Hi Lyude,
> On 30 Sep 2024, at 20:09, Lyude Paul <ly...@redhat.com> wrote:
>
> This is the same thing as OpaqueConnector and OpaqueConnectorState, but for
> CRTCs now.
>
> Signed-off-by: Lyude Paul <ly...@redhat.com>
>
> ---
>
> TODO:
> * Add upcast functions
>
> Signed-off-by: Lyude Paul <ly...@redhat.com>
> ---
> rust/kernel/drm/kms/crtc.rs | 131 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 131 insertions(+)
>
> diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
> index d84db49948380..1a3c9c448afcc 100644
> --- a/rust/kernel/drm/kms/crtc.rs
> +++ b/rust/kernel/drm/kms/crtc.rs
> @@ -234,6 +234,41 @@ pub fn new<'a, 'b: 'a, P, C>(
> // SAFETY: We don't move anything
> Ok(unsafe { &*Box::into_raw(Pin::into_inner_unchecked(this)) })
> }
> +
> + /// Attempt to convert an [`OpaqueCrtc`] into a fully qualified [`Crtc`].
> + ///
> + /// This checks if the given [`OpaqueCrtc`] uses the same [`DriverCrtc`]
> implementation, and
> + /// returns the [`OpaqueCrtc`] as a [`Crtc`] object if so.
> + pub fn try_from_opaque<'a, D>(opaque: &'a OpaqueCrtc<D>) -> Option<&'a
> Self>
> + where
> + D: KmsDriver,
> + T: DriverCrtc<Driver = D>
> + {
> + // SAFETY: The vtables for a `Crtc` are initialized throughout the
> lifetime of the object
> + let funcs = unsafe { (*opaque.crtc.get()).funcs };
> +
> + // SAFETY: We only perform this transmutation if the opaque CRTC
> shares our vtable pointers,
> + // so the underlying `Crtc` must share our data layout.
> + ptr::eq(funcs, &T::OPS.funcs).then(|| unsafe {
> mem::transmute(opaque) })
> + }
> +
> + /// Convert a [`OpaqueCrtc`] into its fully qualified [`Crtc`].
> + ///
> + /// This is an infallible version of [`Self::try_from_opaque`]. This
> function is mainly useful
> + /// for drivers where only a single [`DriverCrtc`] implementation exists.
I am confused. If a driver has a single `DriverCrtc`, why would it care for
`OpaqueCrtc`?
> + ///
> + /// # Panics
> + ///
> + /// This function will panic if the underlying CRTC in the provided
> [`OpaqueCrtc`] does not
> + /// belong to the same [`DriverCrtc`] implementation.
> + pub fn from_opaque<'a, D>(opaque: &'a OpaqueCrtc<D>) -> &'a Self
> + where
> + D: KmsDriver,
> + T: DriverCrtc<Driver = D>
> + {
> + Self::try_from_opaque(opaque)
> + .expect("Passed OpaqueCrtc does not share this DriverCrtc
> implementation")
> + }
> }
>
> /// A trait implemented by any type that acts as a [`struct drm_crtc`]
> interface.
> @@ -267,6 +302,66 @@ unsafe fn from_raw<'a>(ptr: *mut bindings::drm_crtc) ->
> &'a Self {
> }
> }
>
> +/// A [`struct drm_crtc`] without a known [`DriverCrtc`] implementation.
> +///
> +/// This is mainly for situations where our bindings can't infer the
> [`DriverCrtc`] implementation
> +/// for a [`struct drm_crtc`] automatically. It is identical to [`Crtc`],
> except that it does not
> +/// provide access to the driver's private data.
> +///
> +/// It may be upcasted to a full [`Crtc`] using [`Crtc::from_opaque`] or
> +/// [`Crtc::try_from_opaque`].
> +///
> +/// # Invariants
> +///
> +/// - `crtc` is initialized for as long as this object is made available to
> users.
> +/// - The data layout of this structure is equivalent to [`struct drm_crtc`].
nit: Maybe worth clarifying that it’s equivalent to `bindings::drm_crtc`, not
directly to
C’s `struct drm_crtc`. Although it should also be equivalent to that in
practice.
> +///
> +/// [`struct drm_crtc`]: srctree/include/drm/drm_crtc.h
> +#[repr(transparent)]
> +pub struct OpaqueCrtc<T: KmsDriver> {
> + crtc: Opaque<bindings::drm_crtc>,
> + _p: PhantomData<T>
> +}
> +
> +impl<T: KmsDriver> Sealed for OpaqueCrtc<T> {}
> +
> +impl<T: KmsDriver> AsRawCrtc for OpaqueCrtc<T> {
> + type State = OpaqueCrtcState<T>;
> +
> + fn as_raw(&self) -> *mut bindings::drm_crtc {
> + self.crtc.get()
> + }
> +
> + unsafe fn from_raw<'a>(ptr: *mut bindings::drm_crtc) -> &'a Self {
> + // SAFETY: Our data layout starts with `bindings::drm_crtc`
> + unsafe { &*ptr.cast() }
> + }
> +}
> +
> +impl<T: KmsDriver> ModeObject for OpaqueCrtc<T> {
> + type Driver = T;
> +
> + fn drm_dev(&self) -> &Device<Self::Driver> {
> + // SAFETY: The parent device for a DRM connector will never outlive
> the connector, and this
> + // pointer is invariant through the lifetime of the connector
> + unsafe { Device::borrow((*self.as_raw()).dev) }
> + }
> +
> + fn raw_mode_obj(&self) -> *mut bindings::drm_mode_object {
> + // SAFETY: We don't expose DRM connectors to users before `base` is
> initialized
> + unsafe { addr_of_mut!((*self.as_raw()).base) }
> + }
> +}
> +
> +// SAFETY: CRTCs are non-refcounted modesetting objects
> +unsafe impl<T: KmsDriver> StaticModeObject for OpaqueCrtc<T> {}
> +
> +// SAFETY: Our CRTC interface is guaranteed to be thread-safe
> +unsafe impl<T: KmsDriver> Send for OpaqueCrtc<T> {}
> +
> +// SAFETY: Our CRTC interface is guaranteed to be thread-safe
> +unsafe impl<T: KmsDriver> Sync for OpaqueCrtc<T> {}
> +
> unsafe impl Zeroable for bindings::drm_crtc_state { }
>
> impl<T: DriverCrtcState> Sealed for CrtcState<T> {}
> @@ -400,6 +495,42 @@ unsafe fn from_raw<'a>(ptr: *const
> bindings::drm_crtc_state) -> &'a Self {
> }
> }
>
> +/// A [`struct drm_crtc_state`] without a known [`DriverCrtcState`]
> implementation.
> +///
> +/// This is mainly for situations where our bindings can't infer the
> [`DriverCrtcState`]
> +/// implementation for a [`struct drm_crtc_state`] automatically. It is
> identical to [`Crtc`],
> +/// except that it does not provide access to the driver's private data.
> +///
> +/// TODO: Add upcast functions
> +///
> +/// # Invariants
> +///
> +/// - `state` is initialized for as long as this object is exposed to users.
> +/// - The data layout of this type is identical to [`struct drm_crtc_state`].
> +///
> +/// [`struct drm_crtc_state`]: srctree/include/drm/drm_crtc.h
> +#[repr(transparent)]
> +pub struct OpaqueCrtcState<T: KmsDriver> {
> + state: Opaque<bindings::drm_crtc_state>,
> + _p: PhantomData<T>
> +}
> +
> +impl<T: KmsDriver> AsRawCrtcState for OpaqueCrtcState<T> {
> + type Crtc = OpaqueCrtc<T>;
> +}
> +
> +impl<T: KmsDriver> private::AsRawCrtcState for OpaqueCrtcState<T> {
> + fn as_raw(&self) -> *mut bindings::drm_crtc_state {
> + self.state.get()
> + }
> +}
> +
> +impl<T: KmsDriver> FromRawCrtcState for OpaqueCrtcState<T> {
> + unsafe fn from_raw<'a>(ptr: *const bindings::drm_crtc_state) -> &'a Self
> {
> + // SAFETY: Our data layout is identical to `bindings::drm_crtc_state`
> + unsafe { &*(ptr.cast()) }
> + }
> +}
> unsafe extern "C" fn crtc_destroy_callback<T: DriverCrtc>(
> crtc: *mut bindings::drm_crtc
> ) {
> --
> 2.46.1
>
>
— Daniel
