On Thu, 2007-05-17 at 15:17 -0400, Len Brown wrote: > On Thursday 17 May 2007 05:23, Pavel Machek wrote: > > > > ACPI: thermal trip points are read-only > > > > What was the rationale? Can we get this one reverted? > > > > Some machines (HP omnibook xe3) have broken trip points -- too high -- > > so machine will overheat and trigger hw shutdown before starting > > passive cooling. > > > > That's really broken, and write to trip points is reasonable way to > > 'fix' that. (I'd understand if you only ever let trip points to > > decrease... but otoh root should be able to shoot himself....) > > No, writing trip-points is neither a fix, nor it is reasonable. > It is a workaround at best, and it is a dangerous and mis-leading hack. Yes it is a workaround for critical ACPI bugs like that or similar: https://bugs.launchpad.net/ubuntu/+source/linux-source-2.6.17/+bug/22336 It's also convenient to e.g. lower passive trip point to avoid fan noise. Some people are used to it, I already wanted to write a little userspace prog to use them as it is really easy to fake cooling_mode (trip points are modified by BIOS) and eliminate fan noise and other things by e.g. reducing passsive or whatever trip point. This is at least a major sysfs interface change, has this been discussed somewhere before or declared deprecated? It's there for a long time, why is this "a dangerous and mis-leading hack." now? I'd suggest to revert this and I can come with something like "only allow lower values than BIOS provides" patch if the current implementation is considered dangerous. Thomas > The OS has no capability to actually change the ACPI trip points > that are used by the BIOS. Changing the OS copy of them > to make the user think that trip events will actually > happen when the temperature crosses the OS copy is crazy. > > If there are systems with broken thermals and the > ACPI thermal control needs and over-ride to turn > on the fan, then that is fine -- but using > fake trip-points and giving the user the impression > that they are real is not viable. - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
