Hi Luca,
On 10/21/2025 6:31 PM, Luca Ceresoli wrote:
Hello Damon,
On Tue Oct 21, 2025 at 4:31 AM CEST, Damon Ding wrote:
When multiple bridges are present, EDID detection capability
(DRM_BRIDGE_OP_EDID) takes precedence over modes detection
(DRM_BRIDGE_OP_MODES). To ensure the above two capabilities are
determined by the last bridge in the chain, we handle three cases:
Case 1: The later bridge declares only DRM_BRIDGE_OP_MODES
- If the previous bridge declares DRM_BRIDGE_OP_EDID, set
&drm_bridge_connector.bridge_edid to NULL and set
&drm_bridge_connector.bridge_modes to the later bridge.
- Ensure modes detection capability of the later bridge will not
be ignored.
Case 2: The later bridge declares only DRM_BRIDGE_OP_EDID
- If the previous bridge declares DRM_BRIDGE_OP_MODES, set
&drm_bridge_connector.bridge_modes to NULL and set
&drm_bridge_connector.bridge_edid to the later bridge.
- Although EDID detection capability has higher priority, this
operation is for balance and makes sense.
Case 3: the later bridge declares both of them
- Assign later bridge as &drm_bridge_connector.bridge_edid and
and &drm_bridge_connector.bridge_modes to this bridge.
- Just leave transfer of these two capabilities as before.
Signed-off-by: Damon Ding <[email protected]>
Suggested-by: Dmitry Baryshkov <[email protected]>
Tested-by: Marek Szyprowski <[email protected]>
---
Changes in v7:
- As Luca suggested, simplify the code and related comment.
---
drivers/gpu/drm/display/drm_bridge_connector.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c
b/drivers/gpu/drm/display/drm_bridge_connector.c
index baacd21e7341..7c2936d59517 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -673,14 +673,22 @@ struct drm_connector *drm_bridge_connector_init(struct
drm_device *drm,
if (!bridge->ycbcr_420_allowed)
connector->ycbcr_420_allowed = false;
- if (bridge->ops & DRM_BRIDGE_OP_EDID)
- bridge_connector->bridge_edid = bridge;
+ /*
+ * Ensure the last bridge declares OP_EDID or OP_MODES or both.
+ */
+ if (bridge->ops & DRM_BRIDGE_OP_EDID || bridge->ops &
DRM_BRIDGE_OP_MODES) {
+ bridge_connector->bridge_edid = NULL;
+ bridge_connector->bridge_modes = NULL;
+ if (bridge->ops & DRM_BRIDGE_OP_EDID)
+ bridge_connector->bridge_edid = bridge;
+ if (bridge->ops & DRM_BRIDGE_OP_MODES)
+ bridge_connector->bridge_modes = bridge;
+ }
if (bridge->ops & DRM_BRIDGE_OP_HPD)
bridge_connector->bridge_hpd = bridge;
if (bridge->ops & DRM_BRIDGE_OP_DETECT)
bridge_connector->bridge_detect = bridge;
- if (bridge->ops & DRM_BRIDGE_OP_MODES)
- bridge_connector->bridge_modes = bridge;
+
This does not apply on current drm-misc-next, due to the patch I mentioned
in a previous iteration, now applied as commit 2be300f9a0b6 ("drm/display:
bridge_connector: get/put the stored bridges").
However I'm sorry I have to mention that patch turned out being buggy, so
I've sent a series to apply a corrected version [0]. I suggest watching the
disucssion about the fix series, and if that gets approved rebase on top of
that and adapt your changes.
Sorry about the mess. :(
[0]
https://lore.kernel.org/r/20251017-drm-bridge-alloc-getput-bridge-connector-fix-hdmi_cec-v2-0-667abf6d4...@bootlin.com
I saw your fix patches before sending this series. I think your patches
will likely be merged relatively quickly, so I plan to wait until the
other patches in my patch series are confirmed to be fine, then submit
v8 version based on the latest bridge_connector driver. :-)
Best regards,
Damon
