commit 2c4e8fed0d1031b92ec8d9205867a38730726450
author Anson Jacob <ansonkuzhumbil@gmail.com> Tue Jul 01 18:17:20 2014 +0800
committer Dmitry Shmidt <dimitrysh@google.com> Thu Jan 19 13:33:07 2017 -0800
tree 82d82366cd644b0b3fd0f77415eba4b90dd458da
parent 64d81a260c5b3a83d4c437fa6bd591cc6fb82133

ANDROID: usb: gadget: f_audio_source: change max ISO packet size

Re-applying from
https://gitorious.org/shr/linux/commit/eb4c9d2db894c3492c0a848581bd4f6790f93d5f

Most USB-AUDIO devices are limited to 256 byte for max iso buffer size.
If a IN_EP_MAX_PACKET_SIZE is bigger than a USB-AUDIO device's max iso
buffer size, it will cause noise. This patch will prevent this case as
possibe by reducing packet size. When using 44.1khz, 2ch, 16bit audio
data, if max packet size is bigger than 176 bytes, it's no problem.

Credits to: Iliyan Malchev <malchev@google.com>

Change-Id: Ic2a1c19ea65d5fb42bf12926b51b255b465d7215
Signed-off-by: Anson Jacob <ansonkuzhumbil@gmail.com>

drivers/usb/gadget/f_audio_source.c

diff --git a/drivers/usb/gadget/f_audio_source.c b/drivers/usb/gadget/f_audio_source.c
index 56dcf21..65760c4 100644
--- a/drivers/usb/gadget/f_audio_source.c
+++ b/drivers/usb/gadget/f_audio_source.c
@@ -24,7 +24,7 @@
 #define SAMPLE_RATE 44100
 #define FRAMES_PER_MSEC (SAMPLE_RATE / 1000)
 
-#define IN_EP_MAX_PACKET_SIZE 384
+#define IN_EP_MAX_PACKET_SIZE 256
 
 /* Number of requests to allocate */
 #define IN_EP_REQ_COUNT 4