snd_pcm_lib_malloc_pages

snd_pcm_lib_malloc_pages

[Adrian McMenamin]

I am trying to write to a driver on the Dreamcast (SH4) - as far as I
can see there are no ALSA drivers extant for this processor. Does that
mean I should assume this function is implemented or unimplemented on
SH? On a scan through the code I can see no obvious reason why it
wouldn't be working (ie no processor specific code) but there must be
some degree of processor/bus specific code.

Adrian



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Re: snd_pcm_lib_malloc_pages

[Takashi Iwai]

At Sun, 20 Nov 2005 23:12:05 +0000,
Adrian McMenamin wrote:
> 
> I am trying to write to a driver on the Dreamcast (SH4) - as far as I
> can see there are no ALSA drivers extant for this processor. Does that
> mean I should assume this function is implemented or unimplemented on
> SH? On a scan through the code I can see no obvious reason why it
> wouldn't be working (ie no processor specific code) but there must be
> some degree of processor/bus specific code.

You don't have to use snd_pcm_lib_malloc_pages().  This function is
provided for the common case together with the buffer pre-allocation
via snd_pcm_lib_preallocate_pages*() functions.
snd_pcm_lib_malloc_pages() itself doesn't allocate buffers but calls
the allocator in memalloc.c.  Thus, without pre-allocation, this
function doesn't work at all.

What you have to do is just to set up the buffer in hw_params callback
and release in hw_free callback.  Note that these callbacks may called
multiple times per session, so you have to check if the parameters are
identical and reset the bufer if changed.


Takashi


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