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, 116 insertions, 42 deletions

diff --git a/drivers/staging/line6/pcm.h b/drivers/staging/line6/pcm.h
index 47c6d6942b4..5210ec8dbe1 100644
--- a/drivers/staging/line6/pcm.h
+++ b/drivers/staging/line6/pcm.h
@@ -46,57 +46,131 @@
 		(line6pcm->pcm->streams[stream].substream)
 
 /*
-	PCM mode bits and masks.
-	"ALSA": operations triggered by applications via ALSA
-	"MONITOR": software monitoring
-	"IMPULSE": optional impulse response operation
+	PCM mode bits.
+
+	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).
 */
 enum {
-	/* individual bits: */
-	BIT_PCM_ALSA_PLAYBACK,
-	BIT_PCM_ALSA_CAPTURE,
-	BIT_PCM_MONITOR_PLAYBACK,
-	BIT_PCM_MONITOR_CAPTURE,
+	/* individual bit indices: */
+	LINE6_INDEX_PCM_ALSA_PLAYBACK_BUFFER,
+	LINE6_INDEX_PCM_ALSA_PLAYBACK_STREAM,
+	LINE6_INDEX_PCM_ALSA_CAPTURE_BUFFER,
+	LINE6_INDEX_PCM_ALSA_CAPTURE_STREAM,
+	LINE6_INDEX_PCM_MONITOR_PLAYBACK_BUFFER,
+	LINE6_INDEX_PCM_MONITOR_PLAYBACK_STREAM,
+	LINE6_INDEX_PCM_MONITOR_CAPTURE_BUFFER,
+	LINE6_INDEX_PCM_MONITOR_CAPTURE_STREAM,
 #ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
-	BIT_PCM_IMPULSE_PLAYBACK,
-	BIT_PCM_IMPULSE_CAPTURE,
+	LINE6_INDEX_PCM_IMPULSE_PLAYBACK_BUFFER,
+	LINE6_INDEX_PCM_IMPULSE_PLAYBACK_STREAM,
+	LINE6_INDEX_PCM_IMPULSE_CAPTURE_BUFFER,
+	LINE6_INDEX_PCM_IMPULSE_CAPTURE_STREAM,
 #endif
-	BIT_PAUSE_PLAYBACK,
-	BIT_PREPARED,
-
-	/* individual masks: */
-/* *INDENT-OFF* */
-	MASK_PCM_ALSA_PLAYBACK    = 1 << BIT_PCM_ALSA_PLAYBACK,
-	MASK_PCM_ALSA_CAPTURE     = 1 << BIT_PCM_ALSA_CAPTURE,
-	MASK_PCM_MONITOR_PLAYBACK = 1 << BIT_PCM_MONITOR_PLAYBACK,
-	MASK_PCM_MONITOR_CAPTURE  = 1 << BIT_PCM_MONITOR_CAPTURE,
+	LINE6_INDEX_PAUSE_PLAYBACK,
+	LINE6_INDEX_PREPARED,
+
+	/* individual bit masks: */
+	LINE6_BIT(PCM_ALSA_PLAYBACK_BUFFER),
+	LINE6_BIT(PCM_ALSA_PLAYBACK_STREAM),
+	LINE6_BIT(PCM_ALSA_CAPTURE_BUFFER),
+	LINE6_BIT(PCM_ALSA_CAPTURE_STREAM),
+	LINE6_BIT(PCM_MONITOR_PLAYBACK_BUFFER),
+	LINE6_BIT(PCM_MONITOR_PLAYBACK_STREAM),
+	LINE6_BIT(PCM_MONITOR_CAPTURE_BUFFER),
+	LINE6_BIT(PCM_MONITOR_CAPTURE_STREAM),
 #ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
-	MASK_PCM_IMPULSE_PLAYBACK = 1 << BIT_PCM_IMPULSE_PLAYBACK,
-	MASK_PCM_IMPULSE_CAPTURE  = 1 << BIT_PCM_IMPULSE_CAPTURE,
+	LINE6_BIT(PCM_IMPULSE_PLAYBACK_BUFFER),
+	LINE6_BIT(PCM_IMPULSE_PLAYBACK_STREAM),
+	LINE6_BIT(PCM_IMPULSE_CAPTURE_BUFFER),
+	LINE6_BIT(PCM_IMPULSE_CAPTURE_STREAM),
 #endif
-	MASK_PAUSE_PLAYBACK       = 1 << BIT_PAUSE_PLAYBACK,
-	MASK_PREPARED             = 1 << BIT_PREPARED,
-/* *INDENT-ON* */
+	LINE6_BIT(PAUSE_PLAYBACK),
+	LINE6_BIT(PREPARED),
 
-	/* combined masks (by operation): */
-	MASK_PCM_ALSA = MASK_PCM_ALSA_PLAYBACK | MASK_PCM_ALSA_CAPTURE,
-	MASK_PCM_MONITOR = MASK_PCM_MONITOR_PLAYBACK | MASK_PCM_MONITOR_CAPTURE,
+	/* combined bit masks (by operation): */
+	LINE6_BITS_PCM_ALSA_BUFFER =
+	    LINE6_BIT_PCM_ALSA_PLAYBACK_BUFFER |
+	    LINE6_BIT_PCM_ALSA_CAPTURE_BUFFER,
+
+	LINE6_BITS_PCM_ALSA_STREAM =
+	    LINE6_BIT_PCM_ALSA_PLAYBACK_STREAM |
+	    LINE6_BIT_PCM_ALSA_CAPTURE_STREAM,
+
+	LINE6_BITS_PCM_MONITOR =
+	    LINE6_BIT_PCM_MONITOR_PLAYBACK_BUFFER |
+	    LINE6_BIT_PCM_MONITOR_PLAYBACK_STREAM |
+	    LINE6_BIT_PCM_MONITOR_CAPTURE_BUFFER |
+	    LINE6_BIT_PCM_MONITOR_CAPTURE_STREAM,
+
+#ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
+	LINE6_BITS_PCM_IMPULSE =
+	    LINE6_BIT_PCM_IMPULSE_PLAYBACK_BUFFER |
+	    LINE6_BIT_PCM_IMPULSE_PLAYBACK_STREAM |
+	    LINE6_BIT_PCM_IMPULSE_CAPTURE_BUFFER |
+	    LINE6_BIT_PCM_IMPULSE_CAPTURE_STREAM,
+#endif
+
+	/* combined bit masks (by direction): */
+	LINE6_BITS_PLAYBACK_BUFFER =
+#ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
+	    LINE6_BIT_PCM_IMPULSE_PLAYBACK_BUFFER |
+#endif
+	    LINE6_BIT_PCM_ALSA_PLAYBACK_BUFFER |
+	    LINE6_BIT_PCM_MONITOR_PLAYBACK_BUFFER ,
+
+	LINE6_BITS_PLAYBACK_STREAM =
+#ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
+	    LINE6_BIT_PCM_IMPULSE_PLAYBACK_STREAM |
+#endif
+	    LINE6_BIT_PCM_ALSA_PLAYBACK_STREAM |
+	    LINE6_BIT_PCM_MONITOR_PLAYBACK_STREAM ,
+
+	LINE6_BITS_CAPTURE_BUFFER =
 #ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
-	MASK_PCM_IMPULSE = MASK_PCM_IMPULSE_PLAYBACK | MASK_PCM_IMPULSE_CAPTURE,
+	    LINE6_BIT_PCM_IMPULSE_CAPTURE_BUFFER |
 #endif
+	    LINE6_BIT_PCM_ALSA_CAPTURE_BUFFER |
+	    LINE6_BIT_PCM_MONITOR_CAPTURE_BUFFER ,
 
-	/* combined masks (by direction): */
+	LINE6_BITS_CAPTURE_STREAM =
 #ifdef CONFIG_LINE6_USB_IMPULSE_RESPONSE
-	MASK_PLAYBACK =
-	    MASK_PCM_ALSA_PLAYBACK | MASK_PCM_MONITOR_PLAYBACK |
-	    MASK_PCM_IMPULSE_PLAYBACK,
-	MASK_CAPTURE =
-	    MASK_PCM_ALSA_CAPTURE | MASK_PCM_MONITOR_CAPTURE |
-	    MASK_PCM_IMPULSE_CAPTURE
-#else
-	MASK_PLAYBACK = MASK_PCM_ALSA_PLAYBACK | MASK_PCM_MONITOR_PLAYBACK,
-	MASK_CAPTURE = MASK_PCM_ALSA_CAPTURE | MASK_PCM_MONITOR_CAPTURE
+	    LINE6_BIT_PCM_IMPULSE_CAPTURE_STREAM |
 #endif
+	    LINE6_BIT_PCM_ALSA_CAPTURE_STREAM |
+	    LINE6_BIT_PCM_MONITOR_CAPTURE_STREAM,
+	
+	LINE6_BITS_STREAM =
+	    LINE6_BITS_PLAYBACK_STREAM |
+	    LINE6_BITS_CAPTURE_STREAM
 };
 
 struct line6_pcm_properties {
@@ -290,7 +364,7 @@ struct snd_line6_pcm {
 #endif
 
 	/**
-		 Several status bits (see BIT_*).
+		 Several status bits (see LINE6_BIT_*).
 	*/
 	unsigned long flags;
 
@@ -302,7 +376,7 @@ extern int line6_init_pcm(struct usb_line6 *line6,
 extern int snd_line6_trigger(struct snd_pcm_substream *substream, int cmd);
 extern int snd_line6_prepare(struct snd_pcm_substream *substream);
 extern void line6_pcm_disconnect(struct snd_line6_pcm *line6pcm);
-extern int line6_pcm_start(struct snd_line6_pcm *line6pcm, int channels);
-extern int line6_pcm_stop(struct snd_line6_pcm *line6pcm, int channels);
+extern int line6_pcm_acquire(struct snd_line6_pcm *line6pcm, int channels);
+extern int line6_pcm_release(struct snd_line6_pcm *line6pcm, int channels);
 
 #endif