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-rw-r--r--Documentation/usb/power-management.txt14
1 files changed, 9 insertions, 5 deletions
diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt
index 0a94ffe17ab6..b13e031beaa6 100644
--- a/Documentation/usb/power-management.txt
+++ b/Documentation/usb/power-management.txt
@@ -365,11 +365,15 @@ autosuspend the interface's device. When the usage counter is = 0
then the interface is considered to be idle, and the kernel may
autosuspend the device.
-Drivers need not be concerned about balancing changes to the usage
-counter; the USB core will undo any remaining "get"s when a driver
-is unbound from its interface. As a corollary, drivers must not call
-any of the usb_autopm_* functions after their disconnect() routine has
-returned.
+Drivers must be careful to balance their overall changes to the usage
+counter. Unbalanced "get"s will remain in effect when a driver is
+unbound from its interface, preventing the device from going into
+runtime suspend should the interface be bound to a driver again. On
+the other hand, drivers are allowed to achieve this balance by calling
+the ``usb_autopm_*`` functions even after their ``disconnect`` routine
+has returned -- say from within a work-queue routine -- provided they
+retain an active reference to the interface (via ``usb_get_intf`` and
+``usb_put_intf``).
Drivers using the async routines are responsible for their own
synchronization and mutual exclusion.