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:
# 512 * 384 = 196608
## 196608 % 188 != 0
After:
# 512 * 47 * 2 = 48128 (188 * 128 * 2)
## 48128 % 188 = 0
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@xxxxxxxxxxxxxxxx>
---
drivers/media/usb/em28xx/em28xx.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
index c85292c..7be8ac9 100644
--- a/drivers/media/usb/em28xx/em28xx.h
+++ b/drivers/media/usb/em28xx/em28xx.h
@@ -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
--
2.7.4
