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SubjectRe: 2.6.22 regression: thermal trip points
On Thu, Aug 02, 2007 at 01:45:00PM +0200, Thomas Renninger wrote:
> On Thu, 2007-08-02 at 12:13 +0100, Matthew Garrett wrote:
> > I strongly suspect that the vast majority[1] of hardware that "needs"
> > the trip points changing works perfectly well under Windows, so it's
> > likely to be papering over bugs in the kernel. It'd be nice if we fixed
> > those rather than encouraging people to poke stuff into /proc,
> Some arguments against that:
> - You cannot tell a customer: Wait for the kernel in half a year.
> This is the time it at least needs until a laptop got sold, the
> problem is found, a patch is written and checked in and finally
> hits the distribution.

We have to do so frequently. New hardware often exposes bugs in the
kernel.

> - You can also not backport fixes as ACPI patches mostly have the
> potential to break other machines/BIOSes
> - There also exist the policy to not fix up/workaround totally broken
> AML BIOS implementations

The policy has been to attempt to be bug-compatible with Windows
whenever possible for some time now.

> - We do not need to and never will be able to copy or do the same
> Windows is doing

Given that many vendors still only test against Windows, that's exactly
what we need to do.

> > especially when doing so is guaranteed to break in really confusing ways
> > with a lot of hardware. The firmware can reset the trip points at
> > essentially arbitrary times and is well within its rights to expect the
> > OS to actually pay attention to them.
> What the hell is so wrong with:
>
> Let the user override the trip points. If he does so, ignore
> thermal trip point updates from BIOS. Don't care for hysteresis
> BIOS implementations (these are the BIOS trip point updates).

No, that's not the only reason for notifications. Alteration in hardware
state may also force a recalculation of trip point (adding a battery to
a bay rather than a DVD drive may require the platform to be kept at a
lower temperature)

> If user changes them, it's his fault, he doesn't need to...
> Make sure that trip points can only be lowered, compared to the
> initially fetched one from BIOS.

Surely people want this functionality so that they can raise trip
points?

--
Matthew Garrett | mjg59@srcf.ucam.org
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