I have a composite device (multiple serial ports) where each serial
port is controlled by a separate instance of my driver. The driver
instances all use the default control pipe to make configuration
changes on the device via usb_control_msg(). Are there any special
locking requirements that I need to take into account so that the
driver instances do not interfere with each other when they use this
routine? I have been assuming that the answer to that question is
"No!", but I'm running into some surprising (to me) behavior.
It seems that if several drivers concurrently make several
configuration parameter changes via usb_control_msg() I occasionally
see some control transfers duplicated on the bus, and some missing
(each duplicate appears to have taken the place of a transfer from
another driver instance). I have added logging to my driver and see
the interleaved requests from the different driver instances, but the
trace I obtain with the CATC bus analyzer doesn't match with my logs.
I'm grateful for any suggestions,
Rob.
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