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>

7 files changed, 42 insertions, 18 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;
diff --git a/drivers/usb/wusbcore/mmc.c b/drivers/usb/wusbcore/mmc.c
index 021467f86d9e..b71760c8d3ad 100644
--- a/drivers/usb/wusbcore/mmc.c
+++ b/drivers/usb/wusbcore/mmc.c
@@ -195,6 +195,7 @@ int wusbhc_start(struct wusbhc *wusbhc)
         struct device *dev = wusbhc->dev;
 
         WARN_ON(wusbhc->wuie_host_info != NULL);
+        BUG_ON(wusbhc->uwb_rc == NULL);
 
         result = wusbhc_rsv_establish(wusbhc);
         if (result < 0) {
@@ -276,12 +277,38 @@ int wusbhc_chid_set(struct wusbhc *wusbhc, const struct wusb_ckhdid *chid)
                 }
                 wusbhc->chid = *chid;
         }
+
+        /* register with UWB if we haven't already since we are about to start
+            the radio. */
+        if ((chid) && (wusbhc->uwb_rc == NULL)) {
+                wusbhc->uwb_rc = uwb_rc_get_by_grandpa(wusbhc->dev->parent);
+                if (wusbhc->uwb_rc == NULL) {
+                        result = -ENODEV;
+                        dev_err(wusbhc->dev, "Cannot get associated UWB Host Controller\n");
+                        goto error_rc_get;
+                }
+
+                result = wusbhc_pal_register(wusbhc);
+                if (result < 0) {
+                        dev_err(wusbhc->dev, "Cannot register as a UWB PAL\n");
+                        goto error_pal_register;
+                }
+        }
         mutex_unlock(&wusbhc->mutex);
 
         if (chid)
                 result = uwb_radio_start(&wusbhc->pal);
         else
                 uwb_radio_stop(&wusbhc->pal);
+
+        return result;
+
+error_pal_register:
+        uwb_rc_put(wusbhc->uwb_rc);
+        wusbhc->uwb_rc = NULL;
+error_rc_get:
+        mutex_unlock(&wusbhc->mutex);
+
         return result;
 }
 EXPORT_SYMBOL_GPL(wusbhc_chid_set);
diff --git a/drivers/usb/wusbcore/pal.c b/drivers/usb/wusbcore/pal.c
index d0b172c5ecc7..59e100c2eb50 100644
--- a/drivers/usb/wusbcore/pal.c
+++ b/drivers/usb/wusbcore/pal.c
@@ -45,10 +45,11 @@ int wusbhc_pal_register(struct wusbhc *wusbhc)
 }
 
 /**
- * wusbhc_pal_register - unregister the WUSB HC as a UWB PAL
+ * wusbhc_pal_unregister - unregister the WUSB HC as a UWB PAL
  * @wusbhc: the WUSB HC
  */
 void wusbhc_pal_unregister(struct wusbhc *wusbhc)
 {
-        uwb_pal_unregister(&wusbhc->pal);
+        if (wusbhc->uwb_rc)
+                uwb_pal_unregister(&wusbhc->pal);
 }
diff --git a/drivers/usb/wusbcore/reservation.c b/drivers/usb/wusbcore/reservation.c
index 6f4fafdc2401..ead79f793927 100644
--- a/drivers/usb/wusbcore/reservation.c
+++ b/drivers/usb/wusbcore/reservation.c
@@ -80,6 +80,9 @@ int wusbhc_rsv_establish(struct wusbhc *wusbhc)
         struct uwb_dev_addr bcid;
         int ret;
 
+        if (rc == NULL)
+                return -ENODEV;
+
         rsv = uwb_rsv_create(rc, wusbhc_rsv_complete_cb, wusbhc);
         if (rsv == NULL)
                 return -ENOMEM;
diff --git a/drivers/usb/wusbcore/wusbhc.c b/drivers/usb/wusbcore/wusbhc.c
index e712af3e46c2..742c607d1fa3 100644
--- a/drivers/usb/wusbcore/wusbhc.c
+++ b/drivers/usb/wusbcore/wusbhc.c
@@ -325,13 +325,7 @@ int wusbhc_b_create(struct wusbhc *wusbhc)
                 goto error_create_attr_group;
         }
 
-        result = wusbhc_pal_register(wusbhc);
-        if (result < 0)
-                goto error_pal_register;
         return 0;
-
-error_pal_register:
-        sysfs_remove_group(wusbhc_kobj(wusbhc), &wusbhc_attr_group);
 error_create_attr_group:
         return result;
 }
@@ -457,7 +451,8 @@ EXPORT_SYMBOL_GPL(wusbhc_giveback_urb);
  */
 void wusbhc_reset_all(struct wusbhc *wusbhc)
 {
-        uwb_rc_reset_all(wusbhc->uwb_rc);
+        if (wusbhc->uwb_rc)
+                uwb_rc_reset_all(wusbhc->uwb_rc);
 }
 EXPORT_SYMBOL_GPL(wusbhc_reset_all);
 
diff --git a/drivers/uwb/pal.c b/drivers/uwb/pal.c
index 8ee7d90a8c68..690577d2a35b 100644
--- a/drivers/uwb/pal.c
+++ b/drivers/uwb/pal.c
@@ -44,10 +44,12 @@ int uwb_pal_register(struct uwb_pal *pal)
         int ret;
 
         if (pal->device) {
+                /* create a link to the uwb_rc in the PAL device's directory. */
                 ret = sysfs_create_link(&pal->device->kobj,
                                         &rc->uwb_dev.dev.kobj, "uwb_rc");
                 if (ret < 0)
                         return ret;
+                /* create a link to the PAL in the UWB device's directory. */
                 ret = sysfs_create_link(&rc->uwb_dev.dev.kobj,
                                         &pal->device->kobj, pal->name);
                 if (ret < 0) {
diff --git a/drivers/uwb/uwb-internal.h b/drivers/uwb/uwb-internal.h
index a7494bf10081..9a103b100f1e 100644
--- a/drivers/uwb/uwb-internal.h
+++ b/drivers/uwb/uwb-internal.h
@@ -55,7 +55,8 @@ static inline struct uwb_rc *__uwb_rc_get(struct uwb_rc *rc)
 
 static inline void __uwb_rc_put(struct uwb_rc *rc)
 {
-        uwb_dev_put(&rc->uwb_dev);
+        if (rc)
+                uwb_dev_put(&rc->uwb_dev);
 }
 
 extern int uwb_rc_reset(struct uwb_rc *rc);