> >> If that's correct, then is there any need to have an additional mutex
> >> for at24_data?
> >
> > I can't see a need, yes.
> 
> Then I'll see if it can be safely removed in the next iteration.

That would be great, thanks!

> > Yes, a seperate driver for the second address is what I meant to suggest
> > in the above paragraph. Only that the data should probably be exported
> > via the NVMEM framework, not directly via sysfs. We have patches pending
> > doing that for at24.
> 
> Right, but then these patches keep the driver backwards compatible in
> that they keep the 'eeprom' sysfs attribute, so it's still a viable
> option.

Yes, they do it for backwards compatibility. If you do something new,
you can't really claim that ;)

> > What happens if you assign another at24 instance (read-only) to the
> > second address? I mean, there is not only the serial number, but also a
> > MAC address IIRC.
> 
> Nothing - it can't be read with the regular driver. Its protocol
> requires certain bits set just like in the function from patch 4/9 in
> this series.

Maybe it might work if you seek to the right offset and read the right
number of bytes, but this is clumsy, I agree.

> As for the MAC address - I can't find anything in the datasheet, and
> haven't heard about it.

http://www.atmel.com/images/atmel-8807-seeprom-at24mac402-602-datasheet.pdf

That was the first data sheet I found when looking for documentation.
So, we should keep in mind that there might be more than a serial number
in this extra memory space.

Thanks,

   Wolfram