Hi Luca,
On Fri, Oct 31, 2025 at 09:14:45AM +0100, Luca Ceresoli wrote:
> Hello Laurentiu,
>
> On Thu Sep 11, 2025 at 1:37 PM CEST, Laurentiu Palcu wrote:
>
> ...
>
> > +static struct drm_bridge *dcif_crtc_get_bridge(struct drm_crtc *crtc,
> > + struct drm_crtc_state
> > *crtc_state)
> > +{
> > + struct drm_connector_state *conn_state;
> > + struct drm_encoder *encoder;
> > + struct drm_connector *conn;
> > + struct drm_bridge *bridge;
> > + int i;
> > +
> > + for_each_new_connector_in_state(crtc_state->state, conn, conn_state, i)
> > {
> > + if (crtc != conn_state->crtc)
> > + continue;
> > +
> > + encoder = conn_state->best_encoder;
> > +
> > + bridge = drm_bridge_chain_get_first_bridge(encoder);
>
> The bridge returned by drm_bridge_chain_get_first_bridge() is refcounted
> since v6.18-rc1 [0], so you have to put that reference...
>
> > + if (bridge)
> > + return bridge;
> > + }
> > +
> > + return NULL;
> > +}
> > +
> > +static void dcif_crtc_query_output_bus_format(struct drm_crtc *crtc,
> > + struct drm_crtc_state *crtc_state)
> > +{
> > + struct dcif_crtc_state *dcif_state = to_dcif_crtc_state(crtc_state);
> > + struct drm_bridge_state *bridge_state;
> > + struct drm_bridge *bridge;
> > +
> > + dcif_state->bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> > + dcif_state->bus_flags = 0;
> > +
> > + bridge = dcif_crtc_get_bridge(crtc, crtc_state);
> > + if (!bridge)
> > + return;
> > +
> > + bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
> > bridge);
> > + if (!bridge_state)
> > + return;
> > +
> > + dcif_state->bus_format = bridge_state->input_bus_cfg.format;
> > + dcif_state->bus_flags = bridge_state->input_bus_cfg.flags;
>
> ...perhaps here, when both the bridge pointer and the bridge_state pointer
> referencing it go out of scope.
>
> > +}
>
> You can just call drm_bridge_put(bridge) there, or (at your option) use a
> cleanup action:
>
> static void dcif_crtc_query_output_bus_format(struct drm_crtc *crtc,
> struct drm_crtc_state
> *crtc_state)
> {
> struct dcif_crtc_state *dcif_state = to_dcif_crtc_state(crtc_state);
> struct drm_bridge_state *bridge_state;
> - struct drm_bridge *bridge;
>
> dcif_state->bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> dcif_state->bus_flags = 0;
>
> - bridge = dcif_crtc_get_bridge(crtc, crtc_state);
> + struct drm_bridge *bridge __free(drm_bridge_put) =
> dcif_crtc_get_bridge(crtc, crtc_state);
> if (!bridge)
> return;
>
> bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
> bridge);
> if (!bridge_state)
> return;
>
> dcif_state->bus_format = bridge_state->input_bus_cfg.format;
> dcif_state->bus_flags = bridge_state->input_bus_cfg.flags;
> }
>
> This would call drm_bridge_put() at end of scope, i.e. end of function.
>
> You can also have a look at recent commits involving drm_bridge_put (git
> log -p -Gdrm_bridge_put v6.16..origin/master) to see how other parts of the
> kernel have added drm_bridge_put().
Thanks for reviewing and the heads-up on using drm_bridge_put(). I'll
send a v6 next week with the fix.
Thanks,
Laurentiu
>
> [0]
> https://gitlab.freedesktop.org/drm/misc/kernel/-/commit/8fa5909400f377351836419223c33f1131f0f7d3
>
> Best regards,
> Luca
>
> ---
> Luca Ceresoli, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
