// SPDX-License-Identifier: GPL-2.0+
/*
 *  HID driver for UC-Logic devices not fully compliant with HID standard
 *  - tablet initialization and parameter retrieval
 *
 *  Copyright (c) 2018 Nikolai Kondrashov
 */

/*
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 */

#include "hid-uclogic-params.h"
#include "hid-uclogic-rdesc.h"
#include "usbhid/usbhid.h"
#include "hid-ids.h"
#include <linux/ctype.h>
#include <asm/unaligned.h>

/**
 * Convert a pen in-range reporting type to a string.
 *
 * @inrange:    The in-range reporting type to convert.
 *
 * Returns:
 *      The string representing the type, or NULL if the type is unknown.
 */
const char *uclogic_params_pen_inrange_to_str(
                        enum uclogic_params_pen_inrange inrange)
{
        switch (inrange) {
        case UCLOGIC_PARAMS_PEN_INRANGE_NORMAL:
                return "normal";
        case UCLOGIC_PARAMS_PEN_INRANGE_INVERTED:
                return "inverted";
        case UCLOGIC_PARAMS_PEN_INRANGE_NONE:
                return "none";
        default:
                return NULL;
        }
}

/**
 * uclogic_params_get_str_desc - retrieve a string descriptor from a HID
 * device interface, putting it into a kmalloc-allocated buffer as is, without
 * character encoding conversion.
 *
 * @pbuf:       Location for the kmalloc-allocated buffer pointer containing
 *              the retrieved descriptor. Not modified in case of error.
 *              Can be NULL to have retrieved descriptor discarded.
 * @hdev:       The HID device of the tablet interface to retrieve the string
 *              descriptor from. Cannot be NULL.
 * @idx:        Index of the string descriptor to request from the device.
 * @len:        Length of the buffer to allocate and the data to retrieve.
 *
 * Returns:
 *      number of bytes retrieved (<= len),
 *      -EPIPE, if the descriptor was not found, or
 *      another negative errno code in case of other error.
 */
static int uclogic_params_get_str_desc(__u8 **pbuf, struct hid_device *hdev,
                                        __u8 idx, size_t len)
{
        int rc;
        struct usb_device *udev = hid_to_usb_dev(hdev);
        __u8 *buf = NULL;

        /* Check arguments */
        if (hdev == NULL) {
                rc = -EINVAL;
                goto cleanup;
        }

        buf = kmalloc(len, GFP_KERNEL);
        if (buf == NULL) {
                rc = -ENOMEM;
                goto cleanup;
        }

        rc = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
                                USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
                                (USB_DT_STRING << 8) + idx,
                                0x0409, buf, len,
                                USB_CTRL_GET_TIMEOUT);
        if (rc == -EPIPE) {
                hid_dbg(hdev, "string descriptor #%hhu not found\n", idx);
                goto cleanup;
        } else if (rc < 0) {
                hid_err(hdev,
                        "failed retrieving string descriptor #%u: %d\n",
                        idx, rc);
                goto cleanup;
        }

        if (pbuf != NULL) {
                *pbuf = buf;
                buf = NULL;
        }

cleanup:
        kfree(buf);
        return rc;
}

/**
 * uclogic_params_pen_cleanup - free resources used by struct
 * uclogic_params_pen (tablet interface's pen input parameters).
 * Can be called repeatedly.
 *
 * @pen:        Pen input parameters to cleanup. Cannot be NULL.
 */
static void uclogic_params_pen_cleanup(struct uclogic_params_pen *pen)
{
        kfree(pen->desc_ptr);
        memset(pen, 0, sizeof(*pen));
}

/**
 * uclogic_params_pen_init_v1() - initialize tablet interface pen
 * input and retrieve its parameters from the device, using v1 protocol.
 *
 * @pen:        Pointer to the pen parameters to initialize (to be
 *              cleaned up with uclogic_params_pen_cleanup()). Not modified in
 *              case of error, or if parameters are not found. Cannot be NULL.
 * @pfound:     Location for a flag which is set to true if the parameters
 *              were found, and to false if not (e.g. device was
 *              incompatible). Not modified in case of error. Cannot be NULL.
 * @hdev:       The HID device of the tablet interface to initialize and get
 *              parameters from. Cannot be NULL.
 *
 * Returns:
 *      Zero, if successful. A negative errno code on error.
 */
static int uclogic_params_pen_init_v1(struct uclogic_params_pen *pen,
                                      bool *pfound,
                                      struct hid_device *hdev)
{
        int rc;
        bool found = false;
        /* Buffer for (part of) the string descriptor */
        __u8 *buf = NULL;
        /* Minimum descriptor length required, maximum seen so far is 18 */
        const int len = 12;
        s32 resolution;
        /* Pen report descriptor template parameters */
        s32 desc_params[UCLOGIC_RDESC_PEN_PH_ID_NUM];
        __u8 *desc_ptr = NULL;

        /* Check arguments */
        if (pen == NULL || pfound == NULL || hdev == NULL) {
                rc = -EINVAL;
                goto cleanup;
        }

        /*
         * Read string descriptor containing pen input parameters.
         * The specific string descriptor and data were discovered by sniffing
         * the Windows driver traffic.
         * NOTE: This enables fully-functional tablet mode.
         */
        rc = uclogic_params_get_str_desc(&buf, hdev, 100, len);
        if (rc == -EPIPE) {
                hid_dbg(hdev,
                        "string descriptor with pen parameters not found, assuming not compatible\n");
                goto finish;
        } else if (rc < 0) {
                hid_err(hdev, "failed retrieving pen parameters: %d\n", rc);
                goto cleanup;
        } else if (rc != len) {
                hid_dbg(hdev,
                        "string descriptor with pen parameters has invalid length (got %d, expected %d), assuming not compatible\n",
                        rc, len);
                goto finish;
        }

        /*
         * Fill report descriptor parameters from the string descriptor
         */
        desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] =
                get_unaligned_le16(buf + 2);
        desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] =
                get_unaligned_le16(buf + 4);
        desc_params[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] =
                get_unaligned_le16(buf + 8);
        resolution = get_unaligned_le16(buf + 10);
        if (resolution == 0) {
                desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0;
                desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0;
        } else {
                desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] =
                        desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] * 1000 /
                        resolution;
                desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] =
                        desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] * 1000 /
                        resolution;
        }
        kfree(buf);
        buf = NULL;

        /*
         * Generate pen report descriptor
         */
        desc_ptr = uclogic_rdesc_template_apply(
                                uclogic_rdesc_pen_v1_template_arr,
                                uclogic_rdesc_pen_v1_template_size,
                                desc_params, ARRAY_SIZE(desc_params));
        if (desc_ptr == NULL) {
                rc = -ENOMEM;
                goto cleanup;
        }

        /*
         * Fill-in the parameters
         */
        memset(pen, 0, sizeof(*pen));
        pen->desc_ptr = desc_ptr;
        desc_ptr = NULL;
        pen->desc_size = uclogic_rdesc_pen_v1_template_size;
        pen->id = UCLOGIC_RDESC_PEN_V1_ID;
        pen->inrange = UCLOGIC_PARAMS_PEN_INRANGE_INVERTED;
        found = true;
finish:
        *pfound = found;
        rc = 0;
cleanup:
        kfree(desc_ptr);
        kfree(buf);
        return rc;
}

/**
 * uclogic_params_get_le24() - get a 24-bit little-endian number from a
 * buffer.
 *
 * @p:  The pointer to the number buffer.
 *
 * Returns:
 *      The retrieved number
 */
static s32 uclogic_params_get_le24(const void *p)
{
        const __u8 *b = p;
        return b[0] | (b[1] << 8UL) | (b[2] << 16UL);
}

/**
 * uclogic_params_pen_init_v2() - initialize tablet interface pen
 * input and retrieve its parameters from the device, using v2 protocol.
 *
 * @pen:        Pointer to the pen parameters to initialize (to be
 *              cleaned up with uclogic_params_pen_cleanup()). Not modified in
 *              case of error, or if parameters are not found. Cannot be NULL.
 * @pfound:     Location for a flag which is set to true if the parameters
 *              were found, and to false if not (e.g. device was
 *              incompatible). Not modified in case of error. Cannot be NULL.
 * @hdev:       The HID device of the tablet interface to initialize and get
 *              parameters from. Cannot be NULL.
 *
 * Returns:
 *      Zero, if successful. A negative errno code on error.
 */
static int uclogic_params_pen_init_v2(struct uclogic_params_pen *pen,
                                        bool *pfound,
                                        struct hid_device *hdev)
{
        int rc;
        bool found = false;
        /* Buffer for (part of) the string descriptor */
        __u8 *buf = NULL;
        /* Descriptor length required */
        const int len = 18;
        s32 resolution;
        /* Pen report descriptor template parameters */
        s32 desc_params[UCLOGIC_RDESC_PEN_PH_ID_NUM];
        __u8 *desc_ptr = NULL;

        /* Check arguments */
        if (pen == NULL || pfound == NULL || hdev == NULL) {
                rc = -EINVAL;
                goto cleanup;
        }

        /*
         * Read string descriptor containing pen input parameters.
         * The specific string descriptor and data were discovered by sniffing
         * the Windows driver traffic.
         * NOTE: This enables fully-functional tablet mode.
         */
        rc = uclogic_params_get_str_desc(&buf, hdev, 200, len);
        if (rc == -EPIPE) {
                hid_dbg(hdev,
                        "string descriptor with pen parameters not found, assuming not compatible\n");
                goto finish;
        } else if (rc < 0) {
                hid_err(hdev, "failed retrieving pen parameters: %d\n", rc);
                goto cleanup;
        } else if (rc != len) {
                hid_dbg(hdev,
                        "string descriptor with pen parameters has invalid length (got %d, expected %d), assuming not compatible\n",
                        rc, len);
                goto finish;
        } else {
                size_t i;
                /*
                 * Check it's not just a catch-all UTF-16LE-encoded ASCII
                 * string (such as the model name) some tablets put into all
                 * unknown string descriptors.
                 */
                for (i = 2;
                     i < len &&
                        (buf[i] >= 0x20 && buf[i] < 0x7f && buf[i + 1] == 0);
                     i += 2);
                if (i >= len) {
                        hid_dbg(hdev,
                                "string descriptor with pen parameters seems to contain only text, assuming not compatible\n");
                        goto finish;
                }
        }

        /*
         * Fill report descriptor parameters from the string descriptor
         */
        desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] =
                uclogic_params_get_le24(buf + 2);
        desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] =
                uclogic_params_get_le24(buf + 5);
        desc_params[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] =
                get_unaligned_le16(buf + 8);
        resolution = get_unaligned_le16(buf + 10);
        if (resolution == 0) {
                desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0;
                desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0;
        } else {
                desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] =
                        desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] * 1000 /
                        resolution;
                desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] =
                        desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] * 1000 /
                        resolution;
        }
        kfree(buf);
        buf = NULL;

        /*
         * Generate pen report descriptor
         */
        desc_ptr = uclogic_rdesc_template_apply(
                                uclogic_rdesc_pen_v2_template_arr,
                                uclogic_rdesc_pen_v2_template_size,
                                desc_params, ARRAY_SIZE(desc_params));
        if (desc_ptr == NULL) {
                rc = -ENOMEM;
                goto cleanup;
        }

        /*
         * Fill-in the parameters
         */
        memset(pen, 0, sizeof(*pen));
        pen->desc_ptr = desc_ptr;
        desc_ptr = NULL;
        pen->desc_size = uclogic_rdesc_pen_v2_template_size;
        pen->id = UCLOGIC_RDESC_PEN_V2_ID;
        pen->inrange = UCLOGIC_PARAMS_PEN_INRANGE_NONE;
        pen->fragmented_hires = true;
        found = true;
finish:
        *pfound = found;
        rc = 0;
cleanup:
        kfree(desc_ptr);
        kfree(buf);
        return rc;
}

/**
 * uclogic_params_frame_cleanup - free resources used by struct
 * uclogic_params_frame (tablet interface's frame controls input parameters).
 * Can be called repeatedly.
 *
 * @frame:      Frame controls input parameters to cleanup. Cannot be NULL.
 */
static void uclogic_params_frame_cleanup(struct uclogic_params_frame *frame)
{
        kfree(frame->desc_ptr);
        memset(frame, 0, sizeof(*frame));
}

/**
 * uclogic_params_frame_init_with_desc() - initialize tablet's frame control
 * parameters with a static report descriptor.
 *
 * @frame:      Pointer to the frame parameters to initialize (to be cleaned
 *              up with uclogic_params_frame_cleanup()). Not modified in case
 *              of error. Cannot be NULL.
 * @desc_ptr:   Report descriptor pointer. Can be NULL, if desc_size is zero.
 * @desc_size:  Report descriptor size.
 * @id:         Report ID used for frame reports, if they should be tweaked,
 *              zero if not.
 *
 * Returns:
 *      Zero, if successful. A negative errno code on error.
 */
static int uclogic_params_frame_init_with_desc(
                                        struct uclogic_params_frame *frame,
                                        const __u8 *desc_ptr,
                                        size_t desc_size,
                                        unsigned int id)
{
        __u8 *copy_desc_ptr;

        if (frame == NULL || (desc_ptr == NULL && desc_size != 0))
                return -EINVAL;

        copy_desc_ptr = kmemdup(desc_ptr, desc_size, GFP_KERNEL);
        if (copy_desc_ptr == NULL)
                return -ENOMEM;

        memset(frame, 0, sizeof(*frame));
        frame->desc_ptr = copy_desc_ptr;
        frame->desc_size = desc_size;
        frame->id = id;
        return 0;
}

/**
 * uclogic_params_frame_init_v1_buttonpad() - initialize abstract buttonpad
 * on a v1 tablet interface.
 *
 * @frame:      Pointer to the frame parameters to initialize (to be cleaned
 *              up with uclogic_params_frame_cleanup()). Not modified in case
 *              of error, or if parameters are not found. Cannot be NULL.
 * @pfound:     Location for a flag which is set to true if the parameters
 *              were found, and to false if not (e.g. device was
 *              incompatible). Not modified in case of error. Cannot be NULL.
 * @hdev:       The HID device of the tablet interface to initialize and get
 *              parameters from. Cannot be NULL.
 *
 * Returns:
 *      Zero, if successful. A negative errno code on error.
 */
static int uclogic_params_frame_init_v1_buttonpad(
                                        struct uclogic_params_frame *frame,
                                        bool *pfound,
                                        struct hid_device *hdev)
{
        int rc;
        bool found = false;
        struct usb_device *usb_dev = hid_to_usb_dev(hdev);
        char *str_buf = NULL;
        const size_t str_len = 16;

        /* Check arguments */
        if (frame == NULL || pfound == NULL || hdev == NULL) {
                rc = -EINVAL;
                goto cleanup;
        }

        /*
         * Enable generic button mode
         */
        str_buf = kzalloc(str_len, GFP_KERNEL);
        if (str_buf == NULL) {
                rc = -ENOMEM;
                goto cleanup;
        }

        rc = usb_string(usb_dev, 123, str_buf, str_len);
        if (rc == -EPIPE) {
                hid_dbg(hdev,
                        "generic button -enabling string descriptor not found\n");
        } else if (rc < 0) {
                goto cleanup;
        } else if (strncmp(str_buf, "HK On", rc) != 0) {
                hid_dbg(hdev,
                        "invalid response to enabling generic buttons: \"%s\"\n",
                        str_buf);
        } else {
                hid_dbg(hdev, "generic buttons enabled\n");
                rc = uclogic_params_frame_init_with_desc(
                                frame,
                                uclogic_rdesc_buttonpad_v1_arr,
                                uclogic_rdesc_buttonpad_v1_size,
                                UCLOGIC_RDESC_BUTTONPAD_V1_ID);
                if (rc != 0)
                        goto cleanup;
                found = true;
        }

        *pfound = found;
        rc = 0;
cleanup:
        kfree(str_buf);
        return rc;
}

/**
 * uclogic_params_cleanup - free resources used by struct uclogic_params
 * (tablet interface's parameters).
 * Can be called repeatedly.
 *
 * @params:     Input parameters to cleanup. Cannot be NULL.
 */
void uclogic_params_cleanup(struct uclogic_params *params)
{
        if (!params->invalid) {
                kfree(params->desc_ptr);
                if (!params->pen_unused)
                        uclogic_params_pen_cleanup(&params->pen);
                uclogic_params_frame_cleanup(&params->frame);
                memset(params, 0, sizeof(*params));
        }
}

/**
 * Get a replacement report descriptor for a tablet's interface.
 *
 * @params:     The parameters of a tablet interface to get report
 *              descriptor for. Cannot be NULL.
 * @pdesc:      Location for the resulting, kmalloc-allocated report
 *              descriptor pointer, or for NULL, if there's no replacement
 *              report descriptor. Not modified in case of error. Cannot be
 *              NULL.
 * @psize:      Location for the resulting report descriptor size, not set if
 *              there's no replacement report descriptor. Not modified in case
 *              of error. Cannot be NULL.
 *
 * Returns:
 *      Zero, if successful.
 *      -EINVAL, if invalid arguments are supplied.
 *      -ENOMEM, if failed to allocate memory.
 */
int uclogic_params_get_desc(const struct uclogic_params *params,
                                __u8 **pdesc,
                                unsigned int *psize)
{
        bool common_present;
        bool pen_present;
        bool frame_present;
        unsigned int size;
        __u8 *desc = NULL;

        /* Check arguments */
        if (params == NULL || pdesc == NULL || psize == NULL)
                return -EINVAL;

        size = 0;

        common_present = (params->desc_ptr != NULL);
        pen_present = (!params->pen_unused && params->pen.desc_ptr != NULL);
        frame_present = (params->frame.desc_ptr != NULL);

        if (common_present)
                size += params->desc_size;
        if (pen_present)
                size += params->pen.desc_size;
        if (frame_present)
                size += params->frame.desc_size;

        if (common_present || pen_present || frame_present) {
                __u8 *p;

                desc = kmalloc(size, GFP_KERNEL);
                if (desc == NULL)
                        return -ENOMEM;
                p = desc;

                if (common_present) {
                        memcpy(p, params->desc_ptr,
                                params->desc_size);
                        p += params->desc_size;
                }
                if (pen_present) {
                        memcpy(p, params->pen.desc_ptr,
                                params->pen.desc_size);
                        p += params->pen.desc_size;
                }
                if (frame_present) {
                        memcpy(p, params->frame.desc_ptr,
                                params->frame.desc_size);
                        p += params->frame.desc_size;
                }

                WARN_ON(p != desc + size);

                *psize = size;
        }

        *pdesc = desc;
        return 0;
}

/**
 * uclogic_params_init_invalid() - initialize tablet interface parameters,
 * specifying the interface is invalid.
 *
 * @params:             Parameters to initialize (to be cleaned with
 *                      uclogic_params_cleanup()). Cannot be NULL.
 */
static void uclogic_params_init_invalid(struct uclogic_params *params)
{
        params->invalid = true;
}

/**
 * uclogic_params_init_with_opt_desc() - initialize tablet interface
 * parameters with an optional replacement report descriptor. Only modify
 * report descriptor, if the original report descriptor matches the expected
 * size.
 *
 * @params:             Parameters to initialize (to be cleaned with
 *                      uclogic_params_cleanup()). Not modified in case of
 *                      error. Cannot be NULL.
 * @hdev:               The HID device of the tablet interface create the
 *                      parameters for. Cannot be NULL.
 * @orig_desc_size:     Expected size of the original report descriptor to
 *                      be replaced.
 * @desc_ptr:           Pointer to the replacement report descriptor.
 *                      Can be NULL, if desc_size is zero.
 * @desc_size:          Size of the replacement report descriptor.
 *
 * Returns:
 *      Zero, if successful. -EINVAL if an invalid argument was passed.
 *      -ENOMEM, if failed to allocate memory.
 */
static int uclogic_params_init_with_opt_desc(struct uclogic_params *params,
                                             struct hid_device *hdev,
                                             unsigned int orig_desc_size,
                                             __u8 *desc_ptr,
                                             unsigned int desc_size)
{
        __u8 *desc_copy_ptr = NULL;
        unsigned int desc_copy_size;
        int rc;

        /* Check arguments */
        if (params == NULL || hdev == NULL ||
            (desc_ptr == NULL && desc_size != 0)) {
                rc = -EINVAL;
                goto cleanup;
        }

        /* Replace report descriptor, if it matches */
        if (hdev->dev_rsize == orig_desc_size) {
                hid_dbg(hdev,
                        "device report descriptor matches the expected size, replacing\n");
                desc_copy_ptr = kmemdup(desc_ptr, desc_size, GFP_KERNEL);
                if (desc_copy_ptr == NULL) {
                        rc = -ENOMEM;
                        goto cleanup;
                }
                desc_copy_size = desc_size;
        } else {
                hid_dbg(hdev,
                        "device report descriptor doesn't match the expected size (%u != %u), preserving\n",
                        hdev->dev_rsize, orig_desc_size);
                desc_copy_ptr = NULL;
                desc_copy_size = 0;
        }

        /* Output parameters */
        memset(params, 0, sizeof(*params));
        params->desc_ptr = desc_copy_ptr;
        desc_copy_ptr = NULL;
        params->desc_size = desc_copy_size;

        rc = 0;
cleanup:
        kfree(desc_copy_ptr);
        return rc;
}

/**
 * uclogic_params_init_with_pen_unused() - initialize tablet interface
 * parameters preserving original reports and generic HID processing, but
 * disabling pen usage.
 *
 * @params:             Parameters to initialize (to be cleaned with
 *                      uclogic_params_cleanup()). Not modified in case of
 *                      error. Cannot be NULL.
 */
static void uclogic_params_init_with_pen_unused(struct uclogic_params *params)
{
        memset(params, 0, sizeof(*params));
        params->pen_unused = true;
}

/**
 * uclogic_params_init() - initialize a Huion tablet interface and discover
 * its parameters.
 *
 * @params:     Parameters to fill in (to be cleaned with
 *              uclogic_params_cleanup()). Not modified in case of error.
 *              Cannot be NULL.
 * @hdev:       The HID device of the tablet interface to initialize and get
 *              parameters from. Cannot be NULL.
 *
 * Returns:
 *      Zero, if successful. A negative errno code on error.
 */
static int uclogic_params_huion_init(struct uclogic_params *params,
                                     struct hid_device *hdev)
{
        int rc;
        struct usb_device *udev = hid_to_usb_dev(hdev);
        struct usb_interface *iface = to_usb_interface(hdev->dev.parent);
        __u8 bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
        bool found;
        /* The resulting parameters (noop) */
        struct uclogic_params p = {0, };
        static const char transition_ver[] = "HUION_T153_160607";
        char *ver_ptr = NULL;
        const size_t ver_len = sizeof(transition_ver) + 1;

        /* Check arguments */
        if (params == NULL || hdev == NULL) {
                rc = -EINVAL;
                goto cleanup;
        }

        /* If it's not a pen interface */
        if (bInterfaceNumber != 0) {
                /* TODO: Consider marking the interface invalid */
                uclogic_params_init_with_pen_unused(&p);
                goto output;
        }

        /* Try to get firmware version */
        ver_ptr = kzalloc(ver_len, GFP_KERNEL);
        if (ver_ptr == NULL) {
                rc = -ENOMEM;
                goto cleanup;
        }
        rc = usb_string(udev, 201, ver_ptr, ver_len);
        if (rc == -EPIPE) {
                *ver_ptr = '\0';
        } else if (rc < 0) {
                hid_err(hdev,
                        "failed retrieving Huion firmware version: %d\n", rc);
                goto cleanup;
        }

        /* If this is a transition firmware */
        if (strcmp(ver_ptr, transition_ver) == 0) {
                hid_dbg(hdev,
                        "transition firmware detected, not probing pen v2 parameters\n");
        } else {
                /* Try to probe v2 pen parameters */
                rc = uclogic_params_pen_init_v2(&p.pen, &found, hdev);
                if (rc != 0) {
                        hid_err(hdev,
                                "failed probing pen v2 parameters: %d\n", rc);
                        goto cleanup;
                } else if (found) {
                        hid_dbg(hdev, "pen v2 parameters found\n");
                        /* Create v2 buttonpad parameters */
                        rc = uclogic_params_frame_init_with_desc(
                                        &p.frame,
                                        uclogic_rdesc_buttonpad_v2_arr,
                                        uclogic_rdesc_buttonpad_v2_size,
                                        UCLOGIC_RDESC_BUTTONPAD_V2_ID);
                        if (rc != 0) {
                                hid_err(hdev,
                                        "failed creating v2 buttonpad parameters: %d\n",
                                        rc);
                                goto cleanup;
                        }
                        /* Set bitmask marking frame reports in pen reports */
                        p.pen_frame_flag = 0x20;
                        goto output;
                }
                hid_dbg(hdev, "pen v2 parameters not found\n");
        }

        /* Try to probe v1 pen parameters */
        rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
        if (rc != 0) {
                hid_err(hdev,
                        "failed probing pen v1 parameters: %d\n", rc);
                goto cleanup;
        } else if (found) {
                hid_dbg(hdev, "pen v1 parameters found\n");
                /* Try to probe v1 buttonpad */
                rc = uclogic_params_frame_init_v1_buttonpad(
                                                &p.frame,
                                                &found, hdev);
                if (rc != 0) {
                        hid_err(hdev, "v1 buttonpad probing failed: %d\n", rc);
                        goto cleanup;
                }
                hid_dbg(hdev, "buttonpad v1 parameters%s found\n",
                        (found ? "" : " not"));
                if (found) {
                        /* Set bitmask marking frame reports */
                        p.pen_frame_flag = 0x20;
                }
                goto output;
        }
        hid_dbg(hdev, "pen v1 parameters not found\n");

        uclogic_params_init_invalid(&p);

output:
        /* Output parameters */
        memcpy(params, &p, sizeof(*params));
        memset(&p, 0, sizeof(p));
        rc = 0;
cleanup:
        kfree(ver_ptr);
        uclogic_params_cleanup(&p);
        return rc;
}

/**
 * uclogic_params_init() - initialize a tablet interface and discover its
 * parameters.
 *
 * @params:     Parameters to fill in (to be cleaned with
 *              uclogic_params_cleanup()). Not modified in case of error.
 *              Cannot be NULL.
 * @hdev:       The HID device of the tablet interface to initialize and get
 *              parameters from. Cannot be NULL. Must be using the USB low-level
 *              driver, i.e. be an actual USB tablet.
 *
 * Returns:
 *      Zero, if successful. A negative errno code on error.
 */
int uclogic_params_init(struct uclogic_params *params,
                        struct hid_device *hdev)
{
        int rc;
        struct usb_device *udev = hid_to_usb_dev(hdev);
        __u8  bNumInterfaces = udev->config->desc.bNumInterfaces;
        struct usb_interface *iface = to_usb_interface(hdev->dev.parent);
        __u8 bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
        bool found;
        /* The resulting parameters (noop) */
        struct uclogic_params p = {0, };

        /* Check arguments */
        if (params == NULL || hdev == NULL ||
            !hid_is_using_ll_driver(hdev, &usb_hid_driver)) {
                rc = -EINVAL;
                goto cleanup;
        }

        /*
         * Set replacement report descriptor if the original matches the
         * specified size. Otherwise keep interface unchanged.
         */
#define WITH_OPT_DESC(_orig_desc_token, _new_desc_token) \
        uclogic_params_init_with_opt_desc(                  \
                &p, hdev,                                   \
                UCLOGIC_RDESC_##_orig_desc_token##_SIZE,    \
                uclogic_rdesc_##_new_desc_token##_arr,      \
                uclogic_rdesc_##_new_desc_token##_size)

#define VID_PID(_vid, _pid) \
        (((__u32)(_vid) << 16) | ((__u32)(_pid) & U16_MAX))

        /*
         * Handle specific interfaces for specific tablets.
         *
         * Observe the following logic:
         *
         * If the interface is recognized as producing certain useful input:
         *      Mark interface as valid.
         *      Output interface parameters.
         * Else, if the interface is recognized as *not* producing any useful
         * input:
         *      Mark interface as invalid.
         * Else:
         *      Mark interface as valid.
         *      Output noop parameters.
         *
         * Rule of thumb: it is better to disable a broken interface than let
         *                it spew garbage input.
         */

        switch (VID_PID(hdev->vendor, hdev->product)) {
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_TABLET_PF1209):
                rc = WITH_OPT_DESC(PF1209_ORIG, pf1209_fixed);
                if (rc != 0)
                        goto cleanup;
                break;
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_TABLET_WP4030U):
                rc = WITH_OPT_DESC(WPXXXXU_ORIG, wp4030u_fixed);
                if (rc != 0)
                        goto cleanup;
                break;
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_TABLET_WP5540U):
                if (hdev->dev_rsize == UCLOGIC_RDESC_WP5540U_V2_ORIG_SIZE) {
                        if (bInterfaceNumber == 0) {
                                /* Try to probe v1 pen parameters */
                                rc = uclogic_params_pen_init_v1(&p.pen,
                                                                &found, hdev);
                                if (rc != 0) {
                                        hid_err(hdev,
                                                "pen probing failed: %d\n",
                                                rc);
                                        goto cleanup;
                                }
                                if (!found) {
                                        hid_warn(hdev,
                                                 "pen parameters not found");
                                }
                        } else {
                                uclogic_params_init_invalid(&p);
                        }
                } else {
                        rc = WITH_OPT_DESC(WPXXXXU_ORIG, wp5540u_fixed);
                        if (rc != 0)
                                goto cleanup;
                }
                break;
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_TABLET_WP8060U):
                rc = WITH_OPT_DESC(WPXXXXU_ORIG, wp8060u_fixed);
                if (rc != 0)
                        goto cleanup;
                break;
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_TABLET_WP1062):
                rc = WITH_OPT_DESC(WP1062_ORIG, wp1062_fixed);
                if (rc != 0)
                        goto cleanup;
                break;
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_WIRELESS_TABLET_TWHL850):
                switch (bInterfaceNumber) {
                case 0:
                        rc = WITH_OPT_DESC(TWHL850_ORIG0, twhl850_fixed0);
                        if (rc != 0)
                                goto cleanup;
                        break;
                case 1:
                        rc = WITH_OPT_DESC(TWHL850_ORIG1, twhl850_fixed1);
                        if (rc != 0)
                                goto cleanup;
                        break;
                case 2:
                        rc = WITH_OPT_DESC(TWHL850_ORIG2, twhl850_fixed2);
                        if (rc != 0)
                                goto cleanup;
                        break;
                }
                break;
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_TABLET_TWHA60):
                /*
                 * If it is not a three-interface version, which is known to
                 * respond to initialization.
                 */
                if (bNumInterfaces != 3) {
                        switch (bInterfaceNumber) {
                        case 0:
                                rc = WITH_OPT_DESC(TWHA60_ORIG0,
                                                        twha60_fixed0);
                                if (rc != 0)
                                        goto cleanup;
                                break;
                        case 1:
                                rc = WITH_OPT_DESC(TWHA60_ORIG1,
                                                        twha60_fixed1);
                                if (rc != 0)
                                        goto cleanup;
                                break;
                        }
                        break;
                }
                fallthrough;
        case VID_PID(USB_VENDOR_ID_HUION,
                     USB_DEVICE_ID_HUION_TABLET):
        case VID_PID(USB_VENDOR_ID_HUION,
                     USB_DEVICE_ID_HUION_HS64):
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_HUION_TABLET):
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_YIYNOVA_TABLET):
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_UGEE_TABLET_81):
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_DRAWIMAGE_G3):
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_UGEE_TABLET_45):
        case VID_PID(USB_VENDOR_ID_UCLOGIC,
                     USB_DEVICE_ID_UCLOGIC_UGEE_TABLET_47):
                rc = uclogic_params_huion_init(&p, hdev);
                if (rc != 0)
                        goto cleanup;
                break;
        case VID_PID(USB_VENDOR_ID_UGTIZER,
                     USB_DEVICE_ID_UGTIZER_TABLET_GP0610):
        case VID_PID(USB_VENDOR_ID_UGTIZER,

                     USB_DEVICE_ID_UGTIZER_TABLET_GT5040):
        case VID_PID(USB_VENDOR_ID_UGEE,
                     USB_DEVICE_ID_UGEE_XPPEN_TABLET_G540):
        case VID_PID(USB_VENDOR_ID_UGEE,
                     USB_DEVICE_ID_UGEE_XPPEN_TABLET_G640):
        case VID_PID(USB_VENDOR_ID_UGEE,
                     USB_DEVICE_ID_UGEE_TABLET_RAINBOW_CV720):
                /* If this is the pen interface */
                if (bInterfaceNumber == 1) {
                        /* Probe v1 pen parameters */
                        rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
                        if (rc != 0) {
                                hid_err(hdev, "pen probing failed: %d\n", rc);
                                goto cleanup;
                        }
                        if (!found) {
                                hid_warn(hdev, "pen parameters not found");
                                uclogic_params_init_invalid(&p);
                        }
                } else {
                        /* TODO: Consider marking the interface invalid */
                        uclogic_params_init_with_pen_unused(&p);
                }
                break;
        case VID_PID(USB_VENDOR_ID_UGEE,
                     USB_DEVICE_ID_UGEE_XPPEN_TABLET_DECO01):
                /* If this is the pen and frame interface */
                if (bInterfaceNumber == 1) {
                        /* Probe v1 pen parameters */
                        rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
                        if (rc != 0) {
                                hid_err(hdev, "pen probing failed: %d\n", rc);
                                goto cleanup;
                        }
                        /* Initialize frame parameters */
                        rc = uclogic_params_frame_init_with_desc(
                                &p.frame,
                                uclogic_rdesc_xppen_deco01_frame_arr,
                                uclogic_rdesc_xppen_deco01_frame_size,
                                0);
                        if (rc != 0)
                                goto cleanup;
                } else {
                        /* TODO: Consider marking the interface invalid */
                        uclogic_params_init_with_pen_unused(&p);
                }
                break;
        case VID_PID(USB_VENDOR_ID_UGEE,
                     USB_DEVICE_ID_UGEE_TABLET_G5):
                /* Ignore non-pen interfaces */
                if (bInterfaceNumber != 1) {
                        uclogic_params_init_invalid(&p);
                        break;
                }

                rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
                if (rc != 0) {
                        hid_err(hdev, "pen probing failed: %d\n", rc);
                        goto cleanup;
                } else if (found) {
                        rc = uclogic_params_frame_init_with_desc(
                                &p.frame,
                                uclogic_rdesc_ugee_g5_frame_arr,
                                uclogic_rdesc_ugee_g5_frame_size,
                                UCLOGIC_RDESC_UGEE_G5_FRAME_ID);
                        if (rc != 0) {
                                hid_err(hdev,
                                        "failed creating buttonpad parameters: %d\n",
                                        rc);
                                goto cleanup;
                        }
                        p.frame.re_lsb =
                                UCLOGIC_RDESC_UGEE_G5_FRAME_RE_LSB;
                        p.frame.dev_id_byte =
                                UCLOGIC_RDESC_UGEE_G5_FRAME_DEV_ID_BYTE;
                } else {
                        hid_warn(hdev, "pen parameters not found");
                        uclogic_params_init_invalid(&p);
                }

                break;
        case VID_PID(USB_VENDOR_ID_UGEE,
                     USB_DEVICE_ID_UGEE_TABLET_EX07S):
                /* Ignore non-pen interfaces */
                if (bInterfaceNumber != 1) {
                        uclogic_params_init_invalid(&p);
                        break;
                }

                rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
                if (rc != 0) {
                        hid_err(hdev, "pen probing failed: %d\n", rc);
                        goto cleanup;
                } else if (found) {
                        rc = uclogic_params_frame_init_with_desc(
                                &p.frame,
                                uclogic_rdesc_ugee_ex07_buttonpad_arr,
                                uclogic_rdesc_ugee_ex07_buttonpad_size,
                                0);
                        if (rc != 0) {
                                hid_err(hdev,
                                        "failed creating buttonpad parameters: %d\n",
                                        rc);
                                goto cleanup;
                        }
                } else {
                        hid_warn(hdev, "pen parameters not found");
                        uclogic_params_init_invalid(&p);
                }

                break;
        }

#undef VID_PID
#undef WITH_OPT_DESC

        /* Output parameters */
        memcpy(params, &p, sizeof(*params));
        memset(&p, 0, sizeof(p));
        rc = 0;
cleanup:
        uclogic_params_cleanup(&p);
        return rc;
}