Am Donnerstag, 4. Januar 2007 16:38 schrieb Alan Stern:
> On Thu, 4 Jan 2007, Oliver Neukum wrote:
>
> > Hi,
> >
> > quoting from the WCM spec:
> > -
> > The firmware shall interpret GET_ENCAPSULATED_RESPONSE as a request to read
> > response bytes. The firmware shall send the next wLength bytes from the
> > response. The firmware shall allow the host to retrieve data using any
> > number of GET_ENCAPSULATED_RESPONSES. The firmware shall return a
> > zero-length
> > reply if there are no data bytes available.
> > The firmware shall send RESPONSE_AVAILABLE notifications periodically, using
> > any appropriate algorithm, to inform the host that there is data available
> > in the reply buffer. The firmware is allowed to send RESPONSE_AVAILABLE
> > notifications even if there is no data available, but this will obviously
> > reduce overall performance.
> > -
> >
> > Do I read this correctly to mean that I must not treat zero bytes from
> > GET_ENCAPSULATED_RESPONSE as an error, because RESPONSE_AVAILABLE
> > is reliable in one direction only?
>
> The spec certainly says that 0 bytes from GET_ENCAPSULATED_RESPONSE is not
> an error.
>
> I don't know what you mean by "RESPONSE_AVAILABLE is reliable in one
> direction only". The message should be treated as a hint that data may be
> available so the host should attempt to start a transfer -- but it's still
> possible that no data bytes are available.
>
> Alan Stern
>
Jan 4 17:49:22 oenone kernel: usbcore: registered new interface driver cdc_wdm
Jan 4 17:49:32 oenone ifup: No configuration found for usb0
Jan 4 17:49:36 oenone kernel: usb 1-3.2: link qh16-0601/ffff81001fd7c500 start
15 [1/2 us]
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c: Status urb has been
submitted
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c: Tx URB has been
submitted
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c: wdm_out_callback -
status: 0
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c: wdm_int_callback -
0 bytes
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c: Status urb has been
submitted
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c: unknown
notification 90 received: index 23130 len 23130
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c: Error submitting
int urb - -22
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c:
NOTIFY_RESPONSE_AVAILABLE received: index 7 len 0
Jan 4 17:49:36 oenone kernel: usb 1-3.2: unlink qh16-0601/ffff81001fd7c500
start 15 [1/2 us]
Jan 4 17:49:36 oenone kernel: drivers/usb/class/cdc-wdm.c: wdm_in_callback -
status: -32
I am beginning to doubt my interpretations of that spec.
Regards
Oliver
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