Re: Migration from 0.5 to 0.9?

[Takashi Iwai <tiwai@suse.de>]

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