On Mon, Dec 30, 2013 at 08:40:45PM -0200, Henrique de Moraes Holschuh wrote: > On Mon, 30 Dec 2013, Henrique de Moraes Holschuh wrote: > > On Mon, 30 Dec 2013, Julian Andres Klode wrote: > > > On Mon, Nov 11, 2013 at 02:56:30PM +0100, Julian Andres Klode wrote: > > > > Add support for battery charge thresholds in new Sandy Bridge and Ivy Bridge > > > > ThinkPads. Based on the unofficial documentation in tpacpi-bat. > > > > > > > > The threshold files support the values '0' for the controller's default, > > > > and 1-99 as percentages. Values outside of that range are rejected. The > > > > behaviour of '0' might be confusing, especially for the stop case where > > > > it basically seems to mean '100'. > > > > > > Thinking more about this, it might make more sense to simply accept a 100 > > > value and not accept a 0 value in the stop case (I tried multiple times to > > > write 100 to a stop_charge_thresh file, because that feels more natural). > > > > > > Having a 0 mean 100% is just odd. So stop_charge_thresh should simply > > > accepts integer values in the range [1, 100] (and start_charge_thresh > > > should continue accept [0, 99], as 0 really means 0 there). > > > > Indeed. Just return EINVAL for a stop threshold of 0. > > Actually, a stop threshold below the current start threshold is also invalid > and what happens when you try that is implementation-specific. And the > kernel is not the only party who can change the thresholds, so you have to > read them if you really need to know the current value. That's true. The problem is that if we forbid such values, the writes will need to be done in a specific order. Let's say I have a system with start=0 stop=50 and I want to change it to start=60 stop=80 If we return -EINVAL on a case stop < start, the only way to do this is setting stop first and then start, because if we wrote start first, then we would have: start > stop (because 60 > 50). But the error message when doing it the wrong way around will not be very helpful and I think it is confusing. We might be able to work around this by simple setting stop = start if a new write causes the stop threshold to be below the start threshold. But this also seems ugly. > To correct myself, stop threshold being zero is also implementation- > specific. on thinkpads it is not valid. Writing the value 0 effectively means setting the stop threshold to 100%. The EC itself does not accept the value 100. I don't know why they choose to implement it this way. So the code should not accept 0 as an input value and replace an input of 100 with 0. The exact value returned by the ACPI call is 0x80000000, that is, a signed 0 integer with sign bit set to 1. A set sign bit indicates an error. > > For thinkpads, I believe the EC firmware changes the other threshold so that > the boundary condition stop > start is always valid. But I never tried it > with a direct EC write to validate this. If it becomes important, I can > check -- but I'd still prefer to enforce sanity at the driver level just in > case. Don't tempt the gremilins, for they live at boundary conditions and > their sleep is light indeed. It does not seem to do this here. -- Julian Andres Klode - Debian Developer, Ubuntu Member See http://wiki.debian.org/JulianAndresKlode and http://jak-linux.org/. Please do not top-post if possible. ------------------------------------------------------------------------------ Rapidly troubleshoot problems before they affect your business. Most IT organizations don't have a clear picture of how application performance affects their revenue. With AppDynamics, you get 100% visibility into your Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro! http://pubads.g.doubleclick.net/gampad/clk?id=84349831&iu=/4140/ostg.clktrk _______________________________________________ ibm-acpi-devel mailing list ibm-acpi-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/ibm-acpi-devel
