drm: Add a STEREO_3D capability to the SET_CLIENT_CAP ioctl

This capability allows user space to control the delivery of modes with
the 3D flags set. This is to not play games with current user space
users not knowing anything about stereo 3D flags and that could try
to set a mode with one or several of those bits set.

So, the plan is to remove the stereo modes from the list of modes we
give to DRM clients by default, and let them through if we are being
told otherwise.

stereo_allowed is bound to the drm_file structure to make it a
per-client setting, not a global one.

v2: Replace clearing 3D flags by discarding the stereo modes now that
    they are regular modes.
v3: SET_CAP -> SET_CLIENT_CAP rename (Chris Wilson)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_crtc.c

@@ -1581,6 +1581,19 @@ int drm_mode_getcrtc(struct drm_device *dev,
 	return ret;
 }
 
+static bool drm_mode_expose_to_userspace(const struct drm_display_mode *mode,
+					 const struct drm_file *file_priv)
+{
+	/*
+	 * If user-space hasn't configured the driver to expose the stereo 3D
+	 * modes, don't expose them.
+	 */
+	if (!file_priv->stereo_allowed && drm_mode_is_stereo(mode))
+		return false;
+
+	return true;
+}
+
 /**
  * drm_mode_getconnector - get connector configuration
  * @dev: drm device for the ioctl
@@ -1646,7 +1659,8 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
 
 	/* delayed so we get modes regardless of pre-fill_modes state */
 	list_for_each_entry(mode, &connector->modes, head)
-		mode_count++;
+		if (drm_mode_expose_to_userspace(mode, file_priv))
+			mode_count++;
 
 	out_resp->connector_id = connector->base.id;
 	out_resp->connector_type = connector->connector_type;
@@ -1668,6 +1682,9 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
 		copied = 0;
 		mode_ptr = (struct drm_mode_modeinfo __user *)(unsigned long)out_resp->modes_ptr;
 		list_for_each_entry(mode, &connector->modes, head) {
+			if (!drm_mode_expose_to_userspace(mode, file_priv))
+				continue;
+
 			drm_crtc_convert_to_umode(&u_mode, mode);
 			if (copy_to_user(mode_ptr + copied,
 					 &u_mode, sizeof(u_mode))) {

drivers/gpu/drm/drm_ioctl.c

@@ -308,7 +308,19 @@ int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 int
 drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 {
-	return -EINVAL;
+	struct drm_set_client_cap *req = data;
+
+	switch (req->capability) {
+	case DRM_CLIENT_CAP_STEREO_3D:
+		if (req->value > 1)
+			return -EINVAL;
+		file_priv->stereo_allowed = req->value;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
 }
 
 /**

include/drm/drmP.h

@@ -433,6 +433,9 @@ struct drm_file {
 	struct drm_master *master; /* master this node is currently associated with
 				      N.B. not always minor->master */
 
+	/* true when the client has asked us to expose stereo 3D mode flags */
+	bool stereo_allowed;
+
 	/**
 	 * fbs - List of framebuffers associated with this file.
 	 *

include/uapi/drm/drm.h

@@ -627,6 +627,15 @@ struct drm_get_cap {
 	__u64 value;
 };
 
+/**
+ * DRM_CLIENT_CAP_STEREO_3D
+ *
+ * if set to 1, the DRM core will expose the stereo 3D capabilities of the
+ * monitor by advertising the supported 3D layouts in the flags of struct
+ * drm_mode_modeinfo.
+ */
+#define DRM_CLIENT_CAP_STEREO_3D	1
+
 /** DRM_IOCTL_SET_CLIENT_CAP ioctl argument type */
 struct drm_set_client_cap {
 	__u64 capability;