Re: [linux-usb-devel] USB autosuspend and turning of usb pendriveleds
From: Hans de Goede
Date: Sat Sep 22 2007 - 13:11:08 EST
Alan Stern wrote:
On Sat, 22 Sep 2007, Hans de Goede wrote:
I'm afraid that that doesn't work for usb mass-storage devices.
Here is what I did:
1) kill hal
2) insert usb stick -> led lights
3):
echo -n 1 > /sys/bus/usb/devices/.../power/autosuspend
echo -n auto > /sys/bus/usb/devices/.../power/level
4) wait
Nothing happens, where as sending "suspend" to power/level does turn the led
off.
I don't know what went wrong. It works fine on my systems. You did
fill in the correct device path for the "...", right?
Yes, the one that comes and goes as I plug in one of the USB-sticks I ue for
testing.
And you don't
need the "-n" -- adding it shouldn't matter, but you should try reading
back the contents of those files to make sure the values did get
written correctly.
I did read them back and it did get written correctly.
Now call me naive, but I would expect a mass-storage devices with no
partitions mounted to autosuspend when autosuspend is enabled for that device.
Yes, that is naive. The driver has no way to tell whether or not any
partitions are mounted. Furthermore, you might very well want to
access the raw device without mounting any partitions (database
managers frequently do such things to reduce I/O overhead), in which
case you certainly would not the device to be autosuspended.
How does this relate to your "It works fine on my systems" remark, do I need to
do anything other the unmounting the paritions to make the device eligible for
autosuspend, like unbind the sd driver or even the usb-storage driver?
If so I must say I find that a little counter intuitive.
Regards,
Hans
p.s.
As always, please keep me CC-ed, not on the list.
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