On Fri, Jul 19, 2013 at 6:30 PM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote:
> Ming Lei wrote:
>> On Fri, Jul 19, 2013 at 5:06 PM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote:
>>> Ming Lei wrote:
>>>> if (list_empty (&stream->td_list)) {
>>>> if (running from hcd interrupt or tasklet context)
>>>> underrun
>>>> else
>>>> new stream
>>>> }
>>>
>>> Why shouldn't a driver start a stream in an interrupt/tasklet,
>>
>> It should, but actually one driver won't do this because generally
>> usb_set_interface() is required before starting stream.
>
> Not always, and the usb_set_interface() call can be done in a different
> context.
>
>> If stream is started in another non-isoc URB complete(), this approach
>> can cover this situation easily.
>>
>> But do you have examples in which one isoc stream is started in another
>> isoc URB's complete()?
>
> There are quite a few audio devices using implicit rate feedback, where
> playback URBs are submitted from the capture completions handler.
That still can be covered easily by the approach since isoc direction is
different, :-)
>
>>> or delay URB resubmission to a workqueue?
>>
>> Yes, it is possible, and the isoc URBs can be resubmitted in tasklet too,
>> but it isn't a big deal:
>
> But your proposed code would not be able to differentiate a workqueue
> resubmission from a stream start.
As I explained, it isn't a big deal. Either it is working well for long time
in case of underrun with empty queue, or we can change the resubmission
to complete(), right?
Thanks,
--
Ming Lei
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
