ALSA: pcm: add DRM ELD helper

Add a helper for the EDID like data structure, which is typically passed
from a HDMI adapter to its associated audio driver.  This informs the
audio driver of the capabilities of the attached HDMI sink.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/include/sound/pcm_drm_eld.h b/include/sound/pcm_drm_eld.h
new file mode 100644 (file)
index 0000000..93357b2
--- /dev/null
+++ b/include/sound/pcm_drm_eld.h
@@ -0,0 +1,6 @@
+#ifndef __SOUND_PCM_DRM_ELD_H
+#define __SOUND_PCM_DRM_ELD_H
+
+int snd_pcm_hw_constraint_eld(struct snd_pcm_runtime *runtime, void *eld);
+
+#endif

diff --git a/sound/core/Kconfig b/sound/core/Kconfig
index 313f22e9d929d8f5dbd039d224a529788b22c635..b534c8a6046b1f83e6a86ce3f8366932fe264b1f 100644 (file)
--- a/sound/core/Kconfig
+++ b/sound/core/Kconfig
@@ -6,6 +6,9 @@ config SND_PCM
        tristate
        select SND_TIMER
 
+config SND_PCM_ELD
+       bool
+
 config SND_DMAENGINE_PCM
        tristate
 

diff --git a/sound/core/Makefile b/sound/core/Makefile
index 4daf2f58261ced168d2bd616bea7eeb1732e33e8..591b49157b4d49847d572e59f44ad56dbeb8fbe8 100644 (file)
--- a/sound/core/Makefile
+++ b/sound/core/Makefile
@@ -13,6 +13,7 @@ snd-$(CONFIG_SND_JACK)          += jack.o
 snd-pcm-y := pcm.o pcm_native.o pcm_lib.o pcm_timer.o pcm_misc.o \
                pcm_memory.o memalloc.o
 snd-pcm-$(CONFIG_SND_DMA_SGBUF) += sgbuf.o
+snd-pcm-$(CONFIG_SND_PCM_ELD) += pcm_drm_eld.o
 
 # for trace-points
 CFLAGS_pcm_lib.o := -I$(src)

diff --git a/sound/core/pcm_drm_eld.c b/sound/core/pcm_drm_eld.c
new file mode 100644 (file)
index 0000000..e70379f
--- /dev/null
+++ b/sound/core/pcm_drm_eld.c
@@ -0,0 +1,99 @@
+/*
+ *  PCM DRM helpers
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License version 2 as
+ *   published by the Free Software Foundation.
+ */
+#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);
+       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(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);
+       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(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);