linux-kernel - Re: [PATCH 3/3] power/ds2760_battery: use factor of 20 for rated

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Date:	Tue, 11 May 2010 19:25:29 +0200
From:	Daniel Mack <daniel@...aq.de>
To:	Anton Vorontsov <cbouatmailru@...il.com>
Cc:	linux-kernel@...r.kernel.org, Matt Reimer <mreimer@...p.net>,
	Evgeniy Polyakov <zbr@...emap.net>, Tejun Heo <tj@...nel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Len Brown <len.brown@...el.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: [PATCH 3/3] power/ds2760_battery: use factor of 20 for
 rated_capacity

On Tue, May 11, 2010 at 09:19:24PM +0400, Anton Vorontsov wrote:
> On Tue, May 11, 2010 at 06:38:46PM +0200, Daniel Mack wrote:
> >  drivers/power/ds2760_battery.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/power/ds2760_battery.c b/drivers/power/ds2760_battery.c
> > index b82bf92..7b3043f 100644
> > --- a/drivers/power/ds2760_battery.c
> > +++ b/drivers/power/ds2760_battery.c
> > @@ -78,7 +78,7 @@ MODULE_PARM_DESC(current_accum, "current accumulator value");
> >  
> >  /* Some batteries have their rated capacity stored a N * 10 mAh, while
> >   * others use an index into this table. */
> > -#define RATED_CAPACITY_FACTOR 10
> > +#define RATED_CAPACITY_FACTOR 20
> 
> I'm a bit worried about this one.
> 
> Shouldn't this confuse batteries that already store rated
> capacity with factor of ten? If so, please introduce a module
> option.
> 
> Also, you don't update comments and module params description,
> e.g.
> 
>   MODULE_PARM_DESC(rated_capacity, "rated battery capacity, 10*mAh or index");
>   ....
>   /* set rated capacity from module param (given in 10 * mAh) */
> 
> Is that intentionally?

Well, this parameter doesn't change, and hence the comment is left
untouched. If it is passed as module option, it is interpreted as 10*mAh
and converted to the internal value.

You're right though about your concern about batteries that already
stored a value given in mAh (and not as index) - this will break unless
the module is loaded with a proper module parameter. Don't know whether
this is acceptable.

Daniel
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