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>

include/sound/asound.h

@@ -472,6 +472,36 @@ enum {
 	SNDRV_PCM_TSTAMP_TYPE_LAST = SNDRV_PCM_TSTAMP_TYPE_MONOTONIC,
 };
 
+/* channel positions */
+enum {
+	SNDRV_CHMAP_UNKNOWN = 0,
+	SNDRV_CHMAP_FL,		/* front left */
+	SNDRV_CHMAP_FC,		/* front center */
+	SNDRV_CHMAP_FR,		/* front right */
+	SNDRV_CHMAP_FLC,	/* front left center */
+	SNDRV_CHMAP_FRC,	/* front right center */
+	SNDRV_CHMAP_RL,		/* rear left */
+	SNDRV_CHMAP_RC,		/* rear center */
+	SNDRV_CHMAP_RR,		/* rear right */
+	SNDRV_CHMAP_RLC,	/* rear left center */
+	SNDRV_CHMAP_RRC,	/* rear right center */
+	SNDRV_CHMAP_SL,		/* side left */
+	SNDRV_CHMAP_SR,		/* side right */
+	SNDRV_CHMAP_LFE,	/* LFE */
+	SNDRV_CHMAP_FLW,	/* front left wide */
+	SNDRV_CHMAP_FRW,	/* front right wide */
+	SNDRV_CHMAP_FLH,	/* front left high */
+	SNDRV_CHMAP_FCH,	/* front center high */
+	SNDRV_CHMAP_FRH,	/* front right high */
+	SNDRV_CHMAP_TC,		/* top center */
+	SNDRV_CHMAP_NA,		/* N/A, silent */
+	SNDRV_CHMAP_LAST = SNDRV_CHMAP_NA,
+};
+
+#define SNDRV_CHMAP_POSITION_MASK	0xffff
+#define SNDRV_CHMAP_PHASE_INVERSE	(0x01 << 16)
+#define SNDRV_CHMAP_DRIVER_SPEC		(0x02 << 16)
+
 #define SNDRV_PCM_IOCTL_PVERSION	_IOR('A', 0x00, int)
 #define SNDRV_PCM_IOCTL_INFO		_IOR('A', 0x01, struct snd_pcm_info)
 #define SNDRV_PCM_IOCTL_TSTAMP		_IOW('A', 0x02, int)

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 */

include/sound/tlv.h

@@ -86,4 +86,12 @@
 
 #define TLV_DB_GAIN_MUTE	-9999999
 
+/*
+ * channel-mapping TLV items
+ *  TLV length must match with num_channels
+ */
+#define SNDRV_CTL_TLVT_CHMAP_FIXED	0x101	/* fixed channel position */
+#define SNDRV_CTL_TLVT_CHMAP_VAR	0x102	/* channels freely swappable */
+#define SNDRV_CTL_TLVT_CHMAP_PAIRED	0x103	/* pair-wise swappable */
+
 #endif /* __SOUND_TLV_H */