At 04 Apr 2002 15:41:36 +0200,
Leif Lindholm wrote:
>
> Hello
>
> I'm working on a set-top-box based on the National Semiconductor SC1200
> Geode integrated microprocessor.
>
> National have been nice enough to write an Alsa-driver for the built-in
> AC97-controller/audio thingy - unfortunetaly it is written for 0.5.10b.
>
> So now I need to modify this one to use with 0.9.
>
> Can someone give me a few tips/hints or is there possibly a document
> about this that I failed to google up?
unfortunatley (as always :) there is no documentation about the kernel
stuff yet.
since you have already a working 0.5.x driver, it's not too difficult,
though.
as far as i can remember..
- renaming
fragment -> period
channel -> stream
voice -> channel
snd_pcm_subchannel -> snd_pcm_substream
- renaming of constants
generally:
SND_XXX -> SNDRV_XXX
some other changes, too: e.g.
SND_PCM_TRIGGER_GO -> SNDDRV_PCM_TRIGGER_START
- snd_assert() is used instead of snd_debug_check()
(note that the argument is opposite, assert(x) means that "x" is true .)
- no longer difference of stream/blocking modes
- general hardware information is stored in snd_pcm_hardware_t
and passed to the runtime struct in open().
the information is intuitive, look at other sources.
- abstracted ops.
open(substream)
- open the device
- copy the substream->runtime->hw parameter
(not pass the pointer)
- set up the constraints (if any)
hw_params(substream, hw_params)
- allocate a buffer
usually via snd_pcm_lib_malloc_pages
prepare(substream)
- set up the hardware parameters (like 0.5.x)
note that parameters in runtime struct are
stored in frames, not in bytes.
there are functions, snd_pcm_lib_buffer_bytes()
and snd_pcm_lib_period_bytes()
trigger(substream, cmd)
- start, stop, pause (like 0.5.x)
pointer(substream)
- returns the current pointer where the hw refers.
(in frames!)
hw_free(substream)
- free the buffer
usually via snd_pcm_lib_free_pages(substream)
close(substream)
- close the device, clean up.
copy, silence
- needed only if you don't (can't) use mmap.
they are defiend in snd_pcm_ops_t struct and set up in
pcm initizliation routine via snd_pcm_set_ops().
- when the interrupt occurs at period (fragment), call
snd_pcm_period_elapsed(substream)
just once per interrupt.
- no longer snd-xxx functions for allocating port, dma and irqs.
you need to use standard functions.
for releasing struct resources *, you have to use kfree_nocheck()
to avoid malloc-wrapper.
- definitions of pci id table, probe(), remove() (suspend() and
remove() if possible) on struct pci_driver.
- finally and best way - look at drivers on a same chip of both 0.5.x
and 0.9.0, and compare them :)
Takashi
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