about the alsa i2c interface

about the alsa i2c interface

[Tehn-Yit Chin]

Hi,

We are trying to provide support for the CS43L43 device under the ALSA
architecture on an embedded platform.

During my early investigation, I noticed that ALSA has its own i2c code.
What is this required, and why doesn't it use the mainline i2c support?
On our platform, there are one other devices on the i2c bus, so I would
like to use the mainline i2c code.

Any pointers would be appreciated.

Tehn Yit Chin
Software Engineer, Grey Innovation Pty. Ltd.


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Re: about the alsa i2c interface

[Lee Revell]

On Thu, 2005-06-09 at 13:09 +1000, Tehn-Yit Chin wrote:
> Hi,
> 
> We are trying to provide support for the CS43L43 device under the ALSA
> architecture on an embedded platform.
> 
> During my early investigation, I noticed that ALSA has its own i2c code.
> What is this required, and why doesn't it use the mainline i2c support?
> On our platform, there are one other devices on the i2c bus, so I would
> like to use the mainline i2c code.

This is explained in "Writing an ALSA Driver"  (you did read it,
right?).  Basically the kernel's i2c layer is overly complex, and ALSA
only needs a small subset of it, so ALSA implements its own minimal i2c
layer.

Lee



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Re: about the alsa i2c interface

[Tomko]

Lee Revell wrote:

>On Thu, 2005-06-09 at 13:09 +1000, Tehn-Yit Chin wrote:
>  
>
>>Hi,
>>
>>We are trying to provide support for the CS43L43 device under the ALSA
>>architecture on an embedded platform.
>>
>>During my early investigation, I noticed that ALSA has its own i2c code.
>>What is this required, and why doesn't it use the mainline i2c support?
>>On our platform, there are one other devices on the i2c bus, so I would
>>like to use the mainline i2c code.
>>    
>>
>
>This is explained in "Writing an ALSA Driver"  (you did read it,
>right?).  Basically the kernel's i2c layer is overly complex, and ALSA
>only needs a small subset of it, so ALSA implements its own minimal i2c
>layer.
>
>  
>
So will this cause losing control on the I2c device ? for example i have 
4 device on the i2c bus , 3 of them are under the kernel's i2c which the 
the sequence control that they can't access the bus at the same time and 
one of them are under alsa's i2c , what will happen if the alsa's i2c 
device and the kernel's i2c device access the bus together ?

Regards,
TOM


>Lee
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>_______________________________________________
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>Alsa-devel@lists.sourceforge.net
>https://lists.sourceforge.net/lists/listinfo/alsa-devel
>  
>



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Re: about the alsa i2c interface

[Jaroslav Kysela]

On Thu, 9 Jun 2005, Tomko wrote:

> Lee Revell wrote:
> 
> >On Thu, 2005-06-09 at 13:09 +1000, Tehn-Yit Chin wrote:
> >  
> >
> >>Hi,
> >>
> >>We are trying to provide support for the CS43L43 device under the ALSA
> >>architecture on an embedded platform.
> >>
> >>During my early investigation, I noticed that ALSA has its own i2c code.
> >>What is this required, and why doesn't it use the mainline i2c support?
> >>On our platform, there are one other devices on the i2c bus, so I would
> >>like to use the mainline i2c code.
> >>    
> >>
> >
> >This is explained in "Writing an ALSA Driver"  (you did read it,
> >right?).  Basically the kernel's i2c layer is overly complex, and ALSA
> >only needs a small subset of it, so ALSA implements its own minimal i2c
> >layer.
> >
> >  
> >
> So will this cause losing control on the I2c device ? for example i have 
> 4 device on the i2c bus , 3 of them are under the kernel's i2c which the 
> the sequence control that they can't access the bus at the same time and 
> one of them are under alsa's i2c , what will happen if the alsa's i2c 
> device and the kernel's i2c device access the bus together ?

Use the kernel's i2c implementation in this case (see in ppc drivers for 
example). There must be only one arbiter code.

						Jaroslav

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


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RE: about the alsa i2c interface

[Tehn-Yit Chin]

 

> -----Original Message-----
> From: Lee Revell [mailto:rlrevell@joe-job.com] 
> Sent: Thursday, 9 June 2005 4:48 PM
> To: Tehn-Yit Chin
> Cc: alsa-devel@alsa-project.org
> Subject: Re: [Alsa-devel] about the alsa i2c interface
> 
> On Thu, 2005-06-09 at 13:09 +1000, Tehn-Yit Chin wrote:
> > Hi,
> > 
> > We are trying to provide support for the CS43L43 device 
> under the ALSA 
> > architecture on an embedded platform.
> > 
> > During my early investigation, I noticed that ALSA has its 
> own i2c code.
> > What is this required, and why doesn't it use the mainline 
> i2c support?
> > On our platform, there are one other devices on the i2c bus, so I 
> > would like to use the mainline i2c code.
> 
> This is explained in "Writing an ALSA Driver"  (you did read 
> it, right?).  Basically the kernel's i2c layer is overly 
> complex, and ALSA only needs a small subset of it, so ALSA 
> implements its own minimal i2c layer.
> 
> Lee
> 
> 

Many thanks for all the answers and comments.

Yep, I did read "Writing an ALSA Driver" and I also read the bit where
it said that the kernel's I2C is too complex for ALSA. My concern is
that we will have several devices on the I2C bus and acces to it will
need to be controlled, so for our project, it will need to use the
kernel's I2C code.

cheers,

Tehn Yit Chin 
Software Engineer, Grey Innovation Pty. Ltd.


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