[PATCH v3 11/23] rust: drm: kms: expose checked plane geometry

[Mike Lothian]

Expose the requested source rectangle and the visibility and clipped
rectangles produced by drm_atomic_helper_check_plane_state().

Keep 16.16 source coordinates explicit at the raw-state
boundary. Convert helper-clipped source coordinates to integer pixels
only after rejecting negative or fractional values, and return the
clipped destination in CRTC coordinates.

These generic accessors let Rust KMS drivers implement cursor
clipping and validate full-frame scanout without reaching into
generated bindings.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@xxxxxxxxxxxxxx>
---
 rust/kernel/drm/kms/plane.rs | 59 ++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index 3bff4091abb2..bc830503b142 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -758,6 +758,65 @@ fn crtc_h(&self) -> u32 {
         self.as_raw().crtc_h
     }
 
+    /// Return the requested source X coordinate in 16.16 fixed-point pixels.
+    fn source_x_16_16(&self) -> u32 {
+        self.as_raw().src_x
+    }
+
+    /// Return the requested source Y coordinate in 16.16 fixed-point pixels.
+    fn source_y_16_16(&self) -> u32 {
+        self.as_raw().src_y
+    }
+
+    /// Return the requested source width in 16.16 fixed-point pixels.
+    fn source_width_16_16(&self) -> u32 {
+        self.as_raw().src_w
+    }
+
+    /// Return the requested source height in 16.16 fixed-point pixels.
+    fn source_height_16_16(&self) -> u32 {
+        self.as_raw().src_h
+    }
+
+    /// Return whether [`Self::atomic_helper_check`] found any visible part of the plane.
+    fn visible(&self) -> bool {
+        self.as_raw().visible
+    }
+
+    /// Return the helper-clipped source rectangle in integer framebuffer pixels.
+    ///
+    /// This is valid after [`Self::atomic_helper_check`]. Fractional source coordinates are
+    /// rejected with [`EINVAL`].
+    fn visible_source(&self) -> Result<Option<Rect>> {
+        if !self.visible() {
+            return Ok(None);
+        }
+
+        let src = &self.as_raw().src;
+        if src.x1 < 0
+            || src.y1 < 0
+            || src.x2 < 0
+            || src.y2 < 0
+            || (src.x1 | src.y1 | src.x2 | src.y2) & 0xffff != 0
+        {
+            return Err(EINVAL);
+        }
+
+        Ok(Some(Rect {
+            x1: src.x1 >> 16,
+            y1: src.y1 >> 16,
+            x2: src.x2 >> 16,
+            y2: src.y2 >> 16,
+        }))
+    }
+
+    /// Return the helper-clipped destination rectangle in CRTC pixels.
+    ///
+    /// This is valid after [`Self::atomic_helper_check`].
+    fn visible_destination(&self) -> Option<Rect> {
+        self.visible().then(|| Rect::from_raw(&self.as_raw().dst))
+    }
+
     /// The plane's rotation/reflection (`DRM_MODE_ROTATE_*` | `DRM_MODE_REFLECT_*` bitmask), for a
     /// plane with a rotation property (see
     /// [`UnregisteredPlane::create_rotation_property`]). Defaults to `DRM_MODE_ROTATE_0`.