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 be37c863fdfb..5dfe31bc32ba 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);
 }