Comment # 10 on bug 1159811 from Roger Whittaker

For the record, I reported this to Laurent Pinchart.  After looking at lsusb -v
outputs, he identified the change that caused the new behaviour, and wrote:

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[  470.351700] usb 1-1.4.3.1: config 1 interface 2 altsetting 0 endpoint 0x82
has wMaxPacketSize 0, skipping

This seems to be the culprit, and it points to the USB core. One
interface is ignored due to its wMaxPacketSize value, and the uvcvideo
driver then fails to find it.

The wMaxPacketSize check was added in

commit d482c7bb0541d19dea8bff437a9f3c5563b5b2d2
Author: Alan Stern <stern@rowland.harvard.edu>
Date:   Mon Oct 28 10:52:35 2019 -0400

    USB: Skip endpoints with 0 maxpacket length

    Endpoints with a maxpacket length of 0 are probably useless.  They
    can't transfer any data, and it's not at all unlikely that an HCD will
    crash or hang when trying to handle an URB for such an endpoint.

    Currently the USB core does not check for endpoints having a maxpacket
    value of 0.  This patch adds a check, printing a warning and skipping
    over any endpoints it catches.

    Now, the USB spec does not rule out endpoints having maxpacket = 0.
    But since they wouldn't have any practical use, there doesn't seem to
    be any good reason for us to accept them.

    Signed-off-by: Alan Stern <stern@rowland.harvard.edu>

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