USB: HWA: fix device probe failure

This patch fixes a race condition that caused the HWA_HC interface probe
function to occasionally fail.  The HWA_HC would attempt to register
itself with the HWA_RC by searching for a uwb_rc class device with the
same parent device ptr.  If the probe function for the HWA_RC interface
had yet to run, the uwb_rc class device would not have been created
causing the look up to fail and the HWA_HC probe function to return an
error causing the device to be unusable.

The fix is for the HWA to delay registering with the HWA_RC until
receiving the command from userspace to start the wireless channel.  It
is the responsibility of userspace to ensure that the uwb_rc class
device has been created before starting the HWA channel.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 8 deletions

diff --git a/drivers/usb/host/hwa-hc.c b/drivers/usb/host/hwa-hc.c
index 4af750ecfe8f..483990c716aa 100644
--- a/drivers/usb/host/hwa-hc.c
+++ b/drivers/usb/host/hwa-hc.c
@@ -683,12 +683,9 @@ static int hwahc_create(struct hwahc *hwahc, struct usb_interface *iface)
 	wa->usb_dev = usb_get_dev(usb_dev);	/* bind the USB device */
 	wa->usb_iface = usb_get_intf(iface);
 	wusbhc->dev = dev;
-	wusbhc->uwb_rc = uwb_rc_get_by_grandpa(iface->dev.parent);
-	if (wusbhc->uwb_rc == NULL) {
-		result = -ENODEV;
-		dev_err(dev, "Cannot get associated UWB Host Controller\n");
-		goto error_rc_get;
-	}
+	/* defer getting the uwb_rc handle until it is needed since it
+	 * may not have been registered by the hwa_rc driver yet. */
+	wusbhc->uwb_rc = NULL;
 	result = wa_fill_descr(wa);	/* Get the device descriptor */
 	if (result < 0)
 		goto error_fill_descriptor;
@@ -731,8 +728,6 @@ error_wusbhc_create:
 	/* WA Descr fill allocs no resources */
 error_security_create:
 error_fill_descriptor:
-	uwb_rc_put(wusbhc->uwb_rc);
-error_rc_get:
 	usb_put_intf(iface);
 	usb_put_dev(usb_dev);
 	return result;