disp: msm: check if kms is instantiated

This defensive check is now required since the allocation
of driver private data has moved from bind to probe phase.
There is a chance that device shutdown can be called before
bind phase and this can cause invalid memory access.

Change-Id: I2d471a4aff93ae03291e19f6f902f1e5c28dc50f
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>

msm/msm_drv.c

@@ -970,7 +970,10 @@ static void msm_postclose(struct drm_device *dev, struct drm_file *file)
 	struct msm_file_private *ctx = file->driver_priv;
 	struct msm_kms *kms = priv->kms;
 
-	if (kms && kms->funcs && kms->funcs->postclose)
+	if (!kms)
+		return;
+
+	if (kms->funcs && kms->funcs->postclose)
 		kms->funcs->postclose(kms, file);
 
 	mutex_lock(&dev->struct_mutex);
@@ -994,11 +997,14 @@ static void msm_lastclose(struct drm_device *dev)
 	struct msm_kms *kms = priv->kms;
 	int i, rc;
 
+	if (!kms)
+		return;
+
 	/* check for splash status before triggering cleanup
 	 * if we end up here with splash status ON i.e before first
 	 * commit then ignore the last close call
 	 */
-	if (kms && kms->funcs && kms->funcs->check_for_splash
+	if (kms->funcs && kms->funcs->check_for_splash
 		&& kms->funcs->check_for_splash(kms))
 		return;
 
@@ -1026,7 +1032,7 @@ static void msm_lastclose(struct drm_device *dev)
 			DRM_ERROR("client modeset commit failed: %d\n", rc);
 	}
 
-	if (kms && kms->funcs && kms->funcs->lastclose)
+	if (kms->funcs && kms->funcs->lastclose)
 		kms->funcs->lastclose(kms);
 }