Subject: Re: [Fwd: [alsa-devel] embedded sound architecture question]

From: Joachim Förster <[email-masked]>
Date: Tue, 15 May 2007 18:28:00 +0200

Hi Sylvain,

thank you very much for your mail,

On Tue, 2007-05-15 at 09:09 +0200, Sylvain Munaut wrote:
> I'm not an alsa expert but I'm working on a driver right now. And alsa
> provide you a hook so you can allocate your memory buffer your self.
> So as long as your control maps it's memory somewhere in the
> cpu address space you should be fine.

By "hook", do you mean the prepare()/hw_params() callbacks?

I noticed that there is an (undocumented?) mmap() callback, too, so I
think, I have to implement that one and call something like
io_remap_pfn_range() to "connect" the device's memory to the VMA
(virtual memory area) which is provided as an argument to the mmap()
callback, right?

In our case, we are not going to allocate any memory like a typical ALSA
driver does (with DMA) (in prepare()/hw_params() callback), because the
device's IO memory will "be there" - we just have to "announce"/map it
into kernel space, right? Or is this interpretation wrong?

 Joachim