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.
>> 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.
Regards,
Clemens
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