Configure DMA atributes?

Luis R. Rodriguez mcgrof at
Wed Aug 14 03:18:47 EDT 2013

On Mon, Aug 12, 2013 at 10:55 AM, Peter Senna Tschudin
<peter.senna at> wrote:

That's the key here. From Documentation/DMA-API-HOWTO.txt :

The standard 32-bit addressing device would do something like this:

        if (dma_set_mask(dev, DMA_BIT_MASK(32))) {
                       "mydev: No suitable DMA available.\n");
                goto ignore_this_device;

Another common scenario is a 64-bit capable device.  The approach here
is to try for 64-bit addressing, but back down to a 32-bit mask that
should not fail.  The kernel may fail the 64-bit mask not because the
platform is not capable of 64-bit addressing.  Rather, it may fail in
this case simply because 32-bit addressing is done more efficiently
than 64-bit addressing.  For example, Sparc64 PCI SAC addressing is
more efficient than DAC addressing.

Hope that helps.


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