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authorAlan Stern <stern@rowland.harvard.edu>2010-04-02 13:22:16 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2010-05-20 13:21:37 -0700
commita90309860b0935805d49e75499fb8dc59fea8e94 (patch)
tree2d5ed0376a0f0ead945afdaa11be00a48bc0af6c /Documentation/ABI/obsolete
parent9e18c821659d836bd63f88df3c19729327728496 (diff)
downloadlinux-a90309860b0935805d49e75499fb8dc59fea8e94.tar.bz2
USB: deprecate the power/level sysfs attribute
This patch (as1367) deprecates USB's power/level sysfs attribute in favor of the power/control attribute provided by the runtime PM core. The two attributes do the same thing. It would be nice to replace power/level with a symlink to power/control, but at the moment sysfs doesn't offer any way to do so. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation/ABI/obsolete')
-rw-r--r--Documentation/ABI/obsolete/sysfs-bus-usb31
1 files changed, 31 insertions, 0 deletions
diff --git a/Documentation/ABI/obsolete/sysfs-bus-usb b/Documentation/ABI/obsolete/sysfs-bus-usb
new file mode 100644
index 000000000000..bd096d33fbc7
--- /dev/null
+++ b/Documentation/ABI/obsolete/sysfs-bus-usb
@@ -0,0 +1,31 @@
+What: /sys/bus/usb/devices/.../power/level
+Date: March 2007
+KernelVersion: 2.6.21
+Contact: Alan Stern <stern@rowland.harvard.edu>
+Description:
+ Each USB device directory will contain a file named
+ power/level. This file holds a power-level setting for
+ the device, either "on" or "auto".
+
+ "on" means that the device is not allowed to autosuspend,
+ although normal suspends for system sleep will still
+ be honored. "auto" means the device will autosuspend
+ and autoresume in the usual manner, according to the
+ capabilities of its driver.
+
+ During normal use, devices should be left in the "auto"
+ level. The "on" level is meant for administrative uses.
+ If you want to suspend a device immediately but leave it
+ free to wake up in response to I/O requests, you should
+ write "0" to power/autosuspend.
+
+ Device not capable of proper suspend and resume should be
+ left in the "on" level. Although the USB spec requires
+ devices to support suspend/resume, many of them do not.
+ In fact so many don't that by default, the USB core
+ initializes all non-hub devices in the "on" level. Some
+ drivers may change this setting when they are bound.
+
+ This file is deprecated and will be removed after 2010.
+ Use the power/control file instead; it does exactly the
+ same thing.