USB: don't use reset-resume if drivers don't support it

This patch tries to identify which devices are able to accept
reset-resume handling, by checking that there is at least one
interface driver bound and that all of the drivers have a reset_resume
method defined.  If these conditions don't hold then during resume
processing, the device is logicall disconnected.

This is only a temporary fix.  Later on we will explicitly unbind
drivers that can't handle reset-resumes.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Oliver Neukum <oliver@neukum.org>
Cc: Pavel Machek <pavel@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 44 insertions, 2 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 8eb4da332f56..94789be54ca3 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -644,6 +644,48 @@ static void hub_stop(struct usb_hub *hub)
 
 #ifdef CONFIG_PM
 
+/* Try to identify which devices need USB-PERSIST handling */
+static int persistent_device(struct usb_device *udev)
+{
+        int i;
+        int retval;
+        struct usb_host_config *actconfig;
+
+        /* Explicitly not marked persistent? */
+        if (!udev->persist_enabled)
+                return 0;
+
+        /* No active config? */
+        actconfig = udev->actconfig;
+        if (!actconfig)
+                return 0;
+
+        /* FIXME! We should check whether it's open here or not! */
+
+        /*
+         * Check that all the interface drivers have a
+         * 'reset_resume' entrypoint
+         */
+        retval = 0;
+        for (i = 0; i < actconfig->desc.bNumInterfaces; i++) {
+                struct usb_interface *intf;
+                struct usb_driver *driver;
+
+                intf = actconfig->interface[i];
+                if (!intf->dev.driver)
+                        continue;
+                driver = to_usb_driver(intf->dev.driver);
+                if (!driver->reset_resume)
+                        return 0;
+                /*
+                 * We have at least one driver, and that one
+                 * has a reset_resume method.
+                 */
+                retval = 1;
+        }
+        return retval;
+}
+
 static void hub_restart(struct usb_hub *hub, int type)
 {
         struct usb_device *hdev = hub->hdev;
@@ -689,8 +731,8 @@ static void hub_restart(struct usb_hub *hub, int type)
                  * turn off the various status changes to prevent
                  * khubd from disconnecting it later.
                  */
-                if (udev->persist_enabled && status == 0 &&
-                                !(portstatus & USB_PORT_STAT_ENABLE)) {
+                if (status == 0 && !(portstatus & USB_PORT_STAT_ENABLE) &&
+                                persistent_device(udev)) {
                         if (portchange & USB_PORT_STAT_C_ENABLE)
                                 clear_port_feature(hub->hdev, port1,
                                                 USB_PORT_FEAT_C_ENABLE);