On Tue, Jun 25, 2024 at 10:23:14AM GMT, Dmitry Baryshkov wrote: > On Tue, 25 Jun 2024 at 10:19, Maxime Ripard <mripard@xxxxxxxxxx> wrote: > > > > Hi, > > > > On Tue, Jun 25, 2024 at 09:21:27AM GMT, Dmitry Baryshkov wrote: > > > On Tue, 25 Jun 2024 at 01:56, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > On 6/24/2024 3:46 PM, Dmitry Baryshkov wrote: > > > > > On Tue, 25 Jun 2024 at 01:39, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote: > > > > >> > > > > >> + 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 > > > > > > > > > > Yes > > > > > > > > > >> > > > > >> 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. > > > > > > > > > > Well, having the same min and max means that it is impossible to > > > > > change the property. So the property is immutable, but doesn't have > > > > > the flag. > > > > > > > > > > > > > True, then does DRM_MODE_PROP_IMMUTABLE need a doc update too indicating > > > > that even if the min and max is same, property will be interpreted as > > > > immutable. > > > > > > Granted that I'm only doing it for max_bpc property I don't think so. > > > > Yeah, I have to agree with Abhinav here, it does look fishy to me too, > > even more so that it's only ever "documented" through an igt routine > > that has never documented why we want that. > > > > I'm fine with the change if it's indeed what we expect, and it might > > very well be, but I'd like to clear that up and document it first. > > Should I also move the setting of the IMMUTABLE flag to a more generic code? Possibly, but I guess that will depend on the outcome of that discussion Maxime
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