drm/connector: Add support for privacy-screen properties (v4)

Add support for generic electronic privacy screen properties, that
can be added by systems that have an integrated EPS.

Changes in v2 (Hans de Goede)
- Create 2 properties, "privacy-screen sw-state" and
  "privacy-screen hw-state", to deal with devices where the OS might be
  locked out of making state changes
- Write kerneldoc explaining how the 2 properties work together, what
  happens when changes to the state are made outside of the DRM code's
  control, etc.

Changes in v3 (Hans de Goede)
- Some small tweaks to the kerneldoc describing the 2 properties

Changes in v4 (Hans de Goede)
- Change the "Enabled, locked" and "Disabled, locked" hw-state enum value
  names to "Enabled-locked" and "Disabled-locked". The xrandr command shows
  all possible enum values separated by commas in its output, so having a
  comma in an enum name is not a good idea.
- Do not add a privacy_screen_hw_state member to drm_connector_state
  since this property is immutable its value must be directly stored in the
  obj->properties->values array

Signed-off-by: Rajat Jain <rajatja@google.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Mario Limonciello <Mario.limonciello@dell.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Co-developed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005202322.700909-2-hdegoede@redhat.com

2 files changed, 105 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index 909f31833181..cdd31fc78bfc 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -797,6 +797,8 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector,
 						   fence_ptr);
 	} else if (property == connector->max_bpc_property) {
 		state->max_requested_bpc = val;
+	} else if (property == connector->privacy_screen_sw_state_property) {
+		state->privacy_screen_sw_state = val;
 	} else if (connector->funcs->atomic_set_property) {
 		return connector->funcs->atomic_set_property(connector,
 				state, property, val);
@@ -874,6 +876,8 @@ 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->privacy_screen_sw_state_property) {
+		*val = state->privacy_screen_sw_state;
 	} 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 52e20c68813b..ec9ad3f8a83f 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -1271,6 +1271,46 @@ static const struct drm_prop_enum_list dp_colorspaces[] = {
  *	For DVI-I and TVout there is also a matching property "select subconnector"
  *	allowing to switch between signal types.
  *	DP subconnector corresponds to a downstream port.
+ *
+ * privacy-screen sw-state, privacy-screen hw-state:
+ *	These 2 optional properties can be used to query the state of the
+ *	electronic privacy screen that is available on some displays; and in
+ *	some cases also control the state. If a driver implements these
+ *	properties then both properties must be present.
+ *
+ *	"privacy-screen hw-state" is read-only and reflects the actual state
+ *	of the privacy-screen, possible values: "Enabled", "Disabled,
+ *	"Enabled-locked", "Disabled-locked". The locked states indicate
+ *	that the state cannot be changed through the DRM API. E.g. there
+ *	might be devices where the firmware-setup options, or a hardware
+ *	slider-switch, offer always on / off modes.
+ *
+ *	"privacy-screen sw-state" can be set to change the privacy-screen state
+ *	when not locked. In this case the driver must update the hw-state
+ *	property to reflect the new state on completion of the commit of the
+ *	sw-state property. Setting the sw-state property when the hw-state is
+ *	locked must be interpreted by the driver as a request to change the
+ *	state to the set state when the hw-state becomes unlocked. E.g. if
+ *	"privacy-screen hw-state" is "Enabled-locked" and the sw-state
+ *	gets set to "Disabled" followed by the user unlocking the state by
+ *	changing the slider-switch position, then the driver must set the
+ *	state to "Disabled" upon receiving the unlock event.
+ *
+ *	In some cases the privacy-screen's actual state might change outside of
+ *	control of the DRM code. E.g. there might be a firmware handled hotkey
+ *	which toggles the actual state, or the actual state might be changed
+ *	through another userspace API such as writing /proc/acpi/ibm/lcdshadow.
+ *	In this case the driver must update both the hw-state and the sw-state
+ *	to reflect the new value, overwriting any pending state requests in the
+ *	sw-state. Any pending sw-state requests are thus discarded.
+ *
+ *	Note that the ability for the state to change outside of control of
+ *	the DRM master process means that userspace must not cache the value
+ *	of the sw-state. Caching the sw-state value and including it in later
+ *	atomic commits may lead to overriding a state change done through e.g.
+ *	a firmware handled hotkey. Therefor userspace must not include the
+ *	privacy-screen sw-state in an atomic commit unless it wants to change
+ *	its value.
  */
 
 int drm_connector_create_standard_properties(struct drm_device *dev)
@@ -2365,6 +2405,67 @@ int drm_connector_set_panel_orientation_with_quirk(
 }
 EXPORT_SYMBOL(drm_connector_set_panel_orientation_with_quirk);
 
+static const struct drm_prop_enum_list privacy_screen_enum[] = {
+	{ PRIVACY_SCREEN_DISABLED,		"Disabled" },
+	{ PRIVACY_SCREEN_ENABLED,		"Enabled" },
+	{ PRIVACY_SCREEN_DISABLED_LOCKED,	"Disabled-locked" },
+	{ PRIVACY_SCREEN_ENABLED_LOCKED,	"Enabled-locked" },
+};
+
+/**
+ * drm_connector_create_privacy_screen_properties - create the drm connecter's
+ *    privacy-screen properties.
+ * @connector: connector for which to create the privacy-screen properties
+ *
+ * This function creates the "privacy-screen sw-state" and "privacy-screen
+ * hw-state" properties for the connector. They are not attached.
+ */
+void
+drm_connector_create_privacy_screen_properties(struct drm_connector *connector)
+{
+	if (connector->privacy_screen_sw_state_property)
+		return;
+
+	/* Note sw-state only supports the first 2 values of the enum */
+	connector->privacy_screen_sw_state_property =
+		drm_property_create_enum(connector->dev, DRM_MODE_PROP_ENUM,
+				"privacy-screen sw-state",
+				privacy_screen_enum, 2);
+
+	connector->privacy_screen_hw_state_property =
+		drm_property_create_enum(connector->dev,
+				DRM_MODE_PROP_IMMUTABLE | DRM_MODE_PROP_ENUM,
+				"privacy-screen hw-state",
+				privacy_screen_enum,
+				ARRAY_SIZE(privacy_screen_enum));
+}
+EXPORT_SYMBOL(drm_connector_create_privacy_screen_properties);
+
+/**
+ * drm_connector_attach_privacy_screen_properties - attach the drm connecter's
+ *    privacy-screen properties.
+ * @connector: connector on which to attach the privacy-screen properties
+ *
+ * This function attaches the "privacy-screen sw-state" and "privacy-screen
+ * hw-state" properties to the connector. The initial state of both is set
+ * to "Disabled".
+ */
+void
+drm_connector_attach_privacy_screen_properties(struct drm_connector *connector)
+{
+	if (!connector->privacy_screen_sw_state_property)
+		return;
+
+	drm_object_attach_property(&connector->base,
+				   connector->privacy_screen_sw_state_property,
+				   PRIVACY_SCREEN_DISABLED);
+
+	drm_object_attach_property(&connector->base,
+				   connector->privacy_screen_hw_state_property,
+				   PRIVACY_SCREEN_DISABLED);
+}
+EXPORT_SYMBOL(drm_connector_attach_privacy_screen_properties);
+
 int drm_connector_set_obj_prop(struct drm_mode_object *obj,
 				    struct drm_property *property,
 				    uint64_t value)