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>

5 files changed, 305 insertions, 0 deletions

diff --git a/include/sound/asound.h b/include/sound/asound.h
index 0876a1e76aef..376e75632e07 100644
--- a/include/sound/asound.h
+++ b/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)
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 */
diff --git a/include/sound/tlv.h b/include/sound/tlv.h
index a64d8fe3f855..28c65e1ada21 100644
--- a/include/sound/tlv.h
+++ b/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 */
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 1a3070b4e5b5..f2991940b271 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 7ae671923393..565102705eda 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);