dma_alloc_coherent

[Denis Kirjanov]

On 2/5/16, Ran Shalit <ranshalit at gmail.com> wrote:
> Hello,
>
> I read the readme about dma API, but still don't understand how it
> should be used
> It is said that dma_alloc_coherent is responsible for allocating the
> buffer.

>
> 1. But how to trigger the dma transaction to start ?
> 2. Is there a callback when it is finished ?

It's used for data transfer between IO device and system memory. You
allocate a kernel buffer for DMA transaction (in this case dma from
device to system memory) and setup your device for dma transfer. An IO
device usually generates an interrupt when DMA transfer completes.
>
> Thank you,
> Ran
>
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-- 
Regards / Mit besten Grüßen,
Denis