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   1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 *  HID driver for UC-Logic devices not fully compliant with HID standard
   4 *  - tablet initialization and parameter retrieval
   5 *
   6 *  Copyright (c) 2018 Nikolai Kondrashov
   7 */
   8
   9/*
  10 * This program is free software; you can redistribute it and/or modify it
  11 * under the terms of the GNU General Public License as published by the Free
  12 * Software Foundation; either version 2 of the License, or (at your option)
  13 * any later version.
  14 */
  15
  16#include "hid-uclogic-params.h"
  17#include "hid-uclogic-rdesc.h"
  18#include "usbhid/usbhid.h"
  19#include "hid-ids.h"
  20#include <linux/ctype.h>
  21#include <asm/unaligned.h>
  22
  23/**
  24 * Convert a pen in-range reporting type to a string.
  25 *
  26 * @inrange:	The in-range reporting type to convert.
  27 *
  28 * Returns:
  29 *	The string representing the type, or NULL if the type is unknown.
  30 */
  31const char *uclogic_params_pen_inrange_to_str(
  32			enum uclogic_params_pen_inrange inrange)
  33{
  34	switch (inrange) {
  35	case UCLOGIC_PARAMS_PEN_INRANGE_NORMAL:
  36		return "normal";
  37	case UCLOGIC_PARAMS_PEN_INRANGE_INVERTED:
  38		return "inverted";
  39	case UCLOGIC_PARAMS_PEN_INRANGE_NONE:
  40		return "none";
  41	default:
  42		return NULL;
  43	}
  44}
  45
  46/**
  47 * uclogic_params_get_str_desc - retrieve a string descriptor from a HID
  48 * device interface, putting it into a kmalloc-allocated buffer as is, without
  49 * character encoding conversion.
  50 *
  51 * @pbuf:	Location for the kmalloc-allocated buffer pointer containing
  52 *		the retrieved descriptor. Not modified in case of error.
  53 *		Can be NULL to have retrieved descriptor discarded.
  54 * @hdev:	The HID device of the tablet interface to retrieve the string
  55 *		descriptor from. Cannot be NULL.
  56 * @idx:	Index of the string descriptor to request from the device.
  57 * @len:	Length of the buffer to allocate and the data to retrieve.
  58 *
  59 * Returns:
  60 *	number of bytes retrieved (<= len),
  61 *	-EPIPE, if the descriptor was not found, or
  62 *	another negative errno code in case of other error.
  63 */
  64static int uclogic_params_get_str_desc(__u8 **pbuf, struct hid_device *hdev,
  65					__u8 idx, size_t len)
  66{
  67	int rc;
  68	struct usb_device *udev = hid_to_usb_dev(hdev);
  69	__u8 *buf = NULL;
  70
  71	/* Check arguments */
  72	if (hdev == NULL) {
  73		rc = -EINVAL;
  74		goto cleanup;
  75	}
  76
  77	buf = kmalloc(len, GFP_KERNEL);
  78	if (buf == NULL) {
  79		rc = -ENOMEM;
  80		goto cleanup;
  81	}
  82
  83	rc = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
  84				USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
  85				(USB_DT_STRING << 8) + idx,
  86				0x0409, buf, len,
  87				USB_CTRL_GET_TIMEOUT);
  88	if (rc == -EPIPE) {
  89		hid_dbg(hdev, "string descriptor #%hhu not found\n", idx);
  90		goto cleanup;
  91	} else if (rc < 0) {
  92		hid_err(hdev,
  93			"failed retrieving string descriptor #%hhu: %d\n",
  94			idx, rc);
  95		goto cleanup;
  96	}
  97
  98	if (pbuf != NULL) {
  99		*pbuf = buf;
 100		buf = NULL;
 101	}
 102
 103cleanup:
 104	kfree(buf);
 105	return rc;
 106}
 107
 108/**
 109 * uclogic_params_pen_cleanup - free resources used by struct
 110 * uclogic_params_pen (tablet interface's pen input parameters).
 111 * Can be called repeatedly.
 112 *
 113 * @pen:	Pen input parameters to cleanup. Cannot be NULL.
 114 */
 115static void uclogic_params_pen_cleanup(struct uclogic_params_pen *pen)
 116{
 117	kfree(pen->desc_ptr);
 118	memset(pen, 0, sizeof(*pen));
 119}
 120
 121/**
 122 * uclogic_params_pen_init_v1() - initialize tablet interface pen
 123 * input and retrieve its parameters from the device, using v1 protocol.
 124 *
 125 * @pen:	Pointer to the pen parameters to initialize (to be
 126 *		cleaned up with uclogic_params_pen_cleanup()). Not modified in
 127 *		case of error, or if parameters are not found. Cannot be NULL.
 128 * @pfound:	Location for a flag which is set to true if the parameters
 129 *		were found, and to false if not (e.g. device was
 130 *		incompatible). Not modified in case of error. Cannot be NULL.
 131 * @hdev:	The HID device of the tablet interface to initialize and get
 132 *		parameters from. Cannot be NULL.
 133 *
 134 * Returns:
 135 *	Zero, if successful. A negative errno code on error.
 136 */
 137static int uclogic_params_pen_init_v1(struct uclogic_params_pen *pen,
 138				      bool *pfound,
 139				      struct hid_device *hdev)
 140{
 141	int rc;
 142	bool found = false;
 143	/* Buffer for (part of) the string descriptor */
 144	__u8 *buf = NULL;
 145	/* Minimum descriptor length required, maximum seen so far is 18 */
 146	const int len = 12;
 147	s32 resolution;
 148	/* Pen report descriptor template parameters */
 149	s32 desc_params[UCLOGIC_RDESC_PEN_PH_ID_NUM];
 150	__u8 *desc_ptr = NULL;
 151
 152	/* Check arguments */
 153	if (pen == NULL || pfound == NULL || hdev == NULL) {
 154		rc = -EINVAL;
 155		goto cleanup;
 156	}
 157
 158	/*
 159	 * Read string descriptor containing pen input parameters.
 160	 * The specific string descriptor and data were discovered by sniffing
 161	 * the Windows driver traffic.
 162	 * NOTE: This enables fully-functional tablet mode.
 163	 */
 164	rc = uclogic_params_get_str_desc(&buf, hdev, 100, len);
 165	if (rc == -EPIPE) {
 166		hid_dbg(hdev,
 167			"string descriptor with pen parameters not found, assuming not compatible\n");
 168		goto finish;
 169	} else if (rc < 0) {
 170		hid_err(hdev, "failed retrieving pen parameters: %d\n", rc);
 171		goto cleanup;
 172	} else if (rc != len) {
 173		hid_dbg(hdev,
 174			"string descriptor with pen parameters has invalid length (got %d, expected %d), assuming not compatible\n",
 175			rc, len);
 176		goto finish;
 177	}
 178
 179	/*
 180	 * Fill report descriptor parameters from the string descriptor
 181	 */
 182	desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] =
 183		get_unaligned_le16(buf + 2);
 184	desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] =
 185		get_unaligned_le16(buf + 4);
 186	desc_params[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] =
 187		get_unaligned_le16(buf + 8);
 188	resolution = get_unaligned_le16(buf + 10);
 189	if (resolution == 0) {
 190		desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0;
 191		desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0;
 192	} else {
 193		desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] =
 194			desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] * 1000 /
 195			resolution;
 196		desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] =
 197			desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] * 1000 /
 198			resolution;
 199	}
 200	kfree(buf);
 201	buf = NULL;
 202
 203	/*
 204	 * Generate pen report descriptor
 205	 */
 206	desc_ptr = uclogic_rdesc_template_apply(
 207				uclogic_rdesc_pen_v1_template_arr,
 208				uclogic_rdesc_pen_v1_template_size,
 209				desc_params, ARRAY_SIZE(desc_params));
 210	if (desc_ptr == NULL) {
 211		rc = -ENOMEM;
 212		goto cleanup;
 213	}
 214
 215	/*
 216	 * Fill-in the parameters
 217	 */
 218	memset(pen, 0, sizeof(*pen));
 219	pen->desc_ptr = desc_ptr;
 220	desc_ptr = NULL;
 221	pen->desc_size = uclogic_rdesc_pen_v1_template_size;
 222	pen->id = UCLOGIC_RDESC_PEN_V1_ID;
 223	pen->inrange = UCLOGIC_PARAMS_PEN_INRANGE_INVERTED;
 224	found = true;
 225finish:
 226	*pfound = found;
 227	rc = 0;
 228cleanup:
 229	kfree(desc_ptr);
 230	kfree(buf);
 231	return rc;
 232}
 233
 234/**
 235 * uclogic_params_get_le24() - get a 24-bit little-endian number from a
 236 * buffer.
 237 *
 238 * @p:	The pointer to the number buffer.
 239 *
 240 * Returns:
 241 *	The retrieved number
 242 */
 243static s32 uclogic_params_get_le24(const void *p)
 244{
 245	const __u8 *b = p;
 246	return b[0] | (b[1] << 8UL) | (b[2] << 16UL);
 247}
 248
 249/**
 250 * uclogic_params_pen_init_v2() - initialize tablet interface pen
 251 * input and retrieve its parameters from the device, using v2 protocol.
 252 *
 253 * @pen:	Pointer to the pen parameters to initialize (to be
 254 *		cleaned up with uclogic_params_pen_cleanup()). Not modified in
 255 *		case of error, or if parameters are not found. Cannot be NULL.
 256 * @pfound:	Location for a flag which is set to true if the parameters
 257 *		were found, and to false if not (e.g. device was
 258 *		incompatible). Not modified in case of error. Cannot be NULL.
 259 * @hdev:	The HID device of the tablet interface to initialize and get
 260 *		parameters from. Cannot be NULL.
 261 *
 262 * Returns:
 263 *	Zero, if successful. A negative errno code on error.
 264 */
 265static int uclogic_params_pen_init_v2(struct uclogic_params_pen *pen,
 266					bool *pfound,
 267					struct hid_device *hdev)
 268{
 269	int rc;
 270	bool found = false;
 271	/* Buffer for (part of) the string descriptor */
 272	__u8 *buf = NULL;
 273	/* Descriptor length required */
 274	const int len = 18;
 275	s32 resolution;
 276	/* Pen report descriptor template parameters */
 277	s32 desc_params[UCLOGIC_RDESC_PEN_PH_ID_NUM];
 278	__u8 *desc_ptr = NULL;
 279
 280	/* Check arguments */
 281	if (pen == NULL || pfound == NULL || hdev == NULL) {
 282		rc = -EINVAL;
 283		goto cleanup;
 284	}
 285
 286	/*
 287	 * Read string descriptor containing pen input parameters.
 288	 * The specific string descriptor and data were discovered by sniffing
 289	 * the Windows driver traffic.
 290	 * NOTE: This enables fully-functional tablet mode.
 291	 */
 292	rc = uclogic_params_get_str_desc(&buf, hdev, 200, len);
 293	if (rc == -EPIPE) {
 294		hid_dbg(hdev,
 295			"string descriptor with pen parameters not found, assuming not compatible\n");
 296		goto finish;
 297	} else if (rc < 0) {
 298		hid_err(hdev, "failed retrieving pen parameters: %d\n", rc);
 299		goto cleanup;
 300	} else if (rc != len) {
 301		hid_dbg(hdev,
 302			"string descriptor with pen parameters has invalid length (got %d, expected %d), assuming not compatible\n",
 303			rc, len);
 304		goto finish;
 305	} else {
 306		size_t i;
 307		/*
 308		 * Check it's not just a catch-all UTF-16LE-encoded ASCII
 309		 * string (such as the model name) some tablets put into all
 310		 * unknown string descriptors.
 311		 */
 312		for (i = 2;
 313		     i < len &&
 314			(buf[i] >= 0x20 && buf[i] < 0x7f && buf[i + 1] == 0);
 315		     i += 2);
 316		if (i >= len) {
 317			hid_dbg(hdev,
 318				"string descriptor with pen parameters seems to contain only text, assuming not compatible\n");
 319			goto finish;
 320		}
 321	}
 322
 323	/*
 324	 * Fill report descriptor parameters from the string descriptor
 325	 */
 326	desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] =
 327		uclogic_params_get_le24(buf + 2);
 328	desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] =
 329		uclogic_params_get_le24(buf + 5);
 330	desc_params[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] =
 331		get_unaligned_le16(buf + 8);
 332	resolution = get_unaligned_le16(buf + 10);
 333	if (resolution == 0) {
 334		desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0;
 335		desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0;
 336	} else {
 337		desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_PM] =
 338			desc_params[UCLOGIC_RDESC_PEN_PH_ID_X_LM] * 1000 /
 339			resolution;
 340		desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] =
 341			desc_params[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] * 1000 /
 342			resolution;
 343	}
 344	kfree(buf);
 345	buf = NULL;
 346
 347	/*
 348	 * Generate pen report descriptor
 349	 */
 350	desc_ptr = uclogic_rdesc_template_apply(
 351				uclogic_rdesc_pen_v2_template_arr,
 352				uclogic_rdesc_pen_v2_template_size,
 353				desc_params, ARRAY_SIZE(desc_params));
 354	if (desc_ptr == NULL) {
 355		rc = -ENOMEM;
 356		goto cleanup;
 357	}
 358
 359	/*
 360	 * Fill-in the parameters
 361	 */
 362	memset(pen, 0, sizeof(*pen));
 363	pen->desc_ptr = desc_ptr;
 364	desc_ptr = NULL;
 365	pen->desc_size = uclogic_rdesc_pen_v2_template_size;
 366	pen->id = UCLOGIC_RDESC_PEN_V2_ID;
 367	pen->inrange = UCLOGIC_PARAMS_PEN_INRANGE_NONE;
 368	pen->fragmented_hires = true;
 369	found = true;
 370finish:
 371	*pfound = found;
 372	rc = 0;
 373cleanup:
 374	kfree(desc_ptr);
 375	kfree(buf);
 376	return rc;
 377}
 378
 379/**
 380 * uclogic_params_frame_cleanup - free resources used by struct
 381 * uclogic_params_frame (tablet interface's frame controls input parameters).
 382 * Can be called repeatedly.
 383 *
 384 * @frame:	Frame controls input parameters to cleanup. Cannot be NULL.
 385 */
 386static void uclogic_params_frame_cleanup(struct uclogic_params_frame *frame)
 387{
 388	kfree(frame->desc_ptr);
 389	memset(frame, 0, sizeof(*frame));
 390}
 391
 392/**
 393 * uclogic_params_frame_init_with_desc() - initialize tablet's frame control
 394 * parameters with a static report descriptor.
 395 *
 396 * @frame:	Pointer to the frame parameters to initialize (to be cleaned
 397 *		up with uclogic_params_frame_cleanup()). Not modified in case
 398 *		of error. Cannot be NULL.
 399 * @desc_ptr:	Report descriptor pointer. Can be NULL, if desc_size is zero.
 400 * @desc_size:	Report descriptor size.
 401 * @id:		Report ID used for frame reports, if they should be tweaked,
 402 *		zero if not.
 403 *
 404 * Returns:
 405 *	Zero, if successful. A negative errno code on error.
 406 */
 407static int uclogic_params_frame_init_with_desc(
 408					struct uclogic_params_frame *frame,
 409					const __u8 *desc_ptr,
 410					size_t desc_size,
 411					unsigned int id)
 412{
 413	__u8 *copy_desc_ptr;
 414
 415	if (frame == NULL || (desc_ptr == NULL && desc_size != 0))
 416		return -EINVAL;
 417
 418	copy_desc_ptr = kmemdup(desc_ptr, desc_size, GFP_KERNEL);
 419	if (copy_desc_ptr == NULL)
 420		return -ENOMEM;
 421
 422	memset(frame, 0, sizeof(*frame));
 423	frame->desc_ptr = copy_desc_ptr;
 424	frame->desc_size = desc_size;
 425	frame->id = id;
 426	return 0;
 427}
 428
 429/**
 430 * uclogic_params_frame_init_v1_buttonpad() - initialize abstract buttonpad
 431 * on a v1 tablet interface.
 432 *
 433 * @frame:	Pointer to the frame parameters to initialize (to be cleaned
 434 *		up with uclogic_params_frame_cleanup()). Not modified in case
 435 *		of error, or if parameters are not found. Cannot be NULL.
 436 * @pfound:	Location for a flag which is set to true if the parameters
 437 *		were found, and to false if not (e.g. device was
 438 *		incompatible). Not modified in case of error. Cannot be NULL.
 439 * @hdev:	The HID device of the tablet interface to initialize and get
 440 *		parameters from. Cannot be NULL.
 441 *
 442 * Returns:
 443 *	Zero, if successful. A negative errno code on error.
 444 */
 445static int uclogic_params_frame_init_v1_buttonpad(
 446					struct uclogic_params_frame *frame,
 447					bool *pfound,
 448					struct hid_device *hdev)
 449{
 450	int rc;
 451	bool found = false;
 452	struct usb_device *usb_dev = hid_to_usb_dev(hdev);
 453	char *str_buf = NULL;
 454	const size_t str_len = 16;
 455
 456	/* Check arguments */
 457	if (frame == NULL || pfound == NULL || hdev == NULL) {
 458		rc = -EINVAL;
 459		goto cleanup;
 460	}
 461
 462	/*
 463	 * Enable generic button mode
 464	 */
 465	str_buf = kzalloc(str_len, GFP_KERNEL);
 466	if (str_buf == NULL) {
 467		rc = -ENOMEM;
 468		goto cleanup;
 469	}
 470
 471	rc = usb_string(usb_dev, 123, str_buf, str_len);
 472	if (rc == -EPIPE) {
 473		hid_dbg(hdev,
 474			"generic button -enabling string descriptor not found\n");
 475	} else if (rc < 0) {
 476		goto cleanup;
 477	} else if (strncmp(str_buf, "HK On", rc) != 0) {
 478		hid_dbg(hdev,
 479			"invalid response to enabling generic buttons: \"%s\"\n",
 480			str_buf);
 481	} else {
 482		hid_dbg(hdev, "generic buttons enabled\n");
 483		rc = uclogic_params_frame_init_with_desc(
 484				frame,
 485				uclogic_rdesc_buttonpad_v1_arr,
 486				uclogic_rdesc_buttonpad_v1_size,
 487				UCLOGIC_RDESC_BUTTONPAD_V1_ID);
 488		if (rc != 0)
 489			goto cleanup;
 490		found = true;
 491	}
 492
 493	*pfound = found;
 494	rc = 0;
 495cleanup:
 496	kfree(str_buf);
 497	return rc;
 498}
 499
 500/**
 501 * uclogic_params_cleanup - free resources used by struct uclogic_params
 502 * (tablet interface's parameters).
 503 * Can be called repeatedly.
 504 *
 505 * @params:	Input parameters to cleanup. Cannot be NULL.
 506 */
 507void uclogic_params_cleanup(struct uclogic_params *params)
 508{
 509	if (!params->invalid) {
 510		kfree(params->desc_ptr);
 511		if (!params->pen_unused)
 512			uclogic_params_pen_cleanup(&params->pen);
 513		uclogic_params_frame_cleanup(&params->frame);
 514		memset(params, 0, sizeof(*params));
 515	}
 516}
 517
 518/**
 519 * Get a replacement report descriptor for a tablet's interface.
 520 *
 521 * @params:	The parameters of a tablet interface to get report
 522 *		descriptor for. Cannot be NULL.
 523 * @pdesc:	Location for the resulting, kmalloc-allocated report
 524 *		descriptor pointer, or for NULL, if there's no replacement
 525 *		report descriptor. Not modified in case of error. Cannot be
 526 *		NULL.
 527 * @psize:	Location for the resulting report descriptor size, not set if
 528 *		there's no replacement report descriptor. Not modified in case
 529 *		of error. Cannot be NULL.
 530 *
 531 * Returns:
 532 *	Zero, if successful.
 533 *	-EINVAL, if invalid arguments are supplied.
 534 *	-ENOMEM, if failed to allocate memory.
 535 */
 536int uclogic_params_get_desc(const struct uclogic_params *params,
 537				__u8 **pdesc,
 538				unsigned int *psize)
 539{
 540	bool common_present;
 541	bool pen_present;
 542	bool frame_present;
 543	unsigned int size;
 544	__u8 *desc = NULL;
 545
 546	/* Check arguments */
 547	if (params == NULL || pdesc == NULL || psize == NULL)
 548		return -EINVAL;
 549
 550	size = 0;
 551
 552	common_present = (params->desc_ptr != NULL);
 553	pen_present = (!params->pen_unused && params->pen.desc_ptr != NULL);
 554	frame_present = (params->frame.desc_ptr != NULL);
 555
 556	if (common_present)
 557		size += params->desc_size;
 558	if (pen_present)
 559		size += params->pen.desc_size;
 560	if (frame_present)
 561		size += params->frame.desc_size;
 562
 563	if (common_present || pen_present || frame_present) {
 564		__u8 *p;
 565
 566		desc = kmalloc(size, GFP_KERNEL);
 567		if (desc == NULL)
 568			return -ENOMEM;
 569		p = desc;
 570
 571		if (common_present) {
 572			memcpy(p, params->desc_ptr,
 573				params->desc_size);
 574			p += params->desc_size;
 575		}
 576		if (pen_present) {
 577			memcpy(p, params->pen.desc_ptr,
 578				params->pen.desc_size);
 579			p += params->pen.desc_size;
 580		}
 581		if (frame_present) {
 582			memcpy(p, params->frame.desc_ptr,
 583				params->frame.desc_size);
 584			p += params->frame.desc_size;
 585		}
 586
 587		WARN_ON(p != desc + size);
 588
 589		*psize = size;
 590	}
 591
 592	*pdesc = desc;
 593	return 0;
 594}
 595
 596/**
 597 * uclogic_params_init_invalid() - initialize tablet interface parameters,
 598 * specifying the interface is invalid.
 599 *
 600 * @params:		Parameters to initialize (to be cleaned with
 601 *			uclogic_params_cleanup()). Cannot be NULL.
 602 */
 603static void uclogic_params_init_invalid(struct uclogic_params *params)
 604{
 605	params->invalid = true;
 606}
 607
 608/**
 609 * uclogic_params_init_with_opt_desc() - initialize tablet interface
 610 * parameters with an optional replacement report descriptor. Only modify
 611 * report descriptor, if the original report descriptor matches the expected
 612 * size.
 613 *
 614 * @params:		Parameters to initialize (to be cleaned with
 615 *			uclogic_params_cleanup()). Not modified in case of
 616 *			error. Cannot be NULL.
 617 * @hdev:		The HID device of the tablet interface create the
 618 *			parameters for. Cannot be NULL.
 619 * @orig_desc_size:	Expected size of the original report descriptor to
 620 *			be replaced.
 621 * @desc_ptr:		Pointer to the replacement report descriptor.
 622 *			Can be NULL, if desc_size is zero.
 623 * @desc_size:		Size of the replacement report descriptor.
 624 *
 625 * Returns:
 626 *	Zero, if successful. -EINVAL if an invalid argument was passed.
 627 *	-ENOMEM, if failed to allocate memory.
 628 */
 629static int uclogic_params_init_with_opt_desc(struct uclogic_params *params,
 630					     struct hid_device *hdev,
 631					     unsigned int orig_desc_size,
 632					     __u8 *desc_ptr,
 633					     unsigned int desc_size)
 634{
 635	__u8 *desc_copy_ptr = NULL;
 636	unsigned int desc_copy_size;
 637	int rc;
 638
 639	/* Check arguments */
 640	if (params == NULL || hdev == NULL ||
 641	    (desc_ptr == NULL && desc_size != 0)) {
 642		rc = -EINVAL;
 643		goto cleanup;
 644	}
 645
 646	/* Replace report descriptor, if it matches */
 647	if (hdev->dev_rsize == orig_desc_size) {
 648		hid_dbg(hdev,
 649			"device report descriptor matches the expected size, replacing\n");
 650		desc_copy_ptr = kmemdup(desc_ptr, desc_size, GFP_KERNEL);
 651		if (desc_copy_ptr == NULL) {
 652			rc = -ENOMEM;
 653			goto cleanup;
 654		}
 655		desc_copy_size = desc_size;
 656	} else {
 657		hid_dbg(hdev,
 658			"device report descriptor doesn't match the expected size (%u != %u), preserving\n",
 659			hdev->dev_rsize, orig_desc_size);
 660		desc_copy_ptr = NULL;
 661		desc_copy_size = 0;
 662	}
 663
 664	/* Output parameters */
 665	memset(params, 0, sizeof(*params));
 666	params->desc_ptr = desc_copy_ptr;
 667	desc_copy_ptr = NULL;
 668	params->desc_size = desc_copy_size;
 669
 670	rc = 0;
 671cleanup:
 672	kfree(desc_copy_ptr);
 673	return rc;
 674}
 675
 676/**
 677 * uclogic_params_init_with_pen_unused() - initialize tablet interface
 678 * parameters preserving original reports and generic HID processing, but
 679 * disabling pen usage.
 680 *
 681 * @params:		Parameters to initialize (to be cleaned with
 682 *			uclogic_params_cleanup()). Not modified in case of
 683 *			error. Cannot be NULL.
 684 */
 685static void uclogic_params_init_with_pen_unused(struct uclogic_params *params)
 686{
 687	memset(params, 0, sizeof(*params));
 688	params->pen_unused = true;
 689}
 690
 691/**
 692 * uclogic_params_init() - initialize a Huion tablet interface and discover
 693 * its parameters.
 694 *
 695 * @params:	Parameters to fill in (to be cleaned with
 696 *		uclogic_params_cleanup()). Not modified in case of error.
 697 *		Cannot be NULL.
 698 * @hdev:	The HID device of the tablet interface to initialize and get
 699 *		parameters from. Cannot be NULL.
 700 *
 701 * Returns:
 702 *	Zero, if successful. A negative errno code on error.
 703 */
 704static int uclogic_params_huion_init(struct uclogic_params *params,
 705				     struct hid_device *hdev)
 706{
 707	int rc;
 708	struct usb_device *udev = hid_to_usb_dev(hdev);
 709	struct usb_interface *iface = to_usb_interface(hdev->dev.parent);
 710	__u8 bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
 711	bool found;
 712	/* The resulting parameters (noop) */
 713	struct uclogic_params p = {0, };
 714	static const char transition_ver[] = "HUION_T153_160607";
 715	char *ver_ptr = NULL;
 716	const size_t ver_len = sizeof(transition_ver) + 1;
 717
 718	/* Check arguments */
 719	if (params == NULL || hdev == NULL) {
 720		rc = -EINVAL;
 721		goto cleanup;
 722	}
 723
 724	/* If it's not a pen interface */
 725	if (bInterfaceNumber != 0) {
 726		/* TODO: Consider marking the interface invalid */
 727		uclogic_params_init_with_pen_unused(&p);
 728		goto output;
 729	}
 730
 731	/* Try to get firmware version */
 732	ver_ptr = kzalloc(ver_len, GFP_KERNEL);
 733	if (ver_ptr == NULL) {
 734		rc = -ENOMEM;
 735		goto cleanup;
 736	}
 737	rc = usb_string(udev, 201, ver_ptr, ver_len);
 738	if (rc == -EPIPE) {
 739		*ver_ptr = '\0';
 740	} else if (rc < 0) {
 741		hid_err(hdev,
 742			"failed retrieving Huion firmware version: %d\n", rc);
 743		goto cleanup;
 744	}
 745
 746	/* If this is a transition firmware */
 747	if (strcmp(ver_ptr, transition_ver) == 0) {
 748		hid_dbg(hdev,
 749			"transition firmware detected, not probing pen v2 parameters\n");
 750	} else {
 751		/* Try to probe v2 pen parameters */
 752		rc = uclogic_params_pen_init_v2(&p.pen, &found, hdev);
 753		if (rc != 0) {
 754			hid_err(hdev,
 755				"failed probing pen v2 parameters: %d\n", rc);
 756			goto cleanup;
 757		} else if (found) {
 758			hid_dbg(hdev, "pen v2 parameters found\n");
 759			/* Create v2 buttonpad parameters */
 760			rc = uclogic_params_frame_init_with_desc(
 761					&p.frame,
 762					uclogic_rdesc_buttonpad_v2_arr,
 763					uclogic_rdesc_buttonpad_v2_size,
 764					UCLOGIC_RDESC_BUTTONPAD_V2_ID);
 765			if (rc != 0) {
 766				hid_err(hdev,
 767					"failed creating v2 buttonpad parameters: %d\n",
 768					rc);
 769				goto cleanup;
 770			}
 771			/* Set bitmask marking frame reports in pen reports */
 772			p.pen_frame_flag = 0x20;
 773			goto output;
 774		}
 775		hid_dbg(hdev, "pen v2 parameters not found\n");
 776	}
 777
 778	/* Try to probe v1 pen parameters */
 779	rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
 780	if (rc != 0) {
 781		hid_err(hdev,
 782			"failed probing pen v1 parameters: %d\n", rc);
 783		goto cleanup;
 784	} else if (found) {
 785		hid_dbg(hdev, "pen v1 parameters found\n");
 786		/* Try to probe v1 buttonpad */
 787		rc = uclogic_params_frame_init_v1_buttonpad(
 788						&p.frame,
 789						&found, hdev);
 790		if (rc != 0) {
 791			hid_err(hdev, "v1 buttonpad probing failed: %d\n", rc);
 792			goto cleanup;
 793		}
 794		hid_dbg(hdev, "buttonpad v1 parameters%s found\n",
 795			(found ? "" : " not"));
 796		if (found) {
 797			/* Set bitmask marking frame reports */
 798			p.pen_frame_flag = 0x20;
 799		}
 800		goto output;
 801	}
 802	hid_dbg(hdev, "pen v1 parameters not found\n");
 803
 804	uclogic_params_init_invalid(&p);
 805
 806output:
 807	/* Output parameters */
 808	memcpy(params, &p, sizeof(*params));
 809	memset(&p, 0, sizeof(p));
 810	rc = 0;
 811cleanup:
 812	kfree(ver_ptr);
 813	uclogic_params_cleanup(&p);
 814	return rc;
 815}
 816
 817/**
 818 * uclogic_params_init() - initialize a tablet interface and discover its
 819 * parameters.
 820 *
 821 * @params:	Parameters to fill in (to be cleaned with
 822 *		uclogic_params_cleanup()). Not modified in case of error.
 823 *		Cannot be NULL.
 824 * @hdev:	The HID device of the tablet interface to initialize and get
 825 *		parameters from. Cannot be NULL. Must be using the USB low-level
 826 *		driver, i.e. be an actual USB tablet.
 827 *
 828 * Returns:
 829 *	Zero, if successful. A negative errno code on error.
 830 */
 831int uclogic_params_init(struct uclogic_params *params,
 832			struct hid_device *hdev)
 833{
 834	int rc;
 835	struct usb_device *udev = hid_to_usb_dev(hdev);
 836	__u8  bNumInterfaces = udev->config->desc.bNumInterfaces;
 837	struct usb_interface *iface = to_usb_interface(hdev->dev.parent);
 838	__u8 bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
 839	bool found;
 840	/* The resulting parameters (noop) */
 841	struct uclogic_params p = {0, };
 842
 843	/* Check arguments */
 844	if (params == NULL || hdev == NULL ||
 845	    !hid_is_using_ll_driver(hdev, &usb_hid_driver)) {
 846		rc = -EINVAL;
 847		goto cleanup;
 848	}
 849
 850	/*
 851	 * Set replacement report descriptor if the original matches the
 852	 * specified size. Otherwise keep interface unchanged.
 853	 */
 854#define WITH_OPT_DESC(_orig_desc_token, _new_desc_token) \
 855	uclogic_params_init_with_opt_desc(                  \
 856		&p, hdev,                                   \
 857		UCLOGIC_RDESC_##_orig_desc_token##_SIZE,    \
 858		uclogic_rdesc_##_new_desc_token##_arr,      \
 859		uclogic_rdesc_##_new_desc_token##_size)
 860
 861#define VID_PID(_vid, _pid) \
 862	(((__u32)(_vid) << 16) | ((__u32)(_pid) & U16_MAX))
 863
 864	/*
 865	 * Handle specific interfaces for specific tablets.
 866	 *
 867	 * Observe the following logic:
 868	 *
 869	 * If the interface is recognized as producing certain useful input:
 870	 *	Mark interface as valid.
 871	 *	Output interface parameters.
 872	 * Else, if the interface is recognized as *not* producing any useful
 873	 * input:
 874	 *	Mark interface as invalid.
 875	 * Else:
 876	 *	Mark interface as valid.
 877	 *	Output noop parameters.
 878	 *
 879	 * Rule of thumb: it is better to disable a broken interface than let
 880	 *		  it spew garbage input.
 881	 */
 882
 883	switch (VID_PID(hdev->vendor, hdev->product)) {
 884	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 885		     USB_DEVICE_ID_UCLOGIC_TABLET_PF1209):
 886		rc = WITH_OPT_DESC(PF1209_ORIG, pf1209_fixed);
 887		if (rc != 0)
 888			goto cleanup;
 889		break;
 890	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 891		     USB_DEVICE_ID_UCLOGIC_TABLET_WP4030U):
 892		rc = WITH_OPT_DESC(WPXXXXU_ORIG, wp4030u_fixed);
 893		if (rc != 0)
 894			goto cleanup;
 895		break;
 896	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 897		     USB_DEVICE_ID_UCLOGIC_TABLET_WP5540U):
 898		if (hdev->dev_rsize == UCLOGIC_RDESC_WP5540U_V2_ORIG_SIZE) {
 899			if (bInterfaceNumber == 0) {
 900				/* Try to probe v1 pen parameters */
 901				rc = uclogic_params_pen_init_v1(&p.pen,
 902								&found, hdev);
 903				if (rc != 0) {
 904					hid_err(hdev,
 905						"pen probing failed: %d\n",
 906						rc);
 907					goto cleanup;
 908				}
 909				if (!found) {
 910					hid_warn(hdev,
 911						 "pen parameters not found");
 912				}
 913			} else {
 914				uclogic_params_init_invalid(&p);
 915			}
 916		} else {
 917			rc = WITH_OPT_DESC(WPXXXXU_ORIG, wp5540u_fixed);
 918			if (rc != 0)
 919				goto cleanup;
 920		}
 921		break;
 922	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 923		     USB_DEVICE_ID_UCLOGIC_TABLET_WP8060U):
 924		rc = WITH_OPT_DESC(WPXXXXU_ORIG, wp8060u_fixed);
 925		if (rc != 0)
 926			goto cleanup;
 927		break;
 928	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 929		     USB_DEVICE_ID_UCLOGIC_TABLET_WP1062):
 930		rc = WITH_OPT_DESC(WP1062_ORIG, wp1062_fixed);
 931		if (rc != 0)
 932			goto cleanup;
 933		break;
 934	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 935		     USB_DEVICE_ID_UCLOGIC_WIRELESS_TABLET_TWHL850):
 936		switch (bInterfaceNumber) {
 937		case 0:
 938			rc = WITH_OPT_DESC(TWHL850_ORIG0, twhl850_fixed0);
 939			if (rc != 0)
 940				goto cleanup;
 941			break;
 942		case 1:
 943			rc = WITH_OPT_DESC(TWHL850_ORIG1, twhl850_fixed1);
 944			if (rc != 0)
 945				goto cleanup;
 946			break;
 947		case 2:
 948			rc = WITH_OPT_DESC(TWHL850_ORIG2, twhl850_fixed2);
 949			if (rc != 0)
 950				goto cleanup;
 951			break;
 952		}
 953		break;
 954	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 955		     USB_DEVICE_ID_UCLOGIC_TABLET_TWHA60):
 956		/*
 957		 * If it is not a three-interface version, which is known to
 958		 * respond to initialization.
 959		 */
 960		if (bNumInterfaces != 3) {
 961			switch (bInterfaceNumber) {
 962			case 0:
 963				rc = WITH_OPT_DESC(TWHA60_ORIG0,
 964							twha60_fixed0);
 965				if (rc != 0)
 966					goto cleanup;
 967				break;
 968			case 1:
 969				rc = WITH_OPT_DESC(TWHA60_ORIG1,
 970							twha60_fixed1);
 971				if (rc != 0)
 972					goto cleanup;
 973				break;
 974			}
 975			break;
 976		}
 977		fallthrough;
 978	case VID_PID(USB_VENDOR_ID_HUION,
 979		     USB_DEVICE_ID_HUION_TABLET):
 980	case VID_PID(USB_VENDOR_ID_HUION,
 981		     USB_DEVICE_ID_HUION_HS64):
 982	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 983		     USB_DEVICE_ID_HUION_TABLET):
 984	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 985		     USB_DEVICE_ID_YIYNOVA_TABLET):
 986	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 987		     USB_DEVICE_ID_UCLOGIC_UGEE_TABLET_81):
 988	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 989		     USB_DEVICE_ID_UCLOGIC_DRAWIMAGE_G3):
 990	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 991		     USB_DEVICE_ID_UCLOGIC_UGEE_TABLET_45):
 992	case VID_PID(USB_VENDOR_ID_UCLOGIC,
 993		     USB_DEVICE_ID_UCLOGIC_UGEE_TABLET_47):
 994		rc = uclogic_params_huion_init(&p, hdev);
 995		if (rc != 0)
 996			goto cleanup;
 997		break;
 998	case VID_PID(USB_VENDOR_ID_UGTIZER,
 999		     USB_DEVICE_ID_UGTIZER_TABLET_GP0610):
1000	case VID_PID(USB_VENDOR_ID_UGEE,
1001		     USB_DEVICE_ID_UGEE_XPPEN_TABLET_G540):
1002	case VID_PID(USB_VENDOR_ID_UGEE,
1003		     USB_DEVICE_ID_UGEE_XPPEN_TABLET_G640):
1004	case VID_PID(USB_VENDOR_ID_UGEE,
1005		     USB_DEVICE_ID_UGEE_TABLET_RAINBOW_CV720):
1006		/* If this is the pen interface */
1007		if (bInterfaceNumber == 1) {
1008			/* Probe v1 pen parameters */
1009			rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
1010			if (rc != 0) {
1011				hid_err(hdev, "pen probing failed: %d\n", rc);
1012				goto cleanup;
1013			}
1014			if (!found) {
1015				hid_warn(hdev, "pen parameters not found");
1016				uclogic_params_init_invalid(&p);
1017			}
1018		} else {
1019			/* TODO: Consider marking the interface invalid */
1020			uclogic_params_init_with_pen_unused(&p);
1021		}
1022		break;
1023	case VID_PID(USB_VENDOR_ID_UGEE,
1024		     USB_DEVICE_ID_UGEE_XPPEN_TABLET_DECO01):
1025		/* If this is the pen and frame interface */
1026		if (bInterfaceNumber == 1) {
1027			/* Probe v1 pen parameters */
1028			rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
1029			if (rc != 0) {
1030				hid_err(hdev, "pen probing failed: %d\n", rc);
1031				goto cleanup;
1032			}
1033			/* Initialize frame parameters */
1034			rc = uclogic_params_frame_init_with_desc(
1035				&p.frame,
1036				uclogic_rdesc_xppen_deco01_frame_arr,
1037				uclogic_rdesc_xppen_deco01_frame_size,
1038				0);
1039			if (rc != 0)
1040				goto cleanup;
1041		} else {
1042			/* TODO: Consider marking the interface invalid */
1043			uclogic_params_init_with_pen_unused(&p);
1044		}
1045		break;
1046	case VID_PID(USB_VENDOR_ID_UGEE,
1047		     USB_DEVICE_ID_UGEE_TABLET_G5):
1048		/* Ignore non-pen interfaces */
1049		if (bInterfaceNumber != 1) {
1050			uclogic_params_init_invalid(&p);
1051			break;
1052		}
1053
1054		rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
1055		if (rc != 0) {
1056			hid_err(hdev, "pen probing failed: %d\n", rc);
1057			goto cleanup;
1058		} else if (found) {
1059			rc = uclogic_params_frame_init_with_desc(
1060				&p.frame,
1061				uclogic_rdesc_ugee_g5_frame_arr,
1062				uclogic_rdesc_ugee_g5_frame_size,
1063				UCLOGIC_RDESC_UGEE_G5_FRAME_ID);
1064			if (rc != 0) {
1065				hid_err(hdev,
1066					"failed creating buttonpad parameters: %d\n",
1067					rc);
1068				goto cleanup;
1069			}
1070			p.frame.re_lsb =
1071				UCLOGIC_RDESC_UGEE_G5_FRAME_RE_LSB;
1072			p.frame.dev_id_byte =
1073				UCLOGIC_RDESC_UGEE_G5_FRAME_DEV_ID_BYTE;
1074		} else {
1075			hid_warn(hdev, "pen parameters not found");
1076			uclogic_params_init_invalid(&p);
1077		}
1078
1079		break;
1080	case VID_PID(USB_VENDOR_ID_UGEE,
1081		     USB_DEVICE_ID_UGEE_TABLET_EX07S):
1082		/* Ignore non-pen interfaces */
1083		if (bInterfaceNumber != 1) {
1084			uclogic_params_init_invalid(&p);
1085			break;
1086		}
1087
1088		rc = uclogic_params_pen_init_v1(&p.pen, &found, hdev);
1089		if (rc != 0) {
1090			hid_err(hdev, "pen probing failed: %d\n", rc);
1091			goto cleanup;
1092		} else if (found) {
1093			rc = uclogic_params_frame_init_with_desc(
1094				&p.frame,
1095				uclogic_rdesc_ugee_ex07_buttonpad_arr,
1096				uclogic_rdesc_ugee_ex07_buttonpad_size,
1097				0);
1098			if (rc != 0) {
1099				hid_err(hdev,
1100					"failed creating buttonpad parameters: %d\n",
1101					rc);
1102				goto cleanup;
1103			}
1104		} else {
1105			hid_warn(hdev, "pen parameters not found");
1106			uclogic_params_init_invalid(&p);
1107		}
1108
1109		break;
1110	}
1111
1112#undef VID_PID
1113#undef WITH_OPT_DESC
1114
1115	/* Output parameters */
1116	memcpy(params, &p, sizeof(*params));
1117	memset(&p, 0, sizeof(p));
1118	rc = 0;
1119cleanup:
1120	uclogic_params_cleanup(&p);
1121	return rc;
1122}