linux-kernel - [WIP RFC v2 30/35] rust: drm/kms: Add DriverCrtc::atomic_enable() and atomic

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Message-ID: <20240930233257.1189730-31-lyude@redhat.com>
Date: Mon, 30 Sep 2024 19:10:13 -0400
From: Lyude Paul <lyude@...hat.com>
To: dri-devel@...ts.freedesktop.org,
	rust-for-linux@...r.kernel.org
Cc: Asahi Lina <lina@...hilina.net>,
	Danilo Krummrich <dakr@...nel.org>,
	mcanal@...lia.com,
	airlied@...hat.com,
	zhiw@...dia.com,
	cjia@...dia.com,
	jhubbard@...dia.com,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...sung.com>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	linux-kernel@...r.kernel.org (open list)
Subject: [WIP RFC v2 30/35] rust: drm/kms: Add DriverCrtc::atomic_enable() and atomic_disable()

Optional trait methods for implementing the atomic_enable and
atomic_disable callbacks of a CRTC.

Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 rust/kernel/drm/kms/crtc.rs | 76 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 74 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index a4e955364bd8c..ef1b331f742d0 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -80,8 +80,8 @@ pub trait DriverCrtc: Send + Sync + Sized {
         },
 
         helper_funcs: bindings::drm_crtc_helper_funcs {
-            atomic_disable: None,
-            atomic_enable: None,
+            atomic_disable: if Self::HAS_ATOMIC_DISABLE { Some(atomic_disable_callback::<Self>) } else { None },
+            atomic_enable: if Self::HAS_ATOMIC_ENABLE { Some(atomic_enable_callback::<Self>) } else { None },
             atomic_check: if Self::HAS_ATOMIC_CHECK { Some(atomic_check_callback::<Self>) } else { None },
             dpms: None,
             commit: None,
@@ -162,6 +162,34 @@ fn atomic_flush(
     ) {
         build_error::build_error("This should never be reachable")
     }
+
+    /// The optional [`drm_crtc_helper_funcs.atomic_enable`] hook.
+    ///
+    /// This hook will be called before enabling a [`Crtc`] in an atomic commit.
+    ///
+    /// [`drm_crtc_helper_funcs.atomic_enable`]: srctree/include/drm/drm_modeset_helper_vtables.h
+    fn atomic_enable(
+        crtc: &Crtc<Self>,
+        old_state: &CrtcState<Self::State>,
+        new_state: BorrowedCrtcState<'_, CrtcState<Self::State>>,
+        state: &AtomicStateMutator<Self::Driver>
+    ) {
+        build_error::build_error("This should never be reachable")
+    }
+
+    /// The optional [`drm_crtc_helper_funcs.atomic_disable`] hook.
+    ///
+    /// This hook will be called before disabling a [`Crtc`] in an atomic commit.
+    ///
+    /// [`drm_crtc_helper_funcs.atomic_disable`]: srctree/include/drm/drm_modeset_helper_vtables.h
+    fn atomic_disable(
+        crtc: &Crtc<Self>,
+        old_state: &CrtcState<Self::State>,
+        new_state: BorrowedCrtcState<'_, CrtcState<Self::State>>,
+        state: &AtomicStateMutator<Self::Driver>
+    ) {
+        build_error::build_error("This should never be reachable")
+    }
 }
 
 /// The generated C vtable for a [`DriverCrtc`].
@@ -850,3 +878,47 @@ fn as_raw(&self) -> *mut bindings::drm_crtc_state {
 
     T::atomic_flush(crtc, old_state, new_state, &state);
 }
+
+unsafe extern "C" fn atomic_enable_callback<T: DriverCrtc>(
+    crtc: *mut bindings::drm_crtc,
+    state: *mut bindings::drm_atomic_state,
+) {
+    // SAFETY:
+    // * We're guaranteed `crtc` is of type `Crtc<T>` via type invariants.
+    // * We're guaranteed by DRM that `crtc` is pointing to a valid initialized state.
+    let crtc = unsafe { Crtc::from_raw(crtc) };
+
+    // SAFETY: DRM never passes an invalid ptr for `state`
+    let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
+
+    // SAFETY: We're in an atomic enable callback, so we know that both the new and old state are
+    // present
+    let (old_state, new_state) = unsafe {(
+        state.get_old_crtc_state(crtc).unwrap_unchecked(),
+        state.get_new_crtc_state(crtc).unwrap_unchecked(),
+    )};
+
+    T::atomic_enable(crtc, old_state, new_state, &state);
+}
+
+unsafe extern "C" fn atomic_disable_callback<T: DriverCrtc>(
+    crtc: *mut bindings::drm_crtc,
+    state: *mut bindings::drm_atomic_state,
+) {
+    // SAFETY:
+    // * We're guaranteed `crtc` points to a valid instance of `drm_crtc`
+    // * We're guaranteed that `crtc` is of type `Plane<T>` by `DriverPlane`s type invariants.
+    let crtc = unsafe { Crtc::from_raw(crtc) };
+
+    // SAFETY: We're guaranteed that `state` points to a valid `drm_crtc_state` by DRM
+    let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
+
+    // SAFETY: We're in an atomic commit callback, so we know that both the new and old state are
+    // present
+    let (old_state, new_state) = unsafe {(
+        state.get_old_crtc_state(crtc).unwrap_unchecked(),
+        state.get_new_crtc_state(crtc).unwrap_unchecked(),
+    )};
+
+    T::atomic_disable(crtc, old_state, new_state, &state);
+}
-- 
2.46.1