1 /* $Id: pbms.c,v 1.8 2009/03/01 10:18:30 aymeric 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 /* 137 * Debugging output. 138 */ 139 140 141 /* XXX Should be redone, and its use should be added back. */ 142 143 #ifdef PBMS_DEBUG 144 145 /* 146 * Print the error message (preceded by the driver and function) 147 * specified by the string literal fmt (followed by newline) if 148 * pbmsdebug is greater than n. The macro may only be used in the 149 * scope of sc, which must be castable to struct device *. There must 150 * be at least one vararg. Do not define PBMS_DEBUG on non-C99 151 * compilers. 152 */ 153 154 #define DPRINTFN(n, fmt, ...) \ 155 do { \ 156 if (pbmsdebug > (n)) \ 157 logprintf("%s: %s: " fmt "\n", \ 158 ((struct device *) sc)->dv_xname, \ 159 __func__, __VA_ARGS__); \ 160 } while ( /* CONSTCOND */ 0) 161 162 int pbmsdebug = 0; 163 164 #endif /* PBMS_DEBUG */ 165 166 167 /* 168 * Magic numbers. 169 */ 170 171 172 /* The amount of data transfered by the USB device. */ 173 #define PBMS_DATA_LEN 81 174 175 /* The maximum number of sensors. */ 176 #define PBMS_X_SENSORS 26 177 #define PBMS_Y_SENSORS 16 178 #define PBMS_SENSORS (PBMS_X_SENSORS + PBMS_Y_SENSORS) 179 180 /* 181 * Parameters for supported devices. For generality, these parameters 182 * can be different for each device. The meanings of the parameters 183 * are as follows. 184 * 185 * desc: A printable description used for dmesg output. 186 * 187 * noise: Amount of noise in the computed position. This controls 188 * how large a change must be to get reported, and how 189 * large enough changes are smoothed. A good value can 190 * probably only be found experimentally, but something around 191 * 16 seems suitable. 192 * 193 * product: The product ID of the trackpad. 194 * 195 * 196 * threshold: Accumulated changes less than this are ignored. A good 197 * value could be determined experimentally, but 5 is a 198 * reasonable guess. 199 * 200 * vendor: The vendor ID. Currently USB_VENDOR_APPLE for all devices. 201 * 202 * x_factor: Factor used in computations with X-coordinates. If the 203 * x-resolution of the display is x, this should be 204 * (x + 1) / (x_sensors - 1). Other values work fine, but 205 * then the aspect ratio is not necessarily kept. 206 * 207 * x_sensors: The number of sensors in the X-direction. 208 * 209 * y_factor: As x_factors, but for Y-coordinates. 210 * 211 * y_sensors: The number of sensors in the Y-direction. 212 */ 213 214 struct pbms_dev { 215 const char *descr; /* Description of the driver (for dmesg). */ 216 int noise; /* Amount of noise in the computed position. */ 217 int threshold; /* Changes less than this are ignored. */ 218 int x_factor; /* Factor used in computation with X-coordinates. */ 219 int x_sensors; /* The number of X-sensors. */ 220 int y_factor; /* Factor used in computation with Y-coordinates. */ 221 int y_sensors; /* The number of Y-sensors. */ 222 uint16_t product; /* Product ID. */ 223 uint16_t vendor; /* The vendor ID. */ 224 }; 225 226 /* Devices supported by this driver. */ 227 static struct pbms_dev pbms_devices[] = 228 { 229 #define POWERBOOK_TOUCHPAD(inches, prod, x_fact, x_sens, y_fact) \ 230 { \ 231 .descr = #inches " inch PowerBook Trackpad", \ 232 .vendor = USB_VENDOR_APPLE, \ 233 .product = (prod), \ 234 .noise = 16, \ 235 .threshold = 5, \ 236 .x_factor = (x_fact), \ 237 .x_sensors = (x_sens), \ 238 .y_factor = (y_fact), \ 239 .y_sensors = 16 \ 240 } 241 /* 12 inch PowerBooks */ 242 POWERBOOK_TOUCHPAD(12, 0x030a, 69, 16, 52), /* XXX Not tested. */ 243 /* 15 inch PowerBooks */ 244 POWERBOOK_TOUCHPAD(15, 0x020e, 85, 16, 57), /* XXX Not tested. */ 245 POWERBOOK_TOUCHPAD(15, 0x020f, 85, 16, 57), 246 POWERBOOK_TOUCHPAD(15, 0x0215, 90, 15, 107), 247 /* 17 inch PowerBooks */ 248 POWERBOOK_TOUCHPAD(17, 0x020d, 71, 26, 68) /* XXX Not tested. */ 249 #undef POWERBOOK_TOUCHPAD 250 }; 251 252 /* The number of supported devices. */ 253 #define PBMS_NUM_DEVICES (sizeof(pbms_devices) / sizeof(pbms_devices[0])) 254 255 256 /* 257 * Types and prototypes. 258 */ 259 260 261 /* Device data. */ 262 struct pbms_softc { 263 struct uhidev sc_hdev; /* USB parent (got the struct device). */ 264 int is_geyser2; 265 int sc_datalen; 266 int sc_acc[PBMS_SENSORS]; /* Accumulated sensor values. */ 267 unsigned char sc_prev[PBMS_SENSORS]; /* Previous sample. */ 268 unsigned char sc_sample[PBMS_SENSORS]; /* Current sample. */ 269 struct device *sc_wsmousedev; /* WSMouse device. */ 270 int sc_noise; /* Amount of noise. */ 271 int sc_theshold; /* Threshold value. */ 272 int sc_x; /* Virtual position in horizontal 273 * direction (wsmouse position). */ 274 int sc_x_factor; /* X-coordinate factor. */ 275 int sc_x_raw; /* X-position of finger on trackpad. */ 276 int sc_x_sensors; /* Number of X-sensors. */ 277 int sc_y; /* Virtual position in vertical direction 278 * (wsmouse position). */ 279 int sc_y_factor; /* Y-coordinate factor. */ 280 int sc_y_raw; /* Y-position of finger on trackpad. */ 281 int sc_y_sensors; /* Number of Y-sensors. */ 282 uint32_t sc_buttons; /* Button state. */ 283 uint32_t sc_status; /* Status flags. */ 284 #define PBMS_ENABLED 1 /* Is the device enabled? */ 285 #define PBMS_DYING 2 /* Is the device dying? */ 286 #define PBMS_VALID 4 /* Is the previous sample valid? */ 287 }; 288 289 290 /* Static function prototypes. */ 291 static void pbms_intr(struct uhidev *, void *, unsigned int); 292 static int pbms_enable(void *); 293 static void pbms_disable(void *); 294 static int pbms_ioctl(void *, unsigned long, void *, int, struct lwp *); 295 static void reorder_sample(struct pbms_softc *, unsigned char *, unsigned char *); 296 static int compute_delta(struct pbms_softc *, int *, int *, int *, uint32_t *); 297 static int detect_pos(int *, int, int, int, int *, int *); 298 static int smooth_pos(int, int, int); 299 300 /* Access methods for wsmouse. */ 301 const struct wsmouse_accessops pbms_accessops = { 302 pbms_enable, 303 pbms_ioctl, 304 pbms_disable, 305 }; 306 307 /* This take cares also of the basic device registration. */ 308 USB_DECLARE_DRIVER(pbms); 309 310 311 /* 312 * Basic driver. 313 */ 314 315 316 /* Try to match the device at some uhidev. */ 317 318 int 319 pbms_match(struct device *parent, struct cfdata *match, void *aux) 320 { 321 struct uhidev_attach_arg *uha = aux; 322 usb_device_descriptor_t *udd; 323 int i; 324 uint16_t vendor, product; 325 326 /* 327 * We just check if the vendor and product IDs have the magic numbers 328 * we expect. 329 */ 330 if ((udd = usbd_get_device_descriptor(uha->parent->sc_udev)) != NULL) { 331 vendor = UGETW(udd->idVendor); 332 product = UGETW(udd->idProduct); 333 for (i = 0; i < PBMS_NUM_DEVICES; i++) { 334 if (vendor == pbms_devices[i].vendor && 335 product == pbms_devices[i].product) 336 return UMATCH_IFACECLASS; 337 } 338 } 339 return UMATCH_NONE; 340 } 341 342 343 /* Attach the device. */ 344 345 void 346 pbms_attach(struct device *parent, struct device *self, void *aux) 347 { 348 struct wsmousedev_attach_args a; 349 struct uhidev_attach_arg *uha = aux; 350 struct pbms_dev *pd; 351 struct pbms_softc *sc = device_private(self); 352 usb_device_descriptor_t *udd; 353 int i; 354 uint16_t vendor, product; 355 356 sc->sc_hdev.sc_intr = pbms_intr; 357 sc->sc_hdev.sc_parent = uha->parent; 358 sc->sc_hdev.sc_report_id = uha->reportid; 359 360 sc->is_geyser2 = 0; 361 sc->sc_datalen = PBMS_DATA_LEN; 362 363 /* Fill in device-specific parameters. */ 364 if ((udd = usbd_get_device_descriptor(uha->parent->sc_udev)) != NULL) { 365 product = UGETW(udd->idProduct); 366 vendor = UGETW(udd->idVendor); 367 for (i = 0; i < PBMS_NUM_DEVICES; i++) { 368 pd = &pbms_devices[i]; 369 if (product == pd->product && vendor == pd->vendor) { 370 printf(": %s\n", pd->descr); 371 sc->sc_noise = pd->noise; 372 sc->sc_theshold = pd->threshold; 373 sc->sc_x_factor = pd->x_factor; 374 sc->sc_x_sensors = pd->x_sensors; 375 sc->sc_y_factor = pd->y_factor; 376 sc->sc_y_sensors = pd->y_sensors; 377 if (product == 0x0215) { 378 sc->is_geyser2 = 1; 379 sc->sc_datalen = 64; 380 sc->sc_y_sensors = 9; 381 } 382 break; 383 } 384 } 385 } 386 KASSERT(0 <= sc->sc_x_sensors && sc->sc_x_sensors <= PBMS_X_SENSORS); 387 KASSERT(0 <= sc->sc_y_sensors && sc->sc_y_sensors <= PBMS_Y_SENSORS); 388 389 sc->sc_status = 0; 390 391 a.accessops = &pbms_accessops; 392 a.accesscookie = sc; 393 394 sc->sc_wsmousedev = config_found(self, &a, wsmousedevprint); 395 396 USB_ATTACH_SUCCESS_RETURN; 397 } 398 399 400 /* Detach the device. */ 401 402 int 403 pbms_detach(struct device *self, int flags) 404 { 405 struct pbms_softc *sc = (struct pbms_softc *)self; 406 int ret; 407 408 /* The wsmouse driver does all the work. */ 409 ret = 0; 410 if (sc->sc_wsmousedev != NULL) 411 ret = config_detach(sc->sc_wsmousedev, flags); 412 413 return ret; 414 } 415 416 417 /* Activate the device. */ 418 419 int 420 pbms_activate(device_ptr_t self, enum devact act) 421 { 422 struct pbms_softc *sc = (struct pbms_softc *)self; 423 int ret; 424 425 if (act == DVACT_DEACTIVATE) { 426 ret = 0; 427 if (sc->sc_wsmousedev != NULL) 428 ret = config_deactivate(sc->sc_wsmousedev); 429 sc->sc_status |= PBMS_DYING; 430 return ret; 431 } 432 return EOPNOTSUPP; 433 } 434 435 436 /* Enable the device. */ 437 438 static int 439 pbms_enable(void *v) 440 { 441 struct pbms_softc *sc = v; 442 443 /* Check that we are not detaching or already enabled. */ 444 if (sc->sc_status & PBMS_DYING) 445 return EIO; 446 if (sc->sc_status & PBMS_ENABLED) 447 return EBUSY; 448 449 sc->sc_status |= PBMS_ENABLED; 450 sc->sc_status &= ~PBMS_VALID; 451 sc->sc_buttons = 0; 452 memset(sc->sc_sample, 0, sizeof(sc->sc_sample)); 453 454 return uhidev_open(&sc->sc_hdev); 455 } 456 457 458 /* Disable the device. */ 459 460 static void 461 pbms_disable(void *v) 462 { 463 struct pbms_softc *sc = v; 464 465 if (!(sc->sc_status & PBMS_ENABLED)) 466 return; 467 468 sc->sc_status &= ~PBMS_ENABLED; 469 uhidev_close(&sc->sc_hdev); 470 } 471 472 473 /* XXX ioctl not implemented. */ 474 475 static int 476 pbms_ioctl(void *v, unsigned long cmd, void *data, int flag, struct lwp *p) 477 { 478 return EPASSTHROUGH; 479 } 480 481 482 /* 483 * Interrupts & pointer movement. 484 */ 485 486 487 /* Handle interrupts. */ 488 489 void 490 pbms_intr(struct uhidev *addr, void *ibuf, unsigned int len) 491 { 492 struct pbms_softc *sc = (struct pbms_softc *)addr; 493 unsigned char *data; 494 int dx, dy, dz, i, s; 495 uint32_t buttons; 496 497 /* Ignore incomplete data packets. */ 498 if (len != sc->sc_datalen) 499 return; 500 data = ibuf; 501 502 #if 0 503 printf("("); 504 for (i = 0; i < len; i++) 505 printf(" %d", data[i]); 506 printf(" )\n"); 507 #endif 508 509 /* The last byte is 1 if the button is pressed and 0 otherwise. */ 510 buttons = !!data[sc->sc_datalen - 1]; 511 512 /* Everything below assumes that the sample is reordered. */ 513 reorder_sample(sc, sc->sc_sample, data); 514 515 /* Is this the first sample? */ 516 if (!(sc->sc_status & PBMS_VALID)) { 517 sc->sc_status |= PBMS_VALID; 518 sc->sc_x = sc->sc_y = -1; 519 sc->sc_x_raw = sc->sc_y_raw = -1; 520 memcpy(sc->sc_prev, sc->sc_sample, sizeof(sc->sc_prev)); 521 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 522 return; 523 } 524 /* Accumulate the sensor change while keeping it nonnegative. */ 525 for (i = 0; i < PBMS_SENSORS; i++) { 526 sc->sc_acc[i] += 527 (signed char) (sc->sc_sample[i] - sc->sc_prev[i]); 528 if (sc->sc_acc[i] < 0) 529 sc->sc_acc[i] = 0; 530 } 531 memcpy(sc->sc_prev, sc->sc_sample, sizeof(sc->sc_prev)); 532 533 /* Compute change. */ 534 dx = dy = dz = 0; 535 if (!compute_delta(sc, &dx, &dy, &dz, &buttons)) 536 return; 537 538 /* Report to wsmouse. */ 539 if ((dx != 0 || dy != 0 || dz != 0 || buttons != sc->sc_buttons) && 540 sc->sc_wsmousedev != NULL) { 541 s = spltty(); 542 wsmouse_input(sc->sc_wsmousedev, buttons, dx, -dy, dz, 0, 543 WSMOUSE_INPUT_DELTA); 544 splx(s); 545 } 546 sc->sc_buttons = buttons; 547 } 548 549 550 /* 551 * Reorder the sensor values so that all the X-sensors are before the 552 * Y-sensors in the natural order. Note that this might have to be 553 * rewritten if PBMS_X_SENSORS or PBMS_Y_SENSORS change. 554 */ 555 556 static void 557 reorder_sample(struct pbms_softc *sc, unsigned char *to, unsigned char *from) 558 { 559 int i; 560 561 if (sc->is_geyser2) { 562 int j; 563 564 memset(to, 0, PBMS_SENSORS); 565 for (i = 0, j = 19; i < 20; i += 2, j += 3) { 566 to[i] = from[j]; 567 to[i + 1] = from[j + 1]; 568 } 569 for (i = 0, j = 1; i < 9; i += 2, j += 3) { 570 to[PBMS_X_SENSORS + i] = from[j]; 571 to[PBMS_X_SENSORS + i + 1] = from[j + 1]; 572 } 573 } else { 574 for (i = 0; i < 8; i++) { 575 /* X-sensors. */ 576 to[i] = from[5 * i + 2]; 577 to[i + 8] = from[5 * i + 4]; 578 to[i + 16] = from[5 * i + 42]; 579 #if 0 580 /* 581 * XXX This seems to introduce random ventical jumps, so 582 * we ignore these sensors until we figure out their meaning. 583 */ 584 if (i < 2) 585 to[i + 24] = from[5 * i + 44]; 586 #endif /* 0 */ 587 /* Y-sensors. */ 588 to[i + 26] = from[5 * i + 1]; 589 to[i + 34] = from[5 * i + 3]; 590 } 591 } 592 } 593 594 595 /* 596 * Compute the change in x, y and z direction, update the button state 597 * (to simulate more than one button, scrolling etc.), and update the 598 * history. Note that dx, dy, dz and buttons are modified only if 599 * corresponding pressure is detected and should thus be initialised 600 * before the call. Return 0 on error. 601 */ 602 603 /* XXX Could we report something useful in dz? */ 604 605 static int 606 compute_delta(struct pbms_softc *sc, int *dx, int *dy, int *dz, 607 uint32_t * buttons) 608 { 609 int x_det, y_det, x_raw, y_raw, x_fingers, y_fingers, fingers, x, y; 610 611 x_det = detect_pos(sc->sc_acc, sc->sc_x_sensors, sc->sc_theshold, 612 sc->sc_x_factor, &x_raw, &x_fingers); 613 y_det = detect_pos(sc->sc_acc + PBMS_X_SENSORS, sc->sc_y_sensors, 614 sc->sc_theshold, sc->sc_y_factor, 615 &y_raw, &y_fingers); 616 fingers = max(x_fingers, y_fingers); 617 618 /* Check the number of fingers and if we have detected a position. */ 619 if (fingers > 1) { 620 /* More than one finger detected, resetting. */ 621 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 622 sc->sc_x_raw = sc->sc_y_raw = sc->sc_x = sc->sc_y = -1; 623 return 0; 624 } else if (x_det == 0 && y_det == 0) { 625 /* No position detected, resetting. */ 626 memset(sc->sc_acc, 0, sizeof(sc->sc_acc)); 627 sc->sc_x_raw = sc->sc_y_raw = sc->sc_x = sc->sc_y = -1; 628 } else if (x_det > 0 && y_det > 0) { 629 /* Smooth position. */ 630 if (sc->sc_x_raw >= 0) { 631 sc->sc_x_raw = (3 * sc->sc_x_raw + x_raw) / 4; 632 sc->sc_y_raw = (3 * sc->sc_y_raw + y_raw) / 4; 633 /* 634 * Compute virtual position and change if we already 635 * have a decent position. 636 */ 637 if (sc->sc_x >= 0) { 638 x = smooth_pos(sc->sc_x, sc->sc_x_raw, 639 sc->sc_noise); 640 y = smooth_pos(sc->sc_y, sc->sc_y_raw, 641 sc->sc_noise); 642 *dx = x - sc->sc_x; 643 *dy = y - sc->sc_y; 644 sc->sc_x = x; 645 sc->sc_y = y; 646 } else { 647 /* Initialise virtual position. */ 648 sc->sc_x = sc->sc_x_raw; 649 sc->sc_y = sc->sc_y_raw; 650 } 651 } else { 652 /* Initialise raw position. */ 653 sc->sc_x_raw = x_raw; 654 sc->sc_y_raw = y_raw; 655 } 656 } 657 return 1; 658 } 659 660 661 /* 662 * Compute the new smoothed position from the previous smoothed position 663 * and the raw position. 664 */ 665 666 static int 667 smooth_pos(int pos_old, int pos_raw, int noise) 668 { 669 int ad, delta; 670 671 delta = pos_raw - pos_old; 672 ad = abs(delta); 673 674 /* Too small changes are ignored. */ 675 if (ad < noise / 2) 676 delta = 0; 677 /* A bit larger changes are smoothed. */ 678 else if (ad < noise) 679 delta /= 4; 680 else if (ad < 2 * noise) 681 delta /= 2; 682 683 return pos_old + delta; 684 } 685 686 687 /* 688 * Detect the position of the finger. Returns the total pressure. 689 * The position is returned in pos_ret and the number of fingers 690 * is returned in fingers_ret. The position returned in pos_ret 691 * is in [0, (n_sensors - 1) * factor - 1]. 692 */ 693 694 static int 695 detect_pos(int *sensors, int n_sensors, int threshold, int fact, 696 int *pos_ret, int *fingers_ret) 697 { 698 int i, w, s; 699 700 /* 701 * Compute the number of fingers, total pressure, and weighted 702 * position of the fingers. 703 */ 704 *fingers_ret = 0; 705 w = s = 0; 706 for (i = 0; i < n_sensors; i++) { 707 if (sensors[i] >= threshold) { 708 if (i == 0 || sensors[i - 1] < threshold) 709 *fingers_ret += 1; 710 s += sensors[i]; 711 w += sensors[i] * i; 712 } 713 } 714 715 if (s > 0) 716 *pos_ret = w * fact / s; 717 718 return s; 719 } 720