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media: em28xx: USB bulk packet size fix
authorBrad Love <brad@nextdimension.cc>
Fri, 5 Jan 2018 00:04:13 +0000 (19:04 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 30 May 2018 05:49:14 +0000 (07:49 +0200)
commitb2895b916282b09d42ec789dfd234091c788a5ad
treeb336b83cf1a261cdbbe6e8343e4f25d385779958
parent1f8b926275550719fb9f9541df1b039d8caa9e33
media: em28xx: USB bulk packet size fix

[ Upstream commit c7c7e8d7803406daa21e96d00c357de8b77b6764 ]

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>
drivers/media/usb/em28xx/em28xx.h