Re: Driver for pca9541 bus master selector

[Michael Lawnick <ml.lawnick-Mmb7MZpHnFY@public.gmane.org>]

Guenter Roeck said the following:
> On Wed, Sep 29, 2010 at 03:19:28AM -0400, Jean Delvare wrote:
> [ ... ]
>> 
>> I was speaking of the PCA9540. I don't think anyone ever wrote a driver
>> for the PCA9541. And in all honestly I don't think the new i2c-mux
>> infrastructure is ready for this. It was written with single-master
>> topologies in mind. You'll have to rethink a lot of things if you want
>> to add support for "inverted" multiplexers. And I don't have the time
>> to help, sorry.
>> 
> Actually, the infrastructure works quite nicely. I use select_chan
> to acquire the slave, and release_chan to initiate release.
> It behaves like a one-channel multiplexer.
> 
>> I don't quite see the point of such chips, BTW. I2C supports
>> multi-master already, so two masters talking to the same slave
>> sequentially is already supported.
>> 
> Tell that to our HW team, and to them:
> 
> 	http://www.lineagepower.com/oem/pdf/CPLI2C.pdf
> 
I only took a rough look, but it seemed to me that the pca is part of
the main device.
>From abstraction side of view your problem seems a matter of
synchronization of two independent computer systems. You will need a
shared resource. The access to it could either be part of driver code or
by introducing a 'one-channel multiplexer' as you did. But the sync
needs to be done by your code via a shared data object.

-- 
KR
Michael