staging: line6: fixed ALSA/PCM interaction

The PCM subsystem in the Line6 driver is mainly used for PCM playback and
capture by ALSA, but also has other tasks, most notably providing a
low-latency software monitor for devices which don't support hardware
monitoring (e.g., the TonePort series). This patch makes ALSA "play nicely"
with the other components, i.e., prevents it from resetting the isochronous
USB transfer while other PCM tasks (software monitoring) are running.

Signed-off-by: Markus Grabner <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/line6/capture.c

···
 	}
 }
 
+int line6_alloc_capture_buffer(struct snd_line6_pcm *line6pcm)
+{
+	/* We may be invoked multiple times in a row so allocate once only */
+	if (line6pcm->buffer_in)
+		return 0;
+
+	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");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+void line6_free_capture_buffer(struct snd_line6_pcm *line6pcm)
+{
+	kfree(line6pcm->buffer_in);
+	line6pcm->buffer_in = NULL;
+}
+
 /*
  * Callback for completed capture URB.
  */
···
 	}
 	/* -- [FD] end */
 
-	/* 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->flags & MASK_CAPTURE) == 0) {
+		ret = line6_alloc_capture_buffer(line6pcm);
 
-	if (!line6pcm->buffer_in) {
-		dev_err(line6pcm->line6->ifcdev,
-			"cannot malloc capture buffer\n");
-		return -ENOMEM;
+		if (ret < 0)
+			return ret;
 	}
 
 	ret = snd_pcm_lib_malloc_pages(substream,
···
 {
 	struct snd_line6_pcm *line6pcm = snd_pcm_substream_chip(substream);
 
-	line6_unlink_wait_clear_audio_in_urbs(line6pcm);
-	kfree(line6pcm->buffer_in);
-	line6pcm->buffer_in = NULL;
+	if ((line6pcm->flags & MASK_CAPTURE) == 0) {
+		line6_unlink_wait_clear_audio_in_urbs(line6pcm);
+		line6_free_capture_buffer(line6pcm);
+	}
+
 	return snd_pcm_lib_free_pages(substream);
 }
 

drivers/staging/line6/capture.h

···
 
 extern struct snd_pcm_ops snd_line6_capture_ops;
 
+extern int line6_alloc_capture_buffer(struct snd_line6_pcm *line6pcm);
 extern void line6_capture_copy(struct snd_line6_pcm *line6pcm, char *fbuf,
 			       int fsize);
 extern void line6_capture_check_period(struct snd_line6_pcm *line6pcm,
 				       int length);
 extern int line6_create_audio_in_urbs(struct snd_line6_pcm *line6pcm);
+extern void line6_free_capture_buffer(struct snd_line6_pcm *line6pcm);
 extern int line6_submit_audio_in_all_urbs(struct snd_line6_pcm *line6pcm);
 extern void line6_unlink_audio_in_urbs(struct snd_line6_pcm *line6pcm);
 extern void line6_unlink_wait_clear_audio_in_urbs(struct snd_line6_pcm

drivers/staging/line6/pcm.c

···
 
 #endif
 
+static bool test_flags(unsigned long flags0, unsigned long flags1,
+		       unsigned long mask)
+{
+	return ((flags0 & mask) == 0) && ((flags1 & mask) != 0);
+}
+
 int line6_pcm_start(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;
 	int err = 0;
-
+	
 	line6pcm->prev_fbuf = NULL;
 
-	if (((flags_old & MASK_CAPTURE) == 0) &&
-	    ((flags_new & MASK_CAPTURE) != 0)) {
+	if (test_flags(flags_old, flags_new, MASK_CAPTURE)) {
 		/*
 		   Waiting for completion of active URBs in the stop handler is
 		   a bug, we therefore report an error if capturing is restarted
···
 		if (line6pcm->active_urb_in | line6pcm->unlink_urb_in)
 			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;
 		line6pcm->prev_fsize = 0;
 		err = line6_submit_audio_in_all_urbs(line6pcm);
 
-		if (err < 0) {
-			__sync_fetch_and_and(&line6pcm->flags, ~channels);
-			return err;
-		}
+		if (err < 0)
+			goto pcm_start_error;
 	}
 
-	if (((flags_old & MASK_PLAYBACK) == 0) &&
-	    ((flags_new & MASK_PLAYBACK) != 0)) {
+	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 (!(flags_new & MASK_PCM_ALSA_PLAYBACK)) {
+			err = line6_alloc_playback_buffer(line6pcm);
+
+			if (err < 0)
+				goto pcm_start_error;
+		}
+
 		line6pcm->count_out = 0;
 		err = line6_submit_audio_out_all_urbs(line6pcm);
 
-		if (err < 0) {
-			__sync_fetch_and_and(&line6pcm->flags, ~channels);
-			return err;
-		}
+		if (err < 0)
+			goto pcm_start_error;
 	}
 
 	return 0;
+
+pcm_start_error:
+	__sync_fetch_and_and(&line6pcm->flags, ~channels);
+	return err;
 }
 
 int line6_pcm_stop(struct snd_line6_pcm *line6pcm, int channels)
···
 	    __sync_fetch_and_and(&line6pcm->flags, ~channels);
 	unsigned long flags_new = flags_old & ~channels;
 
-	if (((flags_old & MASK_CAPTURE) != 0) &&
-	    ((flags_new & MASK_CAPTURE) == 0)) {
+	if (test_flags(flags_new, flags_old, MASK_CAPTURE)) {
 		line6_unlink_audio_in_urbs(line6pcm);
+
+		if (!(flags_old & MASK_PCM_ALSA_CAPTURE))
+			line6_free_capture_buffer(line6pcm);
 	}
 
-	if (((flags_old & MASK_PLAYBACK) != 0) &&
-	    ((flags_new & MASK_PLAYBACK) == 0)) {
+	if (test_flags(flags_new, flags_old, MASK_PLAYBACK)) {
 		line6_unlink_audio_out_urbs(line6pcm);
+
+		if (!(flags_old & MASK_PCM_ALSA_PLAYBACK))
+			line6_free_playback_buffer(line6pcm);
 	}
 
 	return 0;
···
 
 	switch (substream->stream) {
 	case SNDRV_PCM_STREAM_PLAYBACK:
-		line6_unlink_wait_clear_audio_out_urbs(line6pcm);
+		if ((line6pcm->flags & MASK_PLAYBACK) == 0)
+			line6_unlink_wait_clear_audio_out_urbs(line6pcm);
+
 		break;
 
 	case SNDRV_PCM_STREAM_CAPTURE:
-		line6_unlink_wait_clear_audio_in_urbs(line6pcm);
+		if ((line6pcm->flags & MASK_CAPTURE) == 0)
+			line6_unlink_wait_clear_audio_in_urbs(line6pcm);
+
 		break;
 
 	default:
 		MISSING_CASE;
 	}
-
 
 	if (!test_and_set_bit(BIT_PREPARED, &line6pcm->flags)) {
 		line6pcm->count_out = 0;

drivers/staging/line6/playback.c

···
 	wait_clear_audio_out_urbs(line6pcm);
 }
 
+int line6_alloc_playback_buffer(struct snd_line6_pcm *line6pcm)
+{
+	/* We may be invoked multiple times in a row so allocate once only */
+	if (line6pcm->buffer_out)
+		return 0;
+
+	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");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+void line6_free_playback_buffer(struct snd_line6_pcm *line6pcm)
+{
+	kfree(line6pcm->buffer_out);
+	line6pcm->buffer_out = NULL;
+}
+
 /*
 	Callback for completed playback URB.
 */
···
 	}
 	/* -- [FD] end */
 
-	/* 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->flags & MASK_PLAYBACK) == 0) {
+		ret = line6_alloc_playback_buffer(line6pcm);
 
-	if (!line6pcm->buffer_out) {
-		dev_err(line6pcm->line6->ifcdev,
-			"cannot malloc playback buffer\n");
-		return -ENOMEM;
+		if (ret < 0)
+			return ret;
 	}
 
 	ret = snd_pcm_lib_malloc_pages(substream,
···
 {
 	struct snd_line6_pcm *line6pcm = snd_pcm_substream_chip(substream);
 
-	line6_unlink_wait_clear_audio_out_urbs(line6pcm);
-	kfree(line6pcm->buffer_out);
-	line6pcm->buffer_out = NULL;
+	if ((line6pcm->flags & MASK_PLAYBACK) == 0) {
+		line6_unlink_wait_clear_audio_out_urbs(line6pcm);
+		line6_free_playback_buffer(line6pcm);
+	}
+
 	return snd_pcm_lib_free_pages(substream);
 }
 

drivers/staging/line6/playback.h

···
 
 extern struct snd_pcm_ops snd_line6_playback_ops;
 
+extern int line6_alloc_playback_buffer(struct snd_line6_pcm *line6pcm);
 extern int line6_create_audio_out_urbs(struct snd_line6_pcm *line6pcm);
+extern void line6_free_playback_buffer(struct snd_line6_pcm *line6pcm);
 extern int line6_submit_audio_out_all_urbs(struct snd_line6_pcm *line6pcm);
 extern void line6_unlink_audio_out_urbs(struct snd_line6_pcm *line6pcm);
 extern void line6_unlink_wait_clear_audio_out_urbs(struct snd_line6_pcm

drivers/staging/line6/revision.h

···
 #ifndef DRIVER_REVISION
 /* current subversion revision */
-#define DRIVER_REVISION " (revision 690)"
+#define DRIVER_REVISION " (904)"
 #endif