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USB: change handling of negative autosuspend delays

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This patch (as1327) changes the way negative autosuspend delays
prevent device from autosuspending.  The current code checks for
negative values explicitly in the autosuspend_check() routine.  The
updated code keeps things from getting that far by using
usb_autoresume_device() to increment the usage counter when a negative
delay is set, and by using usb_autosuspend_device() to decrement the
usage counter when a non-negative delay is set.

This complicates the set_autosuspend() attribute method code slightly,
but it will reduce the overall power management overhead.

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 12:57:02 -05:00
committed by Greg Kroah-Hartman
parent 088f7fec8a
commit 5899f1e020
2 changed files with 27 additions and 5 deletions
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22
drivers/usb/core/sysfs.c
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@@ -346,7 +346,8 @@ set_autosuspend(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
struct usb_device *udev = to_usb_device(dev);
int value;
int value, old_delay;
int rc;
if (sscanf(buf, "%d", &value) != 1 || value >= INT_MAX/HZ ||
value <= - INT_MAX/HZ)
@@ -354,13 +355,24 @@ set_autosuspend(struct device *dev, struct device_attribute *attr,
value *= HZ;
usb_lock_device(udev);
old_delay = udev->autosuspend_delay;
udev->autosuspend_delay = value;
if (value >= 0)
usb_try_autosuspend_device(udev);
else {
if (usb_autoresume_device(udev) == 0)
if (old_delay < 0) { /* Autosuspend wasn't allowed */
if (value >= 0)
usb_autosuspend_device(udev);
} else { /* Autosuspend was allowed */
if (value < 0) {
rc = usb_autoresume_device(udev);
if (rc < 0) {
count = rc;
udev->autosuspend_delay = old_delay;
}
} else {
usb_try_autosuspend_device(udev);
}
}
usb_unlock_device(udev);
return count;
}