staging: line6: separate handling of buffer allocation and stream startup

There are several features of the Line6 USB driver which require PCM
data to be exchanged with the device:
*) PCM playback and capture via ALSA
*) software monitoring (for devices without hardware monitoring)
*) optional impulse response measurement
However, from the device's point of view, there is just a single
capture and playback stream, which must be shared between these
subsystems. It is therefore necessary to maintain the state of the
subsystems with respect to PCM usage. We define several constants of
the form LINE6_BIT_PCM_<subsystem>_<direction>_<resource> with the
following meanings:
*) <subsystem> is one of
-) ALSA: PCM playback and capture via ALSA
-) MONITOR: software monitoring
-) IMPULSE: optional impulse response measurement
*) <direction> is one of
-) PLAYBACK: audio output (from host to device)
-) CAPTURE: audio input (from device to host)
*) <resource> is one of
-) BUFFER: buffer required by PCM data stream
-) STREAM: actual PCM data stream

The subsystems call line6_pcm_acquire() to acquire the (shared)
resources needed for a particular operation (e.g., allocate the buffer
for ALSA playback or start the capture stream for software monitoring).
When a resource is no longer needed, it is released by calling
line6_pcm_release(). Buffer allocation and stream startup are handled
separately to allow the ALSA kernel driver to perform them at
appropriate places (since the callback which starts a PCM stream is not
allowed to sleep).

Signed-off-by: Markus Grabner <grabner@icg.tugraz.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 73 insertions, 36 deletions

diff --git a/drivers/staging/line6/pcm.c b/drivers/staging/line6/pcm.c
index 37675e6..90d2d44 100644
--- a/drivers/staging/line6/pcm.c
+++ b/drivers/staging/line6/pcm.c
@@ -52,9 +52,9 @@ static ssize_t pcm_set_impulse_volume(struct device *dev,
 	line6pcm->impulse_volume = value;
 
 	if (value > 0)
-		line6_pcm_start(line6pcm, MASK_PCM_IMPULSE);
+		line6_pcm_acquire(line6pcm, LINE6_BITS_PCM_IMPULSE);
 	else
-		line6_pcm_stop(line6pcm, MASK_PCM_IMPULSE);
+		line6_pcm_release(line6pcm, LINE6_BITS_PCM_IMPULSE);
 
 	return count;
 }
@@ -92,29 +92,43 @@ static bool test_flags(unsigned long flags0, unsigned long flags1,
 	return ((flags0 & mask) == 0) && ((flags1 & mask) != 0);
 }
 
-int line6_pcm_start(struct snd_line6_pcm *line6pcm, int channels)
+int line6_pcm_acquire(struct snd_line6_pcm *line6pcm, int channels)
 {
 	unsigned long flags_old =
 	    __sync_fetch_and_or(&line6pcm->flags, channels);
 	unsigned long flags_new = flags_old | channels;
+	unsigned long flags_final = flags_old;
 	int err = 0;
 	
 	line6pcm->prev_fbuf = NULL;
 
-	if (test_flags(flags_old, flags_new, MASK_CAPTURE)) {
+	if (test_flags(flags_old, flags_new, LINE6_BITS_CAPTURE_BUFFER)) {
+		/* We may be invoked multiple times in a row so allocate once only */
+		if (!line6pcm->buffer_in) {
+			line6pcm->buffer_in =
+				kmalloc(LINE6_ISO_BUFFERS * LINE6_ISO_PACKETS *
+					line6pcm->max_packet_size, GFP_KERNEL);
+
+			if (!line6pcm->buffer_in) {
+				dev_err(line6pcm->line6->ifcdev,
+					"cannot malloc capture buffer\n");
+				err = -ENOMEM;
+				goto pcm_acquire_error;
+			}
+
+			flags_final |= channels & LINE6_BITS_CAPTURE_BUFFER;
+		}
+	}
+
+	if (test_flags(flags_old, flags_new, LINE6_BITS_CAPTURE_STREAM)) {
 		/*
 		   Waiting for completion of active URBs in the stop handler is
 		   a bug, we therefore report an error if capturing is restarted
 		   too soon.
 		 */
-		if (line6pcm->active_urb_in | line6pcm->unlink_urb_in)
+		if (line6pcm->active_urb_in | line6pcm->unlink_urb_in) {
+			dev_err(line6pcm->line6->ifcdev, "Device not yet ready\n");
 			return -EBUSY;
-
-		if (!(flags_new & MASK_PCM_ALSA_CAPTURE)) {
-			err = line6_alloc_capture_buffer(line6pcm);
-
-			if (err < 0)
-				goto pcm_start_error;
 		}
 
 		line6pcm->count_in = 0;
@@ -122,55 +136,78 @@ int line6_pcm_start(struct snd_line6_pcm *line6pcm, int channels)
 		err = line6_submit_audio_in_all_urbs(line6pcm);
 
 		if (err < 0)
-			goto pcm_start_error;
+			goto pcm_acquire_error;
+
+		flags_final |= channels & LINE6_BITS_CAPTURE_STREAM;
 	}
 
-	if (test_flags(flags_old, flags_new, MASK_PLAYBACK)) {
-		/*
-		   See comment above regarding PCM restart.
-		 */
-		if (line6pcm->active_urb_out | line6pcm->unlink_urb_out)
-			return -EBUSY;
+	if (test_flags(flags_old, flags_new, LINE6_BITS_PLAYBACK_BUFFER)) {
+		/* We may be invoked multiple times in a row so allocate once only */
+		if (!line6pcm->buffer_out) {
+			line6pcm->buffer_out =
+				kmalloc(LINE6_ISO_BUFFERS * LINE6_ISO_PACKETS *
+					line6pcm->max_packet_size, GFP_KERNEL);
+
+			if (!line6pcm->buffer_out) {
+				dev_err(line6pcm->line6->ifcdev,
+					"cannot malloc playback buffer\n");
+				err = -ENOMEM;
+				goto pcm_acquire_error;
+			}
 
-		if (!(flags_new & MASK_PCM_ALSA_PLAYBACK)) {
-			err = line6_alloc_playback_buffer(line6pcm);
+			flags_final |= channels & LINE6_BITS_PLAYBACK_BUFFER;
+		}
+	}
 
-			if (err < 0)
-				goto pcm_start_error;
+	if (test_flags(flags_old, flags_new, LINE6_BITS_PLAYBACK_STREAM)) {
+		/*
+		  See comment above regarding PCM restart.
+		*/
+		if (line6pcm->active_urb_out | line6pcm->unlink_urb_out) {
+			dev_err(line6pcm->line6->ifcdev, "Device not yet ready\n");
+			return -EBUSY;
 		}
 
 		line6pcm->count_out = 0;
 		err = line6_submit_audio_out_all_urbs(line6pcm);
 
 		if (err < 0)
-			goto pcm_start_error;
+			goto pcm_acquire_error;
+
+		flags_final |= channels & LINE6_BITS_PLAYBACK_STREAM;
 	}
 
 	return 0;
 
-pcm_start_error:
-	__sync_fetch_and_and(&line6pcm->flags, ~channels);
+pcm_acquire_error:
+	/*
+	   If not all requested resources/streams could be obtained, release
+	   those which were successfully obtained (if any).
+	*/
+	line6_pcm_release(line6pcm, flags_final & channels);
 	return err;
 }
 
-int line6_pcm_stop(struct snd_line6_pcm *line6pcm, int channels)
+int line6_pcm_release(struct snd_line6_pcm *line6pcm, int channels)
 {
 	unsigned long flags_old =
 	    __sync_fetch_and_and(&line6pcm->flags, ~channels);
 	unsigned long flags_new = flags_old & ~channels;
 
-	if (test_flags(flags_new, flags_old, MASK_CAPTURE)) {
+	if (test_flags(flags_new, flags_old, LINE6_BITS_CAPTURE_STREAM))
 		line6_unlink_audio_in_urbs(line6pcm);
 
-		if (!(flags_old & MASK_PCM_ALSA_CAPTURE))
-			line6_free_capture_buffer(line6pcm);
+	if (test_flags(flags_new, flags_old, LINE6_BITS_CAPTURE_BUFFER)) {
+		line6_wait_clear_audio_in_urbs(line6pcm);
+		line6_free_capture_buffer(line6pcm);
 	}
 
-	if (test_flags(flags_new, flags_old, MASK_PLAYBACK)) {
+	if (test_flags(flags_new, flags_old, LINE6_BITS_PLAYBACK_STREAM))
 		line6_unlink_audio_out_urbs(line6pcm);
 
-		if (!(flags_old & MASK_PCM_ALSA_PLAYBACK))
-			line6_free_playback_buffer(line6pcm);
+	if (test_flags(flags_new, flags_old, LINE6_BITS_PLAYBACK_BUFFER)) {
+		line6_wait_clear_audio_out_urbs(line6pcm);
+		line6_free_playback_buffer(line6pcm);
 	}
 
 	return 0;
@@ -185,7 +222,7 @@ int snd_line6_trigger(struct snd_pcm_substream *substream, int cmd)
 	unsigned long flags;
 
 	spin_lock_irqsave(&line6pcm->lock_trigger, flags);
-	clear_bit(BIT_PREPARED, &line6pcm->flags);
+	clear_bit(LINE6_INDEX_PREPARED, &line6pcm->flags);
 
 	snd_pcm_group_for_each_entry(s, substream) {
 		switch (s->stream) {
@@ -498,13 +535,13 @@ int snd_line6_prepare(struct snd_pcm_substream *substream)
 
 	switch (substream->stream) {
 	case SNDRV_PCM_STREAM_PLAYBACK:
-		if ((line6pcm->flags & MASK_PLAYBACK) == 0)
+		if ((line6pcm->flags & LINE6_BITS_PLAYBACK_STREAM) == 0)
 			line6_unlink_wait_clear_audio_out_urbs(line6pcm);
 
 		break;
 
 	case SNDRV_PCM_STREAM_CAPTURE:
-		if ((line6pcm->flags & MASK_CAPTURE) == 0)
+		if ((line6pcm->flags & LINE6_BITS_CAPTURE_STREAM) == 0)
 			line6_unlink_wait_clear_audio_in_urbs(line6pcm);
 
 		break;
@@ -513,7 +550,7 @@ int snd_line6_prepare(struct snd_pcm_substream *substream)
 		MISSING_CASE;
 	}
 
-	if (!test_and_set_bit(BIT_PREPARED, &line6pcm->flags)) {
+	if (!test_and_set_bit(LINE6_INDEX_PREPARED, &line6pcm->flags)) {
 		line6pcm->count_out = 0;
 		line6pcm->pos_out = 0;
 		line6pcm->pos_out_done = 0;