Re: [PATCH] i2c-mux-pca954x: allow downstream bus numbers to be specified in the dts

[Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>]

Hi Frank,

On Thursday 17 April 2014 13:54:44 Frank Bormann wrote:
> Hi Laurent,
> 
> I have a pca9546 on one of my i2c buses. This will create four mux buses in
> Linux. One of those mux buses then has a pca9542 connected to it, creating
> another two mux buses on top of the first ones.
> 
> The 3.8 kernel, I was initially using enumerated, this as:
> 
> pca9546: 3, 4, 5, 6
> pca9542: 7, 8
> 
> However, the new 3.12 kernel, I am using now, has changed that enumeration
> to:
> 
> pca9546: 3, 4, 7, 8
> pca9542: 5, 6
> 
> As you may imagine, the pca9542 is connected to bus 4. Apparently,
> previously, it would finish the initalization of pca9546 before dealing
> with the pca9542. Now it seems to do the pca9542 initialization as soon as
> it sees it on mux bus 4. My application however expects the pca9546 buses
> to be on incremental bus numbers.

I understand that the bus numbers changed, but you still haven't explain *why* 
you need to have fixed bus numbers. Why do you need to know the bus number at 
all ?

-- 
Regards,

Laurent Pinchart