[ALSA] hwdep interface for pcm data

USB,USB USX2Y
Implements 'rawusb' pcm data transfer through hwdep interface:
The usb_hc moves pcm data from/into memory via DMA.
That memory is mmaped by jack's usx2y driver.
Jack's usx2y driver is the first/last executable code to read/write pcm data.
Read/write is a combination of power of 2 period shaping and float/int
conversation.

Compared to standard alsa/jack we leave out power of 2 period shaping
inside snd-usb-usx2y which needs memcpy() and additional buffers.
As a side effect possible unwanted pcm-data coruption resulting of
standard alsa's snd-usb-usx2y period shaping scheme falls away.
Result is sane jack operation at buffering schemes down to 128frames,
2 periods.

Also changed Kconfig file, so snd-usb-usx2y is only available for X86,
PPC or ALPHA platforms, as on others DMA-memory isn't mmapable.
Signed-off-by: Karsten Wiese <annabellesgarden@yahoo.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/Kconfig

@@ -17,7 +17,7 @@ config SND_USB_AUDIO
 
 config SND_USB_USX2Y
 	tristate "Tascam US-122, US-224 and US-428 USB driver"
-	depends on SND && USB
+	depends on SND && USB && (X86 || PPC || ALPHA)
 	select SND_HWDEP
 	select SND_RAWMIDI
 	select SND_PCM

sound/usb/usx2y/Makefile

-snd-usb-usx2y-objs := usbusx2y.o usbusx2yaudio.o usX2Yhwdep.o
+snd-usb-usx2y-objs := usbusx2y.o usX2Yhwdep.o usx2yhwdeppcm.o
 
 obj-$(CONFIG_SND_USB_USX2Y) += snd-usb-usx2y.o

sound/usb/usx2y/usX2Yhwdep.c

@@ -31,6 +31,8 @@
 #include "usbusx2y.h"
 #include "usX2Yhwdep.h"
 
+int usX2Y_hwdep_pcm_new(snd_card_t* card);
+
 
 static struct page * snd_us428ctls_vm_nopage(struct vm_area_struct *area, unsigned long address, int *type)
 {
@@ -196,6 +198,8 @@ static int usX2Y_create_alsa_devices(snd_card_t* card)
 		}
 		if ((err = usX2Y_audio_create(card)) < 0) 
 			break;
+		if ((err = usX2Y_hwdep_pcm_new(card)) < 0)
+			break;
 		if ((err = snd_card_register(card)) < 0)
 			break;
 	} while (0);

sound/usb/usx2y/usbusx2y.h

@@ -20,6 +20,7 @@ typedef struct {
 } snd_usX2Y_urbSeq_t;
 
 typedef struct snd_usX2Y_substream snd_usX2Y_substream_t;
+#include "usx2yhwdeppcm.h"
 
 typedef struct {
 	snd_usb_audio_t 	chip;
@@ -38,6 +39,7 @@ typedef struct {
 	us428ctls_sharedmem_t	*us428ctls_sharedmem;
 	int			wait_iso_frame;
 	wait_queue_head_t	us428ctls_wait_queue_head;
+	snd_usX2Y_hwdep_pcm_shm_t	*hwdep_pcm_shm;
 	snd_usX2Y_substream_t	*subs[4];
 	snd_usX2Y_substream_t	* volatile  prepare_subs;
 	wait_queue_head_t	prepare_wait_queue;

sound/usb/usx2y/usbusx2yaudio.c

@@ -67,7 +67,6 @@
 #endif
 
 
-
 static int usX2Y_urb_capt_retire(snd_usX2Y_substream_t *subs)
 {
 	struct urb	*urb = subs->completed_urb;
@@ -892,6 +891,9 @@ static int snd_usX2Y_pcm_open(snd_pcm_substream_t *substream)
 					 snd_pcm_substream_chip(substream))[substream->stream];
 	snd_pcm_runtime_t	*runtime = substream->runtime;
 
+	if (subs->usX2Y->chip_status & USX2Y_STAT_CHIP_MMAP_PCM_URBS)
+		return -EBUSY;
+
 	runtime->hw = snd_usX2Y_2c;
 	runtime->private_data = subs;
 	subs->pcm_substream = substream;

sound/usb/usx2y/usx2y.h

@@ -27,6 +27,7 @@
 
 /* hwdep id string */
 #define SND_USX2Y_LOADER_ID		"USX2Y Loader"
+#define SND_USX2Y_USBPCM_ID		"USX2Y USBPCM"
 
 /* hardware type */
 enum {
@@ -43,6 +44,7 @@ enum {
 /* chip status */
 enum {
 	USX2Y_STAT_CHIP_INIT	=	(1 << 0),	/* all operational */
+	USX2Y_STAT_CHIP_MMAP_PCM_URBS = (1 << 1),	/* pcm transport over mmaped urbs */
 	USX2Y_STAT_CHIP_HUP	=	(1 << 31),	/* all operational */
 };