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media: em28xx: USB bulk packet size fix

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[ Upstream commit c7c7e8d780 ]

Hauppauge em28xx bulk devices exhibit continuity errors and corrupted
packets, when run in VMWare virtual machines. Unknown if other
manufacturers bulk models exhibit the same issue. KVM/Qemu is unaffected.

According to documentation the maximum packet multiplier for em28xx in bulk
transfer mode is 256 * 188 bytes. This changes the size of bulk transfers
to maximum supported value and have a bonus beneficial alignment.

Before:

After:

This sets up USB to expect just as many bytes as the em28xx is set to emit.

Successful usage under load afterwards natively and in both VMWare
and KVM/Qemu virtual machines.

Signed-off-by: Brad Love <brad@nextdimension.cc>
Reviewed-by: Michael Ira Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Brad Love
2018-01-04 19:04:13 -05:00
committed by Greg Kroah-Hartman
parent f5f6bff50f
commit e4504b80e0
1 changed files with 1 additions and 1 deletions
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2
drivers/media/usb/em28xx/em28xx.h
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@@ -191,7 +191,7 @@
USB 2.0 spec says bulk packet size is always 512 bytes
*/
#define EM28XX_BULK_PACKET_MULTIPLIER 384
#define EM28XX_DVB_BULK_PACKET_MULTIPLIER 384
#define EM28XX_DVB_BULK_PACKET_MULTIPLIER 94
#define EM28XX_INTERLACED_DEFAULT 1