USB: remove CONFIG_USB_PERSIST setting

This patch (as1047) removes the USB_PERSIST Kconfig option, enabling
it permanently.  It also prevents the power/persist attribute from
being created for hub devices; there's no point in having it since
USB-PERSIST is always turned on for hubs.

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

4 files changed, 32 insertions, 54 deletions

diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index a2b0aa48b8ea..c15621d64579 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -102,31 +102,6 @@ config USB_SUSPEND
 
 	  If you are unsure about this, say N here.
 
-config USB_PERSIST
-	bool "USB device persistence during system suspend (DANGEROUS)"
-	depends on USB && PM && EXPERIMENTAL
-	default n
-	help
-
-	  If you say Y here and enable the "power/persist" attribute
-	  for a USB device, the device's data structures will remain
-	  persistent across system suspend, even if the USB bus loses
-	  power.  (This includes hibernation, also known as swsusp or
-	  suspend-to-disk.)  The devices will reappear as if by magic
-	  when the system wakes up, with no need to unmount USB
-	  filesystems, rmmod host-controller drivers, or do anything
-	  else.
-
-	  	WARNING: This option can be dangerous!
-
-	  If a USB device is replaced by another of the same type while
-	  the system is asleep, there's a good chance the kernel won't
-	  detect the change.  Likewise if the media in a USB storage
-	  device is replaced.  When this happens it's almost certain to
-	  cause data corruption and maybe even crash your system.
-
-	  If you are unsure, say N here.
-
 config USB_OTG
 	bool
 	depends on USB && EXPERIMENTAL
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index df68e2562582..6dc589955d75 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -30,12 +30,6 @@
 #include "hcd.h"
 #include "hub.h"
 
-#ifdef	CONFIG_USB_PERSIST
-#define	USB_PERSIST	1
-#else
-#define	USB_PERSIST	0
-#endif
-
 /* if we are in debug mode, always announce new devices */
 #ifdef DEBUG
 #ifndef CONFIG_USB_ANNOUNCE_NEW_DEVICES
@@ -695,7 +689,7 @@ static void hub_restart(struct usb_hub *hub, int type)
 		 * turn off the various status changes to prevent
 		 * khubd from disconnecting it later.
 		 */
-		if (USB_PERSIST && udev->persist_enabled && status == 0 &&
+		if (udev->persist_enabled && status == 0 &&
 				!(portstatus & USB_PORT_STAT_ENABLE)) {
 			if (portchange & USB_PORT_STAT_C_ENABLE)
 				clear_port_feature(hub->hdev, port1,
@@ -1923,9 +1917,8 @@ static int finish_port_resume(struct usb_device *udev)
  * the host and the device is the same as it was when the device
  * suspended.
  *
- * If CONFIG_USB_PERSIST and @udev->reset_resume are both set then this
- * routine won't check that the port is still enabled.  Furthermore,
- * if @udev->reset_resume is set then finish_port_resume() above will
+ * If @udev->reset_resume is set then this routine won't check that the
+ * port is still enabled.  Furthermore, finish_port_resume() above will
  * reset @udev.  The end result is that a broken power session can be
  * recovered and @udev will appear to persist across a loss of VBUS power.
  *
@@ -1937,8 +1930,8 @@ static int finish_port_resume(struct usb_device *udev)
  * to it will be lost.  Using the USB_PERSIST facility, the device can be
  * made to appear as if it had not disconnected.
  *
- * This facility is inherently dangerous.  Although usb_reset_device()
- * makes every effort to insure that the same device is present after the
+ * This facility can be dangerous.  Although usb_reset_device() makes
+ * every effort to insure that the same device is present after the
  * reset as before, it cannot provide a 100% guarantee.  Furthermore it's
  * quite possible for a device to remain unaltered but its media to be
  * changed.  If the user replaces a flash memory card while the system is
@@ -1983,7 +1976,7 @@ int usb_port_resume(struct usb_device *udev)
 		status = hub_port_status(hub, port1, &portstatus, &portchange);
 
  SuspendCleared:
-		if (USB_PERSIST && udev->reset_resume)
+		if (udev->reset_resume)
 			want_flags = USB_PORT_STAT_POWER
 					| USB_PORT_STAT_CONNECTION;
 		else
@@ -2113,10 +2106,10 @@ static int hub_reset_resume(struct usb_interface *intf)
  *
  * The USB host controller driver calls this function when its root hub
  * is resumed and Vbus power has been interrupted or the controller
- * has been reset.  The routine marks @rhdev as having lost power.  When
- * the hub driver is resumed it will take notice; if CONFIG_USB_PERSIST
- * is enabled then it will carry out power-session recovery, otherwise
- * it will disconnect all the child devices.
+ * has been reset.  The routine marks @rhdev as having lost power.
+ * When the hub driver is resumed it will take notice and carry out
+ * power-session recovery for all the "USB-PERSIST"-enabled child devices;
+ * the others will be disconnected.
  */
 void usb_root_hub_lost_power(struct usb_device *rhdev)
 {
diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
index dfc5418ea10c..f384edf35b44 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -97,4 +97,16 @@ void usb_detect_quirks(struct usb_device *udev)
 	if (udev->descriptor.bDeviceClass != USB_CLASS_HUB)
 		udev->autosuspend_disabled = 1;
 #endif
+
+#ifdef	CONFIG_PM
+	/* Hubs are automatically enabled for USB-PERSIST */
+	if (udev->descriptor.bDeviceClass == USB_CLASS_HUB)
+		udev->persist_enabled = 1;
+#else
+	/* In the absense of PM, we can safely enable USB-PERSIST
+	 * for all devices.  It will affect things like hub resets
+	 * and EMF-related port disables.
+	 */
+	udev->persist_enabled = 1;
+#endif	/* CONFIG_PM */
 }
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index a37ccbd1e007..5b20a60de8ba 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -180,11 +180,9 @@ show_urbnum(struct device *dev, struct device_attribute *attr, char *buf)
 static DEVICE_ATTR(urbnum, S_IRUGO, show_urbnum, NULL);
 
 
-#if defined(CONFIG_USB_PERSIST) || defined(CONFIG_USB_SUSPEND)
-static const char power_group[] = "power";
-#endif
+#ifdef	CONFIG_PM
 
-#ifdef	CONFIG_USB_PERSIST
+static const char power_group[] = "power";
 
 static ssize_t
 show_persist(struct device *dev, struct device_attribute *attr, char *buf)
@@ -222,12 +220,13 @@ static int add_persist_attributes(struct device *dev)
 	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);
+		/* Hubs are automatically enabled for USB_PERSIST,
+		 * no point in creating the attribute file.
+		 */
+		if (udev->descriptor.bDeviceClass != USB_CLASS_HUB)
+			rc = sysfs_add_file_to_group(&dev->kobj,
+					&dev_attr_persist.attr,
+					power_group);
 	}
 	return rc;
 }
@@ -238,13 +237,12 @@ static void remove_persist_attributes(struct device *dev)
 			&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 */
+#endif	/* CONFIG_PM */
 
 #ifdef	CONFIG_USB_SUSPEND