[media] em28xx: fix analog streaming with USB bulk transfers (33f6984e) · Commits · 戴 / test

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>

drivers/media/usb/em28xx/em28xx-core.c

+22 −21

Original line number	Diff line number	Diff line
		@@ -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);
		@@ -849,7 +849,9 @@ int em28xx_set_alternate(struct em28xx *dev)
		}

		set_alt:
		if (dev->alt != prev_alt) {
		/* 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;
		@@ -868,7 +870,6 @@ set_alt:
		dev->alt, errCode);
		return errCode;
		}
		}
		return 0;
		}

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