drivers/media/video/em28xx/em28xx-audio.c

   1 /*
   2  *  Empiatech em28x1 audio extension
   3  *
   4  *  Copyright (C) 2006 Markus Rechberger <mrechberger@gmail.com>
   5  *
   6  *  Copyright (C) 2007 Mauro Carvalho Chehab <mchehab@infradead.org>
   7  *      - Port to work with the in-kernel driver
   8  *      - Several cleanups
   9  *
  10  *  This driver is based on my previous au600 usb pstn audio driver
  11  *  and inherits all the copyrights
  12  *
  13  *  This program is free software; you can redistribute it and/or modify
  14  *  it under the terms of the GNU General Public License as published by
  15  *  the Free Software Foundation; either version 2 of the License, or
  16  *  (at your option) any later version.
  17  *
  18  *  This program is distributed in the hope that it will be useful,
  19  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  *  GNU General Public License for more details.
  22  *
  23  *  You should have received a copy of the GNU General Public License
  24  *  along with this program; if not, write to the Free Software
  25  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  26  */
  27
  28 #include <linux/kernel.h>
  29 #include <linux/usb.h>
  30 #include <linux/init.h>
  31 #include <linux/sound.h>
  32 #include <linux/spinlock.h>
  33 #include <linux/soundcard.h>
  34 #include <linux/slab.h>
  35 #include <linux/vmalloc.h>
  36 #include <linux/proc_fs.h>
  37 #include <linux/module.h>
  38 #include <sound/core.h>
  39 #include <sound/pcm.h>
  40 #include <sound/pcm_params.h>
  41 #include <sound/info.h>
  42 #include <sound/initval.h>
  43 #include <sound/control.h>
  44 #include <sound/tlv.h>
  45 #include <media/v4l2-common.h>
  46 #include "em28xx.h"
  47
  48 static int debug;
  49 module_param(debug, int, 0644);
  50 MODULE_PARM_DESC(debug, "activates debug info");
  51
  52 #define dprintk(fmt, arg...) do {                                       \
  53             if (debug)                                                  \
  54                 printk(KERN_INFO "em28xx-audio %s: " fmt,               \
  55                                   __func__, ##arg);             \
  56         } while (0)
  57
  58 static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;
  59
  60 static int em28xx_deinit_isoc_audio(struct em28xx *dev)
  61 {
  62         int i;
  63
  64         dprintk("Stopping isoc\n");
  65         for (i = 0; i < EM28XX_AUDIO_BUFS; i++) {
  66                 if (!irqs_disabled())
  67                         usb_kill_urb(dev->adev.urb[i]);
  68                 else
  69                         usb_unlink_urb(dev->adev.urb[i]);
  70
  71                 usb_free_urb(dev->adev.urb[i]);
  72                 dev->adev.urb[i] = NULL;
  73
  74                 kfree(dev->adev.transfer_buffer[i]);
  75                 dev->adev.transfer_buffer[i] = NULL;
  76         }
  77
  78         return 0;
  79 }
  80
  81 static void em28xx_audio_isocirq(struct urb *urb)
  82 {
  83         struct em28xx            *dev = urb->context;
  84         int                      i;
  85         unsigned int             oldptr;
  86         int                      period_elapsed = 0;
  87         int                      status;
  88         unsigned char            *cp;
  89         unsigned int             stride;
  90         struct snd_pcm_substream *substream;
  91         struct snd_pcm_runtime   *runtime;
  92
  93         switch (urb->status) {
  94         case 0:             /* success */
  95         case -ETIMEDOUT:    /* NAK */
  96                 break;
  97         case -ECONNRESET:   /* kill */
  98         case -ENOENT:
  99         case -ESHUTDOWN:
 100                 return;
 101         default:            /* error */
 102                 dprintk("urb completition error %d.\n", urb->status);
 103                 break;
 104         }
 105
 106         if (atomic_read(&dev->stream_started) == 0)
 107                 return;
 108
 109         if (dev->adev.capture_pcm_substream) {
 110                 substream = dev->adev.capture_pcm_substream;
 111                 runtime = substream->runtime;
 112                 stride = runtime->frame_bits >> 3;
 113
 114                 for (i = 0; i < urb->number_of_packets; i++) {
 115                         int length =
 116                             urb->iso_frame_desc[i].actual_length / stride;
 117                         cp = (unsigned char *)urb->transfer_buffer +
 118                             urb->iso_frame_desc[i].offset;
 119
 120                         if (!length)
 121                                 continue;
 122
 123                         oldptr = dev->adev.hwptr_done_capture;
 124                         if (oldptr + length >= runtime->buffer_size) {
 125                                 unsigned int cnt =
 126                                     runtime->buffer_size - oldptr;
 127                                 memcpy(runtime->dma_area + oldptr * stride, cp,
 128                                        cnt * stride);
 129                                 memcpy(runtime->dma_area, cp + cnt * stride,
 130                                        length * stride - cnt * stride);
 131                         } else {
 132                                 memcpy(runtime->dma_area + oldptr * stride, cp,
 133                                        length * stride);
 134                         }
 135
 136                         snd_pcm_stream_lock(substream);
 137
 138                         dev->adev.hwptr_done_capture += length;
 139                         if (dev->adev.hwptr_done_capture >=
 140                             runtime->buffer_size)
 141                                 dev->adev.hwptr_done_capture -=
 142                                     runtime->buffer_size;
 143
 144                         dev->adev.capture_transfer_done += length;
 145                         if (dev->adev.capture_transfer_done >=
 146                             runtime->period_size) {
 147                                 dev->adev.capture_transfer_done -=
 148                                     runtime->period_size;
 149                                 period_elapsed = 1;
 150                         }
 151
 152                         snd_pcm_stream_unlock(substream);
 153                 }
 154                 if (period_elapsed)
 155                         snd_pcm_period_elapsed(substream);
 156         }
 157         urb->status = 0;
 158
 159         status = usb_submit_urb(urb, GFP_ATOMIC);
 160         if (status < 0) {
 161                 em28xx_errdev("resubmit of audio urb failed (error=%i)\n",
 162                               status);
 163         }
 164         return;
 165 }
 166
 167 static int em28xx_init_audio_isoc(struct em28xx *dev)
 168 {
 169         int       i, errCode;
 170         const int sb_size = EM28XX_NUM_AUDIO_PACKETS *
 171                             EM28XX_AUDIO_MAX_PACKET_SIZE;
 172
 173         dprintk("Starting isoc transfers\n");
 174
 175         for (i = 0; i < EM28XX_AUDIO_BUFS; i++) {
 176                 struct urb *urb;
 177                 int j, k;
 178
 179                 dev->adev.transfer_buffer[i] = kmalloc(sb_size, GFP_ATOMIC);
 180                 if (!dev->adev.transfer_buffer[i])
 181                         return -ENOMEM;
 182
 183                 memset(dev->adev.transfer_buffer[i], 0x80, sb_size);
 184                 urb = usb_alloc_urb(EM28XX_NUM_AUDIO_PACKETS, GFP_ATOMIC);
 185                 if (!urb) {
 186                         em28xx_errdev("usb_alloc_urb failed!\n");
 187                         for (j = 0; j < i; j++) {
 188                                 usb_free_urb(dev->adev.urb[j]);
 189                                 kfree(dev->adev.transfer_buffer[j]);
 190                         }
 191                         return -ENOMEM;
 192                 }
 193
 194                 urb->dev = dev->udev;
 195                 urb->context = dev;
 196                 urb->pipe = usb_rcvisocpipe(dev->udev, 0x83);
 197                 urb->transfer_flags = URB_ISO_ASAP;
 198                 urb->transfer_buffer = dev->adev.transfer_buffer[i];
 199                 urb->interval = 1;
 200                 urb->complete = em28xx_audio_isocirq;
 201                 urb->number_of_packets = EM28XX_NUM_AUDIO_PACKETS;
 202                 urb->transfer_buffer_length = sb_size;
 203
 204                 for (j = k = 0; j < EM28XX_NUM_AUDIO_PACKETS;
 205                              j++, k += EM28XX_AUDIO_MAX_PACKET_SIZE) {
 206                         urb->iso_frame_desc[j].offset = k;
 207                         urb->iso_frame_desc[j].length =
 208                             EM28XX_AUDIO_MAX_PACKET_SIZE;
 209                 }
 210                 dev->adev.urb[i] = urb;
 211         }
 212
 213         for (i = 0; i < EM28XX_AUDIO_BUFS; i++) {
 214                 errCode = usb_submit_urb(dev->adev.urb[i], GFP_ATOMIC);
 215                 if (errCode) {
 216                         em28xx_deinit_isoc_audio(dev);
 217                         return errCode;
 218                 }
 219         }
 220
 221         return 0;
 222 }
 223
 224 static int snd_pcm_alloc_vmalloc_buffer(struct snd_pcm_substream *subs,
 225                                         size_t size)
 226 {
 227         struct snd_pcm_runtime *runtime = subs->runtime;
 228
 229         dprintk("Allocating vbuffer\n");
 230         if (runtime->dma_area) {
 231                 if (runtime->dma_bytes > size)
 232                         return 0;
 233
 234                 vfree(runtime->dma_area);
 235         }
 236         runtime->dma_area = vmalloc(size);
 237         if (!runtime->dma_area)
 238                 return -ENOMEM;
 239
 240         runtime->dma_bytes = size;
 241
 242         return 0;
 243 }
 244
 245 static struct snd_pcm_hardware snd_em28xx_hw_capture = {
 246         .info = SNDRV_PCM_INFO_BLOCK_TRANSFER |
 247                 SNDRV_PCM_INFO_MMAP           |
 248                 SNDRV_PCM_INFO_INTERLEAVED    |
 249                 SNDRV_PCM_INFO_MMAP_VALID,
 250
 251         .formats = SNDRV_PCM_FMTBIT_S16_LE,
 252
 253         .rates = SNDRV_PCM_RATE_CONTINUOUS | SNDRV_PCM_RATE_KNOT,
 254
 255         .rate_min = 48000,
 256         .rate_max = 48000,
 257         .channels_min = 2,
 258         .channels_max = 2,
 259         .buffer_bytes_max = 62720 * 8,  /* just about the value in usbaudio.c */
 260         .period_bytes_min = 64,         /* 12544/2, */
 261         .period_bytes_max = 12544,
 262         .periods_min = 2,
 263         .periods_max = 98,              /* 12544, */
 264 };
 265
 266 static int snd_em28xx_capture_open(struct snd_pcm_substream *substream)
 267 {
 268         struct em28xx *dev = snd_pcm_substream_chip(substream);
 269         struct snd_pcm_runtime *runtime = substream->runtime;
 270         int ret = 0;
 271
 272         dprintk("opening device and trying to acquire exclusive lock\n");
 273
 274         if (!dev) {
 275                 em28xx_err("BUG: em28xx can't find device struct."
 276                                 " Can't proceed with open\n");
 277                 return -ENODEV;
 278         }
 279
 280         /* Sets volume, mute, etc */
 281
 282         dev->mute = 0;
 283         mutex_lock(&dev->lock);
 284         ret = em28xx_audio_analog_set(dev);
 285         if (ret < 0)
 286                 goto err;
 287
 288         runtime->hw = snd_em28xx_hw_capture;
 289         if (dev->alt == 0 && dev->adev.users == 0) {
 290                 dev->alt = 7;
 291                 dprintk("changing alternate number to 7\n");
 292                 usb_set_interface(dev->udev, 0, 7);
 293         }
 294
 295         dev->adev.users++;
 296         mutex_unlock(&dev->lock);
 297
 298         snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
 299         dev->adev.capture_pcm_substream = substream;
 300         runtime->private_data = dev;
 301
 302         return 0;
 303 err:
 304         mutex_unlock(&dev->lock);
 305
 306         em28xx_err("Error while configuring em28xx mixer\n");
 307         return ret;
 308 }
 309
 310 static int snd_em28xx_pcm_close(struct snd_pcm_substream *substream)
 311 {
 312         struct em28xx *dev = snd_pcm_substream_chip(substream);
 313
 314         dprintk("closing device\n");
 315
 316         dev->mute = 1;
 317         mutex_lock(&dev->lock);
 318         dev->adev.users--;
 319         if (atomic_read(&dev->stream_started) > 0) {
 320                 atomic_set(&dev->stream_started, 0);
 321                 schedule_work(&dev->wq_trigger);
 322         }
 323
 324         em28xx_audio_analog_set(dev);
 325         if (substream->runtime->dma_area) {
 326                 dprintk("freeing\n");
 327                 vfree(substream->runtime->dma_area);
 328                 substream->runtime->dma_area = NULL;
 329         }
 330         mutex_unlock(&dev->lock);
 331
 332         return 0;
 333 }
 334
 335 static int snd_em28xx_hw_capture_params(struct snd_pcm_substream *substream,
 336                                         struct snd_pcm_hw_params *hw_params)
 337 {
 338         unsigned int channels, rate, format;
 339         int ret;
 340
 341         dprintk("Setting capture parameters\n");
 342
 343         ret = snd_pcm_alloc_vmalloc_buffer(substream,
 344                                 params_buffer_bytes(hw_params));
 345         if (ret < 0)
 346                 return ret;
 347         format = params_format(hw_params);
 348         rate = params_rate(hw_params);
 349         channels = params_channels(hw_params);
 350
 351         /* TODO: set up em28xx audio chip to deliver the correct audio format,
 352            current default is 48000hz multiplexed => 96000hz mono
 353            which shouldn't matter since analogue TV only supports mono */
 354         return 0;
 355 }
 356
 357 static int snd_em28xx_hw_capture_free(struct snd_pcm_substream *substream)
 358 {
 359         struct em28xx *dev = snd_pcm_substream_chip(substream);
 360
 361         dprintk("Stop capture, if needed\n");
 362
 363         if (atomic_read(&dev->stream_started) > 0) {
 364                 atomic_set(&dev->stream_started, 0);
 365                 schedule_work(&dev->wq_trigger);
 366         }
 367
 368         return 0;
 369 }
 370
 371 static int snd_em28xx_prepare(struct snd_pcm_substream *substream)
 372 {
 373         struct em28xx *dev = snd_pcm_substream_chip(substream);
 374
 375         dev->adev.hwptr_done_capture = 0;
 376         dev->adev.capture_transfer_done = 0;
 377
 378         return 0;
 379 }
 380
 381 static void audio_trigger(struct work_struct *work)
 382 {
 383         struct em28xx *dev = container_of(work, struct em28xx, wq_trigger);
 384
 385         if (atomic_read(&dev->stream_started)) {
 386                 dprintk("starting capture");
 387                 em28xx_init_audio_isoc(dev);
 388         } else {
 389                 dprintk("stopping capture");
 390                 em28xx_deinit_isoc_audio(dev);
 391         }
 392 }
 393
 394 static int snd_em28xx_capture_trigger(struct snd_pcm_substream *substream,
 395                                       int cmd)
 396 {
 397         struct em28xx *dev = snd_pcm_substream_chip(substream);
 398         int retval = 0;
 399
 400         switch (cmd) {
 401         case SNDRV_PCM_TRIGGER_START:
 402                 atomic_set(&dev->stream_started, 1);
 403                 break;
 404         case SNDRV_PCM_TRIGGER_STOP:
 405                 atomic_set(&dev->stream_started, 1);
 406                 break;
 407         default:
 408                 retval = -EINVAL;
 409         }
 410         schedule_work(&dev->wq_trigger);
 411         return retval;
 412 }
 413
 414 static snd_pcm_uframes_t snd_em28xx_capture_pointer(struct snd_pcm_substream
 415                                                     *substream)
 416 {
 417         unsigned long flags;
 418         struct em28xx *dev;
 419         snd_pcm_uframes_t hwptr_done;
 420
 421         dev = snd_pcm_substream_chip(substream);
 422         spin_lock_irqsave(&dev->adev.slock, flags);
 423         hwptr_done = dev->adev.hwptr_done_capture;
 424         spin_unlock_irqrestore(&dev->adev.slock, flags);
 425
 426         return hwptr_done;
 427 }
 428
 429 static struct page *snd_pcm_get_vmalloc_page(struct snd_pcm_substream *subs,
 430                                              unsigned long offset)
 431 {
 432         void *pageptr = subs->runtime->dma_area + offset;
 433
 434         return vmalloc_to_page(pageptr);
 435 }
 436
 437 /*
 438  * AC97 volume control support
 439  */
 440 static int em28xx_vol_info(struct snd_kcontrol *kcontrol,
 441                                 struct snd_ctl_elem_info *info)
 442 {
 443         info->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
 444         info->count = 2;
 445         info->value.integer.min = 0;
 446         info->value.integer.max = 0x1f;
 447
 448         return 0;
 449 }
 450
 451 /* FIXME: should also add mute controls for each */
 452
 453 static int em28xx_vol_put(struct snd_kcontrol *kcontrol,
 454                                struct snd_ctl_elem_value *value)
 455 {
 456         struct em28xx *dev = snd_kcontrol_chip(kcontrol);
 457         u16 val = (value->value.integer.value[0] & 0x1f) |
 458                   (value->value.integer.value[1] & 0x1f) << 8;
 459         int rc;
 460
 461         mutex_lock(&dev->lock);
 462         rc = em28xx_read_ac97(dev, kcontrol->private_value);
 463         if (rc < 0)
 464                 goto err;
 465
 466         val |= rc & 0x8080;     /* Preserve the mute flags */
 467
 468         rc = em28xx_write_ac97(dev, kcontrol->private_value, val);
 469
 470 err:
 471         mutex_unlock(&dev->lock);
 472         return rc;
 473 }
 474
 475 static int em28xx_vol_get(struct snd_kcontrol *kcontrol,
 476                                struct snd_ctl_elem_value *value)
 477 {
 478         struct em28xx *dev = snd_kcontrol_chip(kcontrol);
 479         int val;
 480
 481         mutex_lock(&dev->lock);
 482         val = em28xx_read_ac97(dev, kcontrol->private_value);
 483         mutex_unlock(&dev->lock);
 484         if (val < 0)
 485                 return val;
 486
 487         value->value.integer.value[0] = val & 0x1f;
 488         value->value.integer.value[1] = (val << 8) & 0x1f;
 489
 490         return 0;
 491 }
 492
 493 static const DECLARE_TLV_DB_SCALE(em28xx_db_scale, -3450, 150, 0);
 494
 495 static int em28xx_cvol_new(struct snd_card *card, struct em28xx *dev,
 496                            char *name, int id)
 497 {
 498         int err;
 499         struct snd_kcontrol *kctl;
 500         struct snd_kcontrol_new tmp = {
 501                 .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
 502                 .name  = name,
 503                 .info  = em28xx_vol_info,
 504                 .get   = em28xx_vol_get,
 505                 .put   = em28xx_vol_put,
 506                 .private_value = id,
 507                 .tlv.p = em28xx_db_scale,
 508         };
 509
 510         kctl = snd_ctl_new1(&tmp, dev);
 511
 512         err = snd_ctl_add(card, kctl);
 513         if (err < 0)
 514                 return err;
 515
 516         return 0;
 517 }
 518
 519
 520 /*
 521  * register/unregister code and data
 522  */
 523 static struct snd_pcm_ops snd_em28xx_pcm_capture = {
 524         .open      = snd_em28xx_capture_open,
 525         .close     = snd_em28xx_pcm_close,
 526         .ioctl     = snd_pcm_lib_ioctl,
 527         .hw_params = snd_em28xx_hw_capture_params,
 528         .hw_free   = snd_em28xx_hw_capture_free,
 529         .prepare   = snd_em28xx_prepare,
 530         .trigger   = snd_em28xx_capture_trigger,
 531         .pointer   = snd_em28xx_capture_pointer,
 532         .page      = snd_pcm_get_vmalloc_page,
 533 };
 534
 535 static int em28xx_audio_init(struct em28xx *dev)
 536 {
 537         struct em28xx_audio *adev = &dev->adev;
 538         struct snd_pcm      *pcm;
 539         struct snd_card     *card;
 540         static int          devnr;
 541         int                 err;
 542
 543         if (dev->has_alsa_audio != 1) {
 544                 /* This device does not support the extension (in this case
 545                    the device is expecting the snd-usb-audio module or
 546                    doesn't have analog audio support at all) */
 547                 return 0;
 548         }
 549
 550         printk(KERN_INFO "em28xx-audio.c: probing for em28x1 "
 551                          "non standard usbaudio\n");
 552         printk(KERN_INFO "em28xx-audio.c: Copyright (C) 2006 Markus "
 553                          "Rechberger\n");
 554
 555         err = snd_card_create(index[devnr], "Em28xx Audio", THIS_MODULE, 0,
 556                               &card);
 557         if (err < 0)
 558                 return err;
 559
 560         spin_lock_init(&adev->slock);
 561         err = snd_pcm_new(card, "Em28xx Audio", 0, 0, 1, &pcm);
 562         if (err < 0) {
 563                 snd_card_free(card);
 564                 return err;
 565         }
 566
 567         snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &snd_em28xx_pcm_capture);
 568         pcm->info_flags = 0;
 569         pcm->private_data = dev;
 570         strcpy(pcm->name, "Empia 28xx Capture");
 571
 572         snd_card_set_dev(card, &dev->udev->dev);
 573         strcpy(card->driver, "Em28xx-Audio");
 574         strcpy(card->shortname, "Em28xx Audio");
 575         strcpy(card->longname, "Empia Em28xx Audio");
 576
 577         INIT_WORK(&dev->wq_trigger, audio_trigger);
 578
 579         if (dev->audio_mode.ac97 != EM28XX_NO_AC97) {
 580                 em28xx_cvol_new(card, dev, "Video", AC97_VIDEO_VOL);
 581                 em28xx_cvol_new(card, dev, "Line In", AC97_LINEIN_VOL);
 582                 em28xx_cvol_new(card, dev, "Phone", AC97_PHONE_VOL);
 583                 em28xx_cvol_new(card, dev, "Microphone", AC97_PHONE_VOL);
 584                 em28xx_cvol_new(card, dev, "CD", AC97_CD_VOL);
 585                 em28xx_cvol_new(card, dev, "AUX", AC97_AUX_VOL);
 586                 em28xx_cvol_new(card, dev, "PCM", AC97_PCM_OUT_VOL);
 587
 588                 em28xx_cvol_new(card, dev, "Master", AC97_MASTER_VOL);
 589                 em28xx_cvol_new(card, dev, "Line", AC97_LINE_LEVEL_VOL);
 590                 em28xx_cvol_new(card, dev, "Mono", AC97_MASTER_MONO_VOL);
 591                 em28xx_cvol_new(card, dev, "LFE", AC97_LFE_MASTER_VOL);
 592                 em28xx_cvol_new(card, dev, "Surround", AC97_SURR_MASTER_VOL);
 593         }
 594
 595         err = snd_card_register(card);
 596         if (err < 0) {
 597                 snd_card_free(card);
 598                 return err;
 599         }
 600         adev->sndcard = card;
 601         adev->udev = dev->udev;
 602
 603         return 0;
 604 }
 605
 606 static int em28xx_audio_fini(struct em28xx *dev)
 607 {
 608         if (dev == NULL)
 609                 return 0;
 610
 611         if (dev->has_alsa_audio != 1) {
 612                 /* This device does not support the extension (in this case
 613                    the device is expecting the snd-usb-audio module or
 614                    doesn't have analog audio support at all) */
 615                 return 0;
 616         }
 617
 618         if (dev->adev.sndcard) {
 619                 snd_card_free(dev->adev.sndcard);
 620                 dev->adev.sndcard = NULL;
 621         }
 622
 623         return 0;
 624 }
 625
 626 static struct em28xx_ops audio_ops = {
 627         .id   = EM28XX_AUDIO,
 628         .name = "Em28xx Audio Extension",
 629         .init = em28xx_audio_init,
 630         .fini = em28xx_audio_fini,
 631 };
 632
 633 static int __init em28xx_alsa_register(void)
 634 {
 635         return em28xx_register_extension(&audio_ops);
 636 }
 637
 638 static void __exit em28xx_alsa_unregister(void)
 639 {
 640         em28xx_unregister_extension(&audio_ops);
 641 }
 642
 643 MODULE_LICENSE("GPL");
 644 MODULE_AUTHOR("Markus Rechberger <mrechberger@gmail.com>");
 645 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@infradead.org>");
 646 MODULE_DESCRIPTION("Em28xx Audio driver");
 647
 648 module_init(em28xx_alsa_register);
 649 module_exit(em28xx_alsa_unregister);