linux-kernel - Re: blink driver power saving

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Message-ID: <d120d5000707020531y43d41b6fl46e05c8343dbbeae@mail.gmail.com>
Date:	Mon, 2 Jul 2007 08:31:17 -0400
From:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>
To:	"Andi Kleen" <ak@...e.de>
Cc:	"Indan Zupancic" <indan@....nu>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Stephen Hemminger" <shemminger@...ux-foundation.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: blink driver power saving

On 7/2/07, Andi Kleen <ak@...e.de> wrote:
> On Monday 02 July 2007 13:43:23 Indan Zupancic wrote:
> > On Mon, July 2, 2007 01:59, Andi Kleen wrote:
> > > 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)
> >
> > Pavel's lost key events, mine stopped reacting altogether.
>
> Did you try if the network was still alive? Perhaps it was
> just a locked up keyboard.
>
> >
> > > 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.
> >
> > Dmitry already has a patch for that. He limited it to one event each 50 ms.
>
> Great.
>
> >
> > > 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.
> >
> > CC'ing Dmitry, as I think he doesn't like the blink driver much either. ;-)
>
> Perhaps one of you geniuses who all hate it can find a better way to
> solve the "video output dead after kexec; but need visual feedback to the user
> while crash dumping" problem. I'm waiting for your patches.
>

I don't don't like it ;) Unfortunately too many people end up enabling
it and having issues with their keyboards. Can we have it depend on
DEBUG_KERNEL? And probably KEXEC as well?

Another option would be for it not use panic_blink. Do your kexec
kernels have atkbd support enabled? You could write an new "blink"
input handler that would latch to keyboards supporting leds and blink
by sending EV_LED events.

-- 
Dmitry
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