On 22 Apr 2011, shawn wilson wrote: > On Tue, Apr 19, 2011 at 12:14 PM, Anthony Campbell <a...@acampbell.org.uk> > wrote: > > My HP laptop tends to boot with a dim screen. I can fix this with > > > > echo 10 > /sys/devices/virtual/backlight/acpi_video0/brightness > > > > which I run from /etc/rc,local. > > > > the right way would be to use sysctl. that said, i always do things > the way you've done it :) > > > It works well with all kernels up to 2.6.37. With 2.6.38 there is > > usually no /sys/devices/virtual/backlight... so the above command > > can't work. > > > > i'd check the kernel changelog or maybe the debian kernel package > changelog and see if something was changed for sysfs and see why. i'm > not sure whether this line of question is appropriate for that forum, > but if it is, someone on debian-dev should know. (reading through the > archives, they seem to be hard asses on topicality, so i'd do my > research first). also, you could try to ask on irc in #kernel > > > What is really odd is that if I first boot with a 2.6.37 kernel and then > > reboot with a 2.6.38 version, everything works correctly. The file I > > need to modify is there and there is full brightness. > > > > iirc, this is stored in ram. i'll bet if you booted in the one kernel, > and then did a shutdown -h and immediately powered up into the newer > kernel, you'd notice a fail. that said, i think this is improper > behavior. you didn't mention what version of debian you're running? > ie, i don't think this happens onstable (than again, i'm only on .32, > so...) > > > Is this perhaps something to do with udev? I've found ubuntu bug > > reports describing somewhat similar problems but mostly with backlight > > being too bright rather than too dim. > > > > i would think it is more in the kernel than in udev. (i think udev > gets its info from sysfs and proc - that's probably a bad way of > stating this though. it's fron the kernel at any rate) > > > I would make a bug report if I knew which package was at fault. Can > > anyone shed any light (literally)? It's an annoyance rather than a major > > problem but I've been trying to figure it out for at least two weeks > > wthout success, > > > > this does sound like a bug. it's at least an issue with some default > config. if you can, swap out discs and do a fresh install and see what > happens. i'm pretty sure you'll notice the same thing. however, that > would be the right thing to do before putting in a bug report (and it > would be great of you to follow up on this - helps the community and > all) >
Many thanks for these comments. I'll look into the kernel changelog files though I find them pretty intimidating these days. Time was when I used to compile my own kernels, but for a long time now I've settled for a quiet life and just install the standard Debian kernels. But you are probably right to say that it's a kernel problem. When it goes wrong, it starts up bright but then goes dim at a certain point in the boot process. I couldn't see anything in dmesg to explain this but I'll have another look. Anthony -- Anthony Campbell - a...@acampbell.org.uk Microsoft-free zone - Using Debian GNU/Linux http://www.acampbell.org.uk - sample my ebooks at http://www.smashwords.com/profile/view/acampbell -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20110422150550.gk9...@acampbell.org.uk
