Re: [RFC] URBs and buffer management

Hi Oliver,

> > > > an alternate way would be to extend the usb_kill_anchored_urbs() with
> > > > its own complete handler that gets called for every anchored URB. This
> > > > would make it possible to cleanup the allocated buffers. I attached a
> > > > patch for that, too.
> > > 
> > > No, that would mean an URB could have both its original and the additional
> > > handler or only the additional handler called. That's increasing complexity,
> > > not lowering it.
> > 
> > depends on how you use it. I would only use the original complete
> > handler to do the re-submission of the URB and the additional handler to
> > free the allocated buffers. For that use case it works perfectly fine.
> > 
> > To avoid confusion we could rename it to usb_release_t or something
> > similar.
> 
> One usage is a bit weak to add common code.

this is why I wanna have a general solution for one-shot buffers.

> > > It seems to me that freeing buffers in usbcore is the logical conclusion
> > > of the pattern used in usb-skeleton. It may be used to avoid calling a
> > > completion handler at all.
> > 
> > I agree that it is the cleanest to free the buffers when URB is no
> > longer in use. Normally that means that any allocated buffer for this
> > URB is also not needed anymore.
> > 
> > Actually I am happy with any solution that frees the driver from having
> > to track the buffers for incoming endpoints used by an URB.
> 
> I am fine with your original patch. Perhaps you should resend it.

Greg, did you see that patch? Do you have any comments on it? If the
solution is acceptable, I can complete the patch with the missing
helpers and "officially" submit it.

> > For outgoing URBs the current approach with a separate buffer makes
> > sense. This allows me to use an skb->data directly without copying the
> > data first. Works really nicely in the new driver.
> 
> Nice to hear.

The new USB anchors seem to work pretty fine. No crashes.

Regards

Marcel



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