USB: add USB-Persist facility

This patch (as886) adds the controversial USB-persist facility,
allowing USB devices to persist across a power loss during system
suspend.

The facility is controlled by a new Kconfig option (with appropriate
warnings about the potential dangers); when the option is off the
behavior will remain the same as it is now.  But when the option is
on, people will be able to use suspend-to-disk and keep their USB
filesystems intact -- something particularly valuable for small
machines where the root filesystem is on a USB device!

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

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 56aa2ee21f1b..3d63e0c2dd70 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -403,6 +403,7 @@ struct usb_device {
 
         unsigned auto_pm:1;             /* autosuspend/resume in progress */
         unsigned do_remote_wakeup:1;    /* remote wakeup should be enabled */
+        unsigned reset_resume:1;        /* needs reset instead of resume */
         unsigned autosuspend_disabled:1; /* autosuspend and autoresume */
         unsigned autoresume_disabled:1;  /*  disabled by the user */
 #endif
@@ -819,7 +820,10 @@ struct usbdrv_wrap {
  * @pre_reset: Called by usb_reset_composite_device() when the device
  *      is about to be reset.
  * @post_reset: Called by usb_reset_composite_device() after the device
- *      has been reset.
+ *      has been reset, or in lieu of @resume following a reset-resume
+ *      (i.e., the device is reset instead of being resumed, as might
+ *      happen if power was lost).  The second argument tells which is
+ *      the reason.
  * @id_table: USB drivers use ID table to support hotplugging.
  *      Export this with MODULE_DEVICE_TABLE(usb,...).  This must be set
  *      or your driver's probe function will never get called.
@@ -861,7 +865,7 @@ struct usb_driver {
         int (*resume) (struct usb_interface *intf);
 
         void (*pre_reset) (struct usb_interface *intf);
-        void (*post_reset) (struct usb_interface *intf);
+        void (*post_reset) (struct usb_interface *intf, int reset_resume);
 
         const struct usb_device_id *id_table;