USB: export autosuspend delay in sysfs

This patch (as861) adds sysfs attributes to expose the autosuspend
delay value for each USB device.  If the user changes the delay from 0
(no autosuspend) to a positive value, an autosuspend is attempted.

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

drivers/usb/core/driver.c

@@ -1224,6 +1224,26 @@ void usb_autosuspend_device(struct usb_device *udev)
 	//		__FUNCTION__, udev->pm_usage_cnt);
 }
 
+/**
+ * usb_try_autosuspend_device - attempt an autosuspend of a USB device and its interfaces
+ * @udev: the usb_device to autosuspend
+ *
+ * This routine should be called when a core subsystem thinks @udev may
+ * be ready to autosuspend.
+ *
+ * @udev's usage counter left unchanged.  If it or any of the usage counters
+ * for an active interface is greater than 0, or autosuspend is not allowed
+ * for any other reason, no autosuspend request will be queued.
+ *
+ * This routine can run only in process context.
+ */
+void usb_try_autosuspend_device(struct usb_device *udev)
+{
+	usb_autopm_do_device(udev, 0);
+	// dev_dbg(&udev->dev, "%s: cnt %d\n",
+	// 		__FUNCTION__, udev->pm_usage_cnt);
+}
+
 /**
  * usb_autoresume_device - immediately autoresume a USB device and its interfaces
  * @udev: the usb_device to autoresume

drivers/usb/core/sysfs.c

@@ -158,6 +158,65 @@ show_quirks(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR(quirks, S_IRUGO, show_quirks, NULL);
 
+#ifdef	CONFIG_USB_SUSPEND
+
+static ssize_t
+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);
+}
+
+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;
+
+	if (sscanf(buf, "%u", &value) != 1 || value >= INT_MAX/HZ)
+		return -EINVAL;
+	value *= HZ;
+
+	old = udev->autosuspend_delay;
+	udev->autosuspend_delay = value;
+	if (value > 0 && old == 0)
+		usb_try_autosuspend_device(udev);
+
+	return count;
+}
+
+static DEVICE_ATTR(autosuspend, S_IRUGO | S_IWUSR,
+		show_autosuspend, set_autosuspend);
+
+static char power_group[] = "power";
+
+static int add_power_attributes(struct device *dev)
+{
+	int rc = 0;
+
+	if (is_usb_device(dev))
+		rc = sysfs_add_file_to_group(&dev->kobj,
+				&dev_attr_autosuspend.attr,
+				power_group);
+	return rc;
+}
+
+static void remove_power_attributes(struct device *dev)
+{
+	sysfs_remove_file_from_group(&dev->kobj,
+			&dev_attr_autosuspend.attr,
+			power_group);
+}
+
+#else
+
+#define add_power_attributes(dev)	0
+#define remove_power_attributes(dev)	do {} while (0)
+
+#endif	/* CONFIG_USB_SUSPEND */
+
 /* Descriptor fields */
 #define usb_descriptor_attr_le16(field, format_string)			\
 static ssize_t								\
@@ -230,6 +289,10 @@ int usb_create_sysfs_dev_files(struct usb_device *udev)
 	if (retval)
 		return retval;
 
+	retval = add_power_attributes(dev);
+	if (retval)
+		goto error;
+
 	if (udev->manufacturer) {
 		retval = device_create_file(dev, &dev_attr_manufacturer);
 		if (retval)
@@ -262,6 +325,7 @@ void usb_remove_sysfs_dev_files(struct usb_device *udev)
 	device_remove_file(dev, &dev_attr_manufacturer);
 	device_remove_file(dev, &dev_attr_product);
 	device_remove_file(dev, &dev_attr_serial);
+	remove_power_attributes(dev);
 	sysfs_remove_group(&dev->kobj, &dev_attr_grp);
 }
 

drivers/usb/core/usb.h

@@ -66,11 +66,13 @@ static inline void usb_pm_unlock(struct usb_device *udev) {}
 #ifdef CONFIG_USB_SUSPEND
 
 extern void usb_autosuspend_device(struct usb_device *udev);
+extern void usb_try_autosuspend_device(struct usb_device *udev);
 extern int usb_autoresume_device(struct usb_device *udev);
 
 #else
 
 #define usb_autosuspend_device(udev)		do {} while (0)
+#define usb_try_autosuspend_device(udev)	do {} while (0)
 static inline int usb_autoresume_device(struct usb_device *udev)
 {
 	return 0;