drm: writeback: Add client capability for exposing writeback connectors

Due to the fact that writeback connectors behave in a special way
in DRM (they always report being disconnected) we might confuse some
userspace. Add a client capability for writeback connectors that will
filter them out for clients that don't understand the capability.

Changelog:
 - only accept the capability if the client has already set the
DRM_CLIENT_CAP_ATOMIC one.

Cc: Sean Paul <seanpaul@chromium.org>
Cc: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Link: https://patchwork.freedesktop.org/patch/229038/

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 0d4cfb2..fe49fb0 100644 (file)
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -334,6 +334,13 @@ drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
                        return -EINVAL;
                file_priv->aspect_ratio_allowed = req->value;
                break;
+       case DRM_CLIENT_CAP_WRITEBACK_CONNECTORS:
+               if (!file_priv->atomic)
+                       return -EINVAL;
+               if (req->value > 1)
+                       return -EINVAL;
+               file_priv->writeback_connectors = req->value;
+               break;
        default:
                return -EINVAL;
        }

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index e5c6533..21e353b 100644 (file)
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -145,6 +145,11 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
        count = 0;
        connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
        drm_for_each_connector_iter(connector, &conn_iter) {
+               /* only expose writeback connectors if userspace understands them */
+               if (!file_priv->writeback_connectors &&
+                   (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK))
+                       continue;
+
                if (drm_lease_held(file_priv, connector->base.id)) {
                        if (count < card_res->count_connectors &&
                            put_user(connector->base.id, connector_id + count)) {

diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index 027ac16..26485ac 100644 (file)
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -192,6 +192,13 @@ struct drm_file {
         */
        unsigned aspect_ratio_allowed:1;
 
+       /**
+        * @writeback_connectors:
+        *
+        * True if client understands writeback connectors
+        */
+       unsigned writeback_connectors:1;
+
        /**
         * @is_master:
         *

diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 9c660e1..300f336 100644 (file)
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -687,6 +687,15 @@ struct drm_get_cap {
  */
 #define DRM_CLIENT_CAP_ASPECT_RATIO    4
 
+/**
+ * DRM_CLIENT_CAP_WRITEBACK_CONNECTORS
+ *
+ * If set to 1, the DRM core will expose special connectors to be used for
+ * writing back to memory the scene setup in the commit. Depends on client
+ * also supporting DRM_CLIENT_CAP_ATOMIC
+ */
+#define DRM_CLIENT_CAP_WRITEBACK_CONNECTORS    5
+
 /** DRM_IOCTL_SET_CLIENT_CAP ioctl argument type */
 struct drm_set_client_cap {
        __u64 capability;