1 files changed, 10 insertions, 2 deletions

diff --git a/drivers/gpu/drm/drm_platform.c b/drivers/gpu/drm/drm_platform.c
index ae9db5e2b27c..82431dcae37b 100644
--- a/drivers/gpu/drm/drm_platform.c
+++ b/drivers/gpu/drm/drm_platform.c
@@ -122,7 +122,7 @@ static const char *drm_platform_get_name(struct drm_device *dev)
 
 static int drm_platform_set_busid(struct drm_device *dev, struct drm_master *master)
 {
-        int len, ret;
+        int len, ret, id;
 
         master->unique_len = 13 + strlen(dev->platformdev->name);
         master->unique_size = master->unique_len;
@@ -131,8 +131,16 @@ static int drm_platform_set_busid(struct drm_device *dev, struct drm_master *mas
         if (master->unique == NULL)
                 return -ENOMEM;
 
+        id = dev->platformdev->id;
+
+        /* if only a single instance of the platform device, id will be
+         * set to -1.. use 0 instead to avoid a funny looking bus-id:
+         */
+        if (id == -1)
+                id = 0;
+
         len = snprintf(master->unique, master->unique_len,
-                        "platform:%s:%02d", dev->platformdev->name, dev->platformdev->id);
+                        "platform:%s:%02d", dev->platformdev->name, id);
 
         if (len > master->unique_len) {
                 DRM_ERROR("Unique buffer overflowed\n");