Message-ID: <CAPM=9tyL_Cq3+qWc4A41p7eqnNDLS1APUEeUbaQyJ46YDkipVw@mail.gmail.com>
Date: Wed, 4 Feb 2026 13:55:06 +1000
From: Dave Airlie <airlied@...il.com>
To: Joel Fernandes <joelagnelf@...dia.com>
Cc: linux-kernel@...r.kernel.org, 
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Subject: Re: [PATCH RFC v6 03/26] rust: gpu: Add GPU buddy allocator bindings

> +///
> +/// These flags control the allocation behavior of the buddy allocator.
> +#[derive(Clone, Copy, Default, PartialEq, Eq)]
> +pub struct BuddyFlags(usize);
> +
> +impl BuddyFlags {
> +    /// Range-based allocation from start to end addresses.
> +    pub const RANGE_ALLOCATION: usize = bindings::GPU_BUDDY_RANGE_ALLOCATION;
> +
> +    /// Allocate from top of address space downward.
> +    pub const TOPDOWN_ALLOCATION: usize = bindings::GPU_BUDDY_TOPDOWN_ALLOCATION;
> +
> +    /// Allocate physically contiguous blocks.
> +    pub const CONTIGUOUS_ALLOCATION: usize = bindings::GPU_BUDDY_CONTIGUOUS_ALLOCATION;
> +
> +    /// Request allocation from the cleared (zeroed) memory. The zero'ing is not
> +    /// done by the allocator, but by the caller before freeing old blocks.
> +    pub const CLEAR_ALLOCATION: usize = bindings::GPU_BUDDY_CLEAR_ALLOCATION;
> +
> +    /// Disable trimming of partially used blocks.
> +    pub const TRIM_DISABLE: usize = bindings::GPU_BUDDY_TRIM_DISABLE;
> +
> +    /// Mark blocks as cleared (zeroed) when freeing. When set during free,
> +    /// indicates that the caller has already zeroed the memory.
> +    pub const CLEARED: usize = bindings::GPU_BUDDY_CLEARED;
> +
> +    /// Create [`BuddyFlags`] from a raw value with validation.
> +    ///
> +    /// Use `|` operator to combine flags if needed, before calling this method.
> +    pub fn try_new(flags: usize) -> Result<Self> {
> +        // Flags must not exceed u32::MAX to satisfy the GPU buddy allocator C API.
> +        if flags > u32::MAX as usize {
> +            return Err(EINVAL);
> +        }
> +
> +        // `TOPDOWN_ALLOCATION` only works without `RANGE_ALLOCATION`. When both are
> +        // set, `TOPDOWN_ALLOCATION` is silently ignored by the allocator. Reject this.
> +        if (flags & Self::RANGE_ALLOCATION) != 0 && (flags & Self::TOPDOWN_ALLOCATION) != 0 {
> +            return Err(EINVAL);
> +        }
> +
> +        Ok(Self(flags))
> +    }
> +
> +    /// Get raw value of the flags.
> +    pub(crate) fn as_raw(self) -> usize {
> +        self.0
> +    }
> +}
> +
> +/// Parameters for creating a GPU buddy allocator.
> +#[derive(Clone, Copy)]
> +pub struct GpuBuddyParams {
> +    /// Base offset in bytes where the managed memory region starts.
> +    /// Allocations will be offset by this value.
> +    pub base_offset_bytes: u64,
> +    /// Total physical memory size managed by the allocator in bytes.
> +    pub physical_memory_size_bytes: u64,
> +    /// Minimum allocation unit / chunk size in bytes, must be >= 4KB.
> +    pub chunk_size_bytes: u64,
> +}
> +
> +/// Parameters for allocating blocks from a GPU buddy allocator.
> +#[derive(Clone, Copy)]
> +pub struct GpuBuddyAllocParams {
> +    /// Start of allocation range in bytes. Use 0 for beginning.
> +    pub start_range_address: u64,
> +    /// End of allocation range in bytes. Use 0 for entire range.
> +    pub end_range_address: u64,
> +    /// Total size to allocate in bytes.
> +    pub size_bytes: u64,
> +    /// Minimum block size for fragmented allocations in bytes.
> +    pub min_block_size_bytes: u64,
> +    /// Buddy allocator behavior flags.
> +    pub buddy_flags: BuddyFlags,
> +}
> +

(not a full review)

Any reason these two need Clone, Copy? I'm not seeing a use case for
that, maybe we should pass them as non-mutable references, but I don't
think there is any point in passing them by value ever.

Dave.

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