media: sound/usb: Use Media Controller API to share media resources

Media Device Allocator API to allows multiple drivers share a media device.
This API solves a very common use-case for media devices where one physical
device (an USB stick) provides both audio and video. When such media device
exposes a standard USB Audio class, a proprietary Video class, two or more
independent drivers will share a single physical USB bridge. In such cases,
it is necessary to coordinate access to the shared resource.

Using this API, drivers can allocate a media device with the shared struct
device as the key. Once the media device is allocated by a driver, other
drivers can get a reference to it. The media device is released when all
the references are released.

Change the ALSA driver to use the Media Controller API to share media
resources with DVB, and V4L2 drivers on a AU0828 media device.

The Media Controller specific initialization is done after sound card is
registered. ALSA creates Media interface and entity function graph nodes
for Control, Mixer, PCM Playback, and PCM Capture devices.

snd_usb_hw_params() will call Media Controller enable source handler
interface to request the media resource. If resource request is granted,
it will release it from snd_usb_hw_free(). If resource is busy, -EBUSY is
returned.

Media specific cleanup is done in usb_audio_disconnect().

Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Shuah Khan <shuah@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

1 files changed, 25 insertions, 4 deletions

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 056af0a57b22..5d8494b2a026 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -35,6 +35,7 @@
 #include "pcm.h"
 #include "clock.h"
 #include "power.h"
+#include "media.h"
 
 #define SUBSTREAM_FLAG_DATA_EP_STARTED	0
 #define SUBSTREAM_FLAG_SYNC_EP_STARTED	1
@@ -787,6 +788,10 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
 	struct audioformat *fmt;
 	int ret;
 
+	ret = snd_media_start_pipeline(subs);
+	if (ret)
+		return ret;
+
 	if (snd_usb_use_vmalloc)
 		ret = snd_pcm_lib_alloc_vmalloc_buffer(substream,
 						       params_buffer_bytes(hw_params));
@@ -794,7 +799,7 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
 		ret = snd_pcm_lib_malloc_pages(substream,
 					       params_buffer_bytes(hw_params));
 	if (ret < 0)
-		return ret;
+		goto stop_pipeline;
 
 	subs->pcm_format = params_format(hw_params);
 	subs->period_bytes = params_period_bytes(hw_params);
@@ -808,12 +813,13 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
 		dev_dbg(&subs->dev->dev,
 			"cannot set format: format = %#x, rate = %d, channels = %d\n",
 			   subs->pcm_format, subs->cur_rate, subs->channels);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto stop_pipeline;
 	}
 
 	ret = snd_usb_lock_shutdown(subs->stream->chip);
 	if (ret < 0)
-		return ret;
+		goto stop_pipeline;
 
 	ret = snd_usb_pcm_change_state(subs, UAC3_PD_STATE_D0);
 	if (ret < 0)
@@ -829,6 +835,12 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
 
  unlock:
 	snd_usb_unlock_shutdown(subs->stream->chip);
+	if (ret < 0)
+		goto stop_pipeline;
+	return ret;
+
+ stop_pipeline:
+	snd_media_stop_pipeline(subs);
 	return ret;
 }
 
@@ -841,6 +853,7 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
 {
 	struct snd_usb_substream *subs = substream->runtime->private_data;
 
+	snd_media_stop_pipeline(subs);
 	subs->cur_audiofmt = NULL;
 	subs->cur_rate = 0;
 	subs->period_bytes = 0;
@@ -1313,6 +1326,7 @@ static int snd_usb_pcm_open(struct snd_pcm_substream *substream)
 	struct snd_usb_stream *as = snd_pcm_substream_chip(substream);
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct snd_usb_substream *subs = &as->substream[direction];
+	int ret;
 
 	subs->interface = -1;
 	subs->altset_idx = 0;
@@ -1326,7 +1340,13 @@ static int snd_usb_pcm_open(struct snd_pcm_substream *substream)
 	subs->dsd_dop.channel = 0;
 	subs->dsd_dop.marker = 1;
 
-	return setup_hw_info(runtime, subs);
+	ret = setup_hw_info(runtime, subs);
+	if (ret == 0) {
+		ret = snd_media_stream_init(subs, as->pcm, direction);
+		if (ret)
+			snd_usb_autosuspend(subs->stream->chip);
+	}
+	return ret;
 }
 
 static int snd_usb_pcm_close(struct snd_pcm_substream *substream)
@@ -1337,6 +1357,7 @@ static int snd_usb_pcm_close(struct snd_pcm_substream *substream)
 	int ret;
 
 	stop_endpoints(subs, true);
+	snd_media_stop_pipeline(subs);
 
 	if (!as->chip->keep_iface &&
 	    subs->interface >= 0 &&