USB: Allow autosuspend delay to equal 0

This patch (as867) adds an entry for the new power/autosuspend
attribute in Documentation/ABI/testing, and it changes the behavior of
the delay value.  Now a delay of 0 means to autosuspend as soon as
possible, and negative values will prevent autosuspend.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/ABI/testing/sysfs-bus-usb

@@ -0,0 +1,15 @@
+What:		/sys/bus/usb/devices/.../power/autosuspend
+Date:		March 2007
+KernelVersion:	2.6.21
+Contact:	Alan Stern <stern@rowland.harvard.edu>
+Description:
+		Each USB device directory will contain a file named
+		power/autosuspend.  This file holds the time (in seconds)
+		the device must be idle before it will be autosuspended.
+		0 means the device will be autosuspended as soon as
+		possible.  Negative values will prevent the device from
+		being autosuspended at all, and writing a negative value
+		will resume the device if it is already suspended.
+
+		The autosuspend delay for newly-created devices is set to
+		the value of the usbcore.autosuspend module parameter.

Documentation/kernel-parameters.txt

@@ -1792,7 +1792,7 @@ and is between 256 and 4096 characters. It is defined in the file
 			for newly-detected USB devices (default 2).  This
 			is the time required before an idle device will be
 			autosuspended.  Devices for which the delay is set
-			to 0 won't be autosuspended at all.
+			to a negative value won't be autosuspended at all.
 
 	usbhid.mousepoll=
 			[USBHID] The interval which mice are to be polled at.

drivers/usb/core/driver.c

@@ -970,7 +970,7 @@ static int autosuspend_check(struct usb_device *udev)
 	udev->do_remote_wakeup = device_may_wakeup(&udev->dev);
 	if (udev->pm_usage_cnt > 0)
 		return -EBUSY;
-	if (!udev->autosuspend_delay)
+	if (udev->autosuspend_delay < 0)
 		return -EPERM;
 
 	if (udev->actconfig) {

drivers/usb/core/sysfs.c

@@ -165,25 +165,29 @@ show_autosuspend(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct usb_device *udev = to_usb_device(dev);
 
-	return sprintf(buf, "%u\n", udev->autosuspend_delay / HZ);
+	return sprintf(buf, "%d\n", udev->autosuspend_delay / HZ);
 }
 
 static ssize_t
 set_autosuspend(struct device *dev, struct device_attribute *attr,
 		const char *buf, size_t count)
 {
 	struct usb_device *udev = to_usb_device(dev);
-	unsigned value, old;
+	int value;
 
-	if (sscanf(buf, "%u", &value) != 1 || value >= INT_MAX/HZ)
+	if (sscanf(buf, "%d", &value) != 1 || value >= INT_MAX/HZ ||
+			value <= - INT_MAX/HZ)
 		return -EINVAL;
 	value *= HZ;
 
-	old = udev->autosuspend_delay;
 	udev->autosuspend_delay = value;
-	if (value > 0 && old == 0)
+	if (value >= 0)
 		usb_try_autosuspend_device(udev);
-
+	else {
+		usb_lock_device(udev);
+		usb_external_resume_device(udev);
+		usb_unlock_device(udev);
+	}
 	return count;
 }
 

drivers/usb/core/usb.c

@@ -55,7 +55,7 @@ struct workqueue_struct *ksuspend_usb_wq;
 #ifdef	CONFIG_USB_SUSPEND
 static int usb_autosuspend_delay = 2;		/* Default delay value,
 						 * in seconds */
-module_param_named(autosuspend, usb_autosuspend_delay, uint, 0644);
+module_param_named(autosuspend, usb_autosuspend_delay, int, 0644);
 MODULE_PARM_DESC(autosuspend, "default autosuspend delay");
 
 #else

include/linux/usb.h

@@ -394,7 +394,7 @@ struct usb_device {
 	struct delayed_work autosuspend; /* for delayed autosuspends */
 	struct mutex pm_mutex;		/* protects PM operations */
 
-	unsigned autosuspend_delay;	/* in jiffies */
+	int autosuspend_delay;		/* in jiffies */
 
 	unsigned auto_pm:1;		/* autosuspend/resume in progress */
 	unsigned do_remote_wakeup:1;	/* remote wakeup should be enabled */