ALSA: PCM: channel mapping API implementation

This patch implements the basic data types for the standard channel
mapping API handling.

- The definitions of the channel positions and the new TLV types are
  added in sound/asound.h and sound/tlv.h, so that they can be
  referred from user-space.

- Introduced a new helper function snd_pcm_add_chmap_ctls() to create
  control elements representing the channel maps for each PCM
  (sub)stream.

- Some standard pre-defined channel maps are provided for
  convenience.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 48 insertions, 0 deletions

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index cdca2ab1e711..669c85a7fb03 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -437,6 +437,7 @@ struct snd_pcm_str {
         struct snd_info_entry *proc_xrun_debug_entry;
 #endif
 #endif
+        struct snd_kcontrol *chmap_kctl; /* channel-mapping controls */
 };
 
 struct snd_pcm {
@@ -1086,4 +1087,51 @@ static inline const char *snd_pcm_stream_str(struct snd_pcm_substream *substream
                 return "Capture";
 }
 
+/*
+ * PCM channel-mapping control API
+ */
+/* array element of channel maps */
+struct snd_pcm_chmap_elem {
+        unsigned char channels;
+        unsigned char map[15];
+};
+
+/* channel map information; retrieved via snd_kcontrol_chip() */
+struct snd_pcm_chmap {
+        struct snd_pcm *pcm;    /* assigned PCM instance */
+        int stream;             /* PLAYBACK or CAPTURE */
+        struct snd_kcontrol *kctl;
+        const struct snd_pcm_chmap_elem *chmap;
+        unsigned int max_channels;
+        unsigned int channel_mask;      /* optional: active channels bitmask */
+        void *private_data;     /* optional: private data pointer */
+};
+
+/* get the PCM substream assigned to the given chmap info */
+static inline struct snd_pcm_substream *
+snd_pcm_chmap_substream(struct snd_pcm_chmap *info, unsigned int idx)
+{
+        struct snd_pcm_substream *s;
+        for (s = info->pcm->streams[info->stream].substream; s; s = s->next)
+                if (s->number == idx)
+                        return s;
+        return NULL;
+}
+
+/* ALSA-standard channel maps (RL/RR prior to C/LFE) */
+extern const struct snd_pcm_chmap_elem snd_pcm_std_chmaps[];
+/* Other world's standard channel maps (C/LFE prior to RL/RR) */
+extern const struct snd_pcm_chmap_elem snd_pcm_alt_chmaps[];
+
+/* bit masks to be passed to snd_pcm_chmap.channel_mask field */
+#define SND_PCM_CHMAP_MASK_24   ((1U << 2) | (1U << 4))
+#define SND_PCM_CHMAP_MASK_246  (SND_PCM_CHMAP_MASK_24 | (1U << 6))
+#define SND_PCM_CHMAP_MASK_2468 (SND_PCM_CHMAP_MASK_246 | (1U << 8))
+
+int snd_pcm_add_chmap_ctls(struct snd_pcm *pcm, int stream,
+                           const struct snd_pcm_chmap_elem *chmap,
+                           int max_channels,
+                           unsigned long private_value,
+                           struct snd_pcm_chmap **info_ret);
+
 #endif /* __SOUND_PCM_H */