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. To correct myself, stop threshold being zero is also implementation- specific. on thinkpads it is not valid. 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. -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe platform-driver-x86" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
