On Wed, 20 Dec 2006 10:04:01 -0500 (EST), Alan Stern <[EMAIL PROTECTED]> wrote:
> > Assuming x86 32, -115 = -EINPROGRESS, that means URB still pending, no
> > results yet
>
> All successful Submission ('S') lines will contain this code.
>
> > > e.g. status code "-2"
> >
> > -2 = -ENOENT, specified interface or endpoint does not exist or is not
> > enabled
>
> That's would the code would mean if it appeared on a Submission line. But
> when it appears on a Completion ('C') line it means "URB was synchronously
> unlinked by usb_unlink_urb".
I hate to disappoint you, Alan, but this is not how usbmon works.
Errors in submission are reported with 'E' event immediately after
the submission. So the monitoring application sees 'S' (which is
always successful, the status should be always ignored), and
possibly 'E'.
I consider it a fairly serious deficiency, but I don't have a good
idea how to fix it (without a performance penalty). The naive
approach would be to have a dual hook in the submission path.
The first hook creates a record, which is held back by the usbmon
and not seen by the application. The second hook updates the status
(either success or failure) and releases the record. If a callback
is called on the context of submission, it updates the held record,
or creates a new one. This turns upon the assumption that only one
outcome is possible: a submission error, or a callback, but not both.
Fixing this adds more state into usbmon and thus makes it less
transparent, so I decided to go with confusing definition of 'S',
'C', 'E', but have less bugs in the implementation.
Currently, either 'E' or 'C' always happen, but you do not know
which one at the time 'S' is reported.
-- Pete
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