On Mon, May 9, 2011 at 10:45 AM, Henrique de Moraes Holschuh <hmh@xxxxxxxxxx> wrote: > On Sun, 08 May 2011, Andrew Lutomirski wrote: >> I've figured out how the ThinkPad SMAPI charge control works (at least >> well enough to program thresholds on some models), and I'd like to get > > Yeah, there's a little protocol to talk to the EC, otherwise it simply > ignores writes to the battery threshold registers. I think you had to set > bit 7 before you write the threshold to the relevant EC register, or > something. Found it by trial-and-error a long time ago, I documented it > somewhere but never took it forward. I never bothered to hunt down the > force-drain/battery-select commands, though. > > Anyway, since SMAPI works, and is *stable* (the fact that it works from the > A21 to the latest Lenovos tells you just how stable), which is a lot more > than what I can say about the ACPI stuff, I didn't see any reason to mess > with this. I must have been unclear. I'm using SMAPI -- I've reverse-engineered it from a combination of tp_smapi, the mwave driver, the ancient PDF on Lenovo's site, and trial-and-error on my X220. (The X220 fails requests for the start threshold that work on on the X200s.) >> 2. Integrate it with power_supply. > > Only if we can make it generic enough, but yes, THIS is the better way. > > However, I'd prefer if you went all the way and actually hooked to the SBS > subsystem and exposed all the battery information. There is a way to do > that through the ACPI DSDT (but you will have to do the rev. engineering > yourself, as I said, smapi works just fine across so many models, that I > never bothered with it -- it is far better supported than ACPI). > > It is not even difficult, just look at the methods used to expose the > standard ACPI battery interface, then read the Smart Battery System (SBS) > standard, and you will find out by fast trial-and-error how to map one to > the other. Or you can look at tp_smapi to speed things up (only, tp_smapi > talks directly to the EC instead of doing it over ACPI). > > The SBS interface exposes more data about the battery, including > per-cell-group voltage and pack microcontroller aging counters, alarms, and > the "needs to get through the fuel-gaugue reset procedure" semasphore. If I'm feeling really motivated, I'll look at that. I'm currently more interested in the charging thresholds, though, which I think is independent of the choice of SBS vs ACPI to access the battery state. (From a quick glance at the SBS spec, you can inhibit charging entirely but you can't ask for thresholds. I assume that the EC takes care of that. If I'm wrong, please tell me, but SMAPI seems like a fine way to access the thresholds.) --Andy -- 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
