OLPC battery class

[Richard Hughes]

On Tue, 2007-06-19 at 23:07 +0800, David Woodhouse wrote:
> On Tue, 2007-06-19 at 15:55 +0100, Richard Hughes wrote:
> > Hi,
> > 
> > I've been looking at adding OLPC battery support into HAL so it can be
> > used with OHM and the power meter in sugar.
> 
> Cool, thanks.

No worries, I'm glad I sent the email before I wrote the HAL code! ;-)

> > Putting it bluntly, the "generic battery class" is a bit of a misnomer,
> > as it's very OLPC specific. 
> 
> Not at all. It handles at least two types of batteries already and it's
> not particularly hard to make it handle APM and ACPI too -- these were
> discussed when it was put together.

Sure.

> But it's actually already been revamped -- see Anton's git tree at
> http://git.infradead.org/?p=users/cbou/battery2-2.6.git which will
> shortly turn up in the olpc git tree, as soon as I've finished changing
> it over to use the new EC communication protocol instead of direct
> access. This already addresses some of your comments.

Okay, apologies if I've got stroppy prematurely. Can I use the APM
driver for testing on my laptop (when acpi=off)?

> > * 'capacity' is probably the wrong word to use, in common use it means
> > the battery capacity compared to when nit was new, to measure how the
> > battery has degraded over time.
> > 
> > * 'status' and 'status_cap' violate the one-value-per file mentality
> > of sysfs. This means we have to do string processing in HAL, rather
> > than just read the value of a flag. status_cap shouldn't be used at at
> > all - if the capability does not exist to report this, then do not
> > export the attribute (so no file in sysfs). See below for an example.
> 
> I believe these are both changed in Anton's new code.

Cool.

> > * 'temp1' - why not temperature_ambient?
> > * 'temp2' - why not temperature_internal?
> 
> Because then you have arbitrarily-named properties, rather than _known_
> named properties. But I think Anton changed this anyway.

Okay, good.

> > * Why is the AC adapter exported as a battery of type ac? This is simply
> > wrong, they are _completely_ different types of device.
> 
> No. They're _both_ power supplies. They can both have measurements of
> voltage, current, temperature, etc. The external input is just like an
> infinite battery.

Hmm. I'm not completely convinced (are there any ac adapters that report
temperature current or voltage?) but I'll give the cbou tree a go and
see how it works.

Thanks for the quick response.

Richard.