This is useful when using types that may or may not be empty in generic
code relying on these traits. It is also safe because technically a
no-op.
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://patch.msgid.link/20251215-transmute_unit-v4-1-477d71ec7c23@nvidia.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
The `from_bytes*` family of functions expect a slice of the exact same
size as the requested type. This can be sometimes cumbersome for callers
that deal with dynamic stream of data that needs to be manually cut
before each invocation of `from_bytes`.
To simplify such callers, introduce a new `from_bytes*_prefix` family of
methods, which split the input slice at the index required for the
equivalent `from_bytes` method to succeed, and return its result
alongside with the remainder of the slice.
This design is inspired by zerocopy's `try_*_from_prefix` family of
methods.
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Message-ID: <20251029-nova-vbios-frombytes-v1-1-ac441ebc1de3@nvidia.com>
Message-ID: <20251101-b4-frombytes-prefix-v1-1-0d9c1fd63b34@nvidia.com>
`FromBytes::from_bytes` comes with a few practical limitations:
- It requires the bytes slice to have the same alignment as the returned
type, which might not be guaranteed in the case of a byte stream,
- It returns a reference, requiring the returned type to implement
`Clone` if one wants to keep the value for longer than the lifetime of
the slice.
To overcome these when needed, add a `from_bytes_copy` with a default
implementation in the trait. `from_bytes_copy` returns an owned value
that is populated using an unaligned read, removing the lifetime
constraint and making it usable even on non-aligned byte slices.
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250826-nova_firmware-v2-1-93566252fe3a@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
The two methods added take a slice of bytes and return those bytes in
a specific type. These methods are useful when we need to transform
the stream of bytes into specific type.
Since the `is_aligned` method for pointer types has been stabilized in
`1.79` version and is being used in this patch, I'm enabling the
feature. In this case, using this method is useful to check the
alignment and avoid a giant boilerplate, such as `(foo.as_ptr() as
usize) % core::mem::align_of::<T>() == 0`.
Also add `#[allow(clippy::incompatible_msrv)]` where needed until the
MSRV is updated to `1.79`.
Suggested-by: Benno Lossin <benno.lossin@proton.me>
Link: https://github.com/Rust-for-Linux/linux/issues/1119
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Christian S. Lima <christiansantoslima21@gmail.com>
Link: https://lore.kernel.org/r/20250824213134.27079-1-christiansantoslima21@gmail.com
Acked-by: Miguel Ojeda <ojeda@kernel.org>
[acourbot@nvidia.com: minor rewording of commit messages and doccomments]
[acourbot@nvidia.com: revert slice implementation removal]
[acourbot@nvidia.com: move incompatible_msrv clippy allow closer to site of need]
[acourbot@nvidia.com: call the doctest method]
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Types that implement both `AsBytes` and `FromBytes` can be safely
modified as a slice of bytes. Add a `as_bytes_mut` method for that
purpose.
[acourbot@nvidia.com: use fully qualified `core::mem::size_of_val` to
build with Rust 1.78.]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20250801-as_bytes-v5-2-975f87d5dc85@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Every type that implements `AsBytes` should be able to provide its byte
representation. Introduce the `as_bytes` method that returns the
implementer as a stream of bytes, and provide a default implementation
that should be suitable for any type that satisfies `AsBytes`'s safety
requirements.
[acourbot@nvidia.com: use fully qualified `core::mem::size_of_val` to
build with Rust 1.78.]
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20250801-as_bytes-v5-1-975f87d5dc85@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Refactor the `FromBytes` and `AsBytes` traits from `types.rs` into a new
`transmute.rs` module:
- Add `rust/kernel/transmute.rs` with the definitions of `FromBytes`
and `AsBytes`.
- Remove the same trait definitions from `rust/kernel/types.rs`.
- Update `rust/kernel/uaccess.rs` to import `AsBytes` and `FromBytes`
from `transmute.rs`.
The traits and their implementations remain unchanged.
Suggested-by: Benno Lossin <benno.lossin@proton.me>
Link: https://github.com/Rust-for-Linux/linux/issues/1117
Signed-off-by: Aliet Exposito Garcia <aliet.exposito@gmail.com>
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20240918225115.2309224-2-aliet.exposito@gmail.com
[ Rebased on top of the lints series and slightly reworded. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
