drm/bridge: imx8qxp-pixel-link: get/put the next bridge

This driver obtains a bridge pointer from of_drm_find_bridge() in the probe
function and stores it until driver removal. of_drm_find_bridge() is
deprecated, so move to of_drm_find_and_get_bridge() for the bridge to be
refcounted and use bridge->next_bridge to put the reference on
deallocation.

To keep the code as simple and reliable as possible remove the intermediate
next_bridge and selected_bridge variables.

Get/put operations on the remaining pointer is pl->bridge.next_bridge,
which is tied to the struct imx8qxp_pixel_link lifetime, are:
 - get reference when assigned (by of_drm_find_and_get_bridge())
 - put reference before reassignment if reassignment happens
 - put reference when the struct imx8qxp_pixel_link embedding the
   struct drm_bridge is destroyed (struct drm_bridge::next_bridge)

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Acked-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Link: https://lore.kernel.org/r/20260211-drm-bridge-alloc-getput-drm_of_find_bridge-v6-1-651ddfd13bdb@bootlin.com

diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c b/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c
index 6e43a78b02f14b3c65d5df241390a1d8c3256571..63a8d8b1f76b14075054854877cd60889997bb3b 100644 (file)
--- a/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c
+++ b/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c
@@ -23,7 +23,6 @@
 
 struct imx8qxp_pixel_link {
        struct drm_bridge bridge;
-       struct drm_bridge *next_bridge;
        struct device *dev;
        struct imx_sc_ipc *ipc_handle;
        u8 stream_id;
@@ -140,7 +139,7 @@ static int imx8qxp_pixel_link_bridge_attach(struct drm_bridge *bridge,
        }
 
        return drm_bridge_attach(encoder,
-                                pl->next_bridge, bridge,
+                                pl->bridge.next_bridge, bridge,
                                 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
 }
 
@@ -260,7 +259,6 @@ static int imx8qxp_pixel_link_find_next_bridge(struct imx8qxp_pixel_link *pl)
 {
        struct device_node *np = pl->dev->of_node;
        struct device_node *port;
-       struct drm_bridge *selected_bridge = NULL;
        u32 port_id;
        bool found_port = false;
        int reg;
@@ -297,20 +295,21 @@ static int imx8qxp_pixel_link_find_next_bridge(struct imx8qxp_pixel_link *pl)
                        continue;
                }
 
-               struct drm_bridge *next_bridge = of_drm_find_bridge(remote);
-               if (!next_bridge)
-                       return -EPROBE_DEFER;
-
-               /*
-                * Select the next bridge with companion PXL2DPI if
-                * present, otherwise default to the first bridge
-                */
-               if (!selected_bridge || of_property_present(remote, "fsl,companion-pxl2dpi"))
-                       selected_bridge = next_bridge;
+               if (!pl->bridge.next_bridge) {
+                       /* Select the first bridge by default... */
+                       pl->bridge.next_bridge = of_drm_find_and_get_bridge(remote);
+                       if (!pl->bridge.next_bridge)
+                               return -EPROBE_DEFER;
+               } else if (of_property_present(remote, "fsl,companion-pxl2dpi")) {
+                       /* ... but prefer the companion PXL2DPI if present */
+                       drm_bridge_put(pl->bridge.next_bridge);
+                       pl->bridge.next_bridge = of_drm_find_and_get_bridge(remote);
+                       if (!pl->bridge.next_bridge)
+                               return -EPROBE_DEFER;
+               }
        }
 
        pl->mst_addr = port_id - 1;
-       pl->next_bridge = selected_bridge;
 
        return 0;
 }