drm: Move drm_display_mode an related docs into kerneldoc

This was in the documentation for modeset helper hooks, where it is a
bit misplaced.

v2: Reindent the drm_mode_status enum, inspired by Ville.

v3: Suggestions from Ville and Thierry.

v4: Small fixup that 0day spotted.

v5: Slight change to avoid accidental headings in kerneldoc output.

Cc: ville.syrjala@linux.intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449218769-16577-27-git-send-email-daniel.vetter@ffwll.ch
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v3)
Reviewed-by: Thierry Reding <treding@nvidia.com> (v3)

1 files changed, 296 insertions, 47 deletions

diff --git a/include/drm/drm_modes.h b/include/drm/drm_modes.h
index f9115aee43f4..9e6d7a1cd19b 100644
--- a/include/drm/drm_modes.h
+++ b/include/drm/drm_modes.h
@@ -35,46 +35,91 @@
  * structures).
  */
 
+/**
+ * enum drm_mode_status - hardware support status of a mode
+ * @MODE_OK: Mode OK
+ * @MODE_HSYNC: hsync out of range
+ * @MODE_VSYNC: vsync out of range
+ * @MODE_H_ILLEGAL: mode has illegal horizontal timings
+ * @MODE_V_ILLEGAL: mode has illegal horizontal timings
+ * @MODE_BAD_WIDTH: requires an unsupported linepitch
+ * @MODE_NOMODE: no mode with a matching name
+ * @MODE_NO_INTERLACE: interlaced mode not supported
+ * @MODE_NO_DBLESCAN: doublescan mode not supported
+ * @MODE_NO_VSCAN: multiscan mode not supported
+ * @MODE_MEM: insufficient video memory
+ * @MODE_VIRTUAL_X: mode width too large for specified virtual size
+ * @MODE_VIRTUAL_Y: mode height too large for specified virtual size
+ * @MODE_MEM_VIRT: insufficient video memory given virtual size
+ * @MODE_NOCLOCK: no fixed clock available
+ * @MODE_CLOCK_HIGH: clock required is too high
+ * @MODE_CLOCK_LOW: clock required is too low
+ * @MODE_CLOCK_RANGE: clock/mode isn't in a ClockRange
+ * @MODE_BAD_HVALUE: horizontal timing was out of range
+ * @MODE_BAD_VVALUE: vertical timing was out of range
+ * @MODE_BAD_VSCAN: VScan value out of range
+ * @MODE_HSYNC_NARROW: horizontal sync too narrow
+ * @MODE_HSYNC_WIDE: horizontal sync too wide
+ * @MODE_HBLANK_NARROW: horizontal blanking too narrow
+ * @MODE_HBLANK_WIDE: horizontal blanking too wide
+ * @MODE_VSYNC_NARROW: vertical sync too narrow
+ * @MODE_VSYNC_WIDE: vertical sync too wide
+ * @MODE_VBLANK_NARROW: vertical blanking too narrow
+ * @MODE_VBLANK_WIDE: vertical blanking too wide
+ * @MODE_PANEL: exceeds panel dimensions
+ * @MODE_INTERLACE_WIDTH: width too large for interlaced mode
+ * @MODE_ONE_WIDTH: only one width is supported
+ * @MODE_ONE_HEIGHT: only one height is supported
+ * @MODE_ONE_SIZE: only one resolution is supported
+ * @MODE_NO_REDUCED: monitor doesn't accept reduced blanking
+ * @MODE_NO_STEREO: stereo modes not supported
+ * @MODE_UNVERIFIED: mode needs to reverified
+ * @MODE_BAD: unspecified reason
+ * @MODE_ERROR: error condition
+ *
+ * This enum is used to filter out modes not supported by the driver/hardware
+ * combination.
+ */
 enum drm_mode_status {
-    MODE_OK	= 0,	/* Mode OK */
-    MODE_HSYNC,		/* hsync out of range */
-    MODE_VSYNC,		/* vsync out of range */
-    MODE_H_ILLEGAL,	/* mode has illegal horizontal timings */
-    MODE_V_ILLEGAL,	/* mode has illegal horizontal timings */
-    MODE_BAD_WIDTH,	/* requires an unsupported linepitch */
-    MODE_NOMODE,	/* no mode with a matching name */
-    MODE_NO_INTERLACE,	/* interlaced mode not supported */
-    MODE_NO_DBLESCAN,	/* doublescan mode not supported */
-    MODE_NO_VSCAN,	/* multiscan mode not supported */
-    MODE_MEM,		/* insufficient video memory */
-    MODE_VIRTUAL_X,	/* mode width too large for specified virtual size */
-    MODE_VIRTUAL_Y,	/* mode height too large for specified virtual size */
-    MODE_MEM_VIRT,	/* insufficient video memory given virtual size */
-    MODE_NOCLOCK,	/* no fixed clock available */
-    MODE_CLOCK_HIGH,	/* clock required is too high */
-    MODE_CLOCK_LOW,	/* clock required is too low */
-    MODE_CLOCK_RANGE,	/* clock/mode isn't in a ClockRange */
-    MODE_BAD_HVALUE,	/* horizontal timing was out of range */
-    MODE_BAD_VVALUE,	/* vertical timing was out of range */
-    MODE_BAD_VSCAN,	/* VScan value out of range */
-    MODE_HSYNC_NARROW,	/* horizontal sync too narrow */
-    MODE_HSYNC_WIDE,	/* horizontal sync too wide */
-    MODE_HBLANK_NARROW,	/* horizontal blanking too narrow */
-    MODE_HBLANK_WIDE,	/* horizontal blanking too wide */
-    MODE_VSYNC_NARROW,	/* vertical sync too narrow */
-    MODE_VSYNC_WIDE,	/* vertical sync too wide */
-    MODE_VBLANK_NARROW,	/* vertical blanking too narrow */
-    MODE_VBLANK_WIDE,	/* vertical blanking too wide */
-    MODE_PANEL,         /* exceeds panel dimensions */
-    MODE_INTERLACE_WIDTH, /* width too large for interlaced mode */
-    MODE_ONE_WIDTH,     /* only one width is supported */
-    MODE_ONE_HEIGHT,    /* only one height is supported */
-    MODE_ONE_SIZE,      /* only one resolution is supported */
-    MODE_NO_REDUCED,    /* monitor doesn't accept reduced blanking */
-    MODE_NO_STEREO,	/* stereo modes not supported */
-    MODE_UNVERIFIED = -3, /* mode needs to reverified */
-    MODE_BAD = -2,	/* unspecified reason */
-    MODE_ERROR	= -1	/* error condition */
+	MODE_OK = 0,
+	MODE_HSYNC,
+	MODE_VSYNC,
+	MODE_H_ILLEGAL,
+	MODE_V_ILLEGAL,
+	MODE_BAD_WIDTH,
+	MODE_NOMODE,
+	MODE_NO_INTERLACE,
+	MODE_NO_DBLESCAN,
+	MODE_NO_VSCAN,
+	MODE_MEM,
+	MODE_VIRTUAL_X,
+	MODE_VIRTUAL_Y,
+	MODE_MEM_VIRT,
+	MODE_NOCLOCK,
+	MODE_CLOCK_HIGH,
+	MODE_CLOCK_LOW,
+	MODE_CLOCK_RANGE,
+	MODE_BAD_HVALUE,
+	MODE_BAD_VVALUE,
+	MODE_BAD_VSCAN,
+	MODE_HSYNC_NARROW,
+	MODE_HSYNC_WIDE,
+	MODE_HBLANK_NARROW,
+	MODE_HBLANK_WIDE,
+	MODE_VSYNC_NARROW,
+	MODE_VSYNC_WIDE,
+	MODE_VBLANK_NARROW,
+	MODE_VBLANK_WIDE,
+	MODE_PANEL,
+	MODE_INTERLACE_WIDTH,
+	MODE_ONE_WIDTH,
+	MODE_ONE_HEIGHT,
+	MODE_ONE_SIZE,
+	MODE_NO_REDUCED,
+	MODE_NO_STEREO,
+	MODE_UNVERIFIED = -3,
+	MODE_BAD = -2,
+	MODE_ERROR = -1
 };
 
 #define DRM_MODE_TYPE_CLOCK_CRTC_C (DRM_MODE_TYPE_CLOCK_C | \
@@ -96,17 +141,125 @@ enum drm_mode_status {
 
 #define DRM_MODE_FLAG_3D_MAX	DRM_MODE_FLAG_3D_SIDE_BY_SIDE_HALF
 
+/**
+ * struct drm_display_mode - DRM kernel-internal display mode structure
+ * @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?!
+ * @crtc_hdisplay: hardware mode horizontal display size
+ * @crtc_hblank_start: hardware mode horizontal blank start
+ * @crtc_hblank_end: hardware mode horizontal blank end
+ * @crtc_hsync_start: hardware mode horizontal sync start
+ * @crtc_hsync_end: hardware mode horizontal sync end
+ * @crtc_htotal: hardware mode horizontal total size
+ * @crtc_hskew: hardware mode horizontal skew?!
+ * @crtc_vdisplay: hardware mode vertical display size
+ * @crtc_vblank_start: hardware mode vertical blank start
+ * @crtc_vblank_end: hardware mode vertical blank end
+ * @crtc_vsync_start: hardware mode vertical sync start
+ * @crtc_vsync_end: hardware mode vertical sync end
+ * @crtc_vtotal: hardware mode vertical total size
+ *
+ * The horizontal and vertical timings are defined per the following diagram.
+ *
+ *
+ *               Active                 Front           Sync           Back
+ *              Region                 Porch                          Porch
+ *     <-----------------------><----------------><-------------><-------------->
+ *       //////////////////////|
+ *      ////////////////////// |
+ *     //////////////////////  |..................               ................
+ *                                                _______________
+ *     <----- [hv]display ----->
+ *     <------------- [hv]sync_start ------------>
+ *     <--------------------- [hv]sync_end --------------------->
+ *     <-------------------------------- [hv]total ----------------------------->*
+ *
+ * This structure contains two copies of timings. First are the plain timings,
+ * which specify the logical mode, as it would be for a progressive 1:1 scanout
+ * at the refresh rate userspace can observe through vblank timestamps. Then
+ * there's the hardware timings, which are corrected for interlacing,
+ * double-clocking and similar things. They are provided as a convenience, and
+ * can be appropriately computed using drm_mode_set_crtcinfo().
+ */
 struct drm_display_mode {
-	/* Header */
+	/**
+	 * @head:
+	 *
+	 * struct list_head for mode lists.
+	 */
 	struct list_head head;
+
+	/**
+	 * @base:
+	 *
+	 * A display mode is a normal modeset object, possibly including public
+	 * userspace id.
+	 *
+	 * FIXME:
+	 *
+	 * This can probably be removed since the entire concept of userspace
+	 * managing modes explicitly has never landed in upstream kernel mode
+	 * setting support.
+	 */
 	struct drm_mode_object base;
 
+	/**
+	 * @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_BUILTIN: Meant for hard-coded modes, effectively
+	 *    unused.
+	 *  - 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.
+	 *
+	 * 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:
+	 *
+	 *  - 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.
+	 *  - DRM_MODE_TYPE_USERDEF: Mode defined by userspace, again a vestige
+	 *    from older kms designs where userspace had to first add a custom
+	 *    mode to the kernel's mode list before it could use it. Don't use.
+	 */
 	unsigned int type;
 
-	/* Proposed mode values */
+	/**
+	 * @clock:
+	 *
+	 * Pixel clock in kHz.
+	 */
 	int clock;		/* in kHz */
 	int hdisplay;
 	int hsync_start;
@@ -118,14 +271,74 @@ struct drm_display_mode {
 	int vsync_end;
 	int vtotal;
 	int vscan;
+	/**
+	 * @flags:
+	 *
+	 * Sync and timing flags:
+	 *
+	 *  - DRM_MODE_FLAG_PHSYNC: horizontal sync is active high.
+	 *  - DRM_MODE_FLAG_NHSYNC: horizontal sync is active low.
+	 *  - DRM_MODE_FLAG_PVSYNC: vertical sync is active high.
+	 *  - DRM_MODE_FLAG_NVSYNC: vertical sync is active low.
+	 *  - DRM_MODE_FLAG_INTERLACE: mode is interlaced.
+	 *  - DRM_MODE_FLAG_DBLSCAN: mode uses doublescan.
+	 *  - DRM_MODE_FLAG_CSYNC: mode uses composite sync.
+	 *  - DRM_MODE_FLAG_PCSYNC: composite sync is active high.
+	 *  - DRM_MODE_FLAG_NCSYNC: composite sync is active low.
+	 *  - DRM_MODE_FLAG_HSKEW: hskew provided (not used?).
+	 *  - DRM_MODE_FLAG_BCAST: not used?
+	 *  - DRM_MODE_FLAG_PIXMUX: not used?
+	 *  - DRM_MODE_FLAG_DBLCLK: double-clocked mode.
+	 *  - DRM_MODE_FLAG_CLKDIV2: half-clocked mode.
+	 *
+	 * Additionally there's flags to specify how 3D modes are packed:
+	 *
+	 *  - DRM_MODE_FLAG_3D_NONE: normal, non-3D mode.
+	 *  - DRM_MODE_FLAG_3D_FRAME_PACKING: 2 full frames for left and right.
+	 *  - DRM_MODE_FLAG_3D_FIELD_ALTERNATIVE: interleaved like fields.
+	 *  - DRM_MODE_FLAG_3D_LINE_ALTERNATIVE: interleaved lines.
+	 *  - DRM_MODE_FLAG_3D_SIDE_BY_SIDE_FULL: side-by-side full frames.
+	 *  - DRM_MODE_FLAG_3D_L_DEPTH: ?
+	 *  - DRM_MODE_FLAG_3D_L_DEPTH_GFX_GFX_DEPTH: ?
+	 *  - DRM_MODE_FLAG_3D_TOP_AND_BOTTOM: frame split into top and bottom
+	 *    parts.
+	 *  - DRM_MODE_FLAG_3D_SIDE_BY_SIDE_HALF: frame split into left and
+	 *    right parts.
+	 */
 	unsigned int flags;
 
-	/* Addressable image size (may be 0 for projectors, etc.) */
+	/**
+	 * @width_mm:
+	 *
+	 * Addressable size of the output in mm, projectors should set this to
+	 * 0.
+	 */
 	int width_mm;
+
+	/**
+	 * @height_mm:
+	 *
+	 * Addressable size of the output in mm, projectors should set this to
+	 * 0.
+	 */
 	int height_mm;
 
-	/* Actual mode we give to hw */
-	int crtc_clock;		/* in KHz */
+	/**
+	 * @crtc_clock:
+	 *
+	 * Actual pixel or dot clock in the hardware. This differs from the
+	 * logical @clock when e.g. using interlacing, double-clocking, stereo
+	 * modes or other fancy stuff that changes the timings and signals
+	 * actually sent over the wire.
+	 *
+	 * This is again in kHz.
+	 *
+	 * Note that with digital outputs like HDMI or DP there's usually a
+	 * massive confusion between the dot clock and the signal clock at the
+	 * bit encoding level. Especially when a 8b/10b encoding is used and the
+	 * difference is exactly a factor of 10.
+	 */
+	int crtc_clock;
 	int crtc_hdisplay;
 	int crtc_hblank_start;
 	int crtc_hblank_end;
@@ -140,12 +353,48 @@ struct drm_display_mode {
 	int crtc_vsync_end;
 	int crtc_vtotal;
 
-	/* Driver private mode info */
+	/**
+	 * @private:
+	 *
+	 * Pointer for driver private data. This can only be used for mode
+	 * objects passed to drivers in modeset operations. It shouldn't be used
+	 * by atomic drivers since they can store any additional data by
+	 * subclassing state structures.
+	 */
 	int *private;
+
+	/**
+	 * @private_flags:
+	 *
+	 * Similar to @private, but just an integer.
+	 */
 	int private_flags;
 
-	int vrefresh;		/* in Hz */
-	int hsync;		/* in kHz */
+	/**
+	 * @vrefresh:
+	 *
+	 * Vertical refresh rate, for debug output in human readable form. Not
+	 * used in a functional way.
+	 *
+	 * This value is in Hz.
+	 */
+	int vrefresh;
+
+	/**
+	 * @hsync:
+	 *
+	 * Horizontal refresh rate, for debug output in human readable form. Not
+	 * used in a functional way.
+	 *
+	 * This value is in kHz.
+	 */
+	int hsync;
+
+	/**
+	 * @picture_aspect_ratio:
+	 *
+	 * Field for setting the HDMI picture aspect ratio of a mode.
+	 */
 	enum hdmi_picture_aspect picture_aspect_ratio;
 };