This patch is mostly just a copy paste from Russel King's generic
patchs[1] for the same thing. The patche is included only for testing
purposes. Do not merge!

[1] http://lists.freedesktop.org/archives/dri-devel/2015-April/080525.html

Signed-off-by: Jyri Sarha <jsa...@ti.com>
---
 sound/soc/codecs/hdmi-codec.c | 104 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 103 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/hdmi-codec.c b/sound/soc/codecs/hdmi-codec.c
index c208cef..2d26ce8 100644
--- a/sound/soc/codecs/hdmi-codec.c
+++ b/sound/soc/codecs/hdmi-codec.c
@@ -78,6 +78,103 @@ static int hdmi_codec_new_stream(struct snd_pcm_substream 
*substream,
        return ret;
 }
 
+static const uint8_t *eld_sad(const uint8_t *eld)
+{
+       unsigned int ver, mnl;
+
+       ver = (eld[DRM_ELD_VER] & DRM_ELD_VER_MASK) >> DRM_ELD_VER_SHIFT;
+       if (ver != 2 && ver != 31)
+               return NULL;
+
+       mnl = drm_eld_mnl(eld);
+       if (mnl > 16)
+               return NULL;
+
+       return eld + DRM_ELD_CEA_SAD(mnl, 0);
+}
+
+static const unsigned int eld_rates[] = {
+       32000,
+       44100,
+       48000,
+       88200,
+       96000,
+       176400,
+       192000,
+};
+
+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);
+       unsigned int rate_mask = 7, i;
+       const u8 *sad, *eld = rule->private;
+
+       sad = eld_sad(eld);
+       if (sad) {
+               for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3) {
+                       unsigned channels = 1 + (sad[0] & 7);
+
+                       /*
+                        * Exclude SADs which do not include the
+                        * requested number of channels.
+                        */
+                       if (params_channels(params) == 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 *var = hw_param_interval(params, rule->var);
+       struct snd_interval t = { .min = 1, .max = 2, .integer = 1, };
+       unsigned int i, j;
+       const u8 *sad, *eld = rule->private;
+       int rate = params_rate(params);
+
+       sad = eld_sad(eld);
+       if (!sad)
+               return 0;
+
+       for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3) {
+               for (j = 0; j < ARRAY_SIZE(eld_rates); j++) {
+                       if ((sad[1] & (1<<j)) && rate == eld_rates[j]) {
+                               switch (sad[0] & 0x78) {
+                               case 0x08:
+                                       t.max = max(t.max, (sad[0] & 7) + 1u);
+                                       break;
+                               }
+                       }
+               }
+       }
+
+       return snd_interval_refine(var, &t);
+}
+
+static int hdmi_codec_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_RATE,
+                                 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_CHANNELS,
+                                 SNDRV_PCM_HW_PARAM_RATE, -1);
+
+       return ret;
+}
+
 static int hdmi_codec_startup(struct snd_pcm_substream *substream,
                              struct snd_soc_dai *dai)
 {
@@ -104,7 +201,12 @@ static int hdmi_codec_startup(struct snd_pcm_substream 
*substream,
        if (hcp->hcd.ops->get_eld) {
                hcp->eld = hcp->hcd.ops->get_eld(hcp->hcd.dev);
 
-               /* Call snd_pcm_hw_constraint_eld here */
+               if (hcp->eld) {
+                       ret = hdmi_codec_constraint_eld(substream->runtime,
+                                                       hcp->eld);
+                       if (ret)
+                               return ret;
+               }
        }
        return 0;
 }
-- 
1.9.1

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