question : crash between kernel i2c and alsa i2c

question : crash between kernel i2c and alsa i2c

[Tomko]

Hi everyone,

I know that there is a tiny i2c subsystem inside alsa , i would like to 
know is there any control betwen the kernel i2c subsystem and the alsa 
i2c ?  Will there any crashes if two i2c access the bus togethre ?


Regards,
TOM


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Re: question : crash between kernel i2c and alsa i2c

[Jaroslav Kysela]

On Mon, 13 Jun 2005, Tomko wrote:

> Hi everyone,
> 
> I know that there is a tiny i2c subsystem inside alsa , i would like to 
> know is there any control betwen the kernel i2c subsystem and the alsa 
> i2c ?  Will there any crashes if two i2c access the bus togethre ?

It will not work, because there must be only one arbiter maintaining 
locking and exclusive access for the i2c bus.

						Jaroslav

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


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Re: question : crash between kernel i2c and alsa i2c

[Takashi Iwai]

At Mon, 13 Jun 2005 17:48:32 +0800,
Tomko wrote:
> 
> Hi everyone,
> 
> I know that there is a tiny i2c subsystem inside alsa , i would like to 
> know is there any control betwen the kernel i2c subsystem and the alsa 
> i2c ?  Will there any crashes if two i2c access the bus togethre ?

No, they have no relevence between them at all.
If you try to access the same hardware, of course it would be a
problem.  But ALSA's i2c usually accesses only the chip-connection in
the sound card, which is quite unlikely accessed from kernel i2c.


Takashi


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Re: question : crash between kernel i2c and alsa i2c

[Tomko]

Takashi Iwai wrote:

>At Mon, 13 Jun 2005 17:48:32 +0800,
>Tomko wrote:
>  
>
>>Hi everyone,
>>
>>I know that there is a tiny i2c subsystem inside alsa , i would like to 
>>know is there any control betwen the kernel i2c subsystem and the alsa 
>>i2c ?  Will there any crashes if two i2c access the bus togethre ?
>>    
>>
>
>No, they have no relevence between them at all.
>If you try to access the same hardware, of course it would be a
>problem.  But ALSA's i2c usually accesses only the chip-connection in
>the sound card, which is quite unlikely accessed from kernel i2c.
>
>  
>
No, what i mean is what if they are accessing different device ? for 
example kernel access it's own i2c device but alsa access it's i2c audio 
device , but there is only ONE pair of i2c bus in hardware, just like 
when the alsa's i2c just initiate a "START" and throw out the hardware 
address but kernel's i2c want to initiate a "START" also and throw out 
another hardware address . How's this situation be avoided if there is 
no control between two i2c subsystem?

TOM

>Takashi
>  
>



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Re: question : crash between kernel i2c and alsa i2c

[Takashi Iwai]

At Tue, 14 Jun 2005 09:34:09 +0800,
Tomko wrote:
> 
> Takashi Iwai wrote:
> 
> >At Mon, 13 Jun 2005 17:48:32 +0800,
> >Tomko wrote:
> >  
> >
> >>Hi everyone,
> >>
> >>I know that there is a tiny i2c subsystem inside alsa , i would like to 
> >>know is there any control betwen the kernel i2c subsystem and the alsa 
> >>i2c ?  Will there any crashes if two i2c access the bus togethre ?
> >>    
> >>
> >
> >No, they have no relevence between them at all.
> >If you try to access the same hardware, of course it would be a
> >problem.  But ALSA's i2c usually accesses only the chip-connection in
> >the sound card, which is quite unlikely accessed from kernel i2c.
> >
> >  
> >
> No, what i mean is what if they are accessing different device ? for 
> example kernel access it's own i2c device but alsa access it's i2c audio 
> device , but there is only ONE pair of i2c bus in hardware, just like 
> when the alsa's i2c just initiate a "START" and throw out the hardware 
> address but kernel's i2c want to initiate a "START" also and throw out 
> another hardware address . How's this situation be avoided if there is 
> no control between two i2c subsystem?

In such a case, use kernel i2c layer for all controls.

As mentioned above, ALSA i2c was introduced mainly as a very simple
i2c control _on the sound card_, which the kernel i2c drivers don't cover.
If you have a kernel i2c driver, you should use it. 


Takashi


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