drm: Include the encoder itself in possible_clones

The docs say possible_clones should always include the encoder itself.
Since most drivers don't want to deal with the complexities of cloning
let's allow them to set possible_clones=0 and instead we'll fix that
up in the core.

We can't put this special case into drm_encoder_init() because drivers
will have to fill up possible_clones after adding all the relevant
encoders. Otherwise they wouldn't know the proper encoder indexes to
use. So we'll just do it just before registering the device.

v2: Don't set the bit if possible_clones!=0 so that the
    validation (coming soon) will WARN (Thomas)
    Fix up the docs to allow possible_clones==0 (Daniel)
    .late_register() is too late, introduce drm_mode_config_validate()
    which gets called _before_ we register the char device (Daniel)

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200211162208.16224-2-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 08e6eff6a179..75e357c7e84d 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -532,3 +532,22 @@ void drm_mode_config_cleanup(struct drm_device *dev)
 	drm_modeset_lock_fini(&dev->mode_config.connection_mutex);
 }
 EXPORT_SYMBOL(drm_mode_config_cleanup);
+
+/*
+ * For some reason we want the encoder itself included in
+ * possible_clones. Make life easy for drivers by allowing them
+ * to leave possible_clones unset if no cloning is possible.
+ */
+static void fixup_encoder_possible_clones(struct drm_encoder *encoder)
+{
+	if (encoder->possible_clones == 0)
+		encoder->possible_clones = drm_encoder_mask(encoder);
+}
+
+void drm_mode_config_validate(struct drm_device *dev)
+{
+	struct drm_encoder *encoder;
+
+	drm_for_each_encoder(encoder, dev)
+		fixup_encoder_possible_clones(encoder);
+}