diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/obsolete/sysfs-bus-usb | 31 | ||||
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-usb | 28 | ||||
| -rw-r--r-- | Documentation/usb/power-management.txt | 19 |
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 00000000000..bd096d33fbc --- /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 bcebb9eaedc..294aa864a60 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 2790ad48cfc..b29d8e56cf2 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 |