drm: pahole struct drm_display_mode

Reorganize drm_display_mode to eliminate all the holes.
We'll put all the actual timings to the start of the
struct and all the extra junk to the end.

Gets the size down to 136 bytes on 64bit and 120 bytes on
32bit. With a bit more work we should be able to get this
below the two cacheline mark even on 64bit.

v2: Rebase due to DRM_MODE_TYPE_USERDEF comment change
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200428171940.19552-11-ville.syrjala@linux.intel.com

include/drm/drm_modes.h

@@ -222,57 +222,6 @@ enum drm_mode_status {
  * For printing you can use %DRM_MODE_FMT and DRM_MODE_ARG().
  */
 struct drm_display_mode {
-	/**
-	 * @head:
-	 *
-	 * struct list_head for mode lists.
-	 */
-	struct list_head head;
-
-	/**
-	 * @name:
-	 *
-	 * Human-readable name of the mode, filled out with drm_mode_set_name().
-	 */
-	char name[DRM_DISPLAY_MODE_LEN];
-
-	/**
-	 * @status:
-	 *
-	 * Status of the mode, used to filter out modes not supported by the
-	 * hardware. See enum &drm_mode_status.
-	 */
-	enum drm_mode_status status;
-
-	/**
-	 * @type:
-	 *
-	 * A bitmask of flags, mostly about the source of a mode. Possible flags
-	 * are:
-	 *
-	 *  - DRM_MODE_TYPE_PREFERRED: Preferred mode, usually the native
-	 *    resolution of an LCD panel. There should only be one preferred
-	 *    mode per connector at any given time.
-	 *  - DRM_MODE_TYPE_DRIVER: Mode created by the driver, which is all of
-	 *    them really. Drivers must set this bit for all modes they create
-	 *    and expose to userspace.
-	 *  - DRM_MODE_TYPE_USERDEF: Mode defined or selected via the kernel
-	 *    command line.
-	 *
-	 * Plus a big list of flags which shouldn't be used at all, but are
-	 * still around since these flags are also used in the userspace ABI.
-	 * We no longer accept modes with these types though:
-	 *
-	 *  - DRM_MODE_TYPE_BUILTIN: Meant for hard-coded modes, unused.
-	 *    Use DRM_MODE_TYPE_DRIVER instead.
-	 *  - DRM_MODE_TYPE_DEFAULT: Again a leftover, use
-	 *    DRM_MODE_TYPE_PREFERRED instead.
-	 *  - DRM_MODE_TYPE_CLOCK_C and DRM_MODE_TYPE_CRTC_C: Define leftovers
-	 *    which are stuck around for hysterical raisins only. No one has an
-	 *    idea what they were meant for. Don't use.
-	 */
-	u8 type;
-
 	/**
 	 * @clock:
 	 *
@@ -325,22 +274,6 @@ struct drm_display_mode {
 	 */
 	u32 flags;
 
-	/**
-	 * @width_mm:
-	 *
-	 * Addressable size of the output in mm, projectors should set this to
-	 * 0.
-	 */
-	u16 width_mm;
-
-	/**
-	 * @height_mm:
-	 *
-	 * Addressable size of the output in mm, projectors should set this to
-	 * 0.
-	 */
-	u16 height_mm;
-
 	/**
 	 * @crtc_clock:
 	 *
@@ -371,6 +304,51 @@ struct drm_display_mode {
 	u16 crtc_vsync_end;
 	u16 crtc_vtotal;
 
+	/**
+	 * @width_mm:
+	 *
+	 * Addressable size of the output in mm, projectors should set this to
+	 * 0.
+	 */
+	u16 width_mm;
+
+	/**
+	 * @height_mm:
+	 *
+	 * Addressable size of the output in mm, projectors should set this to
+	 * 0.
+	 */
+	u16 height_mm;
+
+	/**
+	 * @type:
+	 *
+	 * A bitmask of flags, mostly about the source of a mode. Possible flags
+	 * are:
+	 *
+	 *  - DRM_MODE_TYPE_PREFERRED: Preferred mode, usually the native
+	 *    resolution of an LCD panel. There should only be one preferred
+	 *    mode per connector at any given time.
+	 *  - DRM_MODE_TYPE_DRIVER: Mode created by the driver, which is all of
+	 *    them really. Drivers must set this bit for all modes they create
+	 *    and expose to userspace.
+	 *  - DRM_MODE_TYPE_USERDEF: Mode defined or selected via the kernel
+	 *    command line.
+	 *
+	 * Plus a big list of flags which shouldn't be used at all, but are
+	 * still around since these flags are also used in the userspace ABI.
+	 * We no longer accept modes with these types though:
+	 *
+	 *  - DRM_MODE_TYPE_BUILTIN: Meant for hard-coded modes, unused.
+	 *    Use DRM_MODE_TYPE_DRIVER instead.
+	 *  - DRM_MODE_TYPE_DEFAULT: Again a leftover, use
+	 *    DRM_MODE_TYPE_PREFERRED instead.
+	 *  - DRM_MODE_TYPE_CLOCK_C and DRM_MODE_TYPE_CRTC_C: Define leftovers
+	 *    which are stuck around for hysterical raisins only. No one has an
+	 *    idea what they were meant for. Don't use.
+	 */
+	u8 type;
+
 	/**
 	 * @private_flags:
 	 *
@@ -382,11 +360,11 @@ struct drm_display_mode {
 	int private_flags;
 
 	/**
-	 * @picture_aspect_ratio:
+	 * @head:
 	 *
-	 * Field for setting the HDMI picture aspect ratio of a mode.
+	 * struct list_head for mode lists.
 	 */
-	enum hdmi_picture_aspect picture_aspect_ratio;
+	struct list_head head;
 
 	/**
 	 * @export_head:
@@ -400,6 +378,29 @@ struct drm_display_mode {
 	 * avoid overhead of protecting it by mode_config.mutex.
 	 */
 	struct list_head export_head;
+
+	/**
+	 * @name:
+	 *
+	 * Human-readable name of the mode, filled out with drm_mode_set_name().
+	 */
+	char name[DRM_DISPLAY_MODE_LEN];
+
+	/**
+	 * @status:
+	 *
+	 * Status of the mode, used to filter out modes not supported by the
+	 * hardware. See enum &drm_mode_status.
+	 */
+	enum drm_mode_status status;
+
+	/**
+	 * @picture_aspect_ratio:
+	 *
+	 * Field for setting the HDMI picture aspect ratio of a mode.
+	 */
+	enum hdmi_picture_aspect picture_aspect_ratio;
+
 };
 
 /**