Commit 26af8565 authored by Alexandre Courbot's avatar Alexandre Courbot Committed by Danilo Krummrich
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rust: dma: add dma_handle_with_offset method to CoherentAllocation 



Sometimes one may want to obtain a DMA handle starting at a given
offset. This can be done by adding said offset to the result of
`dma_handle()`, but doing so on the client side carries the risk that
the operation will go outside the bounds of the allocation.

Thus, add a `dma_handle_with_offset` method that adds the desired offset
after checking that it is still valid.

Signed-off-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250619-nova-frts-v6-3-ecf41ef99252@nvidia.com


Signed-off-by: default avatarDanilo Krummrich <dakr@kernel.org>
parent c0a3065d

rust/kernel/dma.rs

+14 −0
Original line number Diff line number Diff line
@@ -238,6 +238,20 @@ pub fn dma_handle(&self) -> bindings::dma_addr_t { 
        self.dma_handle

    }



    /// Returns a DMA handle starting at `offset` (in units of `T`) which may be given to the

    /// device as the DMA address base of the region.

    ///

    /// Returns `EINVAL` if `offset` is not within the bounds of the allocation.

    pub fn dma_handle_with_offset(&self, offset: usize) -> Result<bindings::dma_addr_t> {

        if offset >= self.count {

            Err(EINVAL)

        } else {

            // INVARIANT: The type invariant of `Self` guarantees that `size_of::<T> * count` fits

            // into a `usize`, and `offset` is inferior to `count`.

            Ok(self.dma_handle + (offset * core::mem::size_of::<T>()) as bindings::dma_addr_t)

        }

    }



    /// Common helper to validate a range applied from the allocated region in the CPU's virtual

    /// address space.

    fn validate_range(&self, offset: usize, count: usize) -> Result {