drm/doc: Polish plane composition property docs

Try to spec a bit more precisely how they all fit together, now that
at least the code is for all the additional properties is in one
place.

Also remove the entries for the standardized properties from the
table, because that thing is supremely unmaintaineable.

v2: Fix typos Sean spotted.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1474448370-32227-4-git-send-email-daniel.vetter@ffwll.ch

1 files changed, 128 insertions, 18 deletions

diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
index 0b8e227aa175..85172a977bf3 100644
--- a/drivers/gpu/drm/drm_blend.c
+++ b/drivers/gpu/drm/drm_blend.c
@@ -32,6 +32,118 @@
 
 #include "drm_crtc_internal.h"
 
+/**
+ * DOC: overview
+ *
+ * The basic plane composition model supported by standard plane properties only
+ * has a source rectangle (in logical pixels within the &drm_framebuffer), with
+ * sub-pixel accuracy, which is scaled up to a pixel-aligned destination
+ * rectangle in the visible area of a &drm_crtc. The visible area of a CRTC is
+ * defined by the horizontal and vertical visible pixels (stored in @hdisplay
+ * and @vdisplay) of the requested mode (stored in @mode in the
+ * &drm_crtc_state). These two rectangles are both stored in the
+ * &drm_plane_state.
+ *
+ * For the atomic ioctl the following standard (atomic) properties on the plane object
+ * encode the basic plane composition model:
+ *
+ * SRC_X:
+ * 	X coordinate offset for the source rectangle within the
+ * 	&drm_framebuffer, in 16.16 fixed point. Must be positive.
+ * SRC_Y:
+ * 	Y coordinate offset for the source rectangle within the
+ * 	&drm_framebuffer, in 16.16 fixed point. Must be positive.
+ * SRC_W:
+ * 	Width for the source rectangle within the &drm_framebuffer, in 16.16
+ * 	fixed point. SRC_X plus SRC_W must be within the width of the source
+ * 	framebuffer. Must be positive.
+ * SRC_H:
+ * 	Height for the source rectangle within the &drm_framebuffer, in 16.16
+ * 	fixed point. SRC_Y plus SRC_H must be within the height of the source
+ * 	framebuffer. Must be positive.
+ * CRTC_X:
+ * 	X coordinate offset for the destination rectangle. Can be negative.
+ * CRTC_Y:
+ * 	Y coordinate offset for the destination rectangle. Can be negative.
+ * CRTC_W:
+ * 	Width for the destination rectangle. CRTC_X plus CRTC_W can extend past
+ * 	the currently visible horizontal area of the &drm_crtc.
+ * CRTC_H:
+ * 	Height for the destination rectangle. CRTC_Y plus CRTC_H can extend past
+ * 	the currently visible vertical area of the &drm_crtc.
+ * FB_ID:
+ * 	Mode object ID of the &drm_framebuffer this plane should scan out.
+ * CRTC_ID:
+ * 	Mode object ID of the &drm_crtc this plane should be connected to.
+ *
+ * Note that the source rectangle must fully lie within the bounds of the
+ * &drm_framebuffer. The destination rectangle can lie outside of the visible
+ * area of the current mode of the CRTC. It must be apprpriately clipped by the
+ * driver, which can be done by calling drm_plane_helper_check_update(). Drivers
+ * are also allowed to round the subpixel sampling positions appropriately, but
+ * only to the next full pixel. No pixel outside of the source rectangle may
+ * ever be sampled, which is important when applying more sophisticated
+ * filtering than just a bilinear one when scaling. The filtering mode when
+ * scaling is unspecified.
+ *
+ * On top of this basic transformation additional properties can be exposed by
+ * the driver:
+ *
+ * - Rotation is set up with drm_mode_create_rotation_property(). It adds a
+ *   rotation and reflection step between the source and destination rectangles.
+ *   Without this property the rectangle is only scaled, but not rotated or
+ *   reflected.
+ *
+ * - Z position is set up with drm_plane_create_zpos_immutable_property() and
+ *   drm_plane_create_zpos_property(). It controls the visibility of overlapping
+ *   planes. Without this property the primary plane is always below the cursor
+ *   plane, and ordering between all other planes is undefined.
+ *
+ * Note that all the property extensions described here apply either to the
+ * plane or the CRTC (e.g. for the background color, which currently is not
+ * exposed and assumed to be black).
+ */
+
+/**
+ * drm_mode_create_rotation_property - create a new rotation property
+ * @dev: DRM device
+ * @supported_rotations: bitmask of supported rotations and reflections
+ *
+ * This creates a new property with the selected support for transformations.
+ * The resulting property should be stored in @rotation_property in
+ * &drm_mode_config. It then must be attached to each plane which supports
+ * rotations using drm_object_attach_property().
+ *
+ * FIXME: Probably better if the rotation property is created on each plane,
+ * like the zpos property. Otherwise it's not possible to allow different
+ * rotation modes on different planes.
+ *
+ * Since a rotation by 180° degress is the same as reflecting both along the x
+ * and the y axis the rotation property is somewhat redundant. Drivers can use
+ * drm_rotation_simplify() to normalize values of this property.
+ *
+ * The property exposed to userspace is a bitmask property (see
+ * drm_property_create_bitmask()) called "rotation" and has the following
+ * bitmask enumaration values:
+ *
+ * DRM_ROTATE_0:
+ * 	"rotate-0"
+ * DRM_ROTATE_90:
+ * 	"rotate-90"
+ * DRM_ROTATE_180:
+ * 	"rotate-180"
+ * DRM_ROTATE_270:
+ * 	"rotate-270"
+ * DRM_REFLECT_X:
+ * 	"reflect-x"
+ * DRM_REFELCT_Y:
+ * 	"reflect-y"
+ *
+ * Rotation is the specified amount in degrees in counter clockwise direction,
+ * the X and Y axis are within the source rectangle, i.e.  the X/Y axis before
+ * rotation. After reflection, the rotation is applied to the image sampled from
+ * the source rectangle, before scaling it to fit the destination rectangle.
+ */
 struct drm_property *drm_mode_create_rotation_property(struct drm_device *dev,
 						       unsigned int supported_rotations)
 {
@@ -98,10 +210,14 @@ EXPORT_SYMBOL(drm_rotation_simplify);
  * If zpos of some planes cannot be changed (like fixed background or
  * cursor/topmost planes), driver should adjust min/max values and assign those
  * planes immutable zpos property with lower or higher values (for more
- * information, see drm_mode_create_zpos_immutable_property() function). In such
+ * information, see drm_plane_create_zpos_immutable_property() function). In such
  * case driver should also assign proper initial zpos values for all planes in
  * its plane_reset() callback, so the planes will be always sorted properly.
  *
+ * See also drm_atomic_normalize_zpos().
+ *
+ * The property exposed to userspace is called "zpos".
+ *
  * Returns:
  * Zero on success, negative errno on failure.
  */
@@ -137,7 +253,9 @@ EXPORT_SYMBOL(drm_plane_create_zpos_property);
  * support for it in drm core. Using this property driver lets userspace
  * to get the arrangement of the planes for blending operation and notifies
  * it that the hardware (or driver) doesn't support changing of the planes'
- * order.
+ * order. For mutable zpos see drm_plane_create_zpos_property().
+ *
+ * The property exposed to userspace is called "zpos".
  *
  * Returns:
  * Zero on success, negative errno on failure.
@@ -176,20 +294,6 @@ static int drm_atomic_state_zpos_cmp(const void *a, const void *b)
 		return sa->plane->base.id - sb->plane->base.id;
 }
 
-/**
- * drm_atomic_helper_crtc_normalize_zpos - calculate normalized zpos values
- * @crtc: crtc with planes, which have to be considered for normalization
- * @crtc_state: new atomic state to apply
- *
- * This function checks new states of all planes assigned to given crtc and
- * calculates normalized zpos value for them. Planes are compared first by their
- * zpos values, then by plane id (if zpos equals). Plane with lowest zpos value
- * is at the bottom. The plane_state->normalized_zpos is then filled with unique
- * values from 0 to number of active planes in crtc minus one.
- *
- * RETURNS
- * Zero for success or -errno
- */
 static int drm_atomic_helper_crtc_normalize_zpos(struct drm_crtc *crtc,
 					  struct drm_crtc_state *crtc_state)
 {
@@ -247,8 +351,14 @@ done:
  * @state: atomic state of DRM device
  *
  * This function calculates normalized zpos value for all modified planes in
- * the provided atomic state of DRM device. For more information, see
- * drm_atomic_helper_crtc_normalize_zpos() function.
+ * the provided atomic state of DRM device.
+ *
+ * For every CRTC this function checks new states of all planes assigned to
+ * it and calculates normalized zpos value for these planes. Planes are compared
+ * first by their zpos values, then by plane id (if zpos is equal). The plane
+ * with lowest zpos value is at the bottom. The plane_state->normalized_zpos is
+ * then filled with unique values from 0 to number of active planes in crtc
+ * minus one.
  *
  * RETURNS
  * Zero for success or -errno