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由 Alan Stern 提交于
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: NRoger Whittaker <Roger.Whittaker@suse.com> Fixes: d482c7bb ("USB: Skip endpoints with 0 maxpacket length") Signed-off-by: NAlan 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.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
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