Re: [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel()

From: Guennadi Liakhovetski
Date: Fri Mar 30 2012 - 06:40:29 EST

On Fri, 30 Mar 2012, Russell King - ARM Linux wrote:

> On Fri, Mar 16, 2012 at 03:28:39PM +0100, Guennadi Liakhovetski wrote:
> > Yessss!!! Let's do that! :-D Now, you're proposing exactly the same, as
> > what I was proposing! :-) Now you just have to remove the filter function
> > parameter from dma_request_channel() - it is anyway the same for all and
> > implemented in the dmaengine core - and you get
> >
> > dma_request_channel(mask, slave_desc)
> >
> > which is exactly what I was proposing! :-)
> Bollocks it is. You're wanting to use the peripheral address, width
> and burst size to try to determine what channel to use. That's a
> totally crackpot idea, and as I've already said several times it won't
> work in many real life cases we have already.

I'm afraid I'm just somehow failing to explain my thoughts to you,
Russell. I don't think I ever said about using addresses, widths etc. They
are not even used _now_ by the shdma.c driver. Why should I propose that

What I was proposing is to use some kind of an opaque slave ID for that.
Which is, I think, pretty much the same as using a device pointer and DMA

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