linux-kernel - Re: [PATCH] ACPI / battery: Fix reporting "Not charging" when capacity is 100%

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sun, 11 Nov 2018 13:22:43 +0100
From:   Pavel Machek <pavel@....cz>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Daniel Drake <drake@...lessm.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        sebastian.reichel@...labora.co.uk,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        linux@...lessm.com,
        João Paulo Rechi Vita 
        <jprvita@...lessm.com>,
        João Paulo Rechi Vita <jprvita@...il.com>
Subject: Re: [PATCH] ACPI / battery: Fix reporting "Not charging" when
 capacity is 100%

On Sun 2018-11-11 12:57:12, Hans de Goede wrote:
> Hi,
> 
> On 11/7/18 5:53 AM, Daniel Drake wrote:
> >On Mon, Nov 5, 2018 at 1:19 AM Pavel Machek <pavel@....cz> wrote:
> >>Plus, I don't think "100% charge" is right test for "battery full". At
> >>least on thinkpads, there's configuration option, and it is common
> >>_not_ to charge batterry above 95% or so (to increase its lifetime).
> >
> >Hans also touched on this area in his response:
> >
> >>As for this kernel-side fix I do not believe that fixing thus in
> >>the kernel is the right thing to do. We try to stay away from
> >>heuristics using full_charge_capacity in the kernel since that
> >>is not really reliable / deterministic.
> >
> >I'm not fully convinced by this argument though.
> >
> >The ACPI spec is not very clear on what conditions you should apply to
> >decide when the battery is full. Instead, ACPI seems to provide a
> >pretty decent amount of data, and the decision about whether to
> >interpret that as "battery full" is left for consumers.
> 
> Right, but in this case the "discharging" status bit is explicitly
> set, to me it feels wrong to report "full", when the firmware
> is reporting "discharging" IMHO, at best we are "not charging"
> (on AC, below the threshold where a new charge cycle starts) and
> that is what we are currently reporting.
> 
> Anu heurstics to decide that "not charging" is close enough to full
> to report it as full to the user belongs in userspace IMHO.
> 
> Anyways this ultimately is Rafael's call. If Rafael is ok with this
> patch then I would like to see Pavel's comment addressed and otherwise
> it is fine with me.
> 
> Note that we will still often get the case where a laptop is charged,
> reports full, is unplugged for 5 minutes and then replugged and then
> reports a capacity of 97% combined with "not charging", so we will
> still need to fix userspace to handle this.

For the record, I don't think I'm okay with this.

There's nothing special about 100% charge.

This changes userland ABI and I don't think it has good enough reasons
to do that.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Download attachment "signature.asc" of type "application/pgp-signature" (182 bytes)