+ IGT dev
On 6/22/2024 10:40 PM, Dmitry Baryshkov wrote:
With the introduction of the HDMI Connector framework the driver might
end up creating the max_bpc property with min = max = 8. IGT insists
that such properties carry the 'immutable' flag. Automatically set the
flag if the driver asks for the max_bpc property with min == max.
This change does not look right to me.
I wonder why we need this check because DRM_MODE_PROP_IMMUTABLE means
that as per the doc, userspace cannot change the property.
* DRM_MODE_PROP_IMMUTABLE
* Set for properties whose values cannot be changed by
* userspace. The kernel is allowed to update the value of
these
* properties. This is generally used to expose probe state to
* userspace, e.g. the EDID, or the connector path property
on DP
* MST sinks. Kernel can update the value of an immutable
property
* by calling drm_object_property_set_value().
*/
Here we are allowing userspace to change max_bpc
drm_atomic_connector_set_property()
{
**********
} else if (property == connector->max_bpc_property) {
state->max_requested_bpc = val;
**********
}
I believe you are referring to this IGT check right?
https://gitlab.freedesktop.org/drm/igt-gpu-tools/-/blob/master/tests/kms_properties.c#L428
I think we should fix IGT in this case unless there is some reason we
are missing. Because just because it has the same min and max does not
mean its immutable by the doc of the IMMUTABLE flag.
Fixes: aadb3e16b8f3 ("drm/connector: hdmi: Add output BPC to the connector state")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
drivers/gpu/drm/drm_connector.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index ab6ab7ff7ea8..33847fd63628 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -2610,7 +2610,12 @@ int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
prop = connector->max_bpc_property;
if (!prop) {
- prop = drm_property_create_range(dev, 0, "max bpc", min, max);
+ u32 flags = 0;
+
+ if (min == max)
+ flags |= DRM_MODE_PROP_IMMUTABLE;
+
+ prop = drm_property_create_range(dev, flags, "max bpc", min, max);
if (!prop)
return -ENOMEM;
