sound/core/pcm_drm_eld.c

   1 /*
   2  *  PCM DRM helpers
   3  *
   4  *   This program is free software; you can redistribute it and/or modify
   5  *   it under the terms of the GNU General Public License version 2 as
   6  *   published by the Free Software Foundation.
   7  */
   8 #include <linux/export.h>
   9 #include <drm/drm_edid.h>
  10 #include <sound/pcm.h>
  11 #include <sound/pcm_drm_eld.h>
  12
  13 static const unsigned int eld_rates[] = {
  14         32000,
  15         44100,
  16         48000,
  17         88200,
  18         96000,
  19         176400,
  20         192000,
  21 };
  22
  23 static unsigned int sad_max_channels(const u8 *sad)
  24 {
  25         return 1 + (sad[0] & 7);
  26 }
  27
  28 static int eld_limit_rates(struct snd_pcm_hw_params *params,
  29                            struct snd_pcm_hw_rule *rule)
  30 {
  31         struct snd_interval *r = hw_param_interval(params, rule->var);
  32         const struct snd_interval *c;
  33         unsigned int rate_mask = 7, i;
  34         const u8 *sad, *eld = rule->private;
  35
  36         sad = drm_eld_sad(eld);
  37         if (sad) {
  38                 c = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_CHANNELS);
  39
  40                 for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3) {
  41                         unsigned max_channels = sad_max_channels(sad);
  42
  43                         /*
  44                          * Exclude SADs which do not include the
  45                          * requested number of channels.
  46                          */
  47                         if (c->min <= max_channels)
  48                                 rate_mask |= sad[1];
  49                 }
  50         }
  51
  52         return snd_interval_list(r, ARRAY_SIZE(eld_rates), eld_rates,
  53                                  rate_mask);
  54 }
  55
  56 static int eld_limit_channels(struct snd_pcm_hw_params *params,
  57                               struct snd_pcm_hw_rule *rule)
  58 {
  59         struct snd_interval *c = hw_param_interval(params, rule->var);
  60         const struct snd_interval *r;
  61         struct snd_interval t = { .min = 1, .max = 2, .integer = 1, };
  62         unsigned int i;
  63         const u8 *sad, *eld = rule->private;
  64
  65         sad = drm_eld_sad(eld);
  66         if (sad) {
  67                 unsigned int rate_mask = 0;
  68
  69                 /* Convert the rate interval to a mask */
  70                 r = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);
  71                 for (i = 0; i < ARRAY_SIZE(eld_rates); i++)
  72                         if (r->min <= eld_rates[i] && r->max >= eld_rates[i])
  73                                 rate_mask |= BIT(i);
  74
  75                 for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3)
  76                         if (rate_mask & sad[1])
  77                                 t.max = max(t.max, sad_max_channels(sad));
  78         }
  79
  80         return snd_interval_refine(c, &t);
  81 }
  82
  83 int snd_pcm_hw_constraint_eld(struct snd_pcm_runtime *runtime, void *eld)
  84 {
  85         int ret;
  86
  87         ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
  88                                   eld_limit_rates, eld,
  89                                   SNDRV_PCM_HW_PARAM_CHANNELS, -1);
  90         if (ret < 0)
  91                 return ret;
  92
  93         ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
  94                                   eld_limit_channels, eld,
  95                                   SNDRV_PCM_HW_PARAM_RATE, -1);
  96
  97         return ret;
  98 }
  99 EXPORT_SYMBOL_GPL(snd_pcm_hw_constraint_eld);