Re: ALSA Driver for ARM-Linux 2.6

[Takashi Iwai <tiwai@suse.de>]

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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