[alsa-devel] [RFC v2 - AAF PCM plugin 2/5] aaf: Load configuration parameters

[Andre Guedes]

This patch implements the infrastructure to load the plugin
configuration from ALSA configuration file. The configuration
is loaded in open() callback.

All configuration parameters are described in details in doc/aaf.txt
file.

Signed-off-by: Andre Guedes <andre.guedes at intel.com>
---
 aaf/pcm_aaf.c | 126 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 doc/aaf.txt   |  52 ++++++++++++++++++++++++
 2 files changed, 178 insertions(+)

diff --git a/aaf/pcm_aaf.c b/aaf/pcm_aaf.c
index 7890e10..ac0b971 100644
--- a/aaf/pcm_aaf.c
+++ b/aaf/pcm_aaf.c
@@ -20,11 +20,133 @@
 
 #include <alsa/asoundlib.h>
 #include <alsa/pcm_external.h>
+#include <linux/if.h>
+#include <linux/if_ether.h>
+#include <string.h>
+#include <stdint.h>
+
+#define NSEC_PER_USEC 1000ULL
 
 typedef struct {
 	snd_pcm_ioplug_t io;
+
+	char ifname[IFNAMSIZ];
+	uint8_t addr[ETH_ALEN];
+	int prio;
+	uint64_t streamid;
+	int mtt;
+	int t_uncertainty;
+	snd_pcm_uframes_t frames_per_pdu;
 } snd_pcm_aaf_t;
 
+static int aaf_load_config(snd_pcm_aaf_t *aaf, snd_config_t *conf)
+{
+	snd_config_iterator_t cur, next;
+
+	snd_config_for_each(cur, next, conf) {
+		snd_config_t *entry = snd_config_iterator_entry(cur);
+		const char *id;
+
+		if (snd_config_get_id(entry, &id) < 0)
+			goto err;
+
+		if (strcmp(id, "comment") == 0 ||
+		    strcmp(id, "type") == 0 ||
+		    strcmp(id, "hint") == 0)
+			continue;
+
+		if (strcmp(id, "ifname") == 0) {
+			const char *ifname;
+
+			if (snd_config_get_string(entry, &ifname) < 0)
+				goto err;
+
+			snprintf(aaf->ifname, sizeof(aaf->ifname), "%s",
+				 ifname);
+		} else if (strcmp(id, "addr") == 0) {
+			const char *addr;
+			int n;
+
+			if (snd_config_get_string(entry, &addr) < 0)
+				goto err;
+
+			n = sscanf(addr, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx",
+				   &aaf->addr[0], &aaf->addr[1],
+				   &aaf->addr[2], &aaf->addr[3],
+				   &aaf->addr[4], &aaf->addr[5]);
+			if (n != 6)
+				goto err;
+		} else if (strcmp(id, "prio") == 0) {
+			long prio;
+
+			if (snd_config_get_integer(entry, &prio) < 0)
+				goto err;
+
+			if (prio < 0)
+				goto err;
+
+			aaf->prio = prio;
+		} else if (strcmp(id, "streamid") == 0) {
+			const char *streamid;
+			int n;
+			uint64_t buf[7];
+
+			if (snd_config_get_string(entry, &streamid) < 0)
+				goto err;
+
+			n = sscanf(streamid, "%lx:%lx:%lx:%lx:%lx:%lx:%lx",
+				   &buf[0], &buf[1], &buf[2], &buf[3],
+				   &buf[4], &buf[5], &buf[6]);
+			if (n != 7)
+				goto err;
+
+			aaf->streamid = buf[0] << 56 | buf[1] << 48 |
+					buf[2] << 40 | buf[3] << 32 |
+					buf[4] << 24 | buf[5] << 16 |
+					buf[6];
+		} else if (strcmp(id, "mtt") == 0) {
+			long mtt;
+
+			if (snd_config_get_integer(entry, &mtt) < 0)
+				goto err;
+
+			if (mtt < 0)
+				goto err;
+
+			aaf->mtt = mtt * NSEC_PER_USEC;
+		} else if (strcmp(id, "time_uncertainty") == 0) {
+			long t_uncertainty;
+
+			if (snd_config_get_integer(entry, &t_uncertainty) < 0)
+				goto err;
+
+			if (t_uncertainty < 0)
+				goto err;
+
+			aaf->t_uncertainty = t_uncertainty * NSEC_PER_USEC;
+		} else if (strcmp(id, "frames_per_pdu") == 0) {
+			long frames_per_pdu;
+
+			if (snd_config_get_integer(entry, &frames_per_pdu) < 0)
+				goto err;
+
+			if (frames_per_pdu < 0)
+				goto err;
+
+			aaf->frames_per_pdu = frames_per_pdu;
+		} else {
+			SNDERR("Invalid configuration: %s", id);
+			goto err;
+		}
+	}
+
+	return 0;
+
+err:
+	SNDERR("Error loading device configuration");
+	return -EINVAL;
+}
+
 static int aaf_close(snd_pcm_ioplug_t *io)
 {
 	snd_pcm_aaf_t *aaf = io->private_data;
@@ -70,6 +192,10 @@ SND_PCM_PLUGIN_DEFINE_FUNC(aaf)
 		return -ENOMEM;
 	}
 
+	res = aaf_load_config(aaf, conf);
+	if (res < 0)
+		goto err;
+
 	aaf->io.version = SND_PCM_IOPLUG_VERSION;
 	aaf->io.name = "AVTP Audio Format (AAF) Plugin";
 	aaf->io.callback = &aaf_callback;
diff --git a/doc/aaf.txt b/doc/aaf.txt
index b260a26..d817249 100644
--- a/doc/aaf.txt
+++ b/doc/aaf.txt
@@ -16,3 +16,55 @@ The AAF plugin uses libavtp to handle AVTP packetization. Libavtp source code
 can be found in https://github.com/AVnu/libavtp as well as instructions to
 build and install it. If libavtp isn't detected by configure, the plugin isn't
 built.
+
+Plugin Configuration and Usage
+------------------------------
+
+The plugin parameters are passed via ALSA configuration file. They are defined
+as follows:
+
+	* ifname: Network interface used to transmit/receive AVTP packets.
+
+	* addr: Stream destination MAC address.
+
+	* prio: Priority used by the plugin to transmit AVTP traffic. This
+	  option is relevant only when operating in playback mode.
+
+	* streamid: Stream ID associated with the AAF stream transmitted or
+	  received by the plugin.
+
+	* mtt: Maximum Transit Time (in microseconds) as defined in AVTP spec
+	  section 4.3.3. This option is relevant only when operating in
+	  playback mode.
+
+	* time_uncertainty: Maximum Time Uncertainty (in microseconds) as
+	  defined by AVTP spec section 4.3.3. This option is relevant only when
+	  operating in playback mode.
+
+	* frames_per_pdu: Number of audio frames transmitted in one AVTPDU.
+
+The plugin provides the PCM type "aaf". Configure an AAF PCM virtual device
+according to the AAF stream you want to transmit or receive. A hypothetical
+configuration file is shown below:
+
+	pcm.aaf {
+		type aaf
+		ifname eth0
+		addr AA:AA:AA:AA:AA:AA
+		prio 3
+		streamid BB:BB:BB:BB:BB:BB:0001
+		mtt 2000
+		time_uncertainty 125
+		frames_per_pdu 6
+	}
+
+Put the above to ~/.asoundrc (or /etc/asound.conf), and use the AAF PCM virtual
+device with your ALSA apps. For example, to stream the content from a wav file
+through the network, run:
+
+	$ aplay -Daaf foo.wav
+
+To receive the AAF stream generated by the previous command, run the following
+command in another host:
+
+	$ arecord -Daaf
-- 
2.14.4