Lots of noob questions on writing an ALSA driver for SM501

Lots of noob questions on writing an ALSA driver for SM501

[Bill Gatliff]

Guys:


I'm attempting to write my first ALSA driver.  My objective is to get 
sounds to emerge through a UCB1400 connected to an SM501's AC97-link 
controller, and to receive sounds coming from the UCB1400's audio input(s).

I'm going over Takashi Iwai's "Writing an ALSA Driver" document, but 
there are a few things I just don't understand yet.  I'm hoping that 
someone here will be able to set me straight.

The SM501 has an AC97-Link controller, but nothing else related to audio 
as far as I can tell.  In my hardware the SM501 is memory-mapped, and is 
not a PCI device.  The host processor is an AT91RM9200 (ARM).

As far as I can tell, I need a "PCM Interface" driver to provide a PCM 
device file to userspace.  It also looks like I need an "AC97 Interface" 
driver to provide access to the UCB1400 during playback and recording.  
Is this right?

I'm hoping someone will set me straight here.  Thanks!!


b.g.

-- 
Bill Gatliff
bgat@billgatliff.com

The true Southern watermelon is a boon apart, and not to be mentioned
with commoner things.  It is chief of the world's luxuries, king by
the grace of God over all the fruits of the earth.  When one has
tasted it, he knows what the angels eat.  It was not a Southern
watermelon that Eve took; we know it because she repented.
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Re: Lots of noob questions on writing an ALSA driver for SM501

[Jaroslav Kysela]

On Tue, 26 Jul 2005, Bill Gatliff wrote:

> Guys:
> 
> 
> I'm attempting to write my first ALSA driver.  My objective is to get sounds
> to emerge through a UCB1400 connected to an SM501's AC97-link controller, and
> to receive sounds coming from the UCB1400's audio input(s).
> 
> I'm going over Takashi Iwai's "Writing an ALSA Driver" document, but there are
> a few things I just don't understand yet.  I'm hoping that someone here will
> be able to set me straight.
> 
> The SM501 has an AC97-Link controller, but nothing else related to audio as
> far as I can tell.  In my hardware the SM501 is memory-mapped, and is not a
> PCI device.  The host processor is an AT91RM9200 (ARM).
> 
> As far as I can tell, I need a "PCM Interface" driver to provide a PCM device
> file to userspace.  It also looks like I need an "AC97 Interface" driver to
> provide access to the UCB1400 during playback and recording.  Is this right?
> 
> I'm hoping someone will set me straight here.  Thanks!!

Look to drivers in the sound/arm (alsa-kernel/arm) tree for ideas.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs


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Re: Lots of noob questions on writing an ALSA driver for SM501

[Bill Gatliff]

Jaroslav:

Jaroslav Kysela wrote:

>On Tue, 26 Jul 2005, Bill Gatliff wrote:
>  
>
>Look to drivers in the sound/arm (alsa-kernel/arm) tree for ideas.
>
>						Jaroslav
>  
>

I think that the pxa2xx-ac97 and pxa2xx-pcm stuff may be exactly the 
models I'm looking for.

But the sm501 stuff won't be ARM-specific--- it'll be tested on ARM and 
SH, at least.  So where should the source for sm501-pcm.c and sm501-ac97 
be placed?


b.g.

-- 
Bill Gatliff
bgat@billgatliff.com

Today is the last day of your life so far.



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Re: Lots of noob questions on writing an ALSA driver for SM501

[Jaroslav Kysela]

On Tue, 26 Jul 2005, Bill Gatliff wrote:

> But the sm501 stuff won't be ARM-specific--- it'll be tested on ARM and SH, at
> least.  So where should the source for sm501-pcm.c and sm501-ac97 be placed?

Good question. I think drivers/sm501 directory might be ok for the common 
stuff (library) and place the toplevel modules for architectures to arm/ 
and new sh/ directories. If the toplevel code will be very common, 
something like

#define ARCH_SH
#include "../arm/sm501-ac97.c"

might be used in the sh/ directory.

Or leave everything in drivers/sm501 for this time - we can move it later.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs


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Re: Lots of noob questions on writing an ALSA driver for SM501

[Bill Gatliff]

Jaroslav:

Jaroslav Kysela wrote:

>On Tue, 26 Jul 2005, Bill Gatliff wrote:
>
>Or leave everything in drivers/sm501 for this time - we can move it later.
>  
>

Ok.


b.g.

-- 
Bill Gatliff
bgat@billgatliff.com

You have the capacity to learn from mistakes.
You'll learn a lot today.



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