PCM: Implement snd_pcm_query_chmaps_from_hw()

This is a function similar like snd_pcm_query_chmaps() but performs
the query without a PCM handle.  The card, device and substream
numbers are passed as well as stream direction.

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

2 files changed, 79 insertions, 41 deletions

diff --git a/include/pcm.h b/include/pcm.h
index ba72a497..8ae4cd8b 100644
--- a/include/pcm.h
+++ b/include/pcm.h
@@ -526,6 +526,9 @@ typedef struct snd_pcm_chmap_query {
 
 
 snd_pcm_chmap_query_t **snd_pcm_query_chmaps(snd_pcm_t *pcm);
+snd_pcm_chmap_query_t **snd_pcm_query_chmaps_from_hw(int card, int dev,
+						     int subdev,
+						     snd_pcm_stream_t stream);
 void snd_pcm_free_chmaps(snd_pcm_chmap_query_t **maps);
 snd_pcm_chmap_t *snd_pcm_get_chmap(snd_pcm_t *pcm);
 int snd_pcm_set_chmap(snd_pcm_t *pcm, const snd_pcm_chmap_t *map);
diff --git a/src/pcm/pcm_hw.c b/src/pcm/pcm_hw.c
index 4044d874..d24949a0 100644
--- a/src/pcm/pcm_hw.c
+++ b/src/pcm/pcm_hw.c
@@ -1006,80 +1006,82 @@ static int snd_pcm_hw_htimestamp(snd_pcm_t *pcm, snd_pcm_uframes_t *avail,
 	return 0;
 }
 
-static void fill_chmap_ctl_id(snd_pcm_t *pcm, snd_ctl_elem_id_t *id)
+static void __fill_chmap_ctl_id(snd_ctl_elem_id_t *id, int dev, int subdev,
+				int stream)
 {
-	snd_pcm_hw_t *hw = pcm->private_data;
 	snd_ctl_elem_id_set_interface(id, SND_CTL_ELEM_IFACE_PCM);
-	if (pcm->stream == SND_PCM_STREAM_PLAYBACK)
+	if (stream == SND_PCM_STREAM_PLAYBACK)
 		snd_ctl_elem_id_set_name(id, "Playback Channel Map");
 	else
 		snd_ctl_elem_id_set_name(id, "Capture Channel Map");
-	snd_ctl_elem_id_set_device(id, hw->device);
-	snd_ctl_elem_id_set_index(id, hw->subdevice);
-}
-
-static int is_chmap_type(int type)
-{
-	return (type >= SND_CTL_TLVT_CHMAP_FIXED &&
-		type <= SND_CTL_TLVT_CHMAP_PAIRED);
-}
-
-enum { CHMAP_CTL_QUERY, CHMAP_CTL_GET, CHMAP_CTL_SET };
-
-static int chmap_caps(snd_pcm_hw_t *hw, int type)
-{
-	if (hw->chmap_caps & (1 << type))
-		return 1;
-	if (hw->chmap_caps & (1 << (type + 8)))
-		return 0;
-	return 1;
+	snd_ctl_elem_id_set_device(id, dev);
+	snd_ctl_elem_id_set_index(id, subdev);
 }
 
-static void chmap_caps_set_ok(snd_pcm_hw_t *hw, int type)
+static void fill_chmap_ctl_id(snd_pcm_t *pcm, snd_ctl_elem_id_t *id)
 {
-	hw->chmap_caps |= (1 << type);
+	snd_pcm_hw_t *hw = pcm->private_data;
+	return __fill_chmap_ctl_id(id, hw->device, hw->subdevice, pcm->stream);
 }
 
-static void chmap_caps_set_error(snd_pcm_hw_t *hw, int type)
+static int is_chmap_type(int type)
 {
-	hw->chmap_caps |= (1 << (type + 8));
+	return (type >= SND_CTL_TLVT_CHMAP_FIXED &&
+		type <= SND_CTL_TLVT_CHMAP_PAIRED);
 }
 
-static snd_pcm_chmap_query_t **snd_pcm_hw_query_chmaps(snd_pcm_t *pcm)
+/**
+ * \!brief Query the available channel maps
+ * \param card the card number
+ * \param dev the PCM device number
+ * \param subdev the PCM substream index
+ * \param stream the direction of PCM stream
+ * \return the NULL-terminated array of integer pointers, or NULL at error.
+ *
+ * This function works like snd_pcm_query_chmaps() but it takes the card,
+ * device, substream and stream numbers instead of the already opened
+ * snd_pcm_t instance, so that you can query available channel maps of
+ * a PCM before actually opening it.
+ *
+ * As the parameters stand, the query is performed only to the hw PCM
+ * devices, not the abstracted PCM object in alsa-lib.
+ */
+snd_pcm_chmap_query_t **
+snd_pcm_query_chmaps_from_hw(int card, int dev, int subdev,
+			     snd_pcm_stream_t stream)
 {
-	snd_pcm_hw_t *hw = pcm->private_data;
 	snd_ctl_t *ctl;
 	snd_ctl_elem_id_t *id;
 	unsigned int tlv[256], *start;
 	snd_pcm_chmap_query_t **map;
 	int i, ret, nums;
 
-	if (!chmap_caps(hw, CHMAP_CTL_QUERY))
-		return NULL;
-
-	ret = snd_ctl_hw_open(&ctl, NULL, hw->card, 0);
+	ret = snd_ctl_hw_open(&ctl, NULL, card, 0);
 	if (ret < 0) {
 		SYSMSG("Cannot open the associated CTL\n");
-		goto error;
+		return NULL;
 	}
 
 	snd_ctl_elem_id_alloca(&id);
-	fill_chmap_ctl_id(pcm, id);
+	__fill_chmap_ctl_id(id, dev, subdev, stream);
 	ret = snd_ctl_elem_tlv_read(ctl, id, tlv, sizeof(tlv));
 	snd_ctl_close(ctl);
 	if (ret < 0) {
 		SYSMSG("Cannot read Channel Map TLV\n");
-		goto error;
+		return NULL;
 	}
 
 #if 0
 	for (i = 0; i < 32; i++)
 		fprintf(stderr, "%02x: %08x\n", i, tlv[i]);
 #endif
+	/* FIXME: the parser below assumes that the TLV only contains
+	 * chmap-related blocks
+	 */
 	if (tlv[0] != SND_CTL_TLVT_CONTAINER) {
 		if (!is_chmap_type(tlv[0])) {
 			SYSMSG("Invalid TLV type %d\n", tlv[0]);
-			goto error;
+			return NULL;
 		}
 		start = tlv;
 		nums = 1;
@@ -1092,7 +1094,7 @@ static snd_pcm_chmap_query_t **snd_pcm_hw_query_chmaps(snd_pcm_t *pcm)
 		for (p = start; size > 0; ) {
 			if (!is_chmap_type(p[0])) {
 				SYSMSG("Invalid TLV type %d\n", p[0]);
-				goto error;
+				return NULL;
 			}
 			nums++;
 			size -= p[1] + 8;
@@ -1113,12 +1115,45 @@ static snd_pcm_chmap_query_t **snd_pcm_hw_query_chmaps(snd_pcm_t *pcm)
 		memcpy(map[i]->map.pos, start + 2, start[1]);
 		start += start[1] / 4 + 2;
 	}
-	chmap_caps_set_ok(hw, CHMAP_CTL_QUERY);
 	return map;
+}
+
+enum { CHMAP_CTL_QUERY, CHMAP_CTL_GET, CHMAP_CTL_SET };
 
- error:
-	chmap_caps_set_error(hw, CHMAP_CTL_QUERY);
-	return NULL;
+static int chmap_caps(snd_pcm_hw_t *hw, int type)
+{
+	if (hw->chmap_caps & (1 << type))
+		return 1;
+	if (hw->chmap_caps & (1 << (type + 8)))
+		return 0;
+	return 1;
+}
+
+static void chmap_caps_set_ok(snd_pcm_hw_t *hw, int type)
+{
+	hw->chmap_caps |= (1 << type);
+}
+
+static void chmap_caps_set_error(snd_pcm_hw_t *hw, int type)
+{
+	hw->chmap_caps |= (1 << (type + 8));
+}
+
+static snd_pcm_chmap_query_t **snd_pcm_hw_query_chmaps(snd_pcm_t *pcm)
+{
+	snd_pcm_hw_t *hw = pcm->private_data;
+	snd_pcm_chmap_query_t **map;
+
+	if (!chmap_caps(hw, CHMAP_CTL_QUERY))
+		return NULL;
+
+	map = snd_pcm_query_chmaps_from_hw(hw->card, hw->device,
+					   hw->subdevice, pcm->stream);
+	if (map)
+		chmap_caps_set_ok(hw, CHMAP_CTL_QUERY);
+	else
+		chmap_caps_set_error(hw, CHMAP_CTL_QUERY);
+	return map;
 }
 
 static snd_pcm_chmap_t *snd_pcm_hw_get_chmap(snd_pcm_t *pcm)