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USB: implement usb_enable_autosuspend

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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>
This commit is contained in:
Alan Stern
2010-01-08 12:56:54 -05:00
committed by Greg Kroah-Hartman
parent 0c4db6df91
commit 088f7fec8a
6 changed files with 82 additions and 21 deletions
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18
Documentation/usb/power-management.txt
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@ -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