ALSA Driver for ARM-Linux 2.6

ALSA Driver for ARM-Linux 2.6

[Klaus Fetscher]

Hi,

we want to program an ALSA driver for a Codec which communicates over an 
I2S interface with an ARM9 processor.
I have read several messages regarding ALSA-Drivers, Linux 2.6 and ARM 
and know I am a little bit confused.

Is it possible to use ALSA with ARM or need we some patches for the ARM 
CPU ?

I have read, that the sa11xx-uda1341 driver is not a good starting point 
for implementing a driver. Which is a better solution ?

Thanks,

Klaus


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Re: ALSA Driver for ARM-Linux 2.6

[Takashi Iwai]

At Wed, 11 Aug 2004 22:11:33 +0200,
Klaus Fetscher wrote:
> 
> Hi,
> 
> we want to program an ALSA driver for a Codec which communicates over an 
> I2S interface with an ARM9 processor.
> I have read several messages regarding ALSA-Drivers, Linux 2.6 and ARM 
> and know I am a little bit confused.
> 
> Is it possible to use ALSA with ARM or need we some patches for the ARM 
> CPU ?
> 
> I have read, that the sa11xx-uda1341 driver is not a good starting point 
> for implementing a driver. Which is a better solution ?

In general, ALSA has a problem on architectures like ARM about cache
and mmap.  So far, the ALSA should work fine on ARM, too, if the
driver doesn't use mmap.

Russell King has some patches to fix this issue, which I will merge
later on our tree.


Takashi


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Re: ALSA Driver for ARM-Linux 2.6

[Takashi Iwai]

At Mon, 16 Aug 2004 14:32:36 +0200,
Klaus Fetscher wrote:
> 
> Hallo Takashi,
> 
> thanks for your answer.
> 
> >>we want to program an ALSA driver for a Codec which communicates over an 
> >>I2S interface with an ARM9 processor.
> >>I have read several messages regarding ALSA-Drivers, Linux 2.6 and ARM 
> >>and know I am a little bit confused.
> >>
> >>Is it possible to use ALSA with ARM or need we some patches for the ARM 
> >>CPU ?
> >>
> >>I have read, that the sa11xx-uda1341 driver is not a good starting point 
> >>for implementing a driver. Which is a better solution ?
> >>    
> >>
> >
> >  
> >
> Does the driver under sound/arm/sa11xx-uda1341.c in the current 2.6.7 
> kernel tree work with ALSA ?

Well, I'm not sure about this.  Someone told that it's broken.
I even didn't take a deep look yet.  But, as written above, it should
work if the driver doesn't use mmap.

> If yes, I will change this file for my requirements or do you have a 
> better idea ?

Depends.  If the board design is similar with sa11xx-uda1341, it's
an easier start point.  (I believe sa11xx-uda1341 driver can be more
generalized, though.)


> The CPU communicates with the Sound Chip over a I2S interface. Shall I 
> make a new subdirectory  /sound/i2s or /sound/i2c/i2s for the I2S stuff 
> or do you recommand another directory ?

Unless you need the "generic" i2s support over different
architectures, you should put the stuff locally in your driver code.

> 
> >In general, ALSA has a problem on architectures like ARM about cache
> >and mmap.  So far, the ALSA should work fine on ARM, too, if the
> >driver doesn't use mmap.
> >
> >Russell King has some patches to fix this issue, which I will merge
> >later on our tree.
> >
> >  
> >
> If I don't use mmap in the driver (actually, sa11xx-uda1341.c don't use 
> this function) I don't need this patches, correct ?

Yes (but again, I haven't tested ARM at all by myself).


Takashi


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