// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  PCM DRM helpers

   */
  #include <linux/export.h>
  #include <drm/drm_edid.h>
  #include <sound/pcm.h>
  #include <sound/pcm_drm_eld.h>
  
  static const unsigned int eld_rates[] = {
  	32000,
  	44100,
  	48000,
  	88200,
  	96000,
  	176400,
  	192000,
  };
  
  static unsigned int sad_max_channels(const u8 *sad)
  {
  	return 1 + (sad[0] & 7);
  }
  
  static int eld_limit_rates(struct snd_pcm_hw_params *params,
  			   struct snd_pcm_hw_rule *rule)
  {
  	struct snd_interval *r = hw_param_interval(params, rule->var);

  	const struct snd_interval *c;

  	unsigned int rate_mask = 7, i;
  	const u8 *sad, *eld = rule->private;
  
  	sad = drm_eld_sad(eld);
  	if (sad) {

  		c = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_CHANNELS);

  
  		for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3) {
  			unsigned max_channels = sad_max_channels(sad);
  
  			/*
  			 * Exclude SADs which do not include the
  			 * requested number of channels.
  			 */
  			if (c->min <= max_channels)
  				rate_mask |= sad[1];
  		}
  	}
  
  	return snd_interval_list(r, ARRAY_SIZE(eld_rates), eld_rates,
  				 rate_mask);
  }
  
  static int eld_limit_channels(struct snd_pcm_hw_params *params,
  			      struct snd_pcm_hw_rule *rule)
  {
  	struct snd_interval *c = hw_param_interval(params, rule->var);

  	const struct snd_interval *r;

  	struct snd_interval t = { .min = 1, .max = 2, .integer = 1, };
  	unsigned int i;
  	const u8 *sad, *eld = rule->private;
  
  	sad = drm_eld_sad(eld);
  	if (sad) {
  		unsigned int rate_mask = 0;
  
  		/* Convert the rate interval to a mask */

  		r = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);

  		for (i = 0; i < ARRAY_SIZE(eld_rates); i++)
  			if (r->min <= eld_rates[i] && r->max >= eld_rates[i])
  				rate_mask |= BIT(i);
  
  		for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3)
  			if (rate_mask & sad[1])
  				t.max = max(t.max, sad_max_channels(sad));
  	}
  
  	return snd_interval_refine(c, &t);
  }
  
  int snd_pcm_hw_constraint_eld(struct snd_pcm_runtime *runtime, void *eld)
  {
  	int ret;
  
  	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
  				  eld_limit_rates, eld,
  				  SNDRV_PCM_HW_PARAM_CHANNELS, -1);
  	if (ret < 0)
  		return ret;
  
  	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
  				  eld_limit_channels, eld,
  				  SNDRV_PCM_HW_PARAM_RATE, -1);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(snd_pcm_hw_constraint_eld);