Just a temporary holdover to make locking/unlocking the dma_resv lock much easier.
Signed-off-by: Lyude Paul lyude@redhat.com Co-authored-by: Alexandre Courbot acourbot@nvidia.com Signed-off-by: Alexandre Courbot acourbot@nvidia.com Reviewed-by: Alice Ryhl aliceryhl@google.com Acked-by: Danilo Krummrich dakr@kernel.org
--- V17: * Fix format of commit message title V19: * Add NotThreadSafe to DmaResvGuard V20: * s/inline(always)/inline/
rust/kernel/drm/gem/shmem.rs | 39 ++++++++++++++++++++++++++++++++++-- 1 file changed, 37 insertions(+), 2 deletions(-)
diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs index 084b798ce795b..090c5d869fdb7 100644 --- a/rust/kernel/drm/gem/shmem.rs +++ b/rust/kernel/drm/gem/shmem.rs @@ -22,7 +22,10 @@ error::to_result, prelude::*, sync::aref::ARef, - types::Opaque, // + types::{ + NotThreadSafe, + Opaque, // + }, }; use core::{ marker::PhantomData, @@ -30,7 +33,10 @@ Deref, DerefMut, // }, - ptr::NonNull, // + ptr::{ + self, + NonNull, // + }, }; use gem::{ BaseObjectPrivate, @@ -244,3 +250,32 @@ impl<T: DriverObject, C: DeviceContext> driver::AllocImpl for Object<T, C> { dumb_map_offset: None, }; } + +/// Private helper-type for holding the `dma_resv` object for a GEM shmem object. +/// +/// When this is dropped, the `dma_resv` lock is dropped as well. +/// +// TODO: This should be replace with a WwMutex equivalent once we have such bindings in the kernel. +struct DmaResvGuard<'a, T: DriverObject, C: DeviceContext = Registered>( + &'a Object<T, C>, + NotThreadSafe, +); + +impl<'a, T: DriverObject, C: DeviceContext> DmaResvGuard<'a, T, C> { + #[inline] + #[expect(unused)] + fn new(obj: &'a Object<T, C>) -> Self { + // SAFETY: This lock is initialized throughout the lifetime of `object`. + unsafe { bindings::dma_resv_lock(obj.raw_dma_resv(), ptr::null_mut()) }; + + Self(obj, NotThreadSafe) + } +} + +impl<'a, T: DriverObject, C: DeviceContext> Drop for DmaResvGuard<'a, T, C> { + #[inline] + fn drop(&mut self) { + // SAFETY: We are releasing the lock grabbed during the creation of this object. + unsafe { bindings::dma_resv_unlock(self.0.raw_dma_resv()) }; + } +}