root/sound/core/pcm_drm_eld.c

DEFINITIONS

1. sad_max_channels
2. eld_limit_rates
3. eld_limit_channels
4. snd_pcm_hw_constraint_eld

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  PCM DRM helpers
   4  */
   5 #include <linux/export.h>
   6 #include <drm/drm_edid.h>
   7 #include <sound/pcm.h>
   8 #include <sound/pcm_drm_eld.h>
   9 
  10 static const unsigned int eld_rates[] = {
  11         32000,
  12         44100,
  13         48000,
  14         88200,
  15         96000,
  16         176400,
  17         192000,
  18 };
  19 
  20 static unsigned int sad_max_channels(const u8 *sad)
  21 {
  22         return 1 + (sad[0] & 7);
  23 }
  24 
  25 static int eld_limit_rates(struct snd_pcm_hw_params *params,
  26                            struct snd_pcm_hw_rule *rule)
  27 {
  28         struct snd_interval *r = hw_param_interval(params, rule->var);
  29         const struct snd_interval *c;
  30         unsigned int rate_mask = 7, i;
  31         const u8 *sad, *eld = rule->private;
  32 
  33         sad = drm_eld_sad(eld);
  34         if (sad) {
  35                 c = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_CHANNELS);
  36 
  37                 for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3) {
  38                         unsigned max_channels = sad_max_channels(sad);
  39 
  40                         /*
  41                          * Exclude SADs which do not include the
  42                          * requested number of channels.
  43                          */
  44                         if (c->min <= max_channels)
  45                                 rate_mask |= sad[1];
  46                 }
  47         }
  48 
  49         return snd_interval_list(r, ARRAY_SIZE(eld_rates), eld_rates,
  50                                  rate_mask);
  51 }
  52 
  53 static int eld_limit_channels(struct snd_pcm_hw_params *params,
  54                               struct snd_pcm_hw_rule *rule)
  55 {
  56         struct snd_interval *c = hw_param_interval(params, rule->var);
  57         const struct snd_interval *r;
  58         struct snd_interval t = { .min = 1, .max = 2, .integer = 1, };
  59         unsigned int i;
  60         const u8 *sad, *eld = rule->private;
  61 
  62         sad = drm_eld_sad(eld);
  63         if (sad) {
  64                 unsigned int rate_mask = 0;
  65 
  66                 /* Convert the rate interval to a mask */
  67                 r = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);
  68                 for (i = 0; i < ARRAY_SIZE(eld_rates); i++)
  69                         if (r->min <= eld_rates[i] && r->max >= eld_rates[i])
  70                                 rate_mask |= BIT(i);
  71 
  72                 for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3)
  73                         if (rate_mask & sad[1])
  74                                 t.max = max(t.max, sad_max_channels(sad));
  75         }
  76 
  77         return snd_interval_refine(c, &t);
  78 }
  79 
  80 int snd_pcm_hw_constraint_eld(struct snd_pcm_runtime *runtime, void *eld)
  81 {
  82         int ret;
  83 
  84         ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
  85                                   eld_limit_rates, eld,
  86                                   SNDRV_PCM_HW_PARAM_CHANNELS, -1);
  87         if (ret < 0)
  88                 return ret;
  89 
  90         ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
  91                                   eld_limit_channels, eld,
  92                                   SNDRV_PCM_HW_PARAM_RATE, -1);
  93 
  94         return ret;
  95 }
  96 EXPORT_SYMBOL_GPL(snd_pcm_hw_constraint_eld);