linux-kernel - RE: [PATCH 1/7] DMAENGINE: add generic PrimeCell interface to COH 901 318 v6

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Date:	Wed, 12 May 2010 09:39:23 +0200
From:	Linus WALLEIJ <linus.walleij@...ricsson.com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/7] DMAENGINE: add generic PrimeCell interface to COH
 901 	318 v6

[Dan]

> >> +void dma_set_ambaconfig(struct dma_chan *chan,
> >> +                       struct amba_dma_channel_config *config)
> >
> > What happens when two primecell dma devices are present on one soc?
> > Can that happen?  In that case we'll have conflicting providers of
> > dma_set_ambaconfig().
> >
> 
> ...the ->device_control() method is already approaching an ioctl()
> let's just add the argument parameter to complete the capability,
> i.e.:
> 
> int (*device_control)(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> unsigned long arg);

So the unsigned long arg is to match an ioctl? Okidoki...

If it was only for in-kernel use a void* would be preferred
I believe since assuming unsigned long to be == bus width
is ... well, disturbing, since we'll be casting this into
a struct pointer.

So this should also be used for the AMBA configuration stuff
then, so I have to make first a patch to convert all the
device_control functions and then a patch on top of that to
implement the AMBA call as a device_control() thingie?

(Should work out...)

Just a bit of work, so will take some more hours :-)

I will just have to make a proof-of-concept for the AMBA config
interface for Russell first, then I'll be on the ioctl-like API.

Yours,
Linus Walleij
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