1 files changed, 43 insertions, 32 deletions

diff --git a/drivers/media/video/uvc/uvc_driver.c b/drivers/media/video/uvc/uvc_driver.c
index 8d51a6a130b0..e7ce898ad706 100644
--- a/drivers/media/video/uvc/uvc_driver.c
+++ b/drivers/media/video/uvc/uvc_driver.c
@@ -1265,13 +1265,12 @@ static int uvc_scan_chain_entity(struct uvc_video_chain *chain,
                 break;
 
         case UVC_TT_STREAMING:
-                if (uvc_trace_param & UVC_TRACE_PROBE)
-                        printk(" <- IT %d\n", entity->id);
-
-                if (!UVC_ENTITY_IS_ITERM(entity)) {
-                        uvc_trace(UVC_TRACE_DESCR, "Unsupported input "
-                                "terminal %u.\n", entity->id);
-                        return -1;
+                if (UVC_ENTITY_IS_ITERM(entity)) {
+                        if (uvc_trace_param & UVC_TRACE_PROBE)
+                                printk(" <- IT %d\n", entity->id);
+                } else {
+                        if (uvc_trace_param & UVC_TRACE_PROBE)
+                                printk(" OT %d", entity->id);
                 }
 
                 break;
@@ -1351,10 +1350,11 @@ static int uvc_scan_chain_forward(struct uvc_video_chain *chain,
 }
 
 static int uvc_scan_chain_backward(struct uvc_video_chain *chain,
-        struct uvc_entity *entity)
+        struct uvc_entity **_entity)
 {
+        struct uvc_entity *entity = *_entity;
         struct uvc_entity *term;
-        int id = -1, i;
+        int id = -EINVAL, i;
 
         switch (UVC_ENTITY_TYPE(entity)) {
         case UVC_VC_EXTENSION_UNIT:
@@ -1398,34 +1398,49 @@ static int uvc_scan_chain_backward(struct uvc_video_chain *chain,
 
                 id = 0;
                 break;
+
+        case UVC_ITT_VENDOR_SPECIFIC:
+        case UVC_ITT_CAMERA:
+        case UVC_ITT_MEDIA_TRANSPORT_INPUT:
+        case UVC_OTT_VENDOR_SPECIFIC:
+        case UVC_OTT_DISPLAY:
+        case UVC_OTT_MEDIA_TRANSPORT_OUTPUT:
+        case UVC_TT_STREAMING:
+                id = UVC_ENTITY_IS_OTERM(entity) ? entity->output.bSourceID : 0;
+                break;
         }
 
-        return id;
+        if (id <= 0) {
+                *_entity = NULL;
+                return id;
+        }
+
+        entity = uvc_entity_by_id(chain->dev, id);
+        if (entity == NULL) {
+                uvc_trace(UVC_TRACE_DESCR, "Found reference to "
+                        "unknown entity %d.\n", id);
+                return -EINVAL;
+        }
+
+        *_entity = entity;
+        return 0;
 }
 
 static int uvc_scan_chain(struct uvc_video_chain *chain,
-                          struct uvc_entity *oterm)
+                          struct uvc_entity *term)
 {
         struct uvc_entity *entity, *prev;
-        int id;
 
-        entity = oterm;
-        list_add_tail(&entity->chain, &chain->entities);
-        uvc_trace(UVC_TRACE_PROBE, "Scanning UVC chain: OT %d", entity->id);
+        uvc_trace(UVC_TRACE_PROBE, "Scanning UVC chain:");
 
-        id = entity->output.bSourceID;
-        while (id != 0) {
-                prev = entity;
-                entity = uvc_entity_by_id(chain->dev, id);
-                if (entity == NULL) {
-                        uvc_trace(UVC_TRACE_DESCR, "Found reference to "
-                                "unknown entity %d.\n", id);
-                        return -EINVAL;
-                }
+        entity = term;
+        prev = NULL;
 
+        while (entity != NULL) {
+                /* Entity must not be part of an existing chain */
                 if (entity->chain.next || entity->chain.prev) {
                         uvc_trace(UVC_TRACE_DESCR, "Found reference to "
-                                "entity %d already in chain.\n", id);
+                                "entity %d already in chain.\n", entity->id);
                         return -EINVAL;
                 }
 
@@ -1437,14 +1452,10 @@ static int uvc_scan_chain(struct uvc_video_chain *chain,
                 if (uvc_scan_chain_forward(chain, entity, prev) < 0)
                         return -EINVAL;
 
-                /* Stop when a terminal is found. */
-                if (UVC_ENTITY_IS_TERM(entity))
-                        break;
-
                 /* Backward scan */
-                id = uvc_scan_chain_backward(chain, entity);
-                if (id < 0)
-                        return id;
+                prev = entity;
+                if (uvc_scan_chain_backward(chain, &entity) < 0)
+                        return -EINVAL;
         }
 
         return 0;