[media] em28xx-audio: don't hardcode audio URB calculus

The current code hardcodes the number of audio URBs, the number
of packets per URB and the maximum URB size.

This is not a good idea, as it:

- wastes more bandwidth than necessary, by using a very
  large number of packets;

- those constants are bound to an specific scenario, with
  a bandwidth of 48 kHz;

- don't take the maximum endpoint size into account;

- with urb->interval = 1 on xHCI, those constraints cause a "funny"
  setup: URBs with 64 packets inside, with only 24 bytes total. E. g.
  a complete waste of space.

Change the code to do dynamic URB audio calculus and allocation.

For now, use the same constraints as used before this patch, to
avoid regressions.

A good scenario (tested) seems to use those defines, instead:

	#define EM28XX_MAX_AUDIO_BUFS          8
	#define EM28XX_MIN_AUDIO_PACKETS       2

But let's not do such change here, letting the optimization to
happen on latter patches, after more tests.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

1 files changed, 3 insertions, 5 deletions

diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
index efdf38642768..e76f993e3195 100644
--- a/drivers/media/usb/em28xx/em28xx.h
+++ b/drivers/media/usb/em28xx/em28xx.h
@@ -481,9 +481,6 @@ struct em28xx_eeprom {
 	u8 string_idx_table;
 };
 
-#define EM28XX_AUDIO_BUFS 5
-#define EM28XX_NUM_AUDIO_PACKETS 64
-#define EM28XX_AUDIO_MAX_PACKET_SIZE 196 /* static value */
 #define EM28XX_CAPTURE_STREAM_EN 1
 
 /* em28xx extensions */
@@ -498,8 +495,9 @@ struct em28xx_eeprom {
 
 struct em28xx_audio {
 	char name[50];
-	char *transfer_buffer[EM28XX_AUDIO_BUFS];
-	struct urb *urb[EM28XX_AUDIO_BUFS];
+	unsigned num_urb;
+	char **transfer_buffer;
+	struct urb **urb;
 	struct usb_device *udev;
 	unsigned int capture_transfer_done;
 	struct snd_pcm_substream   *capture_pcm_substream;