linux-kernel - Re: [PATCH 4/6] rust: addr: Add a module to declare core address types

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Message-ID: <Z6Da4XV5hcTfBiNH@tardis.local>
Date: Mon, 3 Feb 2025 07:04:01 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Asahi Lina <lina@...hilina.net>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Jann Horn <jannh@...gle.com>, Matthew Wilcox <willy@...radead.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Valentin Obst <kernel@...entinobst.de>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	airlied@...hat.com, Abdiel Janulgue <abdiel.janulgue@...il.com>,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
	asahi@...ts.linux.dev
Subject: Re: [PATCH 4/6] rust: addr: Add a module to declare core address
 types

On Sun, Feb 02, 2025 at 10:05:46PM +0900, Asahi Lina wrote:
> Encapsulates the core physical/DMA address types, so they can be used by
> Rust abstractions.
> 
> Signed-off-by: Asahi Lina <lina@...hilina.net>
> ---
>  rust/kernel/addr.rs | 15 +++++++++++++++
>  rust/kernel/lib.rs  |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/rust/kernel/addr.rs b/rust/kernel/addr.rs
> new file mode 100644
> index 0000000000000000000000000000000000000000..06aff10a0332355597060c5518d7fd6e114cf630
> --- /dev/null
> +++ b/rust/kernel/addr.rs
> @@ -0,0 +1,15 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Kernel core address types.
> +
> +use bindings;
> +use core::ffi;

I think we should use crate::ffi here. See:

	d072acda4862 "rust: use custom FFI integer types"

> +
> +/// A physical memory address (which may be wider than the CPU pointer size)
> +pub type PhysicalAddr = bindings::phys_addr_t;
> +/// A DMA memory address (which may be narrower than `PhysicalAddr` on some systems)
> +pub type DmaAddr = bindings::dma_addr_t;
> +/// A physical resource size, typically the same width as `PhysicalAddr`
> +pub type ResourceSize = bindings::resource_size_t;
> +/// A raw page frame number, not to be confused with the C `pfn_t` which also encodes flags.
> +pub type Pfn = ffi::c_ulong;
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index e1065a7551a39e68d6379031d80d4be336e652a3..eb1a80ba8ff83ab2d1b3b1d11fed4fb704c7a4f5 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -29,6 +29,7 @@
>  
>  pub use ffi;
>  
> +pub mod addr;

I want to share my worry on this `pub mod` list in kernel/lib.rs may get
too long ;-)

I was about to suggest putting `addr` and `page` into `mm` after Alice's
patchset merged, however, seems that `mm` mod only cover userspace
memory management (which is not my impression of what "mm" in kernel
development), thoughts? Alice, do you think we should extend `mm` mod to
contain all memory management mods?

Regards,
Boqun

>  pub mod alloc;
>  #[cfg(CONFIG_BLOCK)]
>  pub mod block;
> 
> -- 
> 2.47.1
>