]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
USB: Fix: Don't skip endpoint descriptors with maxpacket=0
authorAlan Stern <stern@rowland.harvard.edu>
Mon, 6 Jan 2020 15:43:42 +0000 (10:43 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 6 Jan 2020 15:54:09 +0000 (16:54 +0100)
commit2548288b4fb059b2da9ceada172ef763077e8a59
tree30cbcd6e1f09829d6640d14d7932f09bdf213599
parentc215e48e97d232249a33849fc46fc50311043e11
USB: Fix: Don't skip endpoint descriptors with maxpacket=0

It turns out that even though endpoints with a maxpacket length of 0
aren't useful for data transfer, the descriptors do serve other
purposes.  In particular, skipping them will also skip over other
class-specific descriptors for classes such as UVC.  This unexpected
side effect has caused some UVC cameras to stop working.

In addition, the USB spec requires that when isochronous endpoint
descriptors are present in an interface's altsetting 0 (which is true
on some devices), the maxpacket size _must_ be set to 0.  Warning
about such things seems like a bad idea.

This patch updates an earlier commit which would log a warning and
skip these endpoint descriptors.  Now we only log a warning, and we
don't even do that for isochronous endpoints in altsetting 0.

We don't need to worry about preventing endpoints with maxpacket = 0
from ever being used for data transfers; usb_submit_urb() already
checks for this.

Reported-and-tested-by: Roger Whittaker <Roger.Whittaker@suse.com>
Fixes: d482c7bb0541 ("USB: Skip endpoints with 0 maxpacket length")
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://marc.info/?l=linux-usb&m=157790377329882&w=2
Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.2001061040270.1514-100000@iolanthe.rowland.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/usb/core/config.c