Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1136 insertions, 0 deletions

diff --git a/drivers/hid/hid-uclogic-params.c b/drivers/hid/hid-uclogic-params.c
new file mode 100644
index 000000000..38f9bbad8
--- /dev/null
+++ b/drivers/hid/hid-uclogic-params.c
@@ -0,0 +1,1136 @@
+// 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;
+	__u8 *buf = NULL;
+
+	/* Check arguments */
+	if (hdev == NULL) {
+		rc = -EINVAL;
+		goto cleanup;
+	}
+
+	udev = hid_to_usb_dev(hdev);
+
+	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 #%hhu: %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;
+	char *str_buf = NULL;
+	const size_t str_len = 16;
+
+	/* Check arguments */
+	if (frame == NULL || pfound == NULL || hdev == NULL) {
+		rc = -EINVAL;
+		goto cleanup;
+	}
+
+	usb_dev = hid_to_usb_dev(hdev);
+
+	/*
+	 * 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;
+	struct usb_interface *iface;
+	__u8 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;
+	}
+
+	udev = hid_to_usb_dev(hdev);
+	iface = to_usb_interface(hdev->dev.parent);
+	bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
+
+	/* 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;
+	__u8  bNumInterfaces;
+	struct usb_interface *iface;
+	__u8 bInterfaceNumber;
+	bool found;
+	/* The resulting parameters (noop) */
+	struct uclogic_params p = {0, };
+
+	/* Check arguments */
+	if (params == NULL || hdev == NULL || !hid_is_usb(hdev)) {
+		rc = -EINVAL;
+		goto cleanup;
+	}
+
+	udev = hid_to_usb_dev(hdev);
+	bNumInterfaces = udev->config->desc.bNumInterfaces;
+	iface = to_usb_interface(hdev->dev.parent);
+	bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
+
+	/*
+	 * 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;
+}