1 /* $Id: pbms.c,v 1.9 2009/11/05 05:37:30 dyoung 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 * The change in the sensor values over time is more interesting than 75 * their absolute values: if the pressure increases, we know that the 76 * finger has just moved there. 77 * 78 * We keep track of the previous sample (of sensor values in the X and 79 * Y directions) and the accumulated change for each sensor. When we 80 * receive a new sample, we add the difference of the new sensor value 81 * and the old value to the accumulated change. If the accumulator 82 * becomes negative, we set it to zero. The effect is that the 83 * accumulator is large for sensors whose pressure has recently 84 * increased. If there is little change in pressure (or if the 85 * pressure decreases), the accumulator drifts back to zero. 86 * 87 * Since there is some fluctuations, we ignore accumulator values 88 * below a threshold. The raw finger position is computed as a 89 * weighted average of the other sensors (the weights are the 90 * accumulated changes). 91 * 92 * For smoothing, we keep track of the previous raw finger position, 93 * and the virtual position reported to wsmouse. The new raw position 94 * is computed as a weighted average of the old raw position and the 95 * computed raw position. Since this still generates some noise, we 96 * compute a new virtual position as a weighted average of the previous 97 * virtual position and the new raw position. The weights are 98 * controlled by the raw change and a noise parameter. The position 99 * is reported as a relative position. 100 */ 101 102 /* 103 * TODO: 104 * 105 * Add support for other drivers of the same type. 106 * 107 * Add support for tapping and two-finger scrolling? The 108 * implementation already detects two fingers, so this should be 109 * relatively easy. 110 * 111 * Implement some of the mouse ioctls? 112 * 113 * Take care of the XXXs. 114 * 115 */ 116 117 #include <sys/cdefs.h> 118 119 #include <sys/param.h> 120 #include <sys/device.h> 121 #include <sys/errno.h> 122 123 #include <sys/ioctl.h> 124 #include <sys/systm.h> 125 #include <sys/tty.h> 126 127 #include <dev/usb/usb.h> 128 #include <dev/usb/usbdi.h> 129 #include <dev/usb/usbdevs.h> 130 #include <dev/usb/uhidev.h> 131 132 #include <dev/wscons/wsconsio.h> 133 #include <dev/wscons/wsmousevar.h> 134 135 /* 136 * Magic numbers. 137 */ 138 139 140 /* The amount of data transfered by the USB device. */ 141 #define PBMS_DATA_LEN 81 142 143 /* The maximum number of sensors. */ 144 #define PBMS_X_SENSORS 26 145 #define PBMS_Y_SENSORS 16 146 #define PBMS_SENSORS (PBMS_X_SENSORS + PBMS_Y_SENSORS) 147 148 /* 149 * Parameters for supported devices. For generality, these parameters 150 * can be different for each device. The meanings of the parameters 151 * are as follows. 152 * 153 * desc: A printable description used for dmesg output. 154 * 155 * noise: Amount of noise in the computed position. This controls 156 * how large a change must be to get reported, and how 157 * large enough changes are smoothed. A good value can 158 * probably only be found experimentally, but something around 159 * 16 seems suitable. 160 * 161 * product: The product ID of the trackpad. 162 * 163 * 164 * threshold: Accumulated changes less than this are ignored. A good 165 * value could be determined experimentally, but 5 is a 166 * reasonable guess. 167 * 168 * vendor: The vendor ID. Currently USB_VENDOR_APPLE for all devices. 169 * 170 * x_factor: Factor used in computations with X-coordinates. If the 171 * x-resolution of the display is x, this should be 172 * (x + 1) / (x_sensors - 1). Other values work fine, but 173 * then the aspect ratio is not necessarily kept. 174 * 175 * x_sensors: The number of sensors in the X-direction. 176 * 177 * y_factor: As x_factors, but for Y-coordinates. 178 * 179 * y_sensors: The number of sensors in the Y-direction. 180 */ 181 182 struct pbms_dev { 183 const char *descr; /* Description of the driver (for dmesg). */ 184 int noise; /* Amount of noise in the computed position. */ 185 int threshold; /* Changes less than this are ignored. */ 186 int x_factor; /* Factor used in computation with X-coordinates. */ 187 int x_sensors; /* The number of X-sensors. */ 188 int y_factor; /* Factor used in computation with Y-coordinates. */ 189 int y_sensors; /* The number of Y-sensors. */ 190 uint16_t product; /* Product ID. */ 191 uint16_t vendor; /* The vendor ID. */ 192 }; 193 194 /* Devices supported by this driver. */ 195 static struct pbms_dev pbms_devices[] = 196 { 197 #define POWERBOOK_TOUCHPAD(inches, prod, x_fact, x_sens, y_fact) \ 198 { \ 199 .descr = #inches " inch PowerBook Trackpad", \ 200 .vendor = USB_VENDOR_APPLE, \ 201 .product = (prod), \ 202 .noise = 16, \ 203 .threshold = 5, \ 204 .x_factor = (x_fact), \ 205 .x_sensors = (x_sens), \ 206 .y_factor = (y_fact), \ 207 .y_sensors = 16 \ 208 } 209 /* 12 inch PowerBooks */ 210 POWERBOOK_TOUCHPAD(12, 0x030a, 69, 16, 52), /* XXX Not tested. */ 211 /* 15 inch PowerBooks */ 212 POWERBOOK_TOUCHPAD(15, 0x020e, 85, 16, 57), /* XXX Not tested. */ 213 POWERBOOK_TOUCHPAD(15, 0x020f, 85, 16, 57), 214 POWERBOOK_TOUCHPAD(15, 0x0215, 90, 15, 107), 215 /* 17 inch PowerBooks */ 216 POWERBOOK_TOUCHPAD(17, 0x020d, 71, 26, 68) /* XXX Not tested. */ 217 #undef POWERBOOK_TOUCHPAD 218 }; 219 220 /* The number of supported devices. */ 221 #define PBMS_NUM_DEVICES (sizeof(pbms_devices) / sizeof(pbms_devices[0])) 222 223 224 /* 225 * Types and prototypes. 226 */ 227 228 229 /* Device data. */ 230 struct pbms_softc { 231 struct uhidev sc_hdev; /* USB parent (got the struct device). */ 232 int is_geyser2; 233 int sc_datalen; 234 int sc_acc[PBMS_SENSORS]; /* Accumulated sensor values. */ 235 unsigned char sc_prev[PBMS_SENSORS]; /* Previous sample. */ 236 unsigned char sc_sample[PBMS_SENSORS]; /* Current sample. */ 237 device_t sc_wsmousedev; /* WSMouse device. */ 238 int sc_noise; /* Amount of noise. */ 239 int sc_theshold; /* Threshold value. */ 240 int sc_x; /* Virtual position in horizontal 241 * direction (wsmouse position). */ 242 int sc_x_factor; /* X-coordinate factor. */ 243 int sc_x_raw; /* X-position of finger on trackpad. */ 244 int sc_x_sensors; /* Number of X-sensors. */ 245 int sc_y; /* Virtual position in vertical direction 246 * (wsmouse position). */ 247 int sc_y_factor; /* Y-coordinate factor. */ 248 int sc_y_raw; /* Y-position of finger on trackpad. */ 249 int sc_y_sensors; /* Number of Y-sensors. */ 250 uint32_t sc_buttons; /* Button state. */ 251 uint32_t sc_status; /* Status flags. */ 252 #define PBMS_ENABLED 1 /* Is the device enabled? */ 253 #define PBMS_DYING 2 /* Is the device dying? */ 254 #define PBMS_VALID 4 /* Is the previous sample valid? */ 255 }; 256 257 258 /* Static function prototypes. */ 259 static void pbms_intr(struct uhidev *, void *, unsigned int); 260 static int pbms_enable(void *); 261 static void pbms_disable(void *); 262 static int pbms_ioctl(void *, unsigned long, void *, int, struct lwp *); 263 static void reorder_sample(struct pbms_softc *, unsigned char *, unsigned char *); 264 static int compute_delta(struct pbms_softc *, int *, int *, int *, uint32_t *); 265 static int detect_pos(int *, int, int, int, int *, int *); 266 static int smooth_pos(int, int, int); 267 268 /* Access methods for wsmouse. */ 269 const struct wsmouse_accessops pbms_accessops = { 270 pbms_enable, 271 pbms_ioctl, 272 pbms_disable, 273 }; 274 275 /* This take cares also of the basic device registration. */ 276 int pbms_match(device_t, cfdata_t, void *); 277 void pbms_attach(device_t, device_t, void *); 278 int pbms_detach(device_t, int); 279 void pbms_childdet(device_t, device_t); 280 int pbms_activate(device_t, enum devact); 281 extern struct cfdriver pbms_cd; 282 CFATTACH_DECL2_NEW(pbms, sizeof(struct pbms_softc), pbms_match, pbms_attach, 283 pbms_detach, pbms_activate, NULL, pbms_childdet); 284 285 /* 286 * Basic driver. 287 */ 288 289 290 /* Try to match the device at some uhidev. */ 291 292 int 293 pbms_match(device_t parent, cfdata_t match, void *aux) 294 { 295 struct uhidev_attach_arg *uha = aux; 296 usb_device_descriptor_t *udd; 297 int i; 298 uint16_t vendor, product; 299 300 /* 301 * We just check if the vendor and product IDs have the magic numbers 302 * we expect. 303 */ 304 if ((udd = usbd_get_device_descriptor(uha->parent->sc_udev)) != NULL) { 305 vendor = UGETW(udd->idVendor); 306 product = UGETW(udd->idProduct); 307 for (i = 0; i < PBMS_NUM_DEVICES; i++) { 308 if (vendor == pbms_devices[i].vendor && 309 product == pbms_devices[i].product) 310 return UMATCH_IFACECLASS; 311 } 312 } 313 return UMATCH_NONE; 314 } 315 316 317 /* Attach the device. */ 318 319 void 320 pbms_attach(device_t parent, device_t self, void *aux) 321 { 322 struct wsmousedev_attach_args a; 323 struct uhidev_attach_arg *uha = aux; 324 struct pbms_dev *pd; 325 struct pbms_softc *sc = device_private(self); 326 usb_device_descriptor_t *udd; 327 int i; 328 uint16_t vendor, product; 329 330 sc->sc_hdev.sc_intr = pbms_intr; 331 sc->sc_hdev.sc_parent = uha->parent; 332 sc->sc_hdev.sc_report_id = uha->reportid; 333 334 sc->is_geyser2 = 0; 335 sc->sc_datalen = PBMS_DATA_LEN; 336 337 /* Fill in device-specific parameters. */ 338 if ((udd = usbd_get_device_descriptor(uha->parent->sc_udev)) != NULL) { 339 product = UGETW(udd->idProduct); 340 vendor = UGETW(udd->idVendor); 341 for (i = 0; i < PBMS_NUM_DEVICES; i++) { 342 pd = &pbms_devices[i]; 343 if (product == pd->product && vendor == pd->vendor) { 344 printf(": %s\n", pd->descr); 345 sc->sc_noise = pd->noise; 346 sc->sc_theshold = pd->threshold; 347 sc->sc_x_factor = pd->x_factor; 348 sc->sc_x_sensors = pd->x_sensors; 349 sc->sc_y_factor = pd->y_factor; 350 sc->sc_y_sensors = pd->y_sensors; 351 if (product == 0x0215) { 352 sc->is_geyser2 = 1; 353 sc->sc_datalen = 64; 354 sc->sc_y_sensors = 9; 355 } 356 break; 357 } 358 } 359 } 360 KASSERT(0 <= sc->sc_x_sensors && sc->sc_x_sensors <= PBMS_X_SENSORS); 361 KASSERT(0 <= sc->sc_y_sensors && sc->sc_y_sensors <= PBMS_Y_SENSORS); 362 363 sc->sc_status = 0; 364 365 a.accessops = &pbms_accessops; 366 a.accesscookie = sc; 367 368 sc->sc_wsmousedev = config_found(self, &a, wsmousedevprint); 369 370 USB_ATTACH_SUCCESS_RETURN; 371 } 372 373 374 /* Detach the device. */ 375 376 void 377 pbms_childdet(device_t self, device_t child) 378 { 379 struct pbms_softc *sc = device_private(self); 380 381 if (sc->sc_wsmousedev == child) 382 sc->sc_wsmousedev = NULL; 383 } 384 385 int 386 pbms_detach(device_t self, int flags) 387 { 388 /* XXX This could not possibly be sufficient! */ 389 return config_detach_children(self, flags); 390 } 391 392 393 /* Activate the device. */ 394 395 int 396 pbms_activate(device_t self, enum devact act) 397 { 398 struct pbms_softc *sc = device_private(self); 399 400 if (act != DVACT_DEACTIVATE) 401 return EOPNOTSUPP; 402 403 sc->sc_status |= PBMS_DYING; 404 return 0; 405 } 406 407 408 /* Enable the device. */ 409 410 static int 411 pbms_enable(void *v) 412 { 413 struct pbms_softc *sc = v; 414 415 /* Check that we are not detaching or already enabled. */ 416 if (sc->sc_status & PBMS_DYING) 417 return EIO; 418 if (sc->sc_status & PBMS_ENABLED) 419 return EBUSY; 420 421 sc->sc_status |= PBMS_ENABLED; 422 sc->sc_status &= ~PBMS_VALID; 423 sc->sc_buttons = 0; 424 memset(sc->sc_sample, 0, sizeof(sc->sc_sample)); 425 426 return uhidev_open(&sc->sc_hdev); 427 } 428 429 430 /* Disable the device. */ 431 432 static void 433 pbms_disable(void *v) 434 { 435 struct pbms_softc *sc = v; 436 437 if (!(sc->sc_status & PBMS_ENABLED)) 438 return; 439 440 sc->sc_status &= ~PBMS_ENABLED; 441 uhidev_close(&sc->sc_hdev); 442 } 443 444 445 /* XXX ioctl not implemented. */ 446 447 static int 448 pbms_ioctl(void *v, unsigned long cmd, void *data, int flag, struct lwp *p) 449 { 450 return EPASSTHROUGH; 451 } 452 453 454 /* 455 * Interrupts & pointer movement. 456 */ 457 458 459 /* Handle interrupts. */ 460 461 void 462 pbms_intr(struct uhidev *addr, void *ibuf, unsigned int len) 463 { 464 struct pbms_softc *sc = (struct pbms_softc *)addr; 465 unsigned char *data; 466 int dx, dy, dz, i, s; 467 uint32_t buttons; 468 469 /* Ignore incomplete data packets. */ 470 if (len != sc->sc_datalen) 471 return; 472 data = ibuf; 473 474 #if 0 475 printf("("); 476 for (i = 0; i < len; i++) 477 printf(" %d", data[i]); 478 printf(" )\n"); 479 #endif 480 481 /* The last byte is 1 if the button is pressed and 0 otherwise. */ 482 buttons = !!data[sc->sc_datalen - 1]; 483 484 /* Everything below assumes that the sample is reordered. */ 485 reorder_sample(sc, sc->sc_sample, data); 486 487 /* Is this the first sample? */ 488 if (!(sc->sc_status & PBMS_VALID)) { 489 sc->sc_status |= PBMS_VALID; 490 sc->sc_x = sc->sc_y = -1; 491 sc->sc_x_raw = sc->sc_y_raw = -1; 492 memcpy(sc->sc_prev, sc->sc_sample, sizeof(sc->sc_prev)); 493 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 494 return; 495 } 496 /* Accumulate the sensor change while keeping it nonnegative. */ 497 for (i = 0; i < PBMS_SENSORS; i++) { 498 sc->sc_acc[i] += 499 (signed char) (sc->sc_sample[i] - sc->sc_prev[i]); 500 if (sc->sc_acc[i] < 0) 501 sc->sc_acc[i] = 0; 502 } 503 memcpy(sc->sc_prev, sc->sc_sample, sizeof(sc->sc_prev)); 504 505 /* Compute change. */ 506 dx = dy = dz = 0; 507 if (!compute_delta(sc, &dx, &dy, &dz, &buttons)) 508 return; 509 510 /* Report to wsmouse. */ 511 if ((dx != 0 || dy != 0 || dz != 0 || buttons != sc->sc_buttons) && 512 sc->sc_wsmousedev != NULL) { 513 s = spltty(); 514 wsmouse_input(sc->sc_wsmousedev, buttons, dx, -dy, dz, 0, 515 WSMOUSE_INPUT_DELTA); 516 splx(s); 517 } 518 sc->sc_buttons = buttons; 519 } 520 521 522 /* 523 * Reorder the sensor values so that all the X-sensors are before the 524 * Y-sensors in the natural order. Note that this might have to be 525 * rewritten if PBMS_X_SENSORS or PBMS_Y_SENSORS change. 526 */ 527 528 static void 529 reorder_sample(struct pbms_softc *sc, unsigned char *to, unsigned char *from) 530 { 531 int i; 532 533 if (sc->is_geyser2) { 534 int j; 535 536 memset(to, 0, PBMS_SENSORS); 537 for (i = 0, j = 19; i < 20; i += 2, j += 3) { 538 to[i] = from[j]; 539 to[i + 1] = from[j + 1]; 540 } 541 for (i = 0, j = 1; i < 9; i += 2, j += 3) { 542 to[PBMS_X_SENSORS + i] = from[j]; 543 to[PBMS_X_SENSORS + i + 1] = from[j + 1]; 544 } 545 } else { 546 for (i = 0; i < 8; i++) { 547 /* X-sensors. */ 548 to[i] = from[5 * i + 2]; 549 to[i + 8] = from[5 * i + 4]; 550 to[i + 16] = from[5 * i + 42]; 551 #if 0 552 /* 553 * XXX This seems to introduce random ventical jumps, so 554 * we ignore these sensors until we figure out their meaning. 555 */ 556 if (i < 2) 557 to[i + 24] = from[5 * i + 44]; 558 #endif /* 0 */ 559 /* Y-sensors. */ 560 to[i + 26] = from[5 * i + 1]; 561 to[i + 34] = from[5 * i + 3]; 562 } 563 } 564 } 565 566 567 /* 568 * Compute the change in x, y and z direction, update the button state 569 * (to simulate more than one button, scrolling etc.), and update the 570 * history. Note that dx, dy, dz and buttons are modified only if 571 * corresponding pressure is detected and should thus be initialised 572 * before the call. Return 0 on error. 573 */ 574 575 /* XXX Could we report something useful in dz? */ 576 577 static int 578 compute_delta(struct pbms_softc *sc, int *dx, int *dy, int *dz, 579 uint32_t * buttons) 580 { 581 int x_det, y_det, x_raw, y_raw, x_fingers, y_fingers, fingers, x, y; 582 583 x_det = detect_pos(sc->sc_acc, sc->sc_x_sensors, sc->sc_theshold, 584 sc->sc_x_factor, &x_raw, &x_fingers); 585 y_det = detect_pos(sc->sc_acc + PBMS_X_SENSORS, sc->sc_y_sensors, 586 sc->sc_theshold, sc->sc_y_factor, 587 &y_raw, &y_fingers); 588 fingers = max(x_fingers, y_fingers); 589 590 /* Check the number of fingers and if we have detected a position. */ 591 if (fingers > 1) { 592 /* More than one finger detected, resetting. */ 593 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 594 sc->sc_x_raw = sc->sc_y_raw = sc->sc_x = sc->sc_y = -1; 595 return 0; 596 } else if (x_det == 0 && y_det == 0) { 597 /* No position detected, resetting. */ 598 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 599 sc->sc_x_raw = sc->sc_y_raw = sc->sc_x = sc->sc_y = -1; 600 } else if (x_det > 0 && y_det > 0) { 601 /* Smooth position. */ 602 if (sc->sc_x_raw >= 0) { 603 sc->sc_x_raw = (3 * sc->sc_x_raw + x_raw) / 4; 604 sc->sc_y_raw = (3 * sc->sc_y_raw + y_raw) / 4; 605 /* 606 * Compute virtual position and change if we already 607 * have a decent position. 608 */ 609 if (sc->sc_x >= 0) { 610 x = smooth_pos(sc->sc_x, sc->sc_x_raw, 611 sc->sc_noise); 612 y = smooth_pos(sc->sc_y, sc->sc_y_raw, 613 sc->sc_noise); 614 *dx = x - sc->sc_x; 615 *dy = y - sc->sc_y; 616 sc->sc_x = x; 617 sc->sc_y = y; 618 } else { 619 /* Initialise virtual position. */ 620 sc->sc_x = sc->sc_x_raw; 621 sc->sc_y = sc->sc_y_raw; 622 } 623 } else { 624 /* Initialise raw position. */ 625 sc->sc_x_raw = x_raw; 626 sc->sc_y_raw = y_raw; 627 } 628 } 629 return 1; 630 } 631 632 633 /* 634 * Compute the new smoothed position from the previous smoothed position 635 * and the raw position. 636 */ 637 638 static int 639 smooth_pos(int pos_old, int pos_raw, int noise) 640 { 641 int ad, delta; 642 643 delta = pos_raw - pos_old; 644 ad = abs(delta); 645 646 /* Too small changes are ignored. */ 647 if (ad < noise / 2) 648 delta = 0; 649 /* A bit larger changes are smoothed. */ 650 else if (ad < noise) 651 delta /= 4; 652 else if (ad < 2 * noise) 653 delta /= 2; 654 655 return pos_old + delta; 656 } 657 658 659 /* 660 * Detect the position of the finger. Returns the total pressure. 661 * The position is returned in pos_ret and the number of fingers 662 * is returned in fingers_ret. The position returned in pos_ret 663 * is in [0, (n_sensors - 1) * factor - 1]. 664 */ 665 666 static int 667 detect_pos(int *sensors, int n_sensors, int threshold, int fact, 668 int *pos_ret, int *fingers_ret) 669 { 670 int i, w, s; 671 672 /* 673 * Compute the number of fingers, total pressure, and weighted 674 * position of the fingers. 675 */ 676 *fingers_ret = 0; 677 w = s = 0; 678 for (i = 0; i < n_sensors; i++) { 679 if (sensors[i] >= threshold) { 680 if (i == 0 || sensors[i - 1] < threshold) 681 *fingers_ret += 1; 682 s += sensors[i]; 683 w += sensors[i] * i; 684 } 685 } 686 687 if (s > 0) 688 *pos_ret = w * fact / s; 689 690 return s; 691 } 692