Am 07.06.21 um 09:40 schrieb Maxime Ripard:
Hi,
On Fri, Jun 04, 2021 at 07:17:21PM +0200, Werner Sembach wrote:
Add a new general drm property "active bpc" which can be used by graphic drivers
to report the applied bit depth per pixel back to userspace.
Just a heads up, we'll need an open source project that has accepted it
before merging it.
See https://www.kernel.org/doc/html/latest/gpu/drm-uapi.html#open-source-userspace-requirements
Yes, I know.
While "max bpc" can be used to change the color depth, there was no way to check
which one actually got used. While in theory the driver chooses the best/highest
color depth within the max bpc setting a user might not be fully aware what his
hardware is or isn't capable off. This is meant as a quick way to double check
the setup.
In the future, automatic color calibration for screens might also depend on this
information available.
Signed-off-by: Werner Sembach <wse@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_atomic_uapi.c | 2 ++
drivers/gpu/drm/drm_connector.c | 40 +++++++++++++++++++++++++++++++
include/drm/drm_connector.h | 15 ++++++++++++
3 files changed, 57 insertions(+)
diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index 268bb69c2e2f..7ae4e40936b5 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -873,6 +873,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
*val = 0;
} else if (property == connector->max_bpc_property) {
*val = state->max_requested_bpc;
+ } else if (property == connector->active_bpc_property) {
+ *val = state->active_bpc;
} else if (connector->funcs->atomic_get_property) {
return connector->funcs->atomic_get_property(connector,
state, property, val);
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 7631f76e7f34..5f42a5be5822 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -1195,6 +1195,13 @@ static const struct drm_prop_enum_list dp_colorspaces[] = {
* drm_connector_attach_max_bpc_property() to create and attach the
* property to the connector during initialization.
*
+ * active bpc:
+ * This read-only range property is used by userspace check the bit depth
+ * actually applied by the GPU driver after evaluation all hardware
^ display
Depending on the system, the display component might have a GPU attached
or not, and the GPU might have a display component or not.
Ok, I try to bee more clear in the wording
+ * capabilities and max bpc. Drivers to use the function
+ * drm_connector_attach_active_bpc_property() to create and attach the
+ * property to the connector during initialization.
+ *
* Connectors also have one standardized atomic property:
*
* CRTC_ID:
@@ -2150,6 +2157,39 @@ int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
}
EXPORT_SYMBOL(drm_connector_attach_max_bpc_property);
+/**
+ * drm_connector_attach_active_bpc_property - attach "active bpc" property
+ * @connector: connector to attach active bpc property on.
+ * @min: The minimum bit depth supported by the connector.
+ * @max: The maximum bit depth supported by the connector.
+ *
+ * This is used to check the applied bit depth on a connector.
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_connector_attach_active_bpc_property(struct drm_connector *connector,
+ int min, int max)
+{
+ struct drm_device *dev = connector->dev;
+ struct drm_property *prop;
+
+ prop = connector->active_bpc_property;
+ if (!prop) {
+ prop = drm_property_create_range(dev, 0, "active bpc", min, max);
+ if (!prop)
+ return -ENOMEM;
+
+ connector->active_bpc_property = prop;
+ }
+
+ drm_object_attach_property(&connector->base, prop, 0);
+ connector->state->active_bpc = 0;
I guess we want to default to 8?
Maxime
The default state should only be active when no display is connected or
the display is off, so I thought 0 makes more sense, as no active
display = no active bpc.
