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.
Signed-off-by: Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx>
---
drivers/media/usb/em28xx/em28xx-core.c | 43 ++++++++++++++++----------------
1 Datei geändert, 22 Zeilen hinzugefügt(+), 21 Zeilen entfernt(-)
diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
index 80f87bb..ce4f252 100644
--- a/drivers/media/usb/em28xx/em28xx-core.c
+++ b/drivers/media/usb/em28xx/em28xx-core.c
@@ -811,12 +811,12 @@ 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);
@@ -847,25 +847,26 @@ 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;
}
--
1.7.10.4
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