USB: deprecate the power/level sysfs attribute

This patch (as1367) deprecates USB's power/level sysfs attribute in
favor of the power/control attribute provided by the runtime PM core.
The two attributes do the same thing.

It would be nice to replace power/level with a symlink to
power/control, but at the moment sysfs doesn't offer any way to do so.

Signed-off-by: Alan Stern <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: AlanStern

Documentation/ABI/obsolete/sysfs-bus-usb

@@ -0,0 +1,31 @@
+What:		/sys/bus/usb/devices/.../power/level
+Date:		March 2007
+KernelVersion:	2.6.21
+Contact:	Alan Stern <[email protected]>
+Description:
+		Each USB device directory will contain a file named
+		power/level.  This file holds a power-level setting for
+		the device, either "on" or "auto".
+
+		"on" means that the device is not allowed to autosuspend,
+		although normal suspends for system sleep will still
+		be honored.  "auto" means the device will autosuspend
+		and autoresume in the usual manner, according to the
+		capabilities of its driver.
+
+		During normal use, devices should be left in the "auto"
+		level.  The "on" level is meant for administrative uses.
+		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.
+
+		Device not capable of proper suspend and resume should be
+		left in the "on" level.  Although the USB spec requires
+		devices to support suspend/resume, many of them do not.
+		In fact so many don't that by default, the USB core
+		initializes all non-hub devices in the "on" level.  Some
+		drivers may change this setting when they are bound.
+
+		This file is deprecated and will be removed after 2010.
+		Use the power/control file instead; it does exactly the
+		same thing.

Documentation/ABI/testing/sysfs-bus-usb

@@ -14,34 +14,6 @@ Description:
 		The autosuspend delay for newly-created devices is set to
 		the value of the usbcore.autosuspend module parameter.
 
-What:		/sys/bus/usb/devices/.../power/level
-Date:		March 2007
-KernelVersion:	2.6.21
-Contact:	Alan Stern <[email protected]>
-Description:
-		Each USB device directory will contain a file named
-		power/level.  This file holds a power-level setting for
-		the device, either "on" or "auto".
-
-		"on" means that the device is not allowed to autosuspend,
-		although normal suspends for system sleep will still
-		be honored.  "auto" means the device will autosuspend
-		and autoresume in the usual manner, according to the
-		capabilities of its driver.
-
-		During normal use, devices should be left in the "auto"
-		level.  The "on" level is meant for administrative uses.
-		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.
-
-		Device not capable of proper suspend and resume should be
-		left in the "on" level.  Although the USB spec requires
-		devices to support suspend/resume, many of them do not.
-		In fact so many don't that by default, the USB core
-		initializes all non-hub devices in the "on" level.  Some
-		drivers may change this setting when they are bound.
-
 What:		/sys/bus/usb/devices/.../power/persist
 Date:		May 2007
 KernelVersion:	2.6.23

Documentation/usb/power-management.txt

@@ -107,7 +107,9 @@ allowed to issue dynamic suspends.
 The user interface for controlling dynamic PM is located in the power/
 subdirectory of each USB device's sysfs directory, that is, in
 /sys/bus/usb/devices/.../power/ where "..." is the device's ID.  The
-relevant attribute files are: wakeup, level, and autosuspend.
+relevant attribute files are: wakeup, control, and autosuspend.
+(There may also be a file named "level"; this file was deprecated
+as of the 2.6.35 kernel and replaced by the "control" file.)
 
 	power/wakeup
 
@@ -120,7 +122,7 @@ relevant attribute files are: wakeup, level, and autosuspend.
 		while the device is suspended, the change won't take
 		effect until the following suspend.)
 
-	power/level
+	power/control
 
 		This file contains one of two words: "on" or "auto".
 		You can write those words to the file to change the
@@ -148,14 +150,15 @@ relevant attribute files are: wakeup, level, and autosuspend.
 		never to autosuspend.  You can write a number to the
 		file to change the autosuspend idle-delay time.
 
-Writing "-1" to power/autosuspend and writing "on" to power/level do
+Writing "-1" to power/autosuspend and writing "on" to power/control do
 essentially the same thing -- they both prevent the device from being
 autosuspended.  Yes, this is a redundancy in the API.
 
 (In 2.6.21 writing "0" to power/autosuspend would prevent the device
 from being autosuspended; the behavior was changed in 2.6.22.  The
 power/autosuspend attribute did not exist prior to 2.6.21, and the
-power/level attribute did not exist prior to 2.6.22.)
+power/level attribute did not exist prior to 2.6.22.  power/control
+was added in 2.6.34.)
 
 
 	Changing the default idle-delay time
@@ -212,7 +215,7 @@ among printers and scanners, but plenty of other types of device have
 the same deficiency.
 
 For this reason, by default the kernel disables autosuspend (the
-power/level attribute is initialized to "on") for all devices other
+power/control attribute is initialized to "on") for all devices other
 than hubs.  Hubs, at least, appear to be reasonably well-behaved in
 this regard.
 
@@ -373,7 +376,7 @@ usb_autopm_put_interface() in its close or release routine.  But other
 patterns are possible.
 
 The autosuspend attempts mentioned above will often fail for one
-reason or another.  For example, the power/level attribute might be
+reason or another.  For example, the power/control attribute might be
 set to "on", or another interface in the same device might not be
 idle.  This is perfectly normal.  If the reason for failure was that
 the device hasn't been idle for long enough, a timer is scheduled to
@@ -394,12 +397,12 @@ Drivers can enable autosuspend for their devices by calling
 
 in their probe() routine, if they know that the device is capable of
 suspending and resuming correctly.  This is exactly equivalent to
-writing "auto" to the device's power/level attribute.  Likewise,
+writing "auto" to the device's power/control attribute.  Likewise,
 drivers can disable autosuspend by calling
 
 	usb_disable_autosuspend(struct usb_device *udev);
 
-This is exactly the same as writing "on" to the power/level attribute.
+This is exactly the same as writing "on" to the power/control attribute.
 
 Sometimes a driver needs to make sure that remote wakeup is enabled
 during autosuspend.  For example, there's not much point

drivers/usb/core/sysfs.c

@@ -383,12 +383,23 @@ static DEVICE_ATTR(autosuspend, S_IRUGO | S_IWUSR,
 static const char on_string[] = "on";
 static const char auto_string[] = "auto";
 
+static void warn_level(void) {
+	static int level_warned;
+
+	if (!level_warned) {
+		level_warned = 1;
+		printk(KERN_WARNING "WARNING! power/level is deprecated; "
+				"use power/control instead\n");
+	}
+}
+
 static ssize_t
 show_level(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct usb_device *udev = to_usb_device(dev);
 	const char *p = auto_string;
 
+	warn_level();
 	if (udev->state != USB_STATE_SUSPENDED && !udev->dev.power.runtime_auto)
 		p = on_string;
 	return sprintf(buf, "%s\n", p);
@@ -403,6 +414,7 @@ set_level(struct device *dev, struct device_attribute *attr,
 	char *cp;
 	int rc = count;
 
+	warn_level();
 	cp = memchr(buf, '\n', count);
 	if (cp)
 		len = cp - buf;