drm: document drm_mode_modeinfo

This allows `struct drm_mode_modeinfo` references to be linkified.

Some descriptions are borrowed from struct drm_display_mode.

Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/BBtyuxgs3DvcrMtbRyb7KBEWUviGy1dtWO61eB4@cp3-web-016.plabs.ch

include/drm/drm_modes.h

@@ -195,6 +195,9 @@ enum drm_mode_status {
  * @crtc_vsync_end: hardware mode vertical sync end
  * @crtc_vtotal: hardware mode vertical total size
  *
+ * This is the kernel API display mode information structure. For the
+ * user-space version see struct drm_mode_modeinfo.
+ *
  * The horizontal and vertical timings are defined per the following diagram.
  *
  * ::

include/uapi/drm/drm_mode.h

@@ -218,6 +218,27 @@ extern "C" {
 #define DRM_MODE_CONTENT_PROTECTION_DESIRED     1
 #define DRM_MODE_CONTENT_PROTECTION_ENABLED     2
 
+/**
+ * struct drm_mode_modeinfo - Display mode information.
+ * @clock: pixel clock in kHz
+ * @hdisplay: horizontal display size
+ * @hsync_start: horizontal sync start
+ * @hsync_end: horizontal sync end
+ * @htotal: horizontal total size
+ * @hskew: horizontal skew
+ * @vdisplay: vertical display size
+ * @vsync_start: vertical sync start
+ * @vsync_end: vertical sync end
+ * @vtotal: vertical total size
+ * @vscan: vertical scan
+ * @vrefresh: approximate vertical refresh rate in Hz
+ * @flags: bitmask of misc. flags, see DRM_MODE_FLAG_* defines
+ * @type: bitmask of type flags, see DRM_MODE_TYPE_* defines
+ * @name: string describing the mode resolution
+ *
+ * This is the user-space API display mode information structure. For the
+ * kernel version see struct drm_display_mode.
+ */
 struct drm_mode_modeinfo {
 	__u32 clock;
 	__u16 hdisplay;