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>

2 files changed, 219 insertions, 0 deletions

diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 1a3070b..f299194 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -1105,6 +1105,10 @@ static int snd_pcm_dev_disconnect(struct snd_device *device)
 			break;
 		}
 		snd_unregister_device(devtype, pcm->card, pcm->device);
+		if (pcm->streams[cidx].chmap_kctl) {
+			snd_ctl_remove(pcm->card, pcm->streams[cidx].chmap_kctl);
+			pcm->streams[cidx].chmap_kctl = NULL;
+		}
 	}
  unlock:
 	mutex_unlock(&register_mutex);
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 7ae6719..5651027 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -26,6 +26,7 @@
 #include <linux/export.h>
 #include <sound/core.h>
 #include <sound/control.h>
+#include <sound/tlv.h>
 #include <sound/info.h>
 #include <sound/pcm.h>
 #include <sound/pcm_params.h>
@@ -2302,3 +2303,217 @@ snd_pcm_sframes_t snd_pcm_lib_readv(struct snd_pcm_substream *substream,
 }
 
 EXPORT_SYMBOL(snd_pcm_lib_readv);
+
+/*
+ * standard channel mapping helpers
+ */
+
+/* default channel maps for multi-channel playbacks, up to 8 channels */
+const struct snd_pcm_chmap_elem snd_pcm_std_chmaps[] = {
+	{ .channels = 1,
+	  .map = { SNDRV_CHMAP_FC } },
+	{ .channels = 2,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR } },
+	{ .channels = 4,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
+		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
+	{ .channels = 6,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
+		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
+		   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE } },
+	{ .channels = 8,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
+		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
+		   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
+		   SNDRV_CHMAP_SL, SNDRV_CHMAP_SR } },
+	{ }
+};
+EXPORT_SYMBOL_GPL(snd_pcm_std_chmaps);
+
+/* alternative channel maps with CLFE <-> surround swapped for 6/8 channels */
+const struct snd_pcm_chmap_elem snd_pcm_alt_chmaps[] = {
+	{ .channels = 1,
+	  .map = { SNDRV_CHMAP_FC } },
+	{ .channels = 2,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR } },
+	{ .channels = 4,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
+		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
+	{ .channels = 6,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
+		   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
+		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
+	{ .channels = 8,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
+		   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
+		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
+		   SNDRV_CHMAP_SL, SNDRV_CHMAP_SR } },
+	{ }
+};
+EXPORT_SYMBOL_GPL(snd_pcm_alt_chmaps);
+
+static bool valid_chmap_channels(const struct snd_pcm_chmap *info, int ch)
+{
+	if (ch > info->max_channels)
+		return false;
+	return !info->channel_mask || (info->channel_mask & (1U << ch));
+}
+
+static int pcm_chmap_ctl_info(struct snd_kcontrol *kcontrol,
+			      struct snd_ctl_elem_info *uinfo)
+{
+	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
+
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = 0;
+	uinfo->count = info->max_channels;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = SNDRV_CHMAP_LAST;
+	return 0;
+}
+
+/* get callback for channel map ctl element
+ * stores the channel position firstly matching with the current channels
+ */
+static int pcm_chmap_ctl_get(struct snd_kcontrol *kcontrol,
+			     struct snd_ctl_elem_value *ucontrol)
+{
+	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
+	unsigned int idx = snd_ctl_get_ioffidx(kcontrol, &ucontrol->id);
+	struct snd_pcm_substream *substream;
+	const struct snd_pcm_chmap_elem *map;
+
+	if (snd_BUG_ON(!info->chmap))
+		return -EINVAL;
+	substream = snd_pcm_chmap_substream(info, idx);
+	if (!substream)
+		return -ENODEV;
+	memset(ucontrol->value.integer.value, 0,
+	       sizeof(ucontrol->value.integer.value));
+	if (!substream->runtime)
+		return 0; /* no channels set */
+	for (map = info->chmap; map->channels; map++) {
+		int i;
+		if (map->channels == substream->runtime->channels &&
+		    valid_chmap_channels(info, map->channels)) {
+			for (i = 0; i < map->channels; i++)
+				ucontrol->value.integer.value[i] = map->map[i];
+			return 0;
+		}
+	}
+	return -EINVAL;
+}
+
+/* tlv callback for channel map ctl element
+ * expands the pre-defined channel maps in a form of TLV
+ */
+static int pcm_chmap_ctl_tlv(struct snd_kcontrol *kcontrol, int op_flag,
+			     unsigned int size, unsigned int __user *tlv)
+{
+	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
+	const struct snd_pcm_chmap_elem *map;
+	unsigned int __user *dst;
+	int c, count = 0;
+
+	if (snd_BUG_ON(!info->chmap))
+		return -EINVAL;
+	if (size < 8)
+		return -ENOMEM;
+	if (put_user(SNDRV_CTL_TLVT_CONTAINER, tlv))
+		return -EFAULT;
+	size -= 8;
+	dst = tlv + 2;
+	for (map = info->chmap; map->channels; map++) {
+		int chs_bytes = map->channels * 4;
+		if (!valid_chmap_channels(info, map->channels))
+			continue;
+		if (size < 8)
+			return -ENOMEM;
+		if (put_user(SNDRV_CTL_TLVT_CHMAP_FIXED, dst) ||
+		    put_user(chs_bytes, dst + 1))
+			return -EFAULT;
+		dst += 2;
+		size -= 8;
+		count += 8;
+		if (size < chs_bytes)
+			return -ENOMEM;
+		size -= chs_bytes;
+		count += chs_bytes;
+		for (c = 0; c < map->channels; c++) {
+			if (put_user(map->map[c], dst))
+				return -EFAULT;
+			dst++;
+		}
+	}
+	if (put_user(count, tlv + 1))
+		return -EFAULT;
+	return 0;
+}
+
+static void pcm_chmap_ctl_private_free(struct snd_kcontrol *kcontrol)
+{
+	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
+	info->pcm->streams[info->stream].chmap_kctl = NULL;
+	kfree(info);
+}
+
+/**
+ * snd_pcm_add_chmap_ctls - create channel-mapping control elements
+ * @pcm: the assigned PCM instance
+ * @stream: stream direction
+ * @chmap: channel map elements (for query)
+ * @max_channels: the max number of channels for the stream
+ * @private_value: the value passed to each kcontrol's private_value field
+ * @info_ret: store struct snd_pcm_chmap instance if non-NULL
+ *
+ * Create channel-mapping control elements assigned to the given PCM stream(s).
+ * Returns zero if succeed, or a negative error value.
+ */
+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)
+{
+	struct snd_pcm_chmap *info;
+	struct snd_kcontrol_new knew = {
+		.iface = SNDRV_CTL_ELEM_IFACE_PCM,
+		.access = SNDRV_CTL_ELEM_ACCESS_READ |
+			SNDRV_CTL_ELEM_ACCESS_VOLATILE | /* no notification */
+			SNDRV_CTL_ELEM_ACCESS_TLV_READ |
+			SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK,
+		.info = pcm_chmap_ctl_info,
+		.get = pcm_chmap_ctl_get,
+		.tlv.c = pcm_chmap_ctl_tlv,
+	};
+	int err;
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+	info->pcm = pcm;
+	info->stream = stream;
+	info->chmap = chmap;
+	info->max_channels = max_channels;
+	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
+		knew.name = "Playback Channel Map";
+	else
+		knew.name = "Capture Channel Map";
+	knew.device = pcm->device;
+	knew.count = pcm->streams[stream].substream_count;
+	knew.private_value = private_value;
+	info->kctl = snd_ctl_new1(&knew, info);
+	if (!info->kctl) {
+		kfree(info);
+		return -ENOMEM;
+	}
+	info->kctl->private_free = pcm_chmap_ctl_private_free;
+	err = snd_ctl_add(pcm->card, info->kctl);
+	if (err < 0)
+		return err;
+	pcm->streams[stream].chmap_kctl = info->kctl;
+	if (info_ret)
+		*info_ret = info;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_pcm_add_chmap_ctls);