Hello Tilman,
On Thursday 07 July 2005 02:44, Tilman Schmidt wrote:
> What's the proper way to handle the case of a control write
> URB completing with status == -EPIPE?
-EPIPE on control endpoint is a "protocoll stall". The USB device
has not understand what you are saying.
There are two common causes for this event to happen.
a) error in transmission. If you are absolutely sure that the command is
OK, you should do a retry.
b) You have send a command which is not understood by the device.
Retry doesn't make sense. Perhaps sending some other command
instead?
In order to distinguish between these two causes, it might be wise to do
a retry (to opt out a) ), and if the -EPIPE remains, do something else.
Unstalling the control endpoint is not possible. The protocoll stall is
removed by the device on the reception of the next control message.
best regards
Wolfgang
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