Re: [PATCH 0/4] dmaengine redux continued

[Guennadi Liakhovetski]

On Thu, 4 Dec 2008, Dan Williams wrote:

> On Thu, Dec 4, 2008 at 1:51 AM, Guennadi Liakhovetski
> <g.liakhovetski@xxxxxx> wrote:
> > What about the last hunk from the patch at
> >
> > http://marc.info/?l=linux-arm-kernel&m=122607472721145&w=2
> >
> > ? Can we add this tx_free pointer? Would you like me to submit it as a
> > separate patch? I'd like to be able to reuse tx-descriptors in clients, so
> > I then have to explicitly release them in the dmaengine device
> > (controller) driver.
> >
> 
> I took a look but the description does not explain why the driver
> needs an explicit release.  In what cases is the implied release, when
> the descriptor is acked && done, insufficient?

v4l. I think, the proper moment to free tx-descriptors is at VIDIOC_DQBUF 
time. I.e., there is an explicit ioctl from user-space: "free buffers 
now". That's when I want to call .tx_free().

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
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