From: Mauro Carvalho Chehab <m.chehab@samsung.com>
Date: Fri, 10 Jan 2014 08:53:24 +0000 (-0300)
Subject: [media] em28xx-audio: don't hardcode audio URB calculus
X-Git-Tag: v3.14-rc1~20^2~53
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1b3fd2d342667005855deae74200195695433259;p=pandora-kernel.git

[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>
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