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>

2 files changed, 4 insertions, 1 deletions

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);