USB: add power/persist device attribute

This patch (as920) adds an extra level of protection to the
USB-Persist facility.  Now it will apply by default only to hubs; for
all other devices the user must enable it explicitly by setting the
power/persist device attribute.

The disconnect_all_children() routine in hub.c has been removed and
its code placed inline.  This is the way it was originally as part of
hub_pre_reset(); the revised usage in hub_reset_resume() is
sufficiently different that the code can no longer be shared.
Likewise, mark_children_for_reset() is now inline as part of
hub_reset_resume().  The end result looks much cleaner than before.

The sysfs interface is updated to add the new attribute file, and
there are corresponding documentation updates.

Signed-off-by: Alan Stern <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Alan Stern 2007-05-30 15:39:33 -04:00 • committed by Greg Kroah-Hartman
commit b41a60eca8
6 changed files with 149 additions and 69 deletions

View file

@ -39,3 +39,16 @@ Description:
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.
What: /sys/bus/usb/devices/.../power/persist
Date: May 2007
KernelVersion: 2.6.23
Contact: Alan Stern <[email protected]>
Description:
If CONFIG_USB_PERSIST is set, then each USB device directory
will contain a file named power/persist. The file holds a
boolean value (0 or 1) indicating whether or not the
"USB-Persist" facility is enabled for the device. Since the
facility is inherently dangerous, it is disabled by default
for all devices except hubs. For more information, see
Documentation/usb/persist.txt.