diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2010-01-08 12:56:54 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-03-02 14:54:10 -0800 |
| commit | 088f7fec8a0e683db72fd8826c5d3ab914e197b1 (patch) | |
| tree | 971ef100d0db9727e4403865b67c72de62e8247a /Documentation | |
| parent | 0c4db6df915bc470f0cd32fe48287fa6eb6adfb4 (diff) | |
USB: implement usb_enable_autosuspend
This patch (as1326) adds usb_enable_autosuspend() and
usb_disable_autosuspend() routines for use by drivers. If a driver
knows that its device can handle suspends and resumes correctly, it
can enable autosuspend all by itself. This is equivalent to the user
writing "auto" to the device's power/level attribute.
The implementation differs slightly from what it used to be. Now
autosuspend is disabled simply by doing usb_autoresume_device() (to
increment the usage counter) and enabled by doing
usb_autosuspend_device() (to decrement the usage counter).
The set_level() attribute method is updated to use the new routines,
and the USB Power-Management documentation is updated.
The patch adds a usb_enable_autosuspend() call to the hub driver's
probe routine, allowing the special-case code for hubs in quirks.c to
be removed.
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/usb/power-management.txt | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt index 3bf6818c8cf..e3fa189c257 100644 --- a/Documentation/usb/power-management.txt +++ b/Documentation/usb/power-management.txt @@ -229,6 +229,11 @@ necessary operations by hand or add them to a udev script. You can also change the idle-delay time; 2 seconds is not the best choice for every device. +If a driver knows that its device has proper suspend/resume support, +it can enable autosuspend all by itself. For example, the video +driver for a laptop's webcam might do this, since these devices are +rarely used and so should normally be autosuspended. + Sometimes it turns out that even when a device does work okay with autosuspend there are still problems. For example, there are experimental patches adding autosuspend support to the usbhid driver, @@ -384,6 +389,19 @@ autosuspend, there's no delay for an autoresume. Other parts of the driver interface ----------------------------------- +Drivers can enable autosuspend for their devices by calling + + usb_enable_autosuspend(struct usb_device *udev); + +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, +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. + Sometimes a driver needs to make sure that remote wakeup is enabled during autosuspend. For example, there's not much point autosuspending a keyboard if the user can't cause the keyboard to do a |