Re: documentation

[Takashi Iwai <tiwai@suse.de>]

At Wed, 24 Apr 2002 07:26:04 -0700 (PDT),
Guilhem Tardy wrote:
> 
> Hi,
> 
> I am writing an ALSA driver for a new card. I had doc for 0.5.0, but this is
> outdated and so far had to do with examples in the 0.9.0beta12 distribution
> (mainly dummy.c and cs4281.c). Is there any doc available otherwise?

no, unfortunately not yet.
i posted a very brief info recently on alsa-devel.
please check out the archive.


> Any hint as for what I am facing, given that my card doesn't do DMA.
 
then you have to define copy and silence ops additionally.
copy the data on user buffer to the destination in these ops.
you'll need to reschedule ocasionally to avoid too long code path.
an example is found in gus driver (gus_pcm.c).
you can also use need_resched() to check the rescheduling.


> What is required from my part to support memory mapping from the driver to the
> application? Would this be supported through the OSS compatibility layer, too?

hmm...  mmap without dma?
how do you transfer the data on buffer to hardware?

the copy and silence ops are called when write() is called (more
exactly on alsa it's ioctl) - the thread writing to the device does
actually work like DMA.  on mmap mode, there is no such one.  so you
need an extra thread (or if it's not too heavy then tasklet might be
available) anyway.


Takashi