On Thu, 07 Dec 2023, bbaa <bbaa@xxxxxxxx> wrote: > Hello everyone, > > drm_edid_override_connector_update seem return a incorrect value. > > drivers/gpu/drm/drm_edid.c (Linux 6.7-rc4) > 2294 /** > 2295 * drm_edid_override_connector_update - add modes from override/firmware EDID > 2296 * @connector: connector we're probing > 2297 * > 2298 * Add modes from the override/firmware EDID, if available. Only to be used from > 2299 * drm_helper_probe_single_connector_modes() as a fallback for when DDC probe > 2300 * failed during drm_get_edid() and caused the override/firmware EDID to be > 2301 * skipped. > 2302 * > 2303 * Return: The number of modes added or 0 if we couldn't find any. > 2304 */ Thanks for the report. I've sent a patch to hopefully fix this [1]. [1] https://patchwork.freedesktop.org/patch/msgid/20231207093821.2654267-1-jani.nikula@xxxxxxxxx However, please read the documentation comment above: "Only to be used from drm_helper_probe_single_connector_modes() ..." The function is a fallback for a *very* specific and rare scenario. > This will break the EDID override behavior on Nvidia graphics cards. > > NVIDIA/open-gpu-kernel-modules: > kernel-open/nvidia-drm/nvidia-drm-connector.c: > 103 #if defined(NV_DRM_CONNECTOR_HAS_OVERRIDE_EDID) 104 if > (connector->override_edid) { 105 #else 106 if > (drm_edid_override_connector_update(connector) > 0) { 107 #endif > 108 const struct drm_property_blob *edid = > connector->edid_blob_ptr; 109 > drm_edid_override_connector_update(connector) will return zero here. That's an out-of-tree driver that doesn't follow the documentation above. Drivers have no business calling the function. All of the override/firmware EDID handling should be covered transparently via the drm_edid_read*() and drm_get_edid() functions, and the drivers shouldn't have to ever care about overrides, at all. Drivers shouldn't really use connector->edid_blob_ptr directly either. Please report and get that fixed downstream. BR, Jani. -- Jani Nikula, Intel
