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    SubjectRe: blink driver power saving
    On Mon, 2 Jul 2007 01:59:50 +0200
    Andi Kleen <ak@suse.de> wrote:

    > On Monday 02 July 2007 00:14, Linus Torvalds wrote:
    > > On Sun, 1 Jul 2007, Andi Kleen wrote:
    > > > What is so bad with it? Note it's a debugging facility and used
    > > > for kcrash kernels where the video output doesn't work. But they
    > > > normally only run a few minutes to dump the previous state to disk
    > > > and then reboot.
    > >
    > > It has been a total disaster from beginning to end.
    > >
    > > It wastes power.
    >
    > Again:
    > It's not intended for normal kernels. It's a debugging feature.
    > It's not intended for normal kernels. It's a debugging feature.
    > It's not intended for normal kernels. It's a debugging feature.

    It can be generally useful. Until/unless we get proper screen support,
    how do you know hang from panic? If you can talk to some other
    device it would help.

    > Got it now? Power wasting or not just doesn't matter for it.
    >
    > > It hangs machines when it tries to blink.
    >
    > Yes, there seem to be more buggy keyboard controllers
    > around than I anticipated. Very sad that IBM couldn't even
    > get such a simple thing right.
    >
    > Well only those that could be already hung from user space
    > with setleds (that was also confirmed). Actually I thought
    > they didn't hang completely, but just stopped reacting to
    > the keyboard (which is actually pretty bad for every user
    > to be able to trigger)
    >
    > I guess the better way to handle those would be to find out the
    > minimum frequency of blinking that is still ok and rate limit it to that in
    > the keyboard driver.
    >
    > Anyways, Stephen's patch just doesn't make sense:
    > he clearly didn't understand the code at all. Before you
    > apply it and cripple it better drop the driver completely.

    The patch makes sense. You don't need to poll every jiffie to find
    out if system has panic. But I agree with Linus, it is the kind
    of patch that doesn't belong in the mainline kernel. Every developer
    seems to have built up a set of crappy/fragile debug tools, but these
    don't belong in the wild.



    --
    Stephen Hemminger <shemminger@linux-foundation.org>
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