drivers/input/touchscreen/ads7846.c

   1 /*
   2  * ADS7846 based touchscreen and sensor driver
   3  *
   4  * Copyright (c) 2005 David Brownell
   5  *
   6  * Using code from:
   7  *  - corgi_ts.c
   8  *      Copyright (C) 2004-2005 Richard Purdie
   9  *  - omap_ts.[hc], ads7846.h, ts_osk.c
  10  *      Copyright (C) 2002 MontaVista Software
  11  *      Copyright (C) 2004 Texas Instruments
  12  *      Copyright (C) 2005 Dirk Behme
  13  *
  14  *  This program is free software; you can redistribute it and/or modify
  15  *  it under the terms of the GNU General Public License version 2 as
  16  *  published by the Free Software Foundation.
  17  */
  18 #include <linux/device.h>
  19 #include <linux/init.h>
  20 #include <linux/delay.h>
  21 #include <linux/input.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/slab.h>
  24 #include <linux/spi/spi.h>
  25 #include <linux/spi/ads7846.h>
  26
  27 #ifdef  CONFIG_ARM
  28 #include <asm/mach-types.h>
  29 #ifdef  CONFIG_ARCH_OMAP
  30 #include <asm/arch/gpio.h>
  31 #endif
  32 #endif
  33
  34
  35 /*
  36  * This code has been lightly tested on an ads7846.
  37  * Support for ads7843 and ads7845 has only been stubbed in.
  38  *
  39  * Not yet done:  investigate the values reported.  Are x/y/pressure
  40  * event values sane enough for X11?  How accurate are the temperature
  41  * and voltage readings?  (System-specific calibration should support
  42  * accuracy of 0.3 degrees C; otherwise it's 2.0 degrees.)
  43  *
  44  * app note sbaa036 talks in more detail about accurate sampling...
  45  * that ought to help in situations like LCDs inducing noise (which
  46  * can also be helped by using synch signals) and more generally.
  47  */
  48
  49 #define TS_POLL_PERIOD  msecs_to_jiffies(10)
  50
  51 struct ts_event {
  52         /* For portability, we can't read 12 bit values using SPI (which
  53          * would make the controller deliver them as native byteorder u16
  54          * with msbs zeroed).  Instead, we read them as two 8-byte values,
  55          * which need byteswapping then range adjustment.
  56          */
  57         __be16 x;
  58         __be16 y;
  59         __be16 z1, z2;
  60 };
  61
  62 struct ads7846 {
  63         struct input_dev        *input;
  64         char                    phys[32];
  65
  66         struct spi_device       *spi;
  67         u16                     model;
  68         u16                     vref_delay_usecs;
  69         u16                     x_plate_ohms;
  70
  71         struct ts_event         tc;
  72
  73         struct spi_transfer     xfer[8];
  74         struct spi_message      msg;
  75
  76         spinlock_t              lock;
  77         struct timer_list       timer;          /* P: lock */
  78         unsigned                pendown:1;      /* P: lock */
  79         unsigned                pending:1;      /* P: lock */
  80 // FIXME remove "irq_disabled"
  81         unsigned                irq_disabled:1; /* P: lock */
  82 };
  83
  84 /* leave chip selected when we're done, for quicker re-select? */
  85 #if     0
  86 #define CS_CHANGE(xfer) ((xfer).cs_change = 1)
  87 #else
  88 #define CS_CHANGE(xfer) ((xfer).cs_change = 0)
  89 #endif
  90
  91 /*--------------------------------------------------------------------------*/
  92
  93 /* The ADS7846 has touchscreen and other sensors.
  94  * Earlier ads784x chips are somewhat compatible.
  95  */
  96 #define ADS_START               (1 << 7)
  97 #define ADS_A2A1A0_d_y          (1 << 4)        /* differential */
  98 #define ADS_A2A1A0_d_z1         (3 << 4)        /* differential */
  99 #define ADS_A2A1A0_d_z2         (4 << 4)        /* differential */
 100 #define ADS_A2A1A0_d_x          (5 << 4)        /* differential */
 101 #define ADS_A2A1A0_temp0        (0 << 4)        /* non-differential */
 102 #define ADS_A2A1A0_vbatt        (2 << 4)        /* non-differential */
 103 #define ADS_A2A1A0_vaux         (6 << 4)        /* non-differential */
 104 #define ADS_A2A1A0_temp1        (7 << 4)        /* non-differential */
 105 #define ADS_8_BIT               (1 << 3)
 106 #define ADS_12_BIT              (0 << 3)
 107 #define ADS_SER                 (1 << 2)        /* non-differential */
 108 #define ADS_DFR                 (0 << 2)        /* differential */
 109 #define ADS_PD10_PDOWN          (0 << 0)        /* lowpower mode + penirq */
 110 #define ADS_PD10_ADC_ON         (1 << 0)        /* ADC on */
 111 #define ADS_PD10_REF_ON         (2 << 0)        /* vREF on + penirq */
 112 #define ADS_PD10_ALL_ON         (3 << 0)        /* ADC + vREF on */
 113
 114 #define MAX_12BIT       ((1<<12)-1)
 115
 116 /* leave ADC powered up (disables penirq) between differential samples */
 117 #define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
 118         | ADS_12_BIT | ADS_DFR)
 119
 120 static const u8 read_y  = READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON;
 121 static const u8 read_z1 = READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON;
 122 static const u8 read_z2 = READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON;
 123 static const u8 read_x  = READ_12BIT_DFR(x)  | ADS_PD10_PDOWN;  /* LAST */
 124
 125 /* single-ended samples need to first power up reference voltage;
 126  * we leave both ADC and VREF powered
 127  */
 128 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
 129         | ADS_12_BIT | ADS_SER)
 130
 131 static const u8 ref_on = READ_12BIT_DFR(x) | ADS_PD10_ALL_ON;
 132 static const u8 ref_off = READ_12BIT_DFR(y) | ADS_PD10_PDOWN;
 133
 134 /*--------------------------------------------------------------------------*/
 135
 136 /*
 137  * Non-touchscreen sensors only use single-ended conversions.
 138  */
 139
 140 struct ser_req {
 141         u8                      command;
 142         u16                     scratch;
 143         __be16                  sample;
 144         struct spi_message      msg;
 145         struct spi_transfer     xfer[6];
 146 };
 147
 148 static int ads7846_read12_ser(struct device *dev, unsigned command)
 149 {
 150         struct spi_device       *spi = to_spi_device(dev);
 151         struct ads7846          *ts = dev_get_drvdata(dev);
 152         struct ser_req          *req = kzalloc(sizeof *req, SLAB_KERNEL);
 153         int                     status;
 154         int                     sample;
 155         int                     i;
 156
 157         if (!req)
 158                 return -ENOMEM;
 159
 160         INIT_LIST_HEAD(&req->msg.transfers);
 161
 162         /* activate reference, so it has time to settle; */
 163         req->xfer[0].tx_buf = &ref_on;
 164         req->xfer[0].len = 1;
 165         req->xfer[1].rx_buf = &req->scratch;
 166         req->xfer[1].len = 2;
 167
 168         /*
 169          * for external VREF, 0 usec (and assume it's always on);
 170          * for 1uF, use 800 usec;
 171          * no cap, 100 usec.
 172          */
 173         req->xfer[1].delay_usecs = ts->vref_delay_usecs;
 174
 175         /* take sample */
 176         req->command = (u8) command;
 177         req->xfer[2].tx_buf = &req->command;
 178         req->xfer[2].len = 1;
 179         req->xfer[3].rx_buf = &req->sample;
 180         req->xfer[3].len = 2;
 181
 182         /* REVISIT:  take a few more samples, and compare ... */
 183
 184         /* turn off reference */
 185         req->xfer[4].tx_buf = &ref_off;
 186         req->xfer[4].len = 1;
 187         req->xfer[5].rx_buf = &req->scratch;
 188         req->xfer[5].len = 2;
 189
 190         CS_CHANGE(req->xfer[5]);
 191
 192         /* group all the transfers together, so we can't interfere with
 193          * reading touchscreen state; disable penirq while sampling
 194          */
 195         for (i = 0; i < 6; i++)
 196                 spi_message_add_tail(&req->xfer[i], &req->msg);
 197
 198         disable_irq(spi->irq);
 199         status = spi_sync(spi, &req->msg);
 200         enable_irq(spi->irq);
 201
 202         if (req->msg.status)
 203                 status = req->msg.status;
 204         sample = be16_to_cpu(req->sample);
 205         sample = sample >> 4;
 206         kfree(req);
 207
 208         return status ? status : sample;
 209 }
 210
 211 #define SHOW(name) static ssize_t \
 212 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
 213 { \
 214         ssize_t v = ads7846_read12_ser(dev, \
 215                         READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
 216         if (v < 0) \
 217                 return v; \
 218         return sprintf(buf, "%u\n", (unsigned) v); \
 219 } \
 220 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
 221
 222 SHOW(temp0)
 223 SHOW(temp1)
 224 SHOW(vaux)
 225 SHOW(vbatt)
 226
 227 /*--------------------------------------------------------------------------*/
 228
 229 /*
 230  * PENIRQ only kicks the timer.  The timer only reissues the SPI transfer,
 231  * to retrieve touchscreen status.
 232  *
 233  * The SPI transfer completion callback does the real work.  It reports
 234  * touchscreen events and reactivates the timer (or IRQ) as appropriate.
 235  */
 236
 237 static void ads7846_rx(void *ads)
 238 {
 239         struct ads7846          *ts = ads;
 240         struct input_dev        *input_dev = ts->input;
 241         unsigned                Rt;
 242         unsigned                sync = 0;
 243         u16                     x, y, z1, z2;
 244         unsigned long           flags;
 245
 246         /* adjust:  12 bit samples (left aligned), built from
 247          * two 8 bit values writen msb-first.
 248          */
 249         x = be16_to_cpu(ts->tc.x) >> 4;
 250         y = be16_to_cpu(ts->tc.y) >> 4;
 251         z1 = be16_to_cpu(ts->tc.z1) >> 4;
 252         z2 = be16_to_cpu(ts->tc.z2) >> 4;
 253
 254         /* range filtering */
 255         if (x == MAX_12BIT)
 256                 x = 0;
 257
 258         if (x && z1 && ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
 259                 /* compute touch pressure resistance using equation #2 */
 260                 Rt = z2;
 261                 Rt -= z1;
 262                 Rt *= x;
 263                 Rt *= ts->x_plate_ohms;
 264                 Rt /= z1;
 265                 Rt = (Rt + 2047) >> 12;
 266         } else
 267                 Rt = 0;
 268
 269         /* NOTE:  "pendown" is inferred from pressure; we don't rely on
 270          * being able to check nPENIRQ status, or "friendly" trigger modes
 271          * (both-edges is much better than just-falling or low-level).
 272          *
 273          * REVISIT:  some boards may require reading nPENIRQ; it's
 274          * needed on 7843.  and 7845 reads pressure differently...
 275          *
 276          * REVISIT:  the touchscreen might not be connected; this code
 277          * won't notice that, even if nPENIRQ never fires ...
 278          */
 279         if (!ts->pendown && Rt != 0) {
 280                 input_report_key(input_dev, BTN_TOUCH, 1);
 281                 sync = 1;
 282         } else if (ts->pendown && Rt == 0) {
 283                 input_report_key(input_dev, BTN_TOUCH, 0);
 284                 sync = 1;
 285         }
 286
 287         if (Rt) {
 288                 input_report_abs(input_dev, ABS_X, x);
 289                 input_report_abs(input_dev, ABS_Y, y);
 290                 input_report_abs(input_dev, ABS_PRESSURE, Rt);
 291                 sync = 1;
 292         }
 293         if (sync)
 294                 input_sync(input_dev);
 295
 296 #ifdef  VERBOSE
 297         if (Rt || ts->pendown)
 298                 pr_debug("%s: %d/%d/%d%s\n", ts->spi->dev.bus_id,
 299                         x, y, Rt, Rt ? "" : " UP");
 300 #endif
 301
 302         /* don't retrigger while we're suspended */
 303         spin_lock_irqsave(&ts->lock, flags);
 304
 305         ts->pendown = (Rt != 0);
 306         ts->pending = 0;
 307
 308         if (ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
 309                 if (ts->pendown)
 310                         mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
 311                 else if (ts->irq_disabled) {
 312                         ts->irq_disabled = 0;
 313                         enable_irq(ts->spi->irq);
 314                 }
 315         }
 316
 317         spin_unlock_irqrestore(&ts->lock, flags);
 318 }
 319
 320 static void ads7846_timer(unsigned long handle)
 321 {
 322         struct ads7846  *ts = (void *)handle;
 323         int             status = 0;
 324         unsigned long   flags;
 325
 326         spin_lock_irqsave(&ts->lock, flags);
 327         if (!ts->pending) {
 328                 ts->pending = 1;
 329                 if (!ts->irq_disabled) {
 330                         ts->irq_disabled = 1;
 331                         disable_irq(ts->spi->irq);
 332                 }
 333                 status = spi_async(ts->spi, &ts->msg);
 334                 if (status)
 335                         dev_err(&ts->spi->dev, "spi_async --> %d\n",
 336                                         status);
 337         }
 338         spin_unlock_irqrestore(&ts->lock, flags);
 339 }
 340
 341 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
 342 {
 343         ads7846_timer((unsigned long) handle);
 344         return IRQ_HANDLED;
 345 }
 346
 347 /*--------------------------------------------------------------------------*/
 348
 349 static int
 350 ads7846_suspend(struct spi_device *spi, pm_message_t message)
 351 {
 352         struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 353         unsigned long   flags;
 354
 355         spin_lock_irqsave(&ts->lock, flags);
 356
 357         spi->dev.power.power_state = message;
 358
 359         /* are we waiting for IRQ, or polling? */
 360         if (!ts->pendown) {
 361                 if (!ts->irq_disabled) {
 362                         ts->irq_disabled = 1;
 363                         disable_irq(ts->spi->irq);
 364                 }
 365         } else {
 366                 /* polling; force a final SPI completion;
 367                  * that will clean things up neatly
 368                  */
 369                 if (!ts->pending)
 370                         mod_timer(&ts->timer, jiffies);
 371
 372                 while (ts->pendown || ts->pending) {
 373                         spin_unlock_irqrestore(&ts->lock, flags);
 374                         udelay(10);
 375                         spin_lock_irqsave(&ts->lock, flags);
 376                 }
 377         }
 378
 379         /* we know the chip's in lowpower mode since we always
 380          * leave it that way after every request
 381          */
 382
 383         spin_unlock_irqrestore(&ts->lock, flags);
 384         return 0;
 385 }
 386
 387 static int ads7846_resume(struct spi_device *spi)
 388 {
 389         struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 390
 391         ts->irq_disabled = 0;
 392         enable_irq(ts->spi->irq);
 393         spi->dev.power.power_state = PMSG_ON;
 394         return 0;
 395 }
 396
 397 static int __devinit ads7846_probe(struct spi_device *spi)
 398 {
 399         struct ads7846                  *ts;
 400         struct input_dev                *input_dev;
 401         struct ads7846_platform_data    *pdata = spi->dev.platform_data;
 402         struct spi_transfer             *x;
 403         int                             i;
 404         int                             err;
 405
 406         if (!spi->irq) {
 407                 dev_dbg(&spi->dev, "no IRQ?\n");
 408                 return -ENODEV;
 409         }
 410
 411         if (!pdata) {
 412                 dev_dbg(&spi->dev, "no platform data?\n");
 413                 return -ENODEV;
 414         }
 415
 416         /* don't exceed max specified sample rate */
 417         if (spi->max_speed_hz > (125000 * 16)) {
 418                 dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
 419                                 (spi->max_speed_hz/16)/1000);
 420                 return -EINVAL;
 421         }
 422
 423         /* We'd set the wordsize to 12 bits ... except that some controllers
 424          * will then treat the 8 bit command words as 12 bits (and drop the
 425          * four MSBs of the 12 bit result).  Result: inputs must be shifted
 426          * to discard the four garbage LSBs.
 427          */
 428
 429         ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
 430         input_dev = input_allocate_device();
 431         if (!ts || !input_dev) {
 432                 err = -ENOMEM;
 433                 goto err_free_mem;
 434         }
 435
 436         dev_set_drvdata(&spi->dev, ts);
 437         spi->dev.power.power_state = PMSG_ON;
 438
 439         ts->spi = spi;
 440         ts->input = input_dev;
 441
 442         init_timer(&ts->timer);
 443         ts->timer.data = (unsigned long) ts;
 444         ts->timer.function = ads7846_timer;
 445
 446         ts->model = pdata->model ? : 7846;
 447         ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
 448         ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
 449
 450         snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
 451
 452         input_dev->name = "ADS784x Touchscreen";
 453         input_dev->phys = ts->phys;
 454         input_dev->cdev.dev = &spi->dev;
 455
 456         input_dev->evbit[0] = BIT(EV_KEY) | BIT(EV_ABS);
 457         input_dev->keybit[LONG(BTN_TOUCH)] = BIT(BTN_TOUCH);
 458         input_set_abs_params(input_dev, ABS_X,
 459                         pdata->x_min ? : 0,
 460                         pdata->x_max ? : MAX_12BIT,
 461                         0, 0);
 462         input_set_abs_params(input_dev, ABS_Y,
 463                         pdata->y_min ? : 0,
 464                         pdata->y_max ? : MAX_12BIT,
 465                         0, 0);
 466         input_set_abs_params(input_dev, ABS_PRESSURE,
 467                         pdata->pressure_min, pdata->pressure_max, 0, 0);
 468
 469         /* set up the transfers to read touchscreen state; this assumes we
 470          * use formula #2 for pressure, not #3.
 471          */
 472         x = ts->xfer;
 473
 474         /* y- still on; turn on only y+ (and ADC) */
 475         x->tx_buf = &read_y;
 476         x->len = 1;
 477         x++;
 478         x->rx_buf = &ts->tc.y;
 479         x->len = 2;
 480         x++;
 481
 482         /* turn y+ off, x- on; we'll use formula #2 */
 483         if (ts->model == 7846) {
 484                 x->tx_buf = &read_z1;
 485                 x->len = 1;
 486                 x++;
 487                 x->rx_buf = &ts->tc.z1;
 488                 x->len = 2;
 489                 x++;
 490
 491                 x->tx_buf = &read_z2;
 492                 x->len = 1;
 493                 x++;
 494                 x->rx_buf = &ts->tc.z2;
 495                 x->len = 2;
 496                 x++;
 497         }
 498
 499         /* turn y- off, x+ on, then leave in lowpower */
 500         x->tx_buf = &read_x;
 501         x->len = 1;
 502         x++;
 503         x->rx_buf = &ts->tc.x;
 504         x->len = 2;
 505         x++;
 506
 507         CS_CHANGE(x[-1]);
 508
 509         for (i = 0; i < x - ts->xfer; i++)
 510                 spi_message_add_tail(&ts->xfer[i], &ts->msg);
 511         ts->msg.complete = ads7846_rx;
 512         ts->msg.context = ts;
 513
 514         if (request_irq(spi->irq, ads7846_irq,
 515                         SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
 516                         spi->dev.bus_id, ts)) {
 517                 dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
 518                 err = -EBUSY;
 519                 goto err_free_mem;
 520         }
 521
 522         dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
 523
 524         /* take a first sample, leaving nPENIRQ active; avoid
 525          * the touchscreen, in case it's not connected.
 526          */
 527         (void) ads7846_read12_ser(&spi->dev,
 528                           READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
 529
 530         /* ads7843/7845 don't have temperature sensors, and
 531          * use the other sensors a bit differently too
 532          */
 533         if (ts->model == 7846) {
 534                 device_create_file(&spi->dev, &dev_attr_temp0);
 535                 device_create_file(&spi->dev, &dev_attr_temp1);
 536         }
 537         if (ts->model != 7845)
 538                 device_create_file(&spi->dev, &dev_attr_vbatt);
 539         device_create_file(&spi->dev, &dev_attr_vaux);
 540
 541         err = input_register_device(input_dev);
 542         if (err)
 543                 goto err_free_irq;
 544
 545         return 0;
 546
 547  err_free_irq:
 548         free_irq(spi->irq, ts);
 549  err_free_mem:
 550         input_free_device(input_dev);
 551         kfree(ts);
 552         return err;
 553 }
 554
 555 static int __devexit ads7846_remove(struct spi_device *spi)
 556 {
 557         struct ads7846          *ts = dev_get_drvdata(&spi->dev);
 558
 559         ads7846_suspend(spi, PMSG_SUSPEND);
 560         free_irq(ts->spi->irq, ts);
 561         if (ts->irq_disabled)
 562                 enable_irq(ts->spi->irq);
 563
 564         if (ts->model == 7846) {
 565                 device_remove_file(&spi->dev, &dev_attr_temp0);
 566                 device_remove_file(&spi->dev, &dev_attr_temp1);
 567         }
 568         if (ts->model != 7845)
 569                 device_remove_file(&spi->dev, &dev_attr_vbatt);
 570         device_remove_file(&spi->dev, &dev_attr_vaux);
 571
 572         input_unregister_device(ts->input);
 573         kfree(ts);
 574
 575         dev_dbg(&spi->dev, "unregistered touchscreen\n");
 576         return 0;
 577 }
 578
 579 static struct spi_driver ads7846_driver = {
 580         .driver = {
 581                 .name   = "ads7846",
 582                 .bus    = &spi_bus_type,
 583                 .owner  = THIS_MODULE,
 584         },
 585         .probe          = ads7846_probe,
 586         .remove         = __devexit_p(ads7846_remove),
 587         .suspend        = ads7846_suspend,
 588         .resume         = ads7846_resume,
 589 };
 590
 591 static int __init ads7846_init(void)
 592 {
 593         /* grr, board-specific init should stay out of drivers!! */
 594
 595 #ifdef  CONFIG_ARCH_OMAP
 596         if (machine_is_omap_osk()) {
 597                 /* GPIO4 = PENIRQ; GPIO6 = BUSY */
 598                 omap_request_gpio(4);
 599                 omap_set_gpio_direction(4, 1);
 600                 omap_request_gpio(6);
 601                 omap_set_gpio_direction(6, 1);
 602         }
 603         // also TI 1510 Innovator, bitbanging through FPGA
 604         // also Nokia 770
 605         // also Palm Tungsten T2
 606 #endif
 607
 608         // PXA:
 609         // also Dell Axim X50
 610         // also HP iPaq H191x/H192x/H415x/H435x
 611         // also Intel Lubbock (additional to UCB1400; as temperature sensor)
 612         // also Sharp Zaurus C7xx, C8xx (corgi/sheperd/husky)
 613
 614         // Atmel at91sam9261-EK uses ads7843
 615
 616         // also various AMD Au1x00 devel boards
 617
 618         return spi_register_driver(&ads7846_driver);
 619 }
 620 module_init(ads7846_init);
 621
 622 static void __exit ads7846_exit(void)
 623 {
 624         spi_unregister_driver(&ads7846_driver);
 625
 626 #ifdef  CONFIG_ARCH_OMAP
 627         if (machine_is_omap_osk()) {
 628                 omap_free_gpio(4);
 629                 omap_free_gpio(6);
 630         }
 631 #endif
 632
 633 }
 634 module_exit(ads7846_exit);
 635
 636 MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
 637 MODULE_LICENSE("GPL");