USB: Defer Set-Interface for suspended devices

This patch (as1128) fixes one of the problems related to the new PM
infrastructure.  We are not allowed to register new child devices
during the middle of a system sleep transition, but unbinding a USB
driver causes the core to automatically install altsetting 0 and
thereby create new endpoint pseudo-devices.

The patch fixes this problem (and the related problem that installing
altsetting 0 will fail if the device is suspended) by deferring the
Set-Interface call until some later time when it is legal and can
succeed.  Possible later times are: when a new driver is being probed
for the interface, and when the interface is being resumed.

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

1 files changed, 28 insertions, 3 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index ed1cc85..637b2be 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -230,6 +230,13 @@ static int usb_probe_interface(struct device *dev)
 		 */
 		intf->pm_usage_cnt = !(driver->supports_autosuspend);
 
+		/* Carry out a deferred switch to altsetting 0 */
+		if (intf->needs_altsetting0) {
+			usb_set_interface(udev, intf->altsetting[0].
+					desc.bInterfaceNumber, 0);
+			intf->needs_altsetting0 = 0;
+		}
+
 		error = driver->probe(intf, id);
 		if (error) {
 			mark_quiesced(intf);
@@ -266,8 +273,17 @@ static int usb_unbind_interface(struct device *dev)
 
 	driver->disconnect(intf);
 
-	/* reset other interface state */
-	usb_set_interface(udev, intf->altsetting[0].desc.bInterfaceNumber, 0);
+	/* Reset other interface state.
+	 * We cannot do a Set-Interface if the device is suspended or
+	 * if it is prepared for a system sleep (since installing a new
+	 * altsetting means creating new endpoint device entries).
+	 * When either of these happens, defer the Set-Interface.
+	 */
+	if (!error && intf->dev.power.status == DPM_ON)
+		usb_set_interface(udev, intf->altsetting[0].
+				desc.bInterfaceNumber, 0);
+	else
+		intf->needs_altsetting0 = 1;
 	usb_set_intfdata(intf, NULL);
 
 	intf->condition = USB_INTERFACE_UNBOUND;
@@ -975,8 +991,17 @@ static int usb_resume_interface(struct usb_device *udev,
 		goto done;
 
 	/* Can't resume it if it doesn't have a driver. */
-	if (intf->condition == USB_INTERFACE_UNBOUND)
+	if (intf->condition == USB_INTERFACE_UNBOUND) {
+
+		/* Carry out a deferred switch to altsetting 0 */
+		if (intf->needs_altsetting0 &&
+				intf->dev.power.status == DPM_ON) {
+			usb_set_interface(udev, intf->altsetting[0].
+					desc.bInterfaceNumber, 0);
+			intf->needs_altsetting0 = 0;
+		}
 		goto done;
+	}
 
 	/* Don't resume if the interface is marked for rebinding */
 	if (intf->needs_binding)