drm/modes: Add initializer macro DRM_MODE_INIT()

The macro DRM_MODE_INIT() initializes an instance of
struct drm_display_mode with typical parameters. Convert simpledrm
and also update the macro DRM_SIMPLE_MODE().

v3:
	* fix DRM_MODE_INIT() docs (kernel test robot)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905141648.22013-4-tzimmermann@suse.de

drivers/gpu/drm/tiny/simpledrm.c

@@ -30,16 +30,6 @@
 #define DRIVER_MAJOR	1
 #define DRIVER_MINOR	0
 
-/*
- * Assume a monitor resolution of 96 dpi to
- * get a somewhat reasonable screen size.
- */
-#define RES_MM(d)	\
-	(((d) * 254ul) / (96ul * 10ul))
-
-#define SIMPLEDRM_MODE(hd, vd)	\
-	DRM_SIMPLE_MODE(hd, vd, RES_MM(hd), RES_MM(vd))
-
 /*
  * Helpers for simplefb
  */
@@ -641,10 +631,15 @@ static const struct drm_mode_config_funcs simpledrm_mode_config_funcs = {
 static struct drm_display_mode simpledrm_mode(unsigned int width,
 					      unsigned int height)
 {
-	struct drm_display_mode mode = { SIMPLEDRM_MODE(width, height) };
-
-	mode.clock = mode.hdisplay * mode.vdisplay * 60 / 1000 /* kHz */;
-	drm_mode_set_name(&mode);
+	/*
+	 * Assume a monitor resolution of 96 dpi to
+	 * get a somewhat reasonable screen size.
+	 */
+	const struct drm_display_mode mode = {
+		DRM_MODE_INIT(60, width, height,
+			      DRM_MODE_RES_MM(width, 96ul),
+			      DRM_MODE_RES_MM(height, 96ul))
+	};
 
 	return mode;
 }

include/drm/drm_modes.h

@@ -138,6 +138,35 @@ enum drm_mode_status {
 	.vsync_start = (vss), .vsync_end = (vse), .vtotal = (vt), \
 	.vscan = (vs), .flags = (f)
 
+/**
+ * DRM_MODE_RES_MM - Calculates the display size from resolution and DPI
+ * @res: The resolution in pixel
+ * @dpi: The number of dots per inch
+ */
+#define DRM_MODE_RES_MM(res, dpi)	\
+	(((res) * 254ul) / ((dpi) * 10ul))
+
+#define __DRM_MODE_INIT(pix, hd, vd, hd_mm, vd_mm) \
+	.type = DRM_MODE_TYPE_DRIVER, .clock = (pix), \
+	.hdisplay = (hd), .hsync_start = (hd), .hsync_end = (hd), \
+	.htotal = (hd), .vdisplay = (vd), .vsync_start = (vd), \
+	.vsync_end = (vd), .vtotal = (vd), .width_mm = (hd_mm), \
+	.height_mm = (vd_mm)
+
+/**
+ * DRM_MODE_INIT - Initialize display mode
+ * @hz: Vertical refresh rate in Hertz
+ * @hd: Horizontal resolution, width
+ * @vd: Vertical resolution, height
+ * @hd_mm: Display width in millimeters
+ * @vd_mm: Display height in millimeters
+ *
+ * This macro initializes a &drm_display_mode that contains information about
+ * refresh rate, resolution and physical size.
+ */
+#define DRM_MODE_INIT(hz, hd, vd, hd_mm, vd_mm) \
+	__DRM_MODE_INIT((hd) * (vd) * (hz) / 1000 /* kHz */, hd, vd, hd_mm, vd_mm)
+
 /**
  * DRM_SIMPLE_MODE - Simple display mode
  * @hd: Horizontal resolution, width
@@ -149,11 +178,7 @@ enum drm_mode_status {
  * resolution and physical size.
  */
 #define DRM_SIMPLE_MODE(hd, vd, hd_mm, vd_mm) \
-	.type = DRM_MODE_TYPE_DRIVER, .clock = 1 /* pass validation */, \
-	.hdisplay = (hd), .hsync_start = (hd), .hsync_end = (hd), \
-	.htotal = (hd), .vdisplay = (vd), .vsync_start = (vd), \
-	.vsync_end = (vd), .vtotal = (vd), .width_mm = (hd_mm), \
-	.height_mm = (vd_mm)
+	__DRM_MODE_INIT(1 /* pass validation */, hd, vd, hd_mm, vd_mm)
 
 #define CRTC_INTERLACE_HALVE_V	(1 << 0) /* halve V values for interlacing */
 #define CRTC_STEREO_DOUBLE	(1 << 1) /* adjust timings for stereo modes */