On Fri Oct 24, 2025 at 5:51 AM JST, Daniel del Castillo wrote:
> This patch solves one of the existing mentions of COHA, a task
> in the Nova task list about improving the `CoherentAllocation` API.
> It uses the `write` method from `CoherentAllocation`.
>
> Signed-off-by: Daniel del Castillo <[email protected]>
>
> ---
>
> V1 -> V2: Split previous patch into two. One per reference to COHA.
> Added more details in Safety comment. Let me know your thoughts
> Kept the original map to avoid a temporary variable
> ---
> drivers/gpu/nova-core/dma.rs | 15 +++------------
> 1 file changed, 3 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/dma.rs b/drivers/gpu/nova-core/dma.rs
> index 94f44bcfd748..620d31078858 100644
> --- a/drivers/gpu/nova-core/dma.rs
> +++ b/drivers/gpu/nova-core/dma.rs
> @@ -26,18 +26,9 @@ pub(crate) fn new(dev: &device::Device<device::Bound>,
> len: usize) -> Result<Sel
>
> pub(crate) fn from_data(dev: &device::Device<device::Bound>, data:
> &[u8]) -> Result<Self> {
> Self::new(dev, data.len()).map(|mut dma_obj| {
> - // TODO[COHA]: replace with `CoherentAllocation::write()` once
> available.
> - // SAFETY:
> - // - `dma_obj`'s size is at least `data.len()`.
> - // - We have just created this object and there is no other user
> at this stage.
> - unsafe {
> - core::ptr::copy_nonoverlapping(
> - data.as_ptr(),
> - dma_obj.dma.start_ptr_mut(),
> - data.len(),
> - );
> - }
> -
> + // SAFETY: We have just allocated the DMA memory, we are the
> only users and
> + // we haven't made the device aware of the handle yet.
> + unsafe { dma_obj.write(data, 0)? }
This doesn't build for me:
error[E0277]: the `?` operator can only be used in a closure that returns
`Result` or `Option` (or another type that implements `core::ops::FromResidual`)
--> ../drivers/gpu/nova-core/dma.rs:31:44
|
28 | Self::new(dev, data.len()).map(|mut dma_obj| {
| ------------- this function
should return `Result` or `Option` to accept `?`
...
31 | unsafe { dma_obj.write(data, 0)? }
| ^ cannot use the `?`
operator in a closure that returns `dma::DmaObject`
Could you double-check? I guess you will need to change the `map` into
`and_then`.
