USB: add power/persist device attribute

This patch (as920) adds an extra level of protection to the
USB-Persist facility.  Now it will apply by default only to hubs; for
all other devices the user must enable it explicitly by setting the
power/persist device attribute.

The disconnect_all_children() routine in hub.c has been removed and
its code placed inline.  This is the way it was originally as part of
hub_pre_reset(); the revised usage in hub_reset_resume() is
sufficiently different that the code can no longer be shared.
Likewise, mark_children_for_reset() is now inline as part of
hub_reset_resume().  The end result looks much cleaner than before.

The sysfs interface is updated to add the new attribute file, and
there are corresponding documentation updates.

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

1 files changed, 73 insertions, 2 deletions

diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index be37c863fdf..5dfe31bc32b 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -169,6 +169,73 @@ show_quirks(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR(quirks, S_IRUGO, show_quirks, NULL);
 
+
+#if defined(CONFIG_USB_PERSIST) || defined(CONFIG_USB_SUSPEND)
+static const char power_group[] = "power";
+#endif
+
+#ifdef	CONFIG_USB_PERSIST
+
+static ssize_t
+show_persist(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct usb_device *udev = to_usb_device(dev);
+
+	return sprintf(buf, "%d\n", udev->persist_enabled);
+}
+
+static ssize_t
+set_persist(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct usb_device *udev = to_usb_device(dev);
+	int value;
+
+	/* Hubs are always enabled for USB_PERSIST */
+	if (udev->descriptor.bDeviceClass == USB_CLASS_HUB)
+		return -EPERM;
+
+	if (sscanf(buf, "%d", &value) != 1)
+		return -EINVAL;
+	usb_pm_lock(udev);
+	udev->persist_enabled = !!value;
+	usb_pm_unlock(udev);
+	return count;
+}
+
+static DEVICE_ATTR(persist, S_IRUGO | S_IWUSR, show_persist, set_persist);
+
+static int add_persist_attributes(struct device *dev)
+{
+	int rc = 0;
+
+	if (is_usb_device(dev)) {
+		struct usb_device *udev = to_usb_device(dev);
+
+		/* Hubs are automatically enabled for USB_PERSIST */
+		if (udev->descriptor.bDeviceClass == USB_CLASS_HUB)
+			udev->persist_enabled = 1;
+		rc = sysfs_add_file_to_group(&dev->kobj,
+				&dev_attr_persist.attr,
+				power_group);
+	}
+	return rc;
+}
+
+static void remove_persist_attributes(struct device *dev)
+{
+	sysfs_remove_file_from_group(&dev->kobj,
+			&dev_attr_persist.attr,
+			power_group);
+}
+
+#else
+
+#define add_persist_attributes(dev)	0
+#define remove_persist_attributes(dev)	do {} while (0)
+
+#endif	/* CONFIG_USB_PERSIST */
+
 #ifdef	CONFIG_USB_SUSPEND
 
 static ssize_t
@@ -276,8 +343,6 @@ set_level(struct device *dev, struct device_attribute *attr,
 
 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;
@@ -311,6 +376,7 @@ static void remove_power_attributes(struct device *dev)
 
 #endif	/* CONFIG_USB_SUSPEND */
 
+
 /* Descriptor fields */
 #define usb_descriptor_attr_le16(field, format_string)			\
 static ssize_t								\
@@ -384,6 +450,10 @@ int usb_create_sysfs_dev_files(struct usb_device *udev)
 	if (retval)
 		return retval;
 
+	retval = add_persist_attributes(dev);
+	if (retval)
+		goto error;
+
 	retval = add_power_attributes(dev);
 	if (retval)
 		goto error;
@@ -421,6 +491,7 @@ void usb_remove_sysfs_dev_files(struct usb_device *udev)
 	device_remove_file(dev, &dev_attr_product);
 	device_remove_file(dev, &dev_attr_serial);
 	remove_power_attributes(dev);
+	remove_persist_attributes(dev);
 	sysfs_remove_group(&dev->kobj, &dev_attr_grp);
 }