Messages in this thread | | | From | Jani Nikula <> | Subject | Re: [Bug Report] drm/edid: drm_edid_override_connector_update returns a incorrect value | Date | Thu, 07 Dec 2023 11:54:34 +0200 |
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On Thu, 07 Dec 2023, bbaa <bbaa@bbaa.fun> 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@intel.com
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
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