linux-kernel - [RFC v3 30/33] rust: drm/kms: Add Device::num

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Message-ID: <20250305230406.567126-31-lyude@redhat.com>
Date: Wed,  5 Mar 2025 17:59:46 -0500
From: Lyude Paul <lyude@...hat.com>
To: dri-devel@...ts.freedesktop.org,
	rust-for-linux@...r.kernel.org
Cc: Danilo Krummrich <dakr@...nel.org>,
	mcanal@...lia.com,
	Alice Ryhl <aliceryhl@...gle.com>,
	Maxime Ripard <mripard@...nel.org>,
	Simona Vetter <sima@...ll.ch>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...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@...nel.org>,
	Trevor Gross <tmgross@...ch.edu>,
	linux-kernel@...r.kernel.org (open list)
Subject: [RFC v3 30/33] rust: drm/kms: Add Device::num_crtcs()

A binding for checking drm_device.num_crtcs. We'll need this in a moment
for vblank support, since setting it up requires knowing the number of
CRTCs that a driver has initialized.

Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 rust/kernel/drm/kms.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/rust/kernel/drm/kms.rs b/rust/kernel/drm/kms.rs
index 429ce28229c9e..36a0b4c4454ba 100644
--- a/rust/kernel/drm/kms.rs
+++ b/rust/kernel/drm/kms.rs
@@ -311,6 +311,17 @@ pub fn mode_config_lock(&self) -> ModeConfigGuard<'_, T> {
         // held throughout ModeConfigGuard's lifetime.
         ModeConfigGuard(self.mode_config_mutex().lock(), PhantomData)
     }
+
+    /// Return the number of registered CRTCs
+    #[inline]
+    pub fn num_crtcs(&self) -> u32 {
+        // SAFETY:
+        // * This can only be modified during the single-threaded context before registration, so
+        //   this is safe
+        // * num_crtc could be >= 0, but no less - so casting to u32 is fine (and better to prevent
+        //   errors)
+        unsafe { (*self.as_raw()).mode_config.num_crtc as u32 }
+    }
 }
 
 /// A modesetting object in DRM.
-- 
2.48.1