drm/bridge: lt9611: Add atomic_get_input_bus_fmts

Implement .atomic_get_input_bus_fmts callback, which sets up
the input (scanout-engine-end) formats, so that those formats
can then be used in pipeline format negotiation between this
bridge and the scanout engine.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Dave Airlie <airlied@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Maxime Ripard <maxime@cerno.tech>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220331153923.14314-2-marex@denx.de

drivers/gpu/drm/bridge/lontium-lt9611.c

@@ -922,6 +922,32 @@ static void lt9611_bridge_hpd_enable(struct drm_bridge *bridge)
 	lt9611_enable_hpd_interrupts(lt9611);
 }
 
+#define MAX_INPUT_SEL_FORMATS	1
+
+static u32 *
+lt9611_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
+				 struct drm_bridge_state *bridge_state,
+				 struct drm_crtc_state *crtc_state,
+				 struct drm_connector_state *conn_state,
+				 u32 output_fmt,
+				 unsigned int *num_input_fmts)
+{
+	u32 *input_fmts;
+
+	*num_input_fmts = 0;
+
+	input_fmts = kcalloc(MAX_INPUT_SEL_FORMATS, sizeof(*input_fmts),
+			     GFP_KERNEL);
+	if (!input_fmts)
+		return NULL;
+
+	/* This is the DSI-end bus format */
+	input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
+	*num_input_fmts = 1;
+
+	return input_fmts;
+}
+
 static const struct drm_bridge_funcs lt9611_bridge_funcs = {
 	.attach = lt9611_bridge_attach,
 	.mode_valid = lt9611_bridge_mode_valid,
@@ -936,6 +962,7 @@ static const struct drm_bridge_funcs lt9611_bridge_funcs = {
 	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
 	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
 	.atomic_reset = drm_atomic_helper_bridge_reset,
+	.atomic_get_input_bus_fmts = lt9611_atomic_get_input_bus_fmts,
 };
 
 static int lt9611_parse_dt(struct device *dev,