diff options
| author | Frank Schaefer <fschaefer.oss@googlemail.com> | 2013-02-07 20:32:46 +0400 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2013-02-12 00:17:44 +0400 |
| commit | 33f6984ecefb9b84f1b4d1d3b9022731bb8b62d0 (patch) | |
| tree | 52b7d2df6ef5ea77c927aa6c3379ac5ebd63f491 /drivers | |
| parent | 4880f56438ef56457edd5548b257382761591998 (diff) | |
| download | linux-33f6984ecefb9b84f1b4d1d3b9022731bb8b62d0.tar.xz | |
[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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/media/usb/em28xx/em28xx-core.c | 43 |
1 files changed, 22 insertions, 21 deletions
diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c index ee00f9e23420..aaedd11791f2 100644 --- a/drivers/media/usb/em28xx/em28xx-core.c +++ b/drivers/media/usb/em28xx/em28xx-core.c @@ -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; } |