,
                       u16 hid_descriptor_address, u32 quirks)
{
        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;

        i2c_set_clientdata(client, ihid);

        ihid->ops = ops;
        ihid->client = client;
        ihid->wHIDDescRegister = cpu_to_le16(hid_descriptor_address);
        ihid->is_panel_follower = drm_is_panel_follower(&client->dev);

        init_waitqueue_head(&ihid->wait);
        mutex_init(&ihid->cmd_lock);
        mutex_init(&ihid->reset_lock);
        INIT_WORK(&ihid->panel_follower_work, ihid_core_panel_follower_work);

        /* 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)
                return ret;
        device_enable_async_suspend(&client->dev);

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

        ihid->hid = hid;

        hid->driver_data = client;
        hid->ll_driver = &i2c_hid_ll_driver;
        hid->dev.parent = &client->dev;
        hid->bus = BUS_I2C;
        hid->initial_quirks = quirks;

        /* Power on and probe unless device is a panel follower. */
        if (!ihid->is_panel_follower) {
                ret = i2c_hid_core_power_up(ihid);
                if (ret < 0)
                        goto err_destroy_device;

                ret = __i2c_hid_core_probe(ihid);
                if (ret < 0)
                        goto err_power_down;
        }

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

        /*
         * If we're a panel follower, we'll register when the panel turns on;
         * otherwise we do it right away.
         */
        if (ihid->is_panel_follower)
                ret = i2c_hid_core_register_panel_follower(ihid);
        else
                ret = i2c_hid_core_register_hid(ihid);
        if (ret)
                goto err_free_irq;

        return 0;

err_free_irq:
        free_irq(client->irq, ihid);
err_power_down:
        if (!ihid->is_panel_follower)
                i2c_hid_core_power_down(ihid);
err_destroy_device:
        hid_destroy_device(hid);
err_free_buffers:
        i2c_hid_free_buffers(ihid);

        return ret;
}
EXPORT_SYMBOL_GPL(i2c_hid_core_probe);

void i2c_hid_core_remove(struct i2c_client *client)
{
        struct i2c_hid *ihid = i2c_get_clientdata(client);
        struct hid_device *hid;

        /*
         * If we're a follower, the act of unfollowing will cause us to be
         * powered down. Otherwise we need to manually do it.
         */
        if (ihid->is_panel_follower)
                drm_panel_remove_follower(&ihid->panel_follower);
        else
                i2c_hid_core_suspend(ihid, true);

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

        free_irq(client->irq, ihid);

        if (ihid->bufsize)
                i2c_hid_free_buffers(ihid);
}
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(ihid, I2C_HID_PWR_SLEEP);
        free_irq(client->irq, ihid);

        i2c_hid_core_shutdown_tail(ihid);
}
EXPORT_SYMBOL_GPL(i2c_hid_core_shutdown);

static int i2c_hid_core_pm_suspend(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct i2c_hid *ihid = i2c_get_clientdata(client);

        if (ihid->is_panel_follower)
                return 0;

        return i2c_hid_core_suspend(ihid, false);
}

static int i2c_hid_core_pm_resume(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct i2c_hid *ihid = i2c_get_clientdata(client);

        if (ihid->is_panel_follower)
                return 0;

        return i2c_hid_core_resume(ihid);
}

static int i2c_hid_core_pm_restore(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct i2c_hid *ihid = i2c_get_clientdata(client);

        if (ihid->is_panel_follower)
                return 0;

        i2c_hid_core_restore_sequence(ihid);

        return i2c_hid_core_resume(ihid);
}

const struct dev_pm_ops i2c_hid_core_pm = {
        .suspend = pm_sleep_ptr(i2c_hid_core_pm_suspend),
        .resume = pm_sleep_ptr(i2c_hid_core_pm_resume),
        .freeze = pm_sleep_ptr(i2c_hid_core_pm_suspend),
        .thaw = pm_sleep_ptr(i2c_hid_core_pm_resume),
        .poweroff = pm_sleep_ptr(i2c_hid_core_pm_suspend),
        .restore = pm_sleep_ptr(i2c_hid_core_pm_restore),
};
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");