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USB: power-management documenation update 

This patch (as1014) was partly written by Tilman Schmidt.  It
clarifies the USB power-management documentation by explaining that
when a disconnect occurs, a suspend method call might not be followed
by either a resume or a reset_resume call.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2007-11-16 11:58:15 -05:00 committed by Greg Kroah-Hartman
parent bc59462b80
commit 3c886c5048
1 changed files with 8 additions and 0 deletions
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8
Documentation/usb/power-management.txt
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@ -278,6 +278,14 @@ optional. The methods' jobs are quite simple:
(although the interfaces will be in the same altsettings as (although the interfaces will be in the same altsettings as
before the suspend). before the suspend).
If the device is disconnected or powered down while it is suspended,
the disconnect method will be called instead of the resume or
reset_resume method. This is also quite likely to happen when
waking up from hibernation, as many systems do not maintain suspend
current to the USB host controllers during hibernation. (It's
possible to work around the hibernation-forces-disconnect problem by
using the USB Persist facility.)
The reset_resume method is used by the USB Persist facility (see The reset_resume method is used by the USB Persist facility (see
Documentation/usb/persist.txt) and it can also be used under certain Documentation/usb/persist.txt) and it can also be used under certain
circumstances when CONFIG_USB_PERSIST is not enabled. Currently, if a circumstances when CONFIG_USB_PERSIST is not enabled. Currently, if a