From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miguel Ojeda Subject: Re: [PATCH] battery: Fix charge_now returned by broken batteries Date: Sun, 4 Oct 2009 19:46:42 +0200 Message-ID: References: <1254669853.26496.0.camel@carter> <20091004164553.GD10505@khazad-dum.debian.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20091004164553.GD10505@khazad-dum.debian.net> Sender: linux-kernel-owner@vger.kernel.org To: Henrique de Moraes Holschuh Cc: astarikovskiy@suse.de, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-acpi@vger.kernel.org On Sun, Oct 4, 2009 at 6:45 PM, Henrique de Moraes Holschuh wrote: > On Sun, 04 Oct 2009, Miguel Ojeda wrote: >> Some broken batteries like my DELL NR2227 or a friend's DELL GK4798 = return >> the design_capacity (charge_full_design) as capacity_now (charge_now= ) >> when completely charged. >> >> I noticed this when looking at a battery plugin that reported "127% = charged". >> Some of these plugins have already "fixed" this in userspace by codi= ng >> something like min(percentage, 100)). > > A battery can be charged above 100%. =A0It just depends what you call= 100%, > and the "I am full" level *varies* in a non-monotonic way during the = battery > lifetime... > > So, if you don't want to see > 100%, you have to clamp it to 100% and= lose > information (when your "100%" level is actually increasing as the thi= ng > keeps charging and you keep raising the baseline so that it doesn't g= o over > 100%). If the 100% level increased, then full_charge_capacity (a.k.a. "_last_ full capacity" as seen in /proc) will increase as well, won't it? If the battery went over that 100% that means there is a "new" 100%, why are we losing information?. I am asking, I am not an expert on battery stuff. > >> So I discovered that the battery wrongly returns charge_full_design = when >> completely charged instead of charge_full. > > Ick. > >> This patch fixes this by returning min(capacity_now, full_charge_cap= acity) >> on both procfs and sysfs. > > What will it cause on non-broken batteries? =A0Or during gauge reset,= when any > battery that updates full_charge_capacity only at the end of the cycl= e will > really have capacity_now > full_charge_capacity ? Well, does it make sense to have capacity_now higher than full_charge_capacity? Wouldn't that information be broken too? Again, I am just wondering. > >> Now the userspace plugins report the correct 100% and their userspac= e check >> may not be needed (if this error is the only one producing >100% res= ults). > > Like I said, > 100% can happen, unless what you define to be 100% is = very > elastic (and gets updated all the time). I still think it does not make sense to have a battery charged over its 100% capacity whatever the definition of 100% is. Maybe I do not understand your point. > > -- > =A0"One disk to rule them all, One disk to find them. One disk to bri= ng > =A0them all and in the darkness grind them. In the Land of Redmond > =A0where the shadows lie." -- The Silicon Valley Tarot > =A0Henrique Holschuh >