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    SubjectRe: [PATCH, RFC] [1/3] Generic in-kernel AC status
    On Tuesday 14 February 2006 18:44, Thomas Renninger wrote:
    > Pavel Machek wrote:
    > > On Pá 10-02-06 09:06:43, Stefan Seyfried wrote:
    > >> On Wed, Feb 08, 2006 at 12:57:53PM +0000, Matthew Garrett wrote:
    > >>> The included patch adds support for power management methods to register
    > >>> callbacks in order to allow drivers to check if the system is on AC or
    > >>> not. Following patches add support to ACPI and APM. Feedback welcome.
    > >> Ok. Maybe i am not seeing the point. But why do we need this in the kernel?
    > >> Can't we handles this easily in userspace?
    > >
    > > Some kernel parts need to now: for example powernow-k8: some
    > > frequencies are not allowed when you are running off battery. [Just
    > > now it is solved by not allowing those frequencies at all unless ACPI
    > > is available; quite an ugly solution.]
    > >
    > Allowed CPUfreqs are exported via _PPC.
    > This is why a lot hardware sends an ac_adapter and a processor event
    > when (un)plugging ac adapter.
    > Limiting cpufreq already works nice that way.
    > AMD64 laptops are booting with lower freqs per default until they are
    > pushed up, so there shouldn't be anything critical?

    This is not true as far as my box is concerned (Asus L5D). It starts with
    the _highest_ clock available.

    > For the brightness part, I don't see any "laptop is going to explode"
    > issue.
    > I always hated the brightness going down when I unplugged ac on M$

    Currently I have the same problem on Linux, but I don't know the solution
    (yet). Any hints? :-)

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