linux-kernel - [PATCH 3.18 164/185] media: em28xx: USB bulk packet size fix

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Date:   Mon, 28 May 2018 12:03:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Brad Love <brad@...tdimension.cc>,
        Michael Ira Krufky <mkrufky@...uxtv.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 3.18 164/185] media: em28xx: USB bulk packet size fix

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Brad Love <brad@...tdimension.cc>

[ 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@...tdimension.cc>
Reviewed-by: Michael Ira Krufky <mkrufky@...uxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/media/usb/em28xx/em28xx.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/media/usb/em28xx/em28xx.h
+++ b/drivers/media/usb/em28xx/em28xx.h
@@ -183,7 +183,7 @@
    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