On Thursday 19 May 2016 18:11:14 Andrew F. Davis wrote:
> On 05/19/2016 11:06 AM, Pali Rohár wrote:
> > On Thursday 19 May 2016 17:57:34 Andrew F. Davis wrote:
> >> On 05/19/2016 10:51 AM, Pali Rohár wrote:
> >>> On Thursday 19 May 2016 17:48:29 Andrew F. Davis wrote:
> >>>> On 05/19/2016 10:44 AM, Pali Rohár wrote:
> >>>>> On Thursday 19 May 2016 17:38:14 Andrew F. Davis wrote:
> >>>>>> P.S. The code is still a bit strange, I'll probably go grab
> >>>>>> one of the N900s from our test farm and make sure my future
> >>>>>> cleanups don't break this, but are we sure the *name* of a
> >>>>>> driver is an ABI?
> >>>>> 
> >>>>> It is not name of driver, but directory name of sysfs path
> >>>>> where device is exported...
> >>>> 
> >>>> Which is named after the drivers name, so the same question
> >>>> remains.
> >>>> 
> >>>> :/
> >>> 
> >>> No, it is not driver name, but device name. That is different.
> >> 
> >> My bad, that's what I meant, device names should be dynamic,
> >> right? Relying on them being static in software would then be
> >> buggy (like relying on eth0 being the right NIC everytime)?
> >> 
> >> I'm not familiar with the N900 software, but IDR can give out
> >> different numbers and may not always give the first battery #0 (it
> >> does now but is that a guarantee in IDR?) and if not then what is
> >> the userspace response to this changing?
> > 
> > In case N900 would have more bq27xxx batteries, then yes. But N900
> > has exactly *one* bq27200 battery, so there is no IDR problem.
> 
> Right, but if IDR returns 42 instead of 0 would this then break its
> userspace software?

I think it is insane to starts generating random numbers for IDR... Hard 
to decide what happen if such situation occur...

What I can say is that N900 charging software and other battery 
applications stops working. And people who develop kernel for N900 
starts to be angry, because without working battery charging it is not 
possible to develop and fix other kernel bugs on device.

> How is this handled for other power-supply drivers when more that one
> battery exists, they look to give static device names so I'm assuming
> the framework handles giving them new folder names automatically.

N900 software can be happy that this problem does not happen... :-)

But basically in case there will be more batteries of same type, then it 
depends if it is needed to distinguish between them or not. So this is 
depends on exact situation and usage...

-- 
Pali Rohár
pali.rohar@gmail.com