1/* $Id: pbms.c,v 1.20 2022/03/28 12:43:12 riastradh Exp $ */ 2 3/* 4 * Copyright (c) 2005, Johan Wall�n 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions are 9 * met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 14 * 2. Redistributions in binary form must reproduce the above 15 * copyright notice, this list of conditions and the following 16 * disclaimer in the documentation and/or other materials provided 17 * with the distribution. 18 * 19 * 3. The name of the copyright holder may not be used to endorse or 20 * promote products derived from this software without specific 21 * prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER "AS IS" AND ANY 24 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 26 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER BE 27 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 28 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 29 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 30 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 31 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 32 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 33 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 34 */ 35 36/* 37 * The pbms driver provides support for the trackpad on new (post 38 * February 2005) Apple PowerBooks (and iBooks?) that are not standard 39 * USB HID mice. 40 */ 41 42/* 43 * The protocol (that is, the interpretation of the data generated by 44 * the trackpad) is taken from the Linux appletouch driver version 45 * 0.08 by Johannes Berg, Stelian Pop and Frank Arnold. The method 46 * used to detect fingers on the trackpad is also taken from that 47 * driver. 48 */ 49 50/* 51 * To add support for other devices using the same protocol, add an 52 * entry to the pbms_devices table below. See the comments for 53 * pbms_devices and struct pbms_devs. 54 */ 55 56/* 57 * PROTOCOL: 58 * 59 * The driver transfers continuously 81 byte events. The last byte is 60 * 1 if the button is pressed, and is 0 otherwise. Of the remaining 61 * bytes, 26 + 16 = 42 are sensors detecting pressure in the X or 62 * horizontal, and Y or vertical directions, respectively. On 12 and 63 * 15 inch PowerBooks, only the 16 first sensors in the X-direction 64 * are used. In the X-direction, the sensors correspond to byte 65 * positions 66 * 67 * 2, 7, 12, 17, 22, 27, 32, 37, 4, 9, 14, 19, 24, 29, 34, 39, 42, 68 * 47, 52, 57, 62, 67, 72, 77, 44 and 49; 69 * 70 * In the Y direction, the sensors correspond to byte positions 71 * 72 * 1, 6, 11, 16, 21, 26, 31, 36, 3, 8, 13, 18, 23, 28, 33 and 38. 73 * 74 * On 12 inch iBooks only the 9 first sensors in Y-direction are used. 75 * The change in the sensor values over time is more interesting than 76 * their absolute values: if the pressure increases, we know that the 77 * finger has just moved there. 78 * 79 * We keep track of the previous sample (of sensor values in the X and 80 * Y directions) and the accumulated change for each sensor. When we 81 * receive a new sample, we add the difference of the new sensor value 82 * and the old value to the accumulated change. If the accumulator 83 * becomes negative, we set it to zero. The effect is that the 84 * accumulator is large for sensors whose pressure has recently 85 * increased. If there is little change in pressure (or if the 86 * pressure decreases), the accumulator drifts back to zero. 87 * 88 * Since there is some fluctuations, we ignore accumulator values 89 * below a threshold. The raw finger position is computed as a 90 * weighted average of the other sensors (the weights are the 91 * accumulated changes). 92 * 93 * For smoothing, we keep track of the previous raw finger position, 94 * and the virtual position reported to wsmouse. The new raw position 95 * is computed as a weighted average of the old raw position and the 96 * computed raw position. Since this still generates some noise, we 97 * compute a new virtual position as a weighted average of the previous 98 * virtual position and the new raw position. The weights are 99 * controlled by the raw change and a noise parameter. The position 100 * is reported as a relative position. 101 */ 102 103/* 104 * TODO: 105 * 106 * Add support for other drivers of the same type. 107 * 108 * Add support for tapping and two-finger scrolling? The 109 * implementation already detects two fingers, so this should be 110 * relatively easy. 111 * 112 * Implement some of the mouse ioctls? 113 * 114 * Take care of the XXXs. 115 * 116 */ 117 118#include <sys/cdefs.h> 119 120#include <sys/param.h> 121#include <sys/device.h> 122#include <sys/errno.h> 123 124#include <sys/ioctl.h> 125#include <sys/systm.h> 126#include <sys/tty.h> 127 128#include <dev/usb/usb.h> 129#include <dev/usb/usbdi.h> 130#include <dev/usb/usbdevs.h> 131#include <dev/usb/uhidev.h> 132#include <dev/hid/hid.h> 133 134#include <dev/wscons/wsconsio.h> 135#include <dev/wscons/wsmousevar.h> 136 137/* 138 * Magic numbers. 139 */ 140 141 142/* The amount of data transferred by the USB device. */ 143#define PBMS_DATA_LEN 81 144 145/* The maximum number of sensors. */ 146#define PBMS_X_SENSORS 26 147#define PBMS_Y_SENSORS 16 148#define PBMS_SENSORS (PBMS_X_SENSORS + PBMS_Y_SENSORS) 149 150/* 151 * Parameters for supported devices. For generality, these parameters 152 * can be different for each device. The meanings of the parameters 153 * are as follows. 154 * 155 * desc: A printable description used for dmesg output. 156 * 157 * noise: Amount of noise in the computed position. This controls 158 * how large a change must be to get reported, and how 159 * large enough changes are smoothed. A good value can 160 * probably only be found experimentally, but something around 161 * 16 seems suitable. 162 * 163 * product: The product ID of the trackpad. 164 * 165 * 166 * threshold: Accumulated changes less than this are ignored. A good 167 * value could be determined experimentally, but 5 is a 168 * reasonable guess. 169 * 170 * vendor: The vendor ID. Currently USB_VENDOR_APPLE for all devices. 171 * 172 * x_factor: Factor used in computations with X-coordinates. If the 173 * x-resolution of the display is x, this should be 174 * (x + 1) / (x_sensors - 1). Other values work fine, but 175 * then the aspect ratio is not necessarily kept. 176 * 177 * x_sensors: The number of sensors in the X-direction. 178 * 179 * y_factor: As x_factors, but for Y-coordinates. 180 * 181 * y_sensors: The number of sensors in the Y-direction. 182 */ 183 184struct pbms_dev { 185 const char *descr; /* Description of the driver (for dmesg). */ 186 int noise; /* Amount of noise in the computed position. */ 187 int threshold; /* Changes less than this are ignored. */ 188 int x_factor; /* Factor used in computation with X-coordinates. */ 189 int x_sensors; /* The number of X-sensors. */ 190 int y_factor; /* Factor used in computation with Y-coordinates. */ 191 int y_sensors; /* The number of Y-sensors. */ 192 uint16_t product; /* Product ID. */ 193 uint16_t vendor; /* The vendor ID. */ 194}; 195 196/* Devices supported by this driver. */ 197static struct pbms_dev pbms_devices[] = 198{ 199#define POWERBOOK_TOUCHPAD(inches, prod, x_fact, x_sens, y_fact) \ 200 { \ 201 .descr = #inches " inch PowerBook Trackpad", \ 202 .vendor = USB_VENDOR_APPLE, \ 203 .product = (prod), \ 204 .noise = 16, \ 205 .threshold = 5, \ 206 .x_factor = (x_fact), \ 207 .x_sensors = (x_sens), \ 208 .y_factor = (y_fact), \ 209 .y_sensors = 16 \ 210 } 211 /* 12 inch PowerBooks/iBooks */ 212 POWERBOOK_TOUCHPAD(12, 0x030a, 69, 16, 52), /* XXX Not tested. */ 213 POWERBOOK_TOUCHPAD(12, 0x030b, 73, 15, 96), 214 /* 15 inch PowerBooks */ 215 POWERBOOK_TOUCHPAD(15, 0x020e, 85, 16, 57), /* XXX Not tested. */ 216 POWERBOOK_TOUCHPAD(15, 0x020f, 85, 16, 57), 217 POWERBOOK_TOUCHPAD(15, 0x0215, 90, 15, 107), 218 /* 17 inch PowerBooks */ 219 POWERBOOK_TOUCHPAD(17, 0x020d, 71, 26, 68) /* XXX Not tested. */ 220#undef POWERBOOK_TOUCHPAD 221}; 222 223/* The number of supported devices. */ 224#define PBMS_NUM_DEVICES (sizeof(pbms_devices) / sizeof(pbms_devices[0])) 225 226 227/* 228 * Types and prototypes. 229 */ 230 231 232/* Device data. */ 233struct pbms_softc { 234 struct uhidev sc_hdev; /* USB parent */ 235 int is_geyser2; 236 int sc_datalen; /* Size of a data packet */ 237 int sc_bufusage; /* Number of bytes in sc_databuf */ 238 int sc_acc[PBMS_SENSORS]; /* Accumulated sensor values. */ 239 unsigned char sc_prev[PBMS_SENSORS]; /* Previous sample. */ 240 unsigned char sc_sample[PBMS_SENSORS]; /* Current sample. */ 241 uint8_t sc_databuf[PBMS_DATA_LEN]; /* Buffer for a data packet */ 242 device_t sc_wsmousedev; /* WSMouse device. */ 243 int sc_noise; /* Amount of noise. */ 244 int sc_theshold; /* Threshold value. */ 245 int sc_x; /* Virtual position in horizontal 246 * direction (wsmouse position). */ 247 int sc_x_factor; /* X-coordinate factor. */ 248 int sc_x_raw; /* X-position of finger on trackpad. */ 249 int sc_x_sensors; /* Number of X-sensors. */ 250 int sc_y; /* Virtual position in vertical direction 251 * (wsmouse position). */ 252 int sc_y_factor; /* Y-coordinate factor. */ 253 int sc_y_raw; /* Y-position of finger on trackpad. */ 254 int sc_y_sensors; /* Number of Y-sensors. */ 255 uint32_t sc_buttons; /* Button state. */ 256 uint32_t sc_status; /* Status flags. */ 257#define PBMS_ENABLED 1 /* Is the device enabled? */ 258#define PBMS_DYING 2 /* Is the device dying? */ 259#define PBMS_VALID 4 /* Is the previous sample valid? */ 260}; 261 262 263/* Static function prototypes. */ 264static void pbms_intr(struct uhidev *, void *, unsigned int); 265static int pbms_enable(void *); 266static void pbms_disable(void *); 267static int pbms_ioctl(void *, unsigned long, void *, int, struct lwp *); 268static void reorder_sample(struct pbms_softc *, unsigned char *, unsigned char *); 269static int compute_delta(struct pbms_softc *, int *, int *, int *, uint32_t *); 270static int detect_pos(int *, int, int, int, int *, int *); 271static int smooth_pos(int, int, int); 272 273/* Access methods for wsmouse. */ 274const struct wsmouse_accessops pbms_accessops = { 275 pbms_enable, 276 pbms_ioctl, 277 pbms_disable, 278}; 279 280/* This take cares also of the basic device registration. */ 281int pbms_match(device_t, cfdata_t, void *); 282void pbms_attach(device_t, device_t, void *); 283int pbms_detach(device_t, int); 284void pbms_childdet(device_t, device_t); 285int pbms_activate(device_t, enum devact); 286extern struct cfdriver pbms_cd; 287CFATTACH_DECL2_NEW(pbms, sizeof(struct pbms_softc), pbms_match, pbms_attach, 288 pbms_detach, pbms_activate, NULL, pbms_childdet); 289 290/* 291 * Basic driver. 292 */ 293 294 295/* Try to match the device at some uhidev. */ 296 297int 298pbms_match(device_t parent, cfdata_t match, void *aux) 299{ 300 struct uhidev_attach_arg *uha = aux; 301 usb_device_descriptor_t *udd; 302 int i; 303 uint16_t vendor, product; 304 305 /* 306 * We just check if the vendor and product IDs have the magic numbers 307 * we expect. 308 */ 309 if (uha->uiaa->uiaa_proto == UIPROTO_MOUSE && 310 ((udd = usbd_get_device_descriptor(uha->uiaa->uiaa_device)) 311 != NULL)) { 312 vendor = UGETW(udd->idVendor); 313 product = UGETW(udd->idProduct); 314 for (i = 0; i < PBMS_NUM_DEVICES; i++) { 315 if (vendor == pbms_devices[i].vendor && 316 product == pbms_devices[i].product) 317 return UMATCH_IFACECLASS; 318 } 319 } 320 return UMATCH_NONE; 321} 322 323 324/* Attach the device. */ 325 326void 327pbms_attach(device_t parent, device_t self, void *aux) 328{ 329 struct wsmousedev_attach_args a; 330 struct uhidev_attach_arg *uha = aux; 331 struct pbms_dev *pd; 332 struct pbms_softc *sc = device_private(self); 333 struct usbd_device *udev; 334 usb_device_descriptor_t *udd; 335 int i; 336 uint16_t vendor, product; 337 338 sc->sc_hdev.sc_intr = pbms_intr; 339 sc->sc_hdev.sc_parent = uha->parent; 340 sc->sc_hdev.sc_report_id = uha->reportid; 341 342 sc->is_geyser2 = 0; 343 sc->sc_datalen = PBMS_DATA_LEN; 344 345 /* Fill in device-specific parameters. */ 346 udev = uha->uiaa->uiaa_udevice; 347 if ((udd = usbd_get_device_descriptor(udev)) != NULL) { 348 product = UGETW(udd->idProduct); 349 vendor = UGETW(udd->idVendor); 350 for (i = 0; i < PBMS_NUM_DEVICES; i++) { 351 pd = &pbms_devices[i]; 352 if (product == pd->product && vendor == pd->vendor) { 353 printf(": %s\n", pd->descr); 354 sc->sc_noise = pd->noise; 355 sc->sc_theshold = pd->threshold; 356 sc->sc_x_factor = pd->x_factor; 357 sc->sc_x_sensors = pd->x_sensors; 358 sc->sc_y_factor = pd->y_factor; 359 sc->sc_y_sensors = pd->y_sensors; 360 if (product == 0x0215) { 361 sc->is_geyser2 = 1; 362 sc->sc_datalen = 64; 363 sc->sc_y_sensors = 9; 364 } 365 else if (product == 0x030b) 366 sc->sc_y_sensors = 9; 367 break; 368 } 369 } 370 } 371 KASSERT(0 <= sc->sc_x_sensors && sc->sc_x_sensors <= PBMS_X_SENSORS); 372 KASSERT(0 <= sc->sc_y_sensors && sc->sc_y_sensors <= PBMS_Y_SENSORS); 373 374 sc->sc_status = 0; 375 376 a.accessops = &pbms_accessops; 377 a.accesscookie = sc; 378 379 sc->sc_wsmousedev = config_found(self, &a, wsmousedevprint, CFARGS_NONE); 380 381 return; 382} 383 384 385/* Detach the device. */ 386 387void 388pbms_childdet(device_t self, device_t child) 389{ 390 struct pbms_softc *sc = device_private(self); 391 392 if (sc->sc_wsmousedev == child) 393 sc->sc_wsmousedev = NULL; 394} 395 396int 397pbms_detach(device_t self, int flags) 398{ 399 /* XXX This could not possibly be sufficient! */ 400 return config_detach_children(self, flags); 401} 402 403 404/* Activate the device. */ 405 406int 407pbms_activate(device_t self, enum devact act) 408{ 409 struct pbms_softc *sc = device_private(self); 410 411 if (act != DVACT_DEACTIVATE) 412 return EOPNOTSUPP; 413 414 sc->sc_status |= PBMS_DYING; 415 return 0; 416} 417 418 419/* Enable the device. */ 420 421static int 422pbms_enable(void *v) 423{ 424 struct pbms_softc *sc = v; 425 426 /* Check that we are not detaching or already enabled. */ 427 if (sc->sc_status & PBMS_DYING) 428 return EIO; 429 if (sc->sc_status & PBMS_ENABLED) 430 return EBUSY; 431 432 sc->sc_status |= PBMS_ENABLED; 433 sc->sc_status &= ~PBMS_VALID; 434 sc->sc_bufusage = 0; 435 sc->sc_buttons = 0; 436 memset(sc->sc_sample, 0, sizeof(sc->sc_sample)); 437 438 return uhidev_open(&sc->sc_hdev); 439} 440 441 442/* Disable the device. */ 443 444static void 445pbms_disable(void *v) 446{ 447 struct pbms_softc *sc = v; 448 449 if (!(sc->sc_status & PBMS_ENABLED)) 450 return; 451 452 sc->sc_status &= ~PBMS_ENABLED; 453 uhidev_close(&sc->sc_hdev); 454} 455 456 457/* XXX ioctl not implemented. */ 458 459static int 460pbms_ioctl(void *v, unsigned long cmd, void *data, int flag, struct lwp *p) 461{ 462 return EPASSTHROUGH; 463} 464 465 466/* 467 * Interrupts & pointer movement. 468 */ 469 470 471/* Handle interrupts. */ 472 473void 474pbms_intr(struct uhidev *addr, void *ibuf, unsigned int len) 475{ 476 struct pbms_softc *sc = (struct pbms_softc *)addr; 477 uint8_t *data; 478 int dx, dy, dz, i, s; 479 uint32_t buttons; 480 481 /* 482 * We may have to construct the full data packet over two or three 483 * sequential interrupts, as the device only sends us chunks of 484 * 32 or 64 bytes of data. 485 * This also requires some synchronization, to make sure we place 486 * the first protocol-byte at the first byte in the bufffer. 487 */ 488 if (sc->is_geyser2) { 489 /* XXX Need to check this. */ 490 } else { 491 /* the last chunk is always 17 bytes */ 492 if (len == 17 && sc->sc_bufusage + len != sc->sc_datalen) { 493 sc->sc_bufusage = 0; /* discard bad packet */ 494 return; 495 } 496 } 497 498 memcpy(sc->sc_databuf + sc->sc_bufusage, ibuf, len); 499 sc->sc_bufusage += len; 500 if (sc->sc_bufusage != sc->sc_datalen) 501 return; /* wait until packet is complete */ 502 503 /* process the now complete protocol and clear the buffer */ 504 data = sc->sc_databuf; 505 sc->sc_bufusage = 0; 506#if 0 507 for (i = 0; i < sc->sc_datalen; i++) 508 printf(" %02x", data[i]); 509 printf("\n"); 510#endif 511 512 /* The last byte is 1 if the button is pressed and 0 otherwise. */ 513 buttons = !!data[sc->sc_datalen - 1]; 514 515 /* Everything below assumes that the sample is reordered. */ 516 reorder_sample(sc, sc->sc_sample, data); 517 518 /* Is this the first sample? */ 519 if (!(sc->sc_status & PBMS_VALID)) { 520 sc->sc_status |= PBMS_VALID; 521 sc->sc_x = sc->sc_y = -1; 522 sc->sc_x_raw = sc->sc_y_raw = -1; 523 memcpy(sc->sc_prev, sc->sc_sample, sizeof(sc->sc_prev)); 524 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 525 return; 526 } 527 /* Accumulate the sensor change while keeping it nonnegative. */ 528 for (i = 0; i < PBMS_SENSORS; i++) { 529 sc->sc_acc[i] += 530 (signed char) (sc->sc_sample[i] - sc->sc_prev[i]); 531 if (sc->sc_acc[i] < 0) 532 sc->sc_acc[i] = 0; 533 } 534 memcpy(sc->sc_prev, sc->sc_sample, sizeof(sc->sc_prev)); 535 536 /* Compute change. */ 537 dx = dy = dz = 0; 538 if (!compute_delta(sc, &dx, &dy, &dz, &buttons)) 539 return; 540 541 /* Report to wsmouse. */ 542 if ((dx != 0 || dy != 0 || dz != 0 || buttons != sc->sc_buttons) && 543 sc->sc_wsmousedev != NULL) { 544 s = spltty(); 545 wsmouse_input(sc->sc_wsmousedev, buttons, dx, -dy, dz, 0, 546 WSMOUSE_INPUT_DELTA); 547 splx(s); 548 } 549 sc->sc_buttons = buttons; 550} 551 552 553/* 554 * Reorder the sensor values so that all the X-sensors are before the 555 * Y-sensors in the natural order. Note that this might have to be 556 * rewritten if PBMS_X_SENSORS or PBMS_Y_SENSORS change. 557 */ 558 559static void 560reorder_sample(struct pbms_softc *sc, unsigned char *to, unsigned char *from) 561{ 562 int i; 563 564 if (sc->is_geyser2) { 565 int j; 566 567 memset(to, 0, PBMS_SENSORS); 568 for (i = 0, j = 19; i < 20; i += 2, j += 3) { 569 to[i] = from[j]; 570 to[i + 1] = from[j + 1]; 571 } 572 for (i = 0, j = 1; i < 9; i += 2, j += 3) { 573 to[PBMS_X_SENSORS + i] = from[j]; 574 to[PBMS_X_SENSORS + i + 1] = from[j + 1]; 575 } 576 } else { 577 for (i = 0; i < 8; i++) { 578 /* X-sensors. */ 579 to[i] = from[5 * i + 2]; 580 to[i + 8] = from[5 * i + 4]; 581 to[i + 16] = from[5 * i + 42]; 582 #if 0 583 /* 584 * XXX This seems to introduce random ventical jumps, so 585 * we ignore these sensors until we figure out their meaning. 586 */ 587 if (i < 2) 588 to[i + 24] = from[5 * i + 44]; 589 #endif /* 0 */ 590 /* Y-sensors. */ 591 to[i + 26] = from[5 * i + 1]; 592 to[i + 34] = from[5 * i + 3]; 593 } 594 } 595} 596 597 598/* 599 * Compute the change in x, y and z direction, update the button state 600 * (to simulate more than one button, scrolling etc.), and update the 601 * history. Note that dx, dy, dz and buttons are modified only if 602 * corresponding pressure is detected and should thus be initialised 603 * before the call. Return 0 on error. 604 */ 605 606/* XXX Could we report something useful in dz? */ 607 608static int 609compute_delta(struct pbms_softc *sc, int *dx, int *dy, int *dz, 610 uint32_t * buttons) 611{ 612 int x_det, y_det, x_raw, y_raw, x_fingers, y_fingers, fingers, x, y; 613 614 x_det = detect_pos(sc->sc_acc, sc->sc_x_sensors, sc->sc_theshold, 615 sc->sc_x_factor, &x_raw, &x_fingers); 616 y_det = detect_pos(sc->sc_acc + PBMS_X_SENSORS, sc->sc_y_sensors, 617 sc->sc_theshold, sc->sc_y_factor, 618 &y_raw, &y_fingers); 619 fingers = uimax(x_fingers, y_fingers); 620 621 /* Check the number of fingers and if we have detected a position. */ 622 if (fingers > 1) { 623 /* More than one finger detected, resetting. */ 624 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 625 sc->sc_x_raw = sc->sc_y_raw = sc->sc_x = sc->sc_y = -1; 626 return 0; 627 } else if (x_det == 0 && y_det == 0) { 628 /* No position detected, resetting. */ 629 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 630 sc->sc_x_raw = sc->sc_y_raw = sc->sc_x = sc->sc_y = -1; 631 } else if (x_det > 0 && y_det > 0) { 632 /* Smooth position. */ 633 if (sc->sc_x_raw >= 0) { 634 sc->sc_x_raw = (3 * sc->sc_x_raw + x_raw) / 4; 635 sc->sc_y_raw = (3 * sc->sc_y_raw + y_raw) / 4; 636 /* 637 * Compute virtual position and change if we already 638 * have a decent position. 639 */ 640 if (sc->sc_x >= 0) { 641 x = smooth_pos(sc->sc_x, sc->sc_x_raw, 642 sc->sc_noise); 643 y = smooth_pos(sc->sc_y, sc->sc_y_raw, 644 sc->sc_noise); 645 *dx = x - sc->sc_x; 646 *dy = y - sc->sc_y; 647 sc->sc_x = x; 648 sc->sc_y = y; 649 } else { 650 /* Initialise virtual position. */ 651 sc->sc_x = sc->sc_x_raw; 652 sc->sc_y = sc->sc_y_raw; 653 } 654 } else { 655 /* Initialise raw position. */ 656 sc->sc_x_raw = x_raw; 657 sc->sc_y_raw = y_raw; 658 } 659 } 660 return 1; 661} 662 663 664/* 665 * Compute the new smoothed position from the previous smoothed position 666 * and the raw position. 667 */ 668 669static int 670smooth_pos(int pos_old, int pos_raw, int noise) 671{ 672 int ad, delta; 673 674 delta = pos_raw - pos_old; 675 ad = abs(delta); 676 677 /* Too small changes are ignored. */ 678 if (ad < noise / 2) 679 delta = 0; 680 /* A bit larger changes are smoothed. */ 681 else if (ad < noise) 682 delta /= 4; 683 else if (ad < 2 * noise) 684 delta /= 2; 685 686 return pos_old + delta; 687} 688 689 690/* 691 * Detect the position of the finger. Returns the total pressure. 692 * The position is returned in pos_ret and the number of fingers 693 * is returned in fingers_ret. The position returned in pos_ret 694 * is in [0, (n_sensors - 1) * factor - 1]. 695 */ 696 697static int 698detect_pos(int *sensors, int n_sensors, int threshold, int fact, 699 int *pos_ret, int *fingers_ret) 700{ 701 int i, w, s; 702 703 /* 704 * Compute the number of fingers, total pressure, and weighted 705 * position of the fingers. 706 */ 707 *fingers_ret = 0; 708 w = s = 0; 709 for (i = 0; i < n_sensors; i++) { 710 if (sensors[i] >= threshold) { 711 if (i == 0 || sensors[i - 1] < threshold) 712 *fingers_ret += 1; 713 s += sensors[i]; 714 w += sensors[i] * i; 715 } 716 } 717 718 if (s > 0) 719 *pos_ret = w * fact / s; 720 721 return s; 722} 723