linux-kernel - Re: [PATCH] s3c-adc-battery: Add naive POWER_SUPPLY_PROP

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Message-ID: <20111110133052.GA31381@oksana.dev.rtsoft.ru>
Date:	Thu, 10 Nov 2011 17:30:52 +0400
From:	Anton Vorontsov <cbouatmailru@...il.com>
To:	Vasily Khoruzhick <anarsoul@...il.com>
Cc:	Heiko Stübner <heiko@...ech.de>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-kernel@...r.kernel.org,
	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH] s3c-adc-battery: Add naive POWER_SUPPLY_PROP_PRESENT
 implementation

On Thu, Nov 10, 2011 at 02:05:06PM +0300, Vasily Khoruzhick wrote:
> On Thu, 2011-11-10 at 09:56 +0100, Heiko Stübner wrote:
> > Userspace programs like upower seem to depend on the presence of the
> > POWER_SUPPLY_PROP_PRESENT property.
> > 
> > The real presence of the battery cannot be sensed and all other
> > routines of s3c-adc-battery simply expect it to be present.
> > 
> > Therefore we simply return 1, unless the battery struct is not present at all.
> 
> Looks OK for me,
> 
> > Signed-off-by: Heiko Stuebner <heiko@...ech.de>
> Acked-by: Vasily Khoruzhick <anarsoul@...il.com>

I disagree. If the driver behaves like the hardware does not support
hot-pluggable cells, then present property is not necessary.

Upowerd should look at the 'present' only if it is there; and if it
is not, cells assumed to be always present.

[..]
> >  	if (!bat) {
> > +		if (psp == POWER_SUPPLY_PROP_PRESENT) {
> > +			val->intval = 0;
> > +			return 0;
> > +		}
> > +
> >  		dev_err(psy->dev, "%s: no battery infos ?!\n", __func__);

And in this case that dev_err() tells that either hardware does not
support hot-pluggable cells, or driver does not handle this case; which
is actually the same from the userspace point of view.

So, the problem is in upowerd, not this driver.

Thanks,

-- 
Anton Vorontsov
Email: cbouatmailru@...il.com
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