Hi Luca,
On Tue, Feb 03, 2026 at 11:35:25AM +0100, Luca Ceresoli wrote:
> 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. 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, get a reference for
> each pointer that stores a drm_bridge address when it is stored and release
> it when the pointer is overwritten or goes out of scope. Also remove the
> intermediate selected_bridge variable to reduce the refcounted variables in
> the function. The involved pointers are:
>
> * next_bridge loop-local variable:
> - get reference by of_drm_find_and_get_bridge()
> - put reference at the end of the loop iteration (__free)
>
> * pl->bridge.next_bridge, tied to struct imx8qxp_pixel_link lifetime:
> - get reference when assigned (by copy from next_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)
>
> Additionally, split the somewhat complex if() for readability.
>
> Signed-off-by: Luca Ceresoli <[email protected]>
>
> ---
>
> Changes in v5:
> - rewrite commit message after Liu's review to clarify the per-pointer
> get/put idea
> - split the if()s involved in selcting the bridge
> - remove intermediate selected_bridge pointer
> - removed Maxime's R-by, patch changed
> ---
> drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c
> b/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c
> index 91e4f4d55469..e29e099b893a 100644
> --- 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;
> @@ -297,7 +295,8 @@ static int imx8qxp_pixel_link_find_next_bridge(struct
> imx8qxp_pixel_link *pl)
> continue;
> }
>
> - struct drm_bridge *next_bridge = of_drm_find_bridge(remote);
> + struct drm_bridge *next_bridge __free(drm_bridge_put) =
> + of_drm_find_and_get_bridge(remote);
> if (!next_bridge)
> return -EPROBE_DEFER;
>
> @@ -305,12 +304,16 @@ static int imx8qxp_pixel_link_find_next_bridge(struct
> imx8qxp_pixel_link *pl)
> * 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)
> + pl->bridge.next_bridge = drm_bridge_get(next_bridge);
> +
> + if (of_property_present(remote, "fsl,companion-pxl2dpi")) {
> + drm_bridge_put(pl->bridge.next_bridge);
> + pl->bridge.next_bridge = drm_bridge_get(next_bridge);
> + }
Can you drop the intermediate next_bridge variable to simplify the code?
-8<-
if (!pl->bridge.next_bridge) {
pl->bridge.next_bridge = of_drm_find_and_get_bridge(remote);
if (!pl->bridge.next_bridge)
return -EPROBE_DEFER;
}
if (of_property_present(remote, "fsl,companion-pxl2dpi")) {
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;
}
-8<-
> }
>
> pl->mst_addr = port_id - 1;
> - pl->next_bridge = selected_bridge;
>
> return 0;
> }
>
--
Regards,
Liu Ying
