aboutsummaryrefslogtreecommitdiffstats
path: root/src/lib/gamma-linux-drm.c
blob: 2619e0d0846ce730b4edfca9956bf36c05a31c15 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
/**
 * libgamma -- Display server abstraction layer for gamma ramp adjustments
 * Copyright (C) 2014  Mattias Andrée (maandree@member.fsf.org)
 * 
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef HAVE_LIBGAMMA_METHOD_LINUX_DRM
# error Compiling gamma-linux-drm.c without HAVE_LIBGAMMA_METHOD_LINUX_DRM
#endif

#define _GNU_SOURCE

#include "gamma-linux-drm.h"

#include "libgamma-error.h"
#include "edid.h"

#include <limits.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <grp.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>

#include <xf86drm.h>
#include <xf86drmMode.h>

#ifndef O_CLOEXEC
# define O_CLOEXEC  02000000
#endif
#ifndef NGROUPS_MAX
# define NGROUPS_MAX  65536
#endif
#ifndef PATH_MAX
# define PATH_MAX  4096
#endif



/**
 * Graphics card data for the Direct Rendering Manager adjustment method.
 */
typedef struct libgamma_drm_card_data
{
  /**
   * File descriptor for the connection to the graphics card.
   */
  int fd;
  
  /**
   * The graphics card's mode resources.
   */
  drmModeRes* res;
  
  /**
   * Resources for open connectors.
   */
  drmModeConnector** connectors;
  
  /**
   * Resources for open encoders.
   */
  drmModeEncoder** encoders;
  
} libgamma_drm_card_data_t;



/**
 * Return the capabilities of the adjustment method.
 * 
 * @param  this  The data structure to fill with the method's capabilities.
 */
void libgamma_linux_drm_method_capabilities(libgamma_method_capabilities_t* restrict this)
{
  /* Support for all information except gamma ramp support. */
  this->crtc_information = LIBGAMMA_CRTC_INFO_MACRO_EDID
			 | LIBGAMMA_CRTC_INFO_MACRO_VIEWPORT
			 | LIBGAMMA_CRTC_INFO_MACRO_RAMP
			 | LIBGAMMA_CRTC_INFO_SUBPIXEL_ORDER
			 | LIBGAMMA_CRTC_INFO_ACTIVE
			 | LIBGAMMA_CRTC_INFO_MACRO_CONNECTOR;
  /* DRM supports multiple partitions and CRTC:s but not sites. */
  this->default_site_known = 1;
  this->multiple_sites = 0;
  this->multiple_partitions = 1;
  this->multiple_crtcs = 1;
  /* Partitions are graphics cards in DRM. */
  this->partitions_are_graphics_cards = 1;
  /* Linux does not have system restore capabilities. */
  this->site_restore = 0;
  this->partition_restore = 0;
  this->crtc_restore = 0;
  /* Gamma ramp sizes are identical but not fixed. */
  this->identical_gamma_sizes = 1;
  this->fixed_gamma_size = 0;
  /* Gamma ramp depths are fixed. */
  this->fixed_gamma_depth = 1;
  /* DRM is a real non-faked adjustment method */
  this->real = 1;
  this->fake = 0;
}


/**
 * Initialise an allocated site state.
 * 
 * @param   this    The site state to initialise.
 * @param   site    The site identifier, unless it is `NULL` it must a
 *                  `free`:able. One the state is destroyed the library
 *                  will attempt to free it. There you should not free
 *                  it yourself, and it must not be a string constant
 *                  or allocate on the stack. Note however that it will
 *                  not be free:d if this function fails.
 * @return          Zero on success, otherwise (negative) the value of an
 *                  error identifier provided by this library.
 */
int libgamma_linux_drm_site_initialise(libgamma_site_state_t* restrict this,
				       char* restrict site)
{
  char pathname[PATH_MAX];
  struct stat _attr;
  
  if (site != NULL)
    return LIBGAMMA_NO_SUCH_SITE;
  
  /* Count the number of available graphics cards by
     `stat`:ing their existence in an API filesystem. */
  this->partitions_available = 0;
  for (;;)
    {
      /* Construct pathname of graphics card device. */
      snprintf(pathname, sizeof(pathname) / sizeof(char),
	       DRM_DEV_NAME, DRM_DIR_NAME, (int)(this->partitions_available));
      /* `stat` the graphics card's existence. */
      if (stat(pathname, &_attr))
	break;
      /* Move on to next graphics card. */
      if (this->partitions_available++ > INT_MAX)
	return LIBGAMMA_IMPOSSIBLE_AMOUNT;
    }
  return 0;
}


/**
 * Release all resources held by a site state.
 * 
 * @param  this  The site state.
 */
void libgamma_linux_drm_site_destroy(libgamma_site_state_t* restrict this)
{
  (void) this;
}


/**
 * Restore the gamma ramps all CRTC:s with a site to the system settings.
 * 
 * @param   this  The site state.
 * @return        Zero on success, otherwise (negative) the value of an
 *                error identifier provided by this library.
 */
int libgamma_linux_drm_site_restore(libgamma_site_state_t* restrict this)
{
  (void) this;
  return errno = ENOTSUP, LIBGAMMA_ERRNO_SET;
}


/**
 * Figure out why `open` failed for a graphics card
 * 
 * @param   pathname  The pathname of the error card
 * @return            The error code to report
 */
static int figure_out_card_open_error(const char* pathname)
{
  gid_t supplemental_groups[NGROUPS_MAX];
  struct group* group;
  struct stat attr;
  int i, n;
  
  
  /* Check which the device exists. */
  if ((errno == ENXIO) || (errno == ENODEV))
    return LIBGAMMA_NO_SUCH_PARTITION;
  
  
  /* If we did not get access permission, figure out why. */
  
  if (errno != EACCES)
    /* If we could not figure out what
       went wrong, just return the error
       we got. */
    return LIBGAMMA_ERRNO_SET;
  
#define __test(R, W) ((attr.st_mode & (R | W)) == (R | W))
      
  /* Get permission requirement for the file. */
  if (stat(pathname, &attr) < 0)
    return errno == EACCES ? LIBGAMMA_NO_SUCH_PARTITION : LIBGAMMA_ERRNO_SET;
  
  /* Test owner's, group's and others' permissions. */
  if ((attr.st_uid == geteuid() && __test(S_IRUSR, S_IWUSR)) ||
      (attr.st_gid == getegid() && __test(S_IRGRP, S_IWGRP)) ||
      __test(S_IROTH, S_IWOTH))
    return LIBGAMMA_DEVICE_ACCESS_FAILED;
  
  /* The group should be "video", but perhaps
     it is "root" to restrict users. */
  if (attr.st_gid == 0 /* root group */ || __test(S_IRGRP, S_IWGRP))
    return LIBGAMMA_DEVICE_RESTRICTED;
  
  
  /* Get the user's supplemental group membership list. */
  if ((n = getgroups(NGROUPS_MAX, supplemental_groups)) < 0)
    return LIBGAMMA_ERRNO_SET;
  
  /* Test whether any of the supplemental
     group should be satisfactory. */
  for (i = 0; i < n; i++)
    if (supplemental_groups[i] == attr.st_gid)
      break;
  
  /* If one of the supplemental groups
     should be satisfactory, then we
     do not know anything more than
     that access failed. */
  if (i != n)
    return LIBGAMMA_DEVICE_ACCESS_FAILED;
  
  /* Otherwise, try to get the name of
     the group that is required and
     report the missing group membership. */ 
#if _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _BSD_SOURCE || _SVID_SOURCE || _POSIX_SOURCE
  /* Thread-safe. */
  {
    static __thread char buf[1024]; /* My output of `sysconf(_SC_GETGR_R_SIZE_MAX)`. */
    struct group _grp;
    
    errno = getgrgid_r(attr.st_gid, &_grp, buf, sizeof(buf) / sizeof(char), &group);
    if (errno == ERANGE)
      {
	/* The lenght of the group's name is absurdly long, degrade to thread-unsafe. */
	errno = 0;
	group = getgrgid(attr.st_gid);
      }
    else if (errno)
      return LIBGAMMA_ERRNO_SET;
  }
#else
# ifdef __GCC__
#  pragma GCC diagnostic push
#  pragma GCC diagnostic ignored "-Wcpp"
#  warning figure_out_card_open_error is not thread-safe
#  pragma GCC diagnostic pop
# endif
  /* Not thread-safe. */
  errno = 0;
  group = getgrgid(attr.st_gid);
#endif
  
  libgamma_group_gid = attr.st_gid;
  libgamma_group_name = group != NULL ? group->gr_name : NULL;
  return LIBGAMMA_DEVICE_REQUIRE_GROUP;
#undef __test
}


/**
 * Initialise an allocated partition state.
 * 
 * @param   this       The partition state to initialise.
 * @param   site       The site state for the site that the partition belongs to.
 * @param   partition  The the index of the partition within the site.
 * @return             Zero on success, otherwise (negative) the value of an
 *                     error identifier provided by this library.
 */
int libgamma_linux_drm_partition_initialise(libgamma_partition_state_t* restrict this,
					    libgamma_site_state_t* restrict site, size_t partition)
{
  int rc = 0;
  libgamma_drm_card_data_t* restrict data;
  char pathname[PATH_MAX];
  
  (void) site;
  
  /* Check for partition index overflow. */
  if (partition > INT_MAX)
    return LIBGAMMA_NO_SUCH_PARTITION;
  
  /* Allocate and initialise graphics card data.  */
  this->data = NULL;
  data = malloc(sizeof(libgamma_drm_card_data_t));
  if (data == NULL)
    return LIBGAMMA_ERRNO_SET;
  data->fd = -1;
  data->res = NULL;
  data->encoders = NULL;
  data->connectors = NULL;
  
  /* Get the pathname for the graphics card. */
  snprintf(pathname, sizeof(pathname) / sizeof(char),
	   DRM_DEV_NAME, DRM_DIR_NAME, (int)partition);
  
  /* Acquire access to the graphics card. */
  data->fd = open(pathname, O_RDWR | O_CLOEXEC);
  if (data->fd < 0)
    {
      rc = figure_out_card_open_error(pathname);
      goto fail_data;
    }
  
  /* Acquire mode resources. */
  data->res = drmModeGetResources(data->fd);
  if (data->res == NULL)
    {
      rc = LIBGAMMA_ACQUIRING_MODE_RESOURCES_FAILED;
      goto fail_fd;
    }
  
  /* Get the number of CRTC:s that are available in the partition. */
  if (data->res->count_crtcs < 0)
    {
      rc = LIBGAMMA_NEGATIVE_CRTC_COUNT;
      goto fail_res;
    }
  this->crtcs_available = (size_t)(data->res->count_crtcs);
  this->data = data;
  return 0;
  
 fail_res:   drmModeFreeResources(data->res);
 fail_fd:    close(data->fd);
 fail_data:  free(data);
  return rc;
}


/**
 * Release all connectors and encoders.
 * 
 * @param  this  The graphics card data.
 */
static void release_connectors_and_encoders(libgamma_drm_card_data_t* restrict this)
{
  size_t i, n;
  /* Release individual encoders. */
  if (this->encoders != NULL)
    for (i = 0, n = (size_t)(this->res->count_connectors); i < n; i++)
      if (this->encoders[i] != NULL)
	drmModeFreeEncoder(this->encoders[i]);
  /* Release encoder array. */
  free(this->encoders);
  this->encoders = NULL;
  
  /* Release individual connectors. */
  if (this->connectors != NULL)
    for (i = 0, n = (size_t)(this->res->count_connectors); i < n; i++)
      if (this->connectors[i] != NULL)
	drmModeFreeConnector(this->connectors[i]);
  /* Release connector array. */
  free(this->connectors);
  this->connectors = NULL;
}


/**
 * Release all resources held by a partition state.
 * 
 * @param  this  The partition state.
 */
void libgamma_linux_drm_partition_destroy(libgamma_partition_state_t* restrict this)
{
  libgamma_drm_card_data_t* restrict data = this->data;
  release_connectors_and_encoders(data);
  if (data->res != NULL)  drmModeFreeResources(data->res);
  if (data->fd >= 0)      close(data->fd);
  free(data);
}


/**
 * Restore the gamma ramps all CRTC:s with a partition to the system settings.
 * 
 * @param   this  The partition state.
 * @return        Zero on success, otherwise (negative) the value of an
 *                error identifier provided by this library.
 */
int libgamma_linux_drm_partition_restore(libgamma_partition_state_t* restrict this)
{
  (void) this;
  return errno = ENOTSUP, LIBGAMMA_ERRNO_SET;
}



/**
 * Initialise an allocated CRTC state.
 * 
 * @param   this       The CRTC state to initialise.
 * @param   partition  The partition state for the partition that the CRTC belongs to.
 * @param   crtc       The the index of the CRTC within the site.
 * @return             Zero on success, otherwise (negative) the value of an
 *                     error identifier provided by this library.
 */
int libgamma_linux_drm_crtc_initialise(libgamma_crtc_state_t* restrict this,
				       libgamma_partition_state_t* restrict partition, size_t crtc)
{
  libgamma_drm_card_data_t* restrict card = partition->data;
  
  if (crtc >= partition->crtcs_available)
    return LIBGAMMA_NO_SUCH_CRTC;
  this->data = (void*)(size_t)(card->res->crtcs[crtc]);
  return 0;
}


/**
 * Release all resources held by a CRTC state.
 * 
 * @param  this  The CRTC state.
 */
void libgamma_linux_drm_crtc_destroy(libgamma_crtc_state_t* restrict this)
{
  (void) this;
}


/**
 * Restore the gamma ramps for a CRTC to the system settings for that CRTC.
 * 
 * @param   this  The CRTC state.
 * @return        Zero on success, otherwise (negative) the value of an
 *                error identifier provided by this library.
 */
int libgamma_linux_drm_crtc_restore(libgamma_crtc_state_t* restrict this)
{
  (void) this;
  return errno = ENOTSUP, LIBGAMMA_ERRNO_SET;
}


/**
 * Find the connector that a CRTC belongs to.
 * 
 * @param   this   The CRTC state.
 * @param   error  Output of the error value to store of error report
 *                 fields for data that requires the connector.
'* @return         The CRTC's conncetor, `NULL` on error.
 */
static drmModeConnector* find_connector(libgamma_crtc_state_t* restrict this, int* restrict error)
{
  uint32_t crtc_id = (uint32_t)(size_t)(this->data);
  libgamma_drm_card_data_t* restrict card = this->partition->data;
  size_t i, n = (size_t)(card->res->count_connectors);
  /* Open connectors and encoders if not already opened. */
  if (card->connectors == NULL)
    {
      /* Allocate connector and encoder arrays.
	 We use `calloc` so all non-loaded elements are `NULL` after an error. */
      if ((card->connectors = calloc(n, sizeof(drmModeConnector*))) == NULL)  goto fail;
      if ((card->encoders   = calloc(n, sizeof(drmModeEncoder*)))   == NULL)  goto fail;
      /* Fill connector and encoder arrays. */
      for (i = 0; i < n; i++)
	{
	  /* Get connector, */
	  if ((card->connectors[i] = drmModeGetConnector(card->fd, card->res->connectors[i])) == NULL)
	    goto fail;
	  /* Get encoder if the connector is enabled.
	     If it is disabled it will not have an
	     encoder, which is indicated by the
	     encoder ID being 0. In such case, leave
	     the encoder to be `NULL`. */
	  if ((card->connectors[i]->encoder_id != 0) &&
	      ((card->encoders[i] = drmModeGetEncoder(card->fd, card->connectors[i]->encoder_id)) == NULL))
	    goto fail;
	}
    }
  /* No error has occurred yet. */
  *error = 0;
  /* Find connector. */
  for (i = 0; i < n; i++)
    if ((card->encoders[i] != NULL) && (card->encoders[i]->crtc_id == crtc_id))
      return card->connectors[i];
  /* We did not find the connector. */
  *error = LIBGAMMA_CONNECTOR_UNKNOWN;
  return NULL;
  
 fail:
  /* Report the error that got us here, release
     resouces and exit with `NULL` for failure. */
  *error = errno;
  release_connectors_and_encoders(card);
  return NULL;
}


/**
 * Get the size of the gamma ramps for a CRTC.
 * 
 * @param   out   Instance of a data structure to fill with the information about the CRTC.
 * @param   crtc  The state of the CRTC whose information should be read.
 * @return        The value stored in `out->gamma_size_error`.
 */
static int get_gamma_ramp_size(libgamma_crtc_information_t* restrict out, const libgamma_crtc_state_t* restrict crtc)
{
  libgamma_drm_card_data_t* restrict card = crtc->partition->data;
  uint32_t crtc_id = card->res->crtcs[crtc->crtc];
  drmModeCrtc* restrict crtc_info;
  /* Get CRTC information. */
  errno = 0;
  crtc_info = drmModeGetCrtc(card->fd, crtc_id);
  out->gamma_size_error = crtc_info == NULL ? errno : 0;
  /* Get gamma ramp size. */
  if (out->gamma_size_error == 0)
    {
      /* Store gamma ramp size. */
      out->red_gamma_size = out->green_gamma_size = out->blue_gamma_size = (size_t)(crtc_info->gamma_size);
      /* Sanity check gamma ramp size. */
      out->gamma_size_error = crtc_info->gamma_size < 2 ? LIBGAMMA_SINGLETON_GAMMA_RAMP : 0;
      /* Release CRTC information. */
      drmModeFreeCrtc(crtc_info);
    }
  return out->gamma_size_error;
}


/**
 * Get the a monitor's subpixel order
 * 
 * @param  out        Instance of a data structure to fill with the information about the CRTC.
 * @param  connector  The connector.
 */
static void get_subpixel_order(libgamma_crtc_information_t* restrict out,
			       const drmModeConnector* restrict connector)
{
#define __select(value)					    \
  case DRM_MODE_SUBPIXEL_##value:			    \
    out->subpixel_order = LIBGAMMA_SUBPIXEL_ORDER_##value;  \
    break
  
  switch (connector->subpixel)
    {
    __select (UNKNOWN);
    __select (HORIZONTAL_RGB);
    __select (HORIZONTAL_BGR);
    __select (VERTICAL_RGB);
    __select (VERTICAL_BGR);
    __select (NONE);
    default:
      out->subpixel_order_error = LIBGAMMA_SUBPIXEL_ORDER_NOT_RECOGNISED;
      break;
    }
  
#undef __select
}


/**
 * Get a connector's type
 * 
 * @param  out                  Instance of a data structure to fill with the information about the CRTC.
 * @param  connector            The connector.
 * @param  connector_name_base  Output for the basename of the connector.
 */
static void get_connector_type(libgamma_crtc_information_t* restrict out,
			       const drmModeConnector* restrict connector,
			       const char** restrict connector_name_base)
{
#define __select(type, name)				   \
  case DRM_MODE_CONNECTOR_##type:			   \
    out->connector_type = LIBGAMMA_CONNECTOR_TYPE_##type;  \
    *connector_name_base = name;			   \
    break
  
  /* These may not have been included by <xf86drmMode.h>,
     but they should be available. Becuase we define them
     outself, it is best to test them last. */
#ifndef DRM_MODE_CONNECTOR_VIRTUAL
# define DRM_MODE_CONNECTOR_VIRTUAL  15
#endif
#ifndef DRM_MODE_CONNECTOR_DSI
# define DRM_MODE_CONNECTOR_DSI  16
#endif
  
  /* Translate connector type from DRM to libgamma
     and store connector basename. */
  switch (connector->connector_type)
    {
    __select (Unknown,      "Unknown"  );
    __select (VGA,          "VGA"      );
    __select (DVII,         "DVI-I"    );
    __select (DVID,         "DVI-D"    );
    __select (DVIA,         "DVI-A"    );
    __select (Composite,    "Composite");
    __select (SVIDEO,       "SVIDEO"   );
    __select (LVDS,         "LVDS"     );
    __select (Component,    "Component");
    __select (9PinDIN,      "DIN"      );
    __select (DisplayPort,  "DP"       );
    __select (HDMIA,        "HDMI-A"   );
    __select (HDMIB,        "HDMI-B"   );
    __select (TV,           "TV"       );
    __select (eDP,          "eDP"      );
    __select (VIRTUAL,      "VIRTUAL"  );
    __select (DSI,          "DSI"      );
    default:
      out->connector_type_error = LIBGAMMA_CONNECTOR_TYPE_NOT_RECOGNISED;
      out->connector_name_error = LIBGAMMA_CONNECTOR_TYPE_NOT_RECOGNISED;
      break;
    }
  
#undef __select
}


/**
 * Read information from the CRTC's conncetor.
 * 
 * @param   crtc       The state of the CRTC whose information should be read.
 * @param   out        Instance of a data structure to fill with the information about the CRTC.
 * @param   connector  The CRTC's connector.
 * @param   fields     OR:ed identifiers for the information about the CRTC that should be read.
 * @return             Non-zero if at least on error occured.
 */
static int read_connector_data(libgamma_crtc_state_t* restrict crtc, libgamma_crtc_information_t* restrict out,
			       const drmModeConnector* restrict connector, int32_t fields)
{
  const char* connector_name_base = NULL;
  
  /* Get some information that does not require too much work. */
  if ((fields & (LIBGAMMA_CRTC_INFO_MACRO_ACTIVE | LIBGAMMA_CRTC_INFO_MACRO_CONNECTOR)))
    {
      /* Get whether or not a monitor is plugged in. */
      out->active = connector->connection == DRM_MODE_CONNECTED;
      out->active_error = connector->connection == DRM_MODE_UNKNOWNCONNECTION ? LIBGAMMA_STATE_UNKNOWN : 0;
      if (out->active == 0)
	{
	  if ((fields & (LIBGAMMA_CRTC_INFO_MACRO_VIEWPORT | LIBGAMMA_CRTC_INFO_SUBPIXEL_ORDER)))
	    out->width_mm_error = out->height_mm_error = out->subpixel_order_error = LIBGAMMA_NOT_CONNECTED;
	  goto not_connected;
	}
      
      /* Get viewport dimension. */
      out->width_mm = connector->mmWidth;
      out->height_mm = connector->mmHeight;
      
      /* Get subpixel order. */
      get_subpixel_order(out, connector);
      
    not_connected:
      
      /* Get connector type. */
      get_connector_type(out, connector, &connector_name_base);
    }
  
  /* Get the connector's name. */
  if ((fields & LIBGAMMA_CRTC_INFO_CONNECTOR_NAME) && (out->connector_name_error == 0))
    {
      libgamma_drm_card_data_t* restrict card = crtc->partition->data;
      uint32_t type = connector->connector_type;
      size_t i, n = (size_t)(card->res->count_connectors), c = 0;
      
      /* Allocate memory for the name of the connector. */
      out->connector_name = malloc((strlen(connector_name_base) + 12) * sizeof(char));
      if (out->connector_name == NULL)
	return out->connector_name_error = errno;
      
      /* Get the number of connectors with the same type on the same graphics card. */
      for (i = 0; (i < n) && (card->connectors[i] != connector); i++)
	if (card->connectors[i]->connector_type == type)
	  c++;
      
      /* Construct and store connect name that is unique to the graphics card. */
      sprintf(out->connector_name, "%s-%" PRIu32, connector_name_base, (uint32_t)(c + 1));
    }
  
  /* Did something go wrong? */
  return out->subpixel_order_error | out->active_error | out->connector_name_error;
}


/**
 * Get the extended display identification data for a monitor.
 * 
 * @param   crtc       The CRTC state.
 * @param   out        Instance of a data structure to fill with the information about the CRTC.
 * @param   connector  The CRTC's connector.
 * @reutnr             Non-zero on error.
 */
static int get_edid(libgamma_crtc_state_t* restrict crtc,
		    libgamma_crtc_information_t* restrict out, drmModeConnector* connector)
{
  libgamma_drm_card_data_t* restrict card = crtc->partition->data;
  int prop_n = connector->count_props;
  int prop_i;
  drmModePropertyRes* restrict prop;
  drmModePropertyBlobRes* restrict blob;
  
  /* Test all properies on the connector. */
  for (prop_i = 0; prop_i < prop_n; prop_i++)
    {
      /* Get output property, */
      if ((prop = drmModeGetProperty(card->fd, connector->props[prop_i])) == NULL)
	continue;
      /* Is this property the EDID? */
      if (!strcmp(prop->name, "EDID"))
	{
	  /* Get the property value. */
	  if ((blob = drmModeGetPropertyBlob(card->fd, (uint32_t)(connector->prop_values[prop_i]))) == NULL)
	    return drmModeFreeProperty(prop), out->edid_error = LIBGAMMA_PROPERTY_VALUE_QUERY_FAILED;
	  if (blob->data != NULL)
	    {
	      /* Get and store the length of the EDID. */
	      out->edid_length = blob->length;
	      /* Allocate memory for a copy of the EDID that is under our memory control. */
	      if ((out->edid = malloc(out->edid_length * sizeof(unsigned char))) == NULL)
		out->edid_error = errno;
	      else
		/* Copy the EDID so we can free resources that got us here. */
		memcpy(out->edid, blob->data, (size_t)(out->edid_length) * sizeof(char));
	      /* Free the propriety value and the propery. */
	      drmModeFreePropertyBlob(blob);
	      drmModeFreeProperty(prop);
	      /* Were we successful? */
	      return out->edid == NULL;
	    }
	  /* Free the propriety value. */
	  drmModeFreePropertyBlob(blob);
	}
      /* Free the propriety. */
      drmModeFreeProperty(prop);
    }
  /* If we get here, we did not find a EDID. */
  return out->edid_error = LIBGAMMA_EDID_NOT_FOUND;
}


/**
 * Read information about a CRTC.
 * 
 * @param   this    Instance of a data structure to fill with the information about the CRTC.
 * @param   crtc    The state of the CRTC whose information should be read.
 * @param   fields  OR:ed identifiers for the information about the CRTC that should be read.
 * @return          Zero on success, -1 on error. On error refer to the error reports in `this`.
 */
int libgamma_linux_drm_get_crtc_information(libgamma_crtc_information_t* restrict this,
					    libgamma_crtc_state_t* restrict crtc, int32_t fields)
{
#define _E(FIELD)  ((fields & FIELD) ? LIBGAMMA_CRTC_INFO_NOT_SUPPORTED : 0)
  int e = 0;
  drmModeConnector* restrict connector;
  int require_connector;
  int free_edid;
  int error;
  
  
  /* Wipe all error indicators. */
  memset(this, 0, sizeof(libgamma_crtc_information_t));
  
  /* We need to free the EDID after us if it is not explicitly requested.  */
  free_edid = (fields & LIBGAMMA_CRTC_INFO_EDID) == 0;
  
  /* Figure out whether we require the connector to get all information we want. */
  require_connector = fields & (LIBGAMMA_CRTC_INFO_MACRO_ACTIVE | LIBGAMMA_CRTC_INFO_MACRO_CONNECTOR);
  
  /* If we are not interested in the connector or monitor, jump. */
  if (require_connector == 0)
    goto cont;
  /* Find connector. */
  if ((connector = find_connector(crtc, &error)) == NULL)
    {
      perror("connector not found");
      abort();
      /* Store reported error in affected fields. */
      e |= this->width_mm_error       = this->height_mm_error
	 = this->connector_type_error = this->subpixel_order_error
	 = this->active_error         = this->connector_name_error
	 = this->edid_error           = this->gamma_error
	 = this->width_mm_edid_error  = this->height_mm_edid_error = error;
      goto cont;
    }
  
  /* Read connector data and monitor data, excluding EDID.. */
  e |= read_connector_data(crtc, this, connector, fields);
  
  /* If we do not want any EDID information, jump. */
  if ((fields & LIBGAMMA_CRTC_INFO_MACRO_EDID) == 0)
    goto cont;
  /* If there is not monitor that report error in EDID related fields. */
  if (this->active_error || (this->active == 0))
    {
      e |= this->edid_error = this->gamma_error
	 = this->width_mm_edid_error = this->height_mm_edid_error
	 = LIBGAMMA_NOT_CONNECTED;
      goto cont;
    }
  /* Get EDID. */
  e |= get_edid(crtc, this, connector);
  if (this->edid == NULL)
    {
      this->gamma_error = this->width_mm_edid_error = this->height_mm_edid_error = this->edid_error;
      goto cont;
    }
  /* Parse EDID. */
  if ((fields & (LIBGAMMA_CRTC_INFO_MACRO_EDID ^ LIBGAMMA_CRTC_INFO_EDID)))
    e |= libgamma_parse_edid(this, fields);
  
 cont:
  /* Get gamma ramp size. */
  e |= (fields & LIBGAMMA_CRTC_INFO_GAMMA_SIZE) ? get_gamma_ramp_size(this, crtc) : 0;
  /* Store gamma ramp depth. */
  this->gamma_depth = 16;
  /* X RandR does not support quering gamma ramp support. */
  e |= this->gamma_support_error = _E(LIBGAMMA_CRTC_INFO_GAMMA_SUPPORT);
  
  /* Free the EDID after us. */
  if (free_edid)
    {
      free(this->edid);
      this->edid = NULL;
    }
  
  return e ? -1 : 0;
#undef _E
}


/**
 * Get the current gamma ramps for a CRTC, 16-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to fill with the current values.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
int libgamma_linux_drm_crtc_get_gamma_ramps16(libgamma_crtc_state_t* restrict this,
					      libgamma_gamma_ramps16_t* restrict ramps)
{
  libgamma_drm_card_data_t* restrict card = this->partition->data;
  int r;
#ifdef DEBUG
  /* Gamma ramp sizes are identical but not fixed. */
  if ((ramps->red_size != ramps->green_size) ||
      (ramps->red_size != ramps->blue_size))
    return LIBGAMMA_MIXED_GAMMA_RAMP_SIZE;
#endif
  /* Read current gamma ramps. */
  r = drmModeCrtcGetGamma(card->fd, (uint32_t)(size_t)(this->data), (uint32_t)(ramps->red_size),
			  ramps->red, ramps->green, ramps->blue);
  return r ? LIBGAMMA_GAMMA_RAMP_READ_FAILED : 0;
}


/**
 * Set the gamma ramps for a CRTC, 16-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to apply.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
int libgamma_linux_drm_crtc_set_gamma_ramps16(libgamma_crtc_state_t* restrict this,
					      libgamma_gamma_ramps16_t ramps)
{
  libgamma_drm_card_data_t* restrict card = this->partition->data;
  int r;
#ifdef DEBUG
  /* Gamma ramp sizes are identical but not fixed. */
  if ((ramps.red_size != ramps.green_size) ||
      (ramps.red_size != ramps.blue_size))
    return LIBGAMMA_MIXED_GAMMA_RAMP_SIZE;
#endif
  
  /* Apply gamma ramps. */
  r = drmModeCrtcSetGamma(card->fd, (uint32_t)(size_t)(this->data),
			  (uint32_t)(ramps.red_size), ramps.red, ramps.green, ramps.blue);
  /* Check for errors. */
  if (r)
    switch (errno)
      {
      case EACCES:
      case EAGAIN:
      case EIO:
	/* Permission denied errors must be ignored, because we do not
	 * have permission to do this while a display server is active.
	 * We are also checking for some other error codes just in case. */
      case EBUSY:
      case EINPROGRESS:
	/* It is hard to find documentation for DRM (in fact all of this is
	 * just based on the functions names and some testing,) perhaps we
	 * could get this if we are updating to fast. */
	break;
      case EBADF:
      case ENODEV:
      case ENXIO:
	/* XXX: I have not actually tested removing my graphics card or,
	 *      monitor but I imagine either of these is what would happen. */
	return LIBGAMMA_GRAPHICS_CARD_REMOVED;

      default:
	return LIBGAMMA_ERRNO_SET;
      }
  return 0;
}