dma::Coherent & dma::CoherentInit API

[PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization

Posted by Danilo Krummrich 1 month, 1 week ago

Currently, dma::Coherent cannot safely provide (mutable) access to its
underlying memory because the memory might be concurrently accessed by a
DMA device. This makes it difficult to safely initialize the memory
before handing it over to the hardware.

Introduce dma::CoherentInit, a type that encapsulates a dma::Coherent
before its DMA address is exposed to the device. dma::CoherentInit can
guarantee exclusive access to the inner dma::Coherent and implement
Deref and DerefMut.

Once the memory is properly initialized, dma::CoherentInit can be
converted into a regular dma::Coherent.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/dma.rs | 153 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 152 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
index 291fdea3b52b..79dd8717ac47 100644
--- a/rust/kernel/dma.rs
+++ b/rust/kernel/dma.rs
@@ -20,7 +20,13 @@
         FromBytes, //
     }, //
 };
-use core::ptr::NonNull;
+use core::{
+    ops::{
+        Deref,
+        DerefMut, //
+    },
+    ptr::NonNull, //
+};
 
 /// DMA address type.
 ///
@@ -352,6 +358,151 @@ fn from(direction: DataDirection) -> Self {
     }
 }
 
+/// Initializer type for [`Coherent`].
+///
+/// A [`Coherent`] object can't provide access to its memory as (mutable) slice safely, since it
+/// can't fulfill the requirements for creating a slice. For instance, it is not valid to have a
+/// (mutable) slice to of the memory of a [`Coherent`] while the memory might be accessed by a
+/// device.
+///
+/// In contrast, this initializer type is able to fulfill the requirements to safely obtain a
+/// (mutable) slice, as it neither provides access to the DMA address of the embedded [`Coherent`],
+/// nor can it be used with the DMA projection accessors.
+///
+/// Once initialized, this type can be converted to a regular [`Coherent`] object.
+///
+/// # Examples
+///
+/// `CoherentInit<T>`:
+///
+/// ```
+/// # use kernel::device::{
+/// #     Bound,
+/// #     Device,
+/// # };
+/// use kernel::dma::{attrs::*,
+///     Coherent,
+///     CoherentInit,
+/// };
+///
+/// # fn test(dev: &Device<Bound>) -> Result {
+/// let mut dmem: CoherentInit<u64> =
+///     CoherentInit::zeroed_with_attrs(dev, GFP_KERNEL, DMA_ATTR_NO_WARN)?;
+/// *dmem = 42;
+/// let dmem: Coherent<u64> = dmem.into();
+/// # Ok::<(), Error>(()) }
+/// ```
+///
+/// `CoherentInit<[T]>`:
+///
+///
+/// ```
+/// # use kernel::device::{
+/// #     Bound,
+/// #     Device,
+/// # };
+/// use kernel::dma::{attrs::*,
+///     Coherent,
+///     CoherentInit,
+/// };
+///
+/// # fn test(dev: &Device<Bound>) -> Result {
+/// let mut dmem: CoherentInit<[u64]> =
+///     CoherentInit::zeroed_slice_with_attrs(dev, 4, GFP_KERNEL, DMA_ATTR_NO_WARN)?;
+/// dmem.fill(42);
+/// let dmem: Coherent<[u64]> = dmem.into();
+/// # Ok::<(), Error>(()) }
+/// ```
+pub struct CoherentInit<T: AsBytes + FromBytes + KnownSize + ?Sized>(Coherent<T>);
+
+impl<T: AsBytes + FromBytes> CoherentInit<[T]> {
+    /// Initializer variant of [`Coherent::zeroed_slice_with_attrs`].
+    pub fn zeroed_slice_with_attrs(
+        dev: &device::Device<Bound>,
+        count: usize,
+        gfp_flags: kernel::alloc::Flags,
+        dma_attrs: Attrs,
+    ) -> Result<Self> {
+        Coherent::zeroed_slice_with_attrs(dev, count, gfp_flags, dma_attrs).map(Self)
+    }
+
+    /// Same as [CoherentInit::zeroed_slice_with_attrs], but with `dma::Attrs(0)`.
+    pub fn zeroed_slice(
+        dev: &device::Device<Bound>,
+        count: usize,
+        gfp_flags: kernel::alloc::Flags,
+    ) -> Result<Self> {
+        Self::zeroed_slice_with_attrs(dev, count, gfp_flags, Attrs(0))
+    }
+
+    /// Initializes the element at `i` using the given initializer.
+    ///
+    /// Returns `EINVAL` if `i` is out of bounds.
+    pub fn init_at<E>(&mut self, i: usize, init: impl Init<T, E>) -> Result
+    where
+        Error: From<E>,
+    {
+        if i >= self.0.len() {
+            return Err(EINVAL);
+        }
+
+        let ptr = core::ptr::from_mut(&mut self[i]);
+
+        // SAFETY:
+        // - `ptr` is valid, properly aligned, and within this allocation.
+        // - `T: AsBytes + FromBytes` guarantees all bit patterns are valid, so partial writes on
+        //   error cannot leave the element in an invalid state.
+        // - The DMA address has not been exposed yet, so there is no concurrent device access.
+        unsafe { init.__init(ptr)? };
+
+        Ok(())
+    }
+}
+
+impl<T: AsBytes + FromBytes> CoherentInit<T> {
+    /// Same as [`CoherentInit::zeroed_slice_with_attrs`], but for a single element.
+    pub fn zeroed_with_attrs(
+        dev: &device::Device<Bound>,
+        gfp_flags: kernel::alloc::Flags,
+        dma_attrs: Attrs,
+    ) -> Result<Self> {
+        Coherent::zeroed_with_attrs(dev, gfp_flags, dma_attrs).map(Self)
+    }
+
+    /// Same as [`CoherentInit::zeroed_slice`], but for a single element.
+    pub fn zeroed(dev: &device::Device<Bound>, gfp_flags: kernel::alloc::Flags) -> Result<Self> {
+        Self::zeroed_with_attrs(dev, gfp_flags, Attrs(0))
+    }
+}
+
+impl<T: AsBytes + FromBytes + KnownSize + ?Sized> Deref for CoherentInit<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        // SAFETY:
+        // - We have not exposed the DMA address yet, so there can't be any concurrent access by a
+        //   device.
+        // - We have exclusive access to `self.0`.
+        unsafe { self.0.as_ref() }
+    }
+}
+
+impl<T: AsBytes + FromBytes + KnownSize + ?Sized> DerefMut for CoherentInit<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        // SAFETY:
+        // - We have not exposed the DMA address yet, so there can't be any concurrent access by a
+        //   device.
+        // - We have exclusive access to `self.0`.
+        unsafe { self.0.as_mut() }
+    }
+}
+
+impl<T: AsBytes + FromBytes + KnownSize + ?Sized> From<CoherentInit<T>> for Coherent<T> {
+    fn from(value: CoherentInit<T>) -> Self {
+        value.0
+    }
+}
+
 /// An abstraction of the `dma_alloc_coherent` API.
 ///
 /// This is an abstraction around the `dma_alloc_coherent` API which is used to allocate and map
-- 
2.53.0

Re: [PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization

Posted by Alexandre Courbot 2 weeks, 6 days ago

On Wed Mar 4, 2026 at 1:22 AM JST, Danilo Krummrich wrote:
<snip>
> @@ -352,6 +358,151 @@ fn from(direction: DataDirection) -> Self {
>      }
>  }
>  
> +/// Initializer type for [`Coherent`].
> +///
> +/// A [`Coherent`] object can't provide access to its memory as (mutable) slice safely, since it
> +/// can't fulfill the requirements for creating a slice. For instance, it is not valid to have a
> +/// (mutable) slice to of the memory of a [`Coherent`] while the memory might be accessed by a
> +/// device.
> +///
> +/// In contrast, this initializer type is able to fulfill the requirements to safely obtain a
> +/// (mutable) slice, as it neither provides access to the DMA address of the embedded [`Coherent`],
> +/// nor can it be used with the DMA projection accessors.
> +///
> +/// Once initialized, this type can be converted to a regular [`Coherent`] object.
> +///
> +/// # Examples
> +///
> +/// `CoherentInit<T>`:
> +///
> +/// ```
> +/// # use kernel::device::{
> +/// #     Bound,
> +/// #     Device,
> +/// # };
> +/// use kernel::dma::{attrs::*,
> +///     Coherent,
> +///     CoherentInit,
> +/// };
> +///
> +/// # fn test(dev: &Device<Bound>) -> Result {
> +/// let mut dmem: CoherentInit<u64> =
> +///     CoherentInit::zeroed_with_attrs(dev, GFP_KERNEL, DMA_ATTR_NO_WARN)?;

Since this is an example, shall we use the simpler
`CoherentInit::zeroed`?

> +/// *dmem = 42;
> +/// let dmem: Coherent<u64> = dmem.into();
> +/// # Ok::<(), Error>(()) }
> +/// ```
> +///
> +/// `CoherentInit<[T]>`:
> +///
> +///
> +/// ```
> +/// # use kernel::device::{
> +/// #     Bound,
> +/// #     Device,
> +/// # };
> +/// use kernel::dma::{attrs::*,
> +///     Coherent,
> +///     CoherentInit,
> +/// };
> +///
> +/// # fn test(dev: &Device<Bound>) -> Result {
> +/// let mut dmem: CoherentInit<[u64]> =
> +///     CoherentInit::zeroed_slice_with_attrs(dev, 4, GFP_KERNEL, DMA_ATTR_NO_WARN)?;

Same here.

> +/// dmem.fill(42);
> +/// let dmem: Coherent<[u64]> = dmem.into();
> +/// # Ok::<(), Error>(()) }
> +/// ```
> +pub struct CoherentInit<T: AsBytes + FromBytes + KnownSize + ?Sized>(Coherent<T>);
> +
> +impl<T: AsBytes + FromBytes> CoherentInit<[T]> {
> +    /// Initializer variant of [`Coherent::zeroed_slice_with_attrs`].
> +    pub fn zeroed_slice_with_attrs(
> +        dev: &device::Device<Bound>,
> +        count: usize,
> +        gfp_flags: kernel::alloc::Flags,
> +        dma_attrs: Attrs,
> +    ) -> Result<Self> {
> +        Coherent::zeroed_slice_with_attrs(dev, count, gfp_flags, dma_attrs).map(Self)
> +    }
> +
> +    /// Same as [CoherentInit::zeroed_slice_with_attrs], but with `dma::Attrs(0)`.
> +    pub fn zeroed_slice(
> +        dev: &device::Device<Bound>,
> +        count: usize,
> +        gfp_flags: kernel::alloc::Flags,
> +    ) -> Result<Self> {
> +        Self::zeroed_slice_with_attrs(dev, count, gfp_flags, Attrs(0))
> +    }
> +
> +    /// Initializes the element at `i` using the given initializer.
> +    ///
> +    /// Returns `EINVAL` if `i` is out of bounds.
> +    pub fn init_at<E>(&mut self, i: usize, init: impl Init<T, E>) -> Result

Should this method be introduced in the next patch, or even in its own
patch? It feels a bit out of place at this stage since the non-array
`CoherentInit` doesn't have an equivalent.

I was also wondering whether we could have an `init` method that
initializes all the elements without having to zero the whole array
first, but I guess it might be a bit difficult to implement in a
flexible enough way.

Re: [PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization

Posted by Danilo Krummrich 2 weeks, 6 days ago

On 3/20/2026 3:35 PM, Alexandre Courbot wrote:
> On Wed Mar 4, 2026 at 1:22 AM JST, Danilo Krummrich wrote:
>> +/// # fn test(dev: &Device<Bound>) -> Result {
>> +/// let mut dmem: CoherentInit<u64> =
>> +///     CoherentInit::zeroed_with_attrs(dev, GFP_KERNEL, DMA_ATTR_NO_WARN)?;
> 
> Since this is an example, shall we use the simpler
> `CoherentInit::zeroed`?

Sure.

>> +    /// Initializes the element at `i` using the given initializer.
>> +    ///
>> +    /// Returns `EINVAL` if `i` is out of bounds.
>> +    pub fn init_at<E>(&mut self, i: usize, init: impl Init<T, E>) -> Result
> 
> Should this method be introduced in the next patch, or even in its own
> patch? It feels a bit out of place at this stage since the non-array
> `CoherentInit` doesn't have an equivalent.

The non-slice variant doesn't need it.

I don't see an advantage creating a separate patch for this.

> I was also wondering whether we could have an `init` method that
> initializes all the elements without having to zero the whole array
> first, but I guess it might be a bit difficult to implement in a
> flexible enough way.

You have this in the next patch, Coherent::init() works with arrays.

Re: [PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization

Posted by Alice Ryhl 3 weeks, 2 days ago

On Tue, Mar 03, 2026 at 05:22:55PM +0100, Danilo Krummrich wrote:
> Currently, dma::Coherent cannot safely provide (mutable) access to its
> underlying memory because the memory might be concurrently accessed by a
> DMA device. This makes it difficult to safely initialize the memory
> before handing it over to the hardware.
> 
> Introduce dma::CoherentInit, a type that encapsulates a dma::Coherent
> before its DMA address is exposed to the device. dma::CoherentInit can
> guarantee exclusive access to the inner dma::Coherent and implement
> Deref and DerefMut.
> 
> Once the memory is properly initialized, dma::CoherentInit can be
> converted into a regular dma::Coherent.
> 
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

overall LGTM

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

> +        let ptr = core::ptr::from_mut(&mut self[i]);

&raw mut self[i].

Alice

Re: [PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization

Posted by Danilo Krummrich 3 weeks, 2 days ago

On Tue Mar 17, 2026 at 7:52 AM CET, Alice Ryhl wrote:
> On Tue, Mar 03, 2026 at 05:22:55PM +0100, Danilo Krummrich wrote:
>> Currently, dma::Coherent cannot safely provide (mutable) access to its
>> underlying memory because the memory might be concurrently accessed by a
>> DMA device. This makes it difficult to safely initialize the memory
>> before handing it over to the hardware.
>> 
>> Introduce dma::CoherentInit, a type that encapsulates a dma::Coherent
>> before its DMA address is exposed to the device. dma::CoherentInit can
>> guarantee exclusive access to the inner dma::Coherent and implement
>> Deref and DerefMut.
>> 
>> Once the memory is properly initialized, dma::CoherentInit can be
>> converted into a regular dma::Coherent.
>> 
>> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
>
> overall LGTM
>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Gary and me concluded that dma::CoherentBox would probably be a better name for
what this structure represents. I.e. you can carry it around and use it similar
to a "real" Box until it is converted to dma::Coherent in order to make it
available to the device.

Is your RB still valid with this rename?

>> +        let ptr = core::ptr::from_mut(&mut self[i]);
>
> &raw mut self[i].
>
> Alice

Re: [PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization

Posted by Alice Ryhl 3 weeks, 2 days ago

On Tue, Mar 17, 2026 at 3:40 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> On Tue Mar 17, 2026 at 7:52 AM CET, Alice Ryhl wrote:
> > On Tue, Mar 03, 2026 at 05:22:55PM +0100, Danilo Krummrich wrote:
> >> Currently, dma::Coherent cannot safely provide (mutable) access to its
> >> underlying memory because the memory might be concurrently accessed by a
> >> DMA device. This makes it difficult to safely initialize the memory
> >> before handing it over to the hardware.
> >>
> >> Introduce dma::CoherentInit, a type that encapsulates a dma::Coherent
> >> before its DMA address is exposed to the device. dma::CoherentInit can
> >> guarantee exclusive access to the inner dma::Coherent and implement
> >> Deref and DerefMut.
> >>
> >> Once the memory is properly initialized, dma::CoherentInit can be
> >> converted into a regular dma::Coherent.
> >>
> >> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> >
> > overall LGTM
> >
> > Reviewed-by: Alice Ryhl <aliceryhl@google.com>
>
> Gary and me concluded that dma::CoherentBox would probably be a better name for
> what this structure represents. I.e. you can carry it around and use it similar
> to a "real" Box until it is converted to dma::Coherent in order to make it
> available to the device.
>
> Is your RB still valid with this rename?

Yes.

Re: [PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization

Posted by Gary Guo 4 weeks ago

On Tue Mar 3, 2026 at 4:22 PM GMT, Danilo Krummrich wrote:
> Currently, dma::Coherent cannot safely provide (mutable) access to its
> underlying memory because the memory might be concurrently accessed by a
> DMA device. This makes it difficult to safely initialize the memory
> before handing it over to the hardware.
>
> Introduce dma::CoherentInit, a type that encapsulates a dma::Coherent
> before its DMA address is exposed to the device. dma::CoherentInit can
> guarantee exclusive access to the inner dma::Coherent and implement
> Deref and DerefMut.
>
> Once the memory is properly initialized, dma::CoherentInit can be
> converted into a regular dma::Coherent.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  rust/kernel/dma.rs | 153 ++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 152 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
> index 291fdea3b52b..79dd8717ac47 100644
> --- a/rust/kernel/dma.rs
> +++ b/rust/kernel/dma.rs
> @@ -20,7 +20,13 @@
>          FromBytes, //
>      }, //
>  };
> -use core::ptr::NonNull;
> +use core::{
> +    ops::{
> +        Deref,
> +        DerefMut, //
> +    },
> +    ptr::NonNull, //
> +};
>  
>  /// DMA address type.
>  ///
> @@ -352,6 +358,151 @@ fn from(direction: DataDirection) -> Self {
>      }
>  }
>  
> +/// Initializer type for [`Coherent`].
> +///
> +/// A [`Coherent`] object can't provide access to its memory as (mutable) slice safely, since it
> +/// can't fulfill the requirements for creating a slice. For instance, it is not valid to have a
> +/// (mutable) slice to of the memory of a [`Coherent`] while the memory might be accessed by a
> +/// device.
> +///
> +/// In contrast, this initializer type is able to fulfill the requirements to safely obtain a
> +/// (mutable) slice, as it neither provides access to the DMA address of the embedded [`Coherent`],
> +/// nor can it be used with the DMA projection accessors.
> +///
> +/// Once initialized, this type can be converted to a regular [`Coherent`] object.
> +///
> +/// # Examples
> +///
> +/// `CoherentInit<T>`:
> +///
> +/// ```
> +/// # use kernel::device::{
> +/// #     Bound,
> +/// #     Device,
> +/// # };
> +/// use kernel::dma::{attrs::*,
> +///     Coherent,
> +///     CoherentInit,
> +/// };
> +///
> +/// # fn test(dev: &Device<Bound>) -> Result {
> +/// let mut dmem: CoherentInit<u64> =
> +///     CoherentInit::zeroed_with_attrs(dev, GFP_KERNEL, DMA_ATTR_NO_WARN)?;
> +/// *dmem = 42;
> +/// let dmem: Coherent<u64> = dmem.into();
> +/// # Ok::<(), Error>(()) }
> +/// ```
> +///
> +/// `CoherentInit<[T]>`:
> +///
> +///
> +/// ```
> +/// # use kernel::device::{
> +/// #     Bound,
> +/// #     Device,
> +/// # };
> +/// use kernel::dma::{attrs::*,
> +///     Coherent,
> +///     CoherentInit,
> +/// };
> +///
> +/// # fn test(dev: &Device<Bound>) -> Result {
> +/// let mut dmem: CoherentInit<[u64]> =
> +///     CoherentInit::zeroed_slice_with_attrs(dev, 4, GFP_KERNEL, DMA_ATTR_NO_WARN)?;
> +/// dmem.fill(42);
> +/// let dmem: Coherent<[u64]> = dmem.into();
> +/// # Ok::<(), Error>(()) }
> +/// ```
> +pub struct CoherentInit<T: AsBytes + FromBytes + KnownSize + ?Sized>(Coherent<T>);
> +
> +impl<T: AsBytes + FromBytes> CoherentInit<[T]> {
> +    /// Initializer variant of [`Coherent::zeroed_slice_with_attrs`].
> +    pub fn zeroed_slice_with_attrs(
> +        dev: &device::Device<Bound>,
> +        count: usize,
> +        gfp_flags: kernel::alloc::Flags,
> +        dma_attrs: Attrs,
> +    ) -> Result<Self> {
> +        Coherent::zeroed_slice_with_attrs(dev, count, gfp_flags, dma_attrs).map(Self)
> +    }
> +
> +    /// Same as [CoherentInit::zeroed_slice_with_attrs], but with `dma::Attrs(0)`.
> +    pub fn zeroed_slice(
> +        dev: &device::Device<Bound>,
> +        count: usize,
> +        gfp_flags: kernel::alloc::Flags,
> +    ) -> Result<Self> {
> +        Self::zeroed_slice_with_attrs(dev, count, gfp_flags, Attrs(0))
> +    }
> +
> +    /// Initializes the element at `i` using the given initializer.
> +    ///
> +    /// Returns `EINVAL` if `i` is out of bounds.
> +    pub fn init_at<E>(&mut self, i: usize, init: impl Init<T, E>) -> Result
> +    where
> +        Error: From<E>,
> +    {
> +        if i >= self.0.len() {
> +            return Err(EINVAL);
> +        }
> +
> +        let ptr = core::ptr::from_mut(&mut self[i]);
> +
> +        // SAFETY:
> +        // - `ptr` is valid, properly aligned, and within this allocation.
> +        // - `T: AsBytes + FromBytes` guarantees all bit patterns are valid, so partial writes on
> +        //   error cannot leave the element in an invalid state.
> +        // - The DMA address has not been exposed yet, so there is no concurrent device access.
> +        unsafe { init.__init(ptr)? };
> +
> +        Ok(())
> +    }
> +}
> +
> +impl<T: AsBytes + FromBytes> CoherentInit<T> {
> +    /// Same as [`CoherentInit::zeroed_slice_with_attrs`], but for a single element.
> +    pub fn zeroed_with_attrs(
> +        dev: &device::Device<Bound>,
> +        gfp_flags: kernel::alloc::Flags,
> +        dma_attrs: Attrs,
> +    ) -> Result<Self> {
> +        Coherent::zeroed_with_attrs(dev, gfp_flags, dma_attrs).map(Self)
> +    }
> +
> +    /// Same as [`CoherentInit::zeroed_slice`], but for a single element.
> +    pub fn zeroed(dev: &device::Device<Bound>, gfp_flags: kernel::alloc::Flags) -> Result<Self> {
> +        Self::zeroed_with_attrs(dev, gfp_flags, Attrs(0))
> +    }
> +}
> +
> +impl<T: AsBytes + FromBytes + KnownSize + ?Sized> Deref for CoherentInit<T> {
> +    type Target = T;
> +

The deref impls should be `#[inline]`.

Some other methods could be as well.

Best,
Gary

> +    fn deref(&self) -> &Self::Target {
> +        // SAFETY:
> +        // - We have not exposed the DMA address yet, so there can't be any concurrent access by a
> +        //   device.
> +        // - We have exclusive access to `self.0`.
> +        unsafe { self.0.as_ref() }
> +    }
> +}
> +
> +impl<T: AsBytes + FromBytes + KnownSize + ?Sized> DerefMut for CoherentInit<T> {
> +    fn deref_mut(&mut self) -> &mut Self::Target {
> +        // SAFETY:
> +        // - We have not exposed the DMA address yet, so there can't be any concurrent access by a
> +        //   device.
> +        // - We have exclusive access to `self.0`.
> +        unsafe { self.0.as_mut() }
> +    }
> +}
> +
> +impl<T: AsBytes + FromBytes + KnownSize + ?Sized> From<CoherentInit<T>> for Coherent<T> {
> +    fn from(value: CoherentInit<T>) -> Self {
> +        value.0
> +    }
> +}
> +
>  /// An abstraction of the `dma_alloc_coherent` API.
>  ///
>  /// This is an abstraction around the `dma_alloc_coherent` API which is used to allocate and map

[PATCH 1/8] rust: dma: use "kernel vertical" style for imports
[PATCH 2/8] rust: dma: add generalized container for types other than slices
[PATCH 3/8] rust: dma: add zeroed constructor to `Coherent`
[PATCH 4/8] rust: dma: introduce dma::CoherentInit for memory initialization
[PATCH 5/8] rust: dma: add Coherent:init() and Coherent::init_with_attrs()
[PATCH 6/8] gpu: nova-core: use Coherent::init to initialize GspFwWprMeta
[PATCH 7/8] gpu: nova-core: convert Gsp::new() to use CoherentInit
[PATCH 8/8] gpu: nova-core: convert to new dma::Coherent API