USB: add power/level sysfs attribute

This patch (as874) adds another piece to the user-visible part of the
USB autosuspend interface.  The new power/level sysfs attribute allows
users to force the device on (with autosuspend off), force the device
to sleep (with autoresume off), or return to normal automatic operation.

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

1 files changed, 77 insertions, 4 deletions

diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index 731001f7d2c1..2ea47a38aefa 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -11,6 +11,7 @@
 
 
 #include <linux/kernel.h>
+#include <linux/string.h>
 #include <linux/usb.h>
 #include "usb.h"
 
@@ -184,9 +185,8 @@ set_autosuspend(struct device *dev, struct device_attribute *attr,
 	if (value >= 0)
 		usb_try_autosuspend_device(udev);
 	else {
-		usb_lock_device(udev);
-		usb_external_resume_device(udev);
-		usb_unlock_device(udev);
+		if (usb_autoresume_device(udev) == 0)
+			usb_autosuspend_device(udev);
 	}
 	return count;
 }
@@ -194,22 +194,95 @@ set_autosuspend(struct device *dev, struct device_attribute *attr,
 static DEVICE_ATTR(autosuspend, S_IRUGO | S_IWUSR,
 		show_autosuspend, set_autosuspend);
 
+static const char on_string[] = "on";
+static const char auto_string[] = "auto";
+static const char suspend_string[] = "suspend";
+
+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;
+
+	if (udev->state == USB_STATE_SUSPENDED) {
+		if (udev->autoresume_disabled)
+			p = suspend_string;
+	} else {
+		if (udev->autosuspend_disabled)
+			p = on_string;
+	}
+	return sprintf(buf, "%s\n", p);
+}
+
+static ssize_t
+set_level(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct usb_device *udev = to_usb_device(dev);
+	int len = count;
+	char *cp;
+	int rc = 0;
+
+	cp = memchr(buf, '\n', count);
+	if (cp)
+		len = cp - buf;
+
+	usb_lock_device(udev);
+
+	/* Setting the flags without calling usb_pm_lock is a subject to
+	 * races, but who cares...
+	 */
+	if (len == sizeof on_string - 1 &&
+			strncmp(buf, on_string, len) == 0) {
+		udev->autosuspend_disabled = 1;
+		udev->autoresume_disabled = 0;
+		rc = usb_external_resume_device(udev);
+
+	} else if (len == sizeof auto_string - 1 &&
+			strncmp(buf, auto_string, len) == 0) {
+		udev->autosuspend_disabled = 0;
+		udev->autoresume_disabled = 0;
+		rc = usb_external_resume_device(udev);
+
+	} else if (len == sizeof suspend_string - 1 &&
+			strncmp(buf, suspend_string, len) == 0) {
+		udev->autosuspend_disabled = 0;
+		udev->autoresume_disabled = 1;
+		rc = usb_external_suspend_device(udev, PMSG_SUSPEND);
+
+	} else
+		rc = -EINVAL;
+
+	usb_unlock_device(udev);
+	return (rc < 0 ? rc : count);
+}
+
+static DEVICE_ATTR(level, S_IRUGO | S_IWUSR, show_level, set_level);
+
 static char power_group[] = "power";
 
 static int add_power_attributes(struct device *dev)
 {
 	int rc = 0;
 
-	if (is_usb_device(dev))
+	if (is_usb_device(dev)) {
 		rc = sysfs_add_file_to_group(&dev->kobj,
 				&dev_attr_autosuspend.attr,
 				power_group);
+		if (rc == 0)
+			rc = sysfs_add_file_to_group(&dev->kobj,
+					&dev_attr_level.attr,
+					power_group);
+	}
 	return rc;
 }
 
 static void remove_power_attributes(struct device *dev)
 {
 	sysfs_remove_file_from_group(&dev->kobj,
+			&dev_attr_level.attr,
+			power_group);
+	sysfs_remove_file_from_group(&dev->kobj,
 			&dev_attr_autosuspend.attr,
 			power_group);
 }