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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
parent9e18c821659d836bd63f88df3c19729327728496 (diff)
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')
-rw-r--r--Documentation/ABI/obsolete/sysfs-bus-usb31
-rw-r--r--Documentation/ABI/testing/sysfs-bus-usb28
-rw-r--r--Documentation/usb/power-management.txt19
3 files changed, 42 insertions, 36 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.
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index bcebb9eaedce..294aa864a60a 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -14,34 +14,6 @@ Description:
The autosuspend delay for newly-created devices is set to
the value of the usbcore.autosuspend module parameter.
-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.
-
What: /sys/bus/usb/devices/.../power/persist
Date: May 2007
KernelVersion: 2.6.23
diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt
index 2790ad48cfc2..b29d8e56cf28 100644
--- a/Documentation/usb/power-management.txt
+++ b/Documentation/usb/power-management.txt
@@ -107,7 +107,9 @@ allowed to issue dynamic suspends.
The user interface for controlling dynamic PM is located in the power/
subdirectory of each USB device's sysfs directory, that is, in
/sys/bus/usb/devices/.../power/ where "..." is the device's ID. The
-relevant attribute files are: wakeup, level, and autosuspend.
+relevant attribute files are: wakeup, control, and autosuspend.
+(There may also be a file named "level"; this file was deprecated
+as of the 2.6.35 kernel and replaced by the "control" file.)
power/wakeup
@@ -120,7 +122,7 @@ relevant attribute files are: wakeup, level, and autosuspend.
while the device is suspended, the change won't take
effect until the following suspend.)
- power/level
+ power/control
This file contains one of two words: "on" or "auto".
You can write those words to the file to change the
@@ -148,14 +150,15 @@ relevant attribute files are: wakeup, level, and autosuspend.
never to autosuspend. You can write a number to the
file to change the autosuspend idle-delay time.
-Writing "-1" to power/autosuspend and writing "on" to power/level do
+Writing "-1" to power/autosuspend and writing "on" to power/control do
essentially the same thing -- they both prevent the device from being
autosuspended. Yes, this is a redundancy in the API.
(In 2.6.21 writing "0" to power/autosuspend would prevent the device
from being autosuspended; the behavior was changed in 2.6.22. The
power/autosuspend attribute did not exist prior to 2.6.21, and the
-power/level attribute did not exist prior to 2.6.22.)
+power/level attribute did not exist prior to 2.6.22. power/control
+was added in 2.6.34.)
Changing the default idle-delay time
@@ -212,7 +215,7 @@ among printers and scanners, but plenty of other types of device have
the same deficiency.
For this reason, by default the kernel disables autosuspend (the
-power/level attribute is initialized to "on") for all devices other
+power/control attribute is initialized to "on") for all devices other
than hubs. Hubs, at least, appear to be reasonably well-behaved in
this regard.
@@ -373,7 +376,7 @@ usb_autopm_put_interface() in its close or release routine. But other
patterns are possible.
The autosuspend attempts mentioned above will often fail for one
-reason or another. For example, the power/level attribute might be
+reason or another. For example, the power/control attribute might be
set to "on", or another interface in the same device might not be
idle. This is perfectly normal. If the reason for failure was that
the device hasn't been idle for long enough, a timer is scheduled to
@@ -394,12 +397,12 @@ Drivers can enable autosuspend for their devices by calling
in their probe() routine, if they know that the device is capable of
suspending and resuming correctly. This is exactly equivalent to
-writing "auto" to the device's power/level attribute. Likewise,
+writing "auto" to the device's power/control attribute. Likewise,
drivers can disable autosuspend by calling
usb_disable_autosuspend(struct usb_device *udev);
-This is exactly the same as writing "on" to the power/level attribute.
+This is exactly the same as writing "on" to the power/control attribute.
Sometimes a driver needs to make sure that remote wakeup is enabled
during autosuspend. For example, there's not much point