drm/mediatek: Add crtc path enum for all_drm_priv array

Add mtk_drm_crtc_path enum for each display path.

Instead of using array index of all_drm_priv in mtk_drm_kms_init(),
mtk_drm_crtc_path enum can make code more readable.
Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: Fei Shao <fshao@chromium.org>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Tested-by: Fei Shao <fshao@chromium.org>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20231004024013.18956-3-jason-jh.lin@mediatek.com/Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

drivers/gpu/drm/mediatek/mtk_drm_drv.c

@@ -469,21 +469,21 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 		for (j = 0; j < private->data->mmsys_dev_num; j++) {
 			priv_n = private->all_drm_private[j];
 
-			if (i == 0 && priv_n->data->main_len) {
+			if (i == CRTC_MAIN && priv_n->data->main_len) {
 				ret = mtk_drm_crtc_create(drm, priv_n->data->main_path,
 							  priv_n->data->main_len, j);
 				if (ret)
 					goto err_component_unbind;
 
 				continue;
-			} else if (i == 1 && priv_n->data->ext_len) {
+			} else if (i == CRTC_EXT && priv_n->data->ext_len) {
 				ret = mtk_drm_crtc_create(drm, priv_n->data->ext_path,
 							  priv_n->data->ext_len, j);
 				if (ret)
 					goto err_component_unbind;
 
 				continue;
-			} else if (i == 2 && priv_n->data->third_len) {
+			} else if (i == CRTC_THIRD && priv_n->data->third_len) {
 				ret = mtk_drm_crtc_create(drm, priv_n->data->third_path,
 							  priv_n->data->third_len, j);
 				if (ret)

drivers/gpu/drm/mediatek/mtk_drm_drv.h

@@ -9,11 +9,17 @@
 #include <linux/io.h>
 #include "mtk_drm_ddp_comp.h"
 
-#define MAX_CRTC	3
 #define MAX_CONNECTOR	2
 #define DDP_COMPONENT_DRM_OVL_ADAPTOR (DDP_COMPONENT_ID_MAX + 1)
 #define DDP_COMPONENT_DRM_ID_MAX (DDP_COMPONENT_DRM_OVL_ADAPTOR + 1)
 
+enum mtk_drm_crtc_path {
+	CRTC_MAIN,
+	CRTC_EXT,
+	CRTC_THIRD,
+	MAX_CRTC,
+};
+
 struct device;
 struct device_node;
 struct drm_crtc;