Re: Is there a binding for IORESOURCE_DMA population?

On Fri, Jul 15, 2011 at 08:11:41PM +0200, Arnd Bergmann wrote:

On Friday 15 July 2011 18:45:38 Tabi Timur-B04825 wrote:

quoted

On Fri, Jul 15, 2011 at 11:32 AM, Shawn Guo [off-list ref] wrote:

quoted

First of all, using powerpc dma-channel binding on such dma event
seems not reflecting the hardware facts.  Secondly, the binding in
this case (below) looks silly.  Thirdly, device driver need to make
code change for simply getting a dma event number.

Take a look at p1022ds.dts or mpc8610hpcd.dts.  We create separate DMA
channel nodes on Freescale PowerPC parts because the channels really
are independent.  On these two boards, some of the DMA channels are
used by the async DMA driver, and two of the channels are used by the
audio driver.

I think this is much better than using IORESOURCE_DMA fields, which
basically are only well-defined for PC-style i8237 DMA controllers
used in stuff like floppy drives and ISA sound cards.

However, we should find a way to standardize finding the dma_chan
for an platform_device based on a phandle. Maybe a little helper
that will scan a well-known property (dma-channels?) for phandles
to a device_node that is backing a struct dma_chan.

That sounds appropriate.

g.