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[media] em28xx: fix analog streaming with USB bulk transfers 

With the conversion to videobuf2, some unnecessary calls of
em28xx_set_alternate() have been removed. It is now called at analog streaming
start only.
This has unveiled a bug that causes USB bulk transfers to fail with all urbs
having status -EVOERFLOW.
The reason is, that for bulk transfers usb_set_interface() needs to be called
even if the previous alt setting was the same (side note: bulk transfers seem
to work only with alt=0).
While it seems to be NOT necessary for isoc transfers, it's reasonable to just
call usb_set_interface() unconditionally in em28xx_set_alternate().
Also add a comment that explains the issue to prevent regressions in the future.

Cc: stable@vger.kernel.org # for 3.8
Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Frank Schaefer 2013-02-07 13:32:46 -03:00 committed by Mauro Carvalho Chehab
parent 4880f56438
commit 33f6984ece
1 changed files with 22 additions and 21 deletions
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43
drivers/media/usb/em28xx/em28xx-core.c
View File

@ -813,12 +813,12 @@ int em28xx_resolution_set(struct em28xx *dev)
/* Set USB alternate setting for analog video */
int em28xx_set_alternate(struct em28xx *dev)
{
int errCode, prev_alt = dev->alt;
int errCode;
int i;
unsigned int min_pkt_size = dev->width * 2 + 4;
/* NOTE: for isoc transfers, only alt settings > 0 are allowed
for bulk transfers, use alt=0 as default value */
bulk transfers seem to work only with alt=0 ! */
dev->alt = 0;
if ((alt > 0) && (alt < dev->num_alt)) {
em28xx_coredbg("alternate forced to %d\n", dev->alt);
@ -849,25 +849,26 @@ int em28xx_set_alternate(struct em28xx *dev)
}
set_alt:
if (dev->alt != prev_alt) {
if (dev->analog_xfer_bulk) {
dev->max_pkt_size = 512; /* USB 2.0 spec */
dev->packet_multiplier = EM28XX_BULK_PACKET_MULTIPLIER;
} else { /* isoc */
em28xx_coredbg("minimum isoc packet size: %u (alt=%d)\n",
min_pkt_size, dev->alt);
dev->max_pkt_size =
dev->alt_max_pkt_size_isoc[dev->alt];
dev->packet_multiplier = EM28XX_NUM_ISOC_PACKETS;
}
em28xx_coredbg("setting alternate %d with wMaxPacketSize=%u\n",
dev->alt, dev->max_pkt_size);
errCode = usb_set_interface(dev->udev, 0, dev->alt);
if (errCode < 0) {
em28xx_errdev("cannot change alternate number to %d (error=%i)\n",
dev->alt, errCode);
return errCode;
}
/* NOTE: for bulk transfers, we need to call usb_set_interface()
* even if the previous settings were the same. Otherwise streaming
* fails with all urbs having status = -EOVERFLOW ! */
if (dev->analog_xfer_bulk) {
dev->max_pkt_size = 512; /* USB 2.0 spec */
dev->packet_multiplier = EM28XX_BULK_PACKET_MULTIPLIER;
} else { /* isoc */
em28xx_coredbg("minimum isoc packet size: %u (alt=%d)\n",
min_pkt_size, dev->alt);
dev->max_pkt_size =
dev->alt_max_pkt_size_isoc[dev->alt];
dev->packet_multiplier = EM28XX_NUM_ISOC_PACKETS;
}
em28xx_coredbg("setting alternate %d with wMaxPacketSize=%u\n",
dev->alt, dev->max_pkt_size);
errCode = usb_set_interface(dev->udev, 0, dev->alt);
if (errCode < 0) {
em28xx_errdev("cannot change alternate number to %d (error=%i)\n",
dev->alt, errCode);
return errCode;
}
return 0;
}