USB: change handling of negative autosuspend delays

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>

2 files changed, 27 insertions, 5 deletions

diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
index 4314f259524..f073c5cb4e7 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -103,11 +103,21 @@ void usb_detect_quirks(struct usb_device *udev)
                 dev_dbg(&udev->dev, "USB quirks for this device: %x\n",
                                 udev->quirks);
 
+#ifdef  CONFIG_USB_SUSPEND
+
         /* By default, disable autosuspend for all devices.  The hub driver
          * will enable it for hubs.
          */
         usb_disable_autosuspend(udev);
 
+        /* Autosuspend can also be disabled if the initial autosuspend_delay
+         * is negative.
+         */
+        if (udev->autosuspend_delay < 0)
+                usb_autoresume_device(udev);
+
+#endif
+
         /* For the present, all devices default to USB-PERSIST enabled */
 #if 0           /* was: #ifdef CONFIG_PM */
         /* Hubs are automatically enabled for USB-PERSIST */
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index 313e241f5cc..43c002e3a9a 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -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;
 }