drm/bridge: imx: fix mixed module-builtin object

With CONFIG_DRM_IMX8QM_LDB=m and CONFIG_DRM_IMX8QXP_LDB=y (or vice
versa), imx-ldb-helper.o is linked to a module and also to vmlinux
even though the expected CFLAGS are different between builtins and
modules.

This is the same situation as fixed by commit 637a642f ("zstd:
Fixing mixed module-builtin objects").

Split imx-ldb-helper.c into a separate module.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230605120021.1774711-1-masahiroy@kernel.org

drivers/gpu/drm/bridge/imx/Kconfig

 if ARCH_MXC || COMPILE_TEST
 
+config DRM_IMX_LDB_HELPER
+	tristate
+
 config DRM_IMX8QM_LDB
 	tristate "Freescale i.MX8QM LVDS display bridge"
 	depends on OF
 	depends on COMMON_CLK
+	select DRM_IMX_LDB_HELPER
 	select DRM_KMS_HELPER
 	help
 	  Choose this to enable the internal LVDS Display Bridge(LDB) found in
@@ -13,6 +17,7 @@ config DRM_IMX8QXP_LDB
 	tristate "Freescale i.MX8QXP LVDS display bridge"
 	depends on OF
 	depends on COMMON_CLK
+	select DRM_IMX_LDB_HELPER
 	select DRM_KMS_HELPER
 	help
 	  Choose this to enable the internal LVDS Display Bridge(LDB) found in

drivers/gpu/drm/bridge/imx/Makefile

-imx8qm-ldb-objs := imx-ldb-helper.o imx8qm-ldb-drv.o
+obj-$(CONFIG_DRM_IMX_LDB_HELPER) += imx-ldb-helper.o
+imx8qm-ldb-objs := imx8qm-ldb-drv.o
 obj-$(CONFIG_DRM_IMX8QM_LDB) += imx8qm-ldb.o
 
-imx8qxp-ldb-objs := imx-ldb-helper.o imx8qxp-ldb-drv.o
+imx8qxp-ldb-objs := imx8qxp-ldb-drv.o
 obj-$(CONFIG_DRM_IMX8QXP_LDB) += imx8qxp-ldb.o
 
 obj-$(CONFIG_DRM_IMX8QXP_PIXEL_COMBINER) += imx8qxp-pixel-combiner.o

drivers/gpu/drm/bridge/imx/imx-ldb-helper.c

@@ -4,8 +4,10 @@
  * Copyright 2019,2020,2022 NXP
  */
 
+#include <linux/export.h>
 #include <linux/media-bus-format.h>
 #include <linux/mfd/syscon.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/regmap.h>
 
@@ -19,12 +21,14 @@ bool ldb_channel_is_single_link(struct ldb_channel *ldb_ch)
 {
 	return ldb_ch->link_type == LDB_CH_SINGLE_LINK;
 }
+EXPORT_SYMBOL_GPL(ldb_channel_is_single_link);
 
 bool ldb_channel_is_split_link(struct ldb_channel *ldb_ch)
 {
 	return ldb_ch->link_type == LDB_CH_DUAL_LINK_EVEN_ODD_PIXELS ||
 	       ldb_ch->link_type == LDB_CH_DUAL_LINK_ODD_EVEN_PIXELS;
 }
+EXPORT_SYMBOL_GPL(ldb_channel_is_split_link);
 
 int ldb_bridge_atomic_check_helper(struct drm_bridge *bridge,
 				   struct drm_bridge_state *bridge_state,
@@ -38,6 +42,7 @@ int ldb_bridge_atomic_check_helper(struct drm_bridge *bridge,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(ldb_bridge_atomic_check_helper);
 
 void ldb_bridge_mode_set_helper(struct drm_bridge *bridge,
 				const struct drm_display_mode *mode,
@@ -69,6 +74,7 @@ void ldb_bridge_mode_set_helper(struct drm_bridge *bridge,
 		break;
 	}
 }
+EXPORT_SYMBOL_GPL(ldb_bridge_mode_set_helper);
 
 void ldb_bridge_enable_helper(struct drm_bridge *bridge)
 {
@@ -81,6 +87,7 @@ void ldb_bridge_enable_helper(struct drm_bridge *bridge)
 	 */
 	regmap_write(ldb->regmap, ldb->ctrl_reg, ldb->ldb_ctrl);
 }
+EXPORT_SYMBOL_GPL(ldb_bridge_enable_helper);
 
 void ldb_bridge_disable_helper(struct drm_bridge *bridge)
 {
@@ -95,6 +102,7 @@ void ldb_bridge_disable_helper(struct drm_bridge *bridge)
 
 	regmap_write(ldb->regmap, ldb->ctrl_reg, ldb->ldb_ctrl);
 }
+EXPORT_SYMBOL_GPL(ldb_bridge_disable_helper);
 
 int ldb_bridge_attach_helper(struct drm_bridge *bridge,
 			     enum drm_bridge_attach_flags flags)
@@ -117,6 +125,7 @@ int ldb_bridge_attach_helper(struct drm_bridge *bridge,
 				ldb_ch->next_bridge, bridge,
 				DRM_BRIDGE_ATTACH_NO_CONNECTOR);
 }
+EXPORT_SYMBOL_GPL(ldb_bridge_attach_helper);
 
 int ldb_init_helper(struct ldb *ldb)
 {
@@ -157,6 +166,7 @@ int ldb_init_helper(struct ldb *ldb)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(ldb_init_helper);
 
 int ldb_find_next_bridge_helper(struct ldb *ldb)
 {
@@ -184,6 +194,7 @@ int ldb_find_next_bridge_helper(struct ldb *ldb)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(ldb_find_next_bridge_helper);
 
 void ldb_add_bridge_helper(struct ldb *ldb,
 			   const struct drm_bridge_funcs *bridge_funcs)
@@ -204,6 +215,7 @@ void ldb_add_bridge_helper(struct ldb *ldb,
 		drm_bridge_add(&ldb_ch->bridge);
 	}
 }
+EXPORT_SYMBOL_GPL(ldb_add_bridge_helper);
 
 void ldb_remove_bridge_helper(struct ldb *ldb)
 {
@@ -219,3 +231,8 @@ void ldb_remove_bridge_helper(struct ldb *ldb)
 		drm_bridge_remove(&ldb_ch->bridge);
 	}
 }
+EXPORT_SYMBOL_GPL(ldb_remove_bridge_helper);
+
+MODULE_DESCRIPTION("i.MX8 LVDS Display Bridge(LDB)/Pixel Mapper bridge helper");
+MODULE_AUTHOR("Liu Ying <victor.liu@nxp.com>");
+MODULE_LICENSE("GPL");