[alsa-devel] Getting physical address of the DMA buffer

Clemens Ladisch cladisch at fastmail.net
Wed Jun 27 13:23:10 CEST 2007

Pharaoh . wrote:
> On 6/27/07, Clemens Ladisch <cladisch at fastmail.net> wrote:
> > SNDRV_DMA_TYPE_CONTINUOUS is for a buffer that cannot be accessed
> > over DMA.
> >
> > What kind of bus does your hardware use, and how would you
> > allocate memory for it?
> Continuous buffers unrelated to the bus type can be allocated using
> SNDRV_DMA_TYPE_CONTINUOUS right? I am referring a standard driver from
> omap source tree, and the buffer allocation functions I have copied
> from there and they should be same for the range of OMAPs since the
> dma handling is same for them.

I don't know anything about OMAP.

If the processor doesn't use a MMU, then the memory addresses as seen
by the CPU are the same as those used by a device using DMA.  In that
case, you could use SNDRV_DMA_TYPE_CONTINUOUS and the correct address
would be available as runtime->dma_area.


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