Dear Arjan,
thank you again for your quick response.
Am Freitag, den 10.02.2012, 13:39 -0800 schrieb Arjan van de Ven:
> On 2/10/2012 1:19 PM, Paul Menzel wrote:
> > looking at the output of PowerTOP (version 1.97) on every system I
> > looked at »Runtime PM for PCI Device …« is marked as bad.
> >
> > I know that I can enable it by hitting return in PowerTOP or by
> > executing the following command [1].
> >
> > echo auto > /sys/bus/pci/devices/*/power/control
> >
> > But I wonder why this is not enabled by default? What userspace program
> > would be responsible to enable this? I cannot imagine that users should
> > write scripts or edit start up files to enable this. A Linux kernel
> > option to turn this on globally would be nice to have. Does that exist?
>
> I suspect the answer will end up being that UDEV will be the one that
> needs to do this....
thank you for the pointer. As a side note though, the sound subsystem
ALSA provides such a (module(?)) parameter.
Searching for »udev enable runtime power management« I found several
pointers. First the documentation for USB power management [2] suggests
the abandoned project HAl to do this job or otherwise like you did
writing UDEV rules. I hope some of the successors of HAL will be able to
do that.
There is an example UDEV rules file in the Gentoo Wiki [1].
SUBSYSTEM!="pci", GOTO="power_runtime_rules_end"
ACTION!="add", GOTO="power_runtime_rules_end"
KERNEL=="????:??:??.?" #, WAIT_FOR_SYSFS="bInterfaceProtocol"
PROGRAM="/bin/sleep 0.1"
ATTR{power/control}=="*", ATTR{power/control}="auto"
LABEL="power_runtime_rules_end"
I also found a commit to MeeGo [3] adding such a rule to a certain EHCI
device.
ACTION=="add|change", SUBSYSTEM=="pci", ATTRS{vendor}=="0x8086",
ATTRS{device}=="0x0806", ATTR{power/control}="auto"
Basically they are doing the same – of course the second only for one
device – and I should dive into UDEV if the `sleep` in the Gentoo file
is needed or not. It also needs to be considered if it has any impact on
the start up time.
Thanks,
Paul
PS: By the way, does anyone have some statistics if that increased the
“on battery operation time” with certain laptops?
[1] http://wiki.gentoo.org/wiki/Runtime_Powermanagement
[2]
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/usb/power-management.txt;h=12511c98cc4faecaf17f31db16f1db347936dad2;hb=HEAD
[3] http://lists.meego.com/pipermail/meego-commits/2011-April/021975.html
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