I switched to the current Debian release, "Squeeze", quite a few
months ago on my Sony Vaio laptop. I've found that Squeeze, with its older
kernel and good attention to power management (compared to the
management regressions in more recent kernels), gets much better
battery life than either Arch Linux or Ubuntu on this machine. I'm using
Squeeze as the primary OS at least until the other distros get their
kernel power management sorted out.
I did have to solve a couple of minor problems when switching over, though.
The first problem was that my Vaio TX650 would freeze on resuming from
suspend -- something that every other Linux distro has handled out of
the box on this machine.
The solution turned out to be simple though
non-obvious, apparently a problem with controlling power to the display:
sudo pm-suspend --quirk-dpms-on
That wasn't easy to find, but ever since then the machine has been
suspending without a single glitch. And it's a true suspend, unlike
Ubuntu Natty, which on this machine will use up a full battery if I
leave it suspended all day -- Natty uses nearly as much power when
suspended as it does running.
Adjusting screen brightness: debugging ACPI
Of course, once I got that sorted out, there were the usual collection
of little changes I needed to make. Number one was that it didn't
automatically handle brightness adjustment with the Fn-F5 and Fn-F6 keys.
It turned out my
technique for handling the brightness keys
didn't work, because the names of the ACPI events in /etc/acpi/events
had changed. Previously, /etc/acpi/events/sony-brightness-down
had contained references to the Sony I/O Control, or SPIC:
event=sony/hotkey SPIC 00000001 00000010
That device didn't exist on Squeeze. To find out what I needed now,
and typed the function-key combos in question.
That gave me the codes I needed. I changed the sony-brightness-down
file to read:
event=video/brightnessdown BRTDN 00000087 00000000
It's probably a good thing, changing to be less Sony-specific ...
but as a user it's one of those niggling annoyances that I have to
go chase down every time I upgrade to a new Linux version.
[ 11:07 Aug 27, 2011
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My laptop, a Sony Vaio TX650P, badly needed a kernel update.
188.8.131.52 had been running so well that I just hadn't gotten around
to changing it. When I finally updated to 184.108.40.206, nearly everything
worked, with one exception:
Fn-F5 and Fn-F6 no longer adjusted screen brightness.
I found that there were lots of bugs filed on this problem --
and so on. A few of them had terse comments like "Can you try this
patched binary release?" but none of them had a source patch,
or any hints as to the actual nature of the problem.
But one of them did point me to
/sys/class/backlight. In my working 220.127.116.11 kernel, that
directory contained a sony subdirectory containing useful files
that let me query or change the brightness:
echo 1 >/sys/class/backlight/sony/brightness
On my nonworking 18.104.22.168 kernel, I had /sys/class/backlight
but there was no sony subdirectory there.
grep SONY .config in
the two kernels revealed that my working kernel had SONY_LAPTOP set,
while the nonworking one did not. No problem! Just figure out where
SONY_LAPTOP is in the configuration (it turns out to be at the very
end of "device drivers" under "X86 Platform Specific Device Drivers"),
make menuconfig, set SONY_LAPTOP and rebuild ... right?
make menuconfig showed me lots of laptop
manufacturers in the "Platform Specific" category, but Sony
wasn't one of them. Of course, since it didn't show the option it
also didn't offer a chance to read the help for the option either,
which might have told me what its dependencies were.
Time for a recursive grep of kernel source:
grep -r SONY_LAPTOP .
arch/x86/configs/i386_defconfig told me the option did indeed
still exist, and where to find it. drivers/platform/x86/Kconfig
lists the option itself, and says it depends on INPUT and RFKILL.
RFKILL? A bit more poking around located that one near the end of
"Networking support", with the name "RF switch subsystem support".
(I love how user-visible names for kernel options only marginally
resemble the CONFIG names.)
It's apparently intended for
"control over RF switches found on many WiFi and Bluetooth cards,"
something I don't seem to need on this laptop (my WiFi works fine
without it) -- except that the kernel for some reason won't let me
build the ACPI brightness control without it.
So that's the secret. Go to "Networking support", set
"RF switch subsystem support", then back up
to "Device drivers", scroll down to the end to find
"X86 Platform Specific Device Drivers" and inside it you'll now see
"Sony Laptop Extras". Enable that, and the Fn-F5/F6 keys (as well as
/sys/class/backlight/sony/brightness) will work again.
[ 09:07 Nov 02, 2009
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