Hi. I am trying to write a Linux sound driver. I have some questions
that I hope someone here can answer.
1. (the big question) This device requires a single DMA buffer of up
to 8 Kb in main memory. It reads/writes the buffer circularly. It
can't chain buffers. Can I use the OSS DMA routines to set that
up somehow (how?), or do I have to write a non-OSS driver?
What does this imply for mmap?
2. This device is capable of telling how many samples it has
read/written, with an accuracy of 1 sample. I'd like to export
that via the SNDCTL_DSP_GET{I,O}PTR, ioctls, but I can't see how
my driver can get control on those ioctls.
3. This device has memory-mapped registers. I want to write a probe
routine that can verify that the device is there at the address
it's supposed to be. Is there a Linux routine to "read memory and
trap any fault"?
4. The mixer doesn't have a capability that corresponds to
SOUND_MIXER_VOLUME. If I don't implement SOUND_MIXER_VOLUME, will
I be incompatible with 99% of the apps? If I have to, I can fake
it -- maintain a SW volume setting and merge it into the level
I send to all the other faders...
That's enough questions for now. Hopefully, these are easy for
someone who's familiar with the Linux sound architecture.
Thanks for any help.
K<bob>
