linux-kernel - [PATCH rust-next v2 0/3] rust: miscdevice: add llseek support

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Message-ID: <20251015040246.151141-1-ryasuoka@redhat.com>
Date: Wed, 15 Oct 2025 13:02:40 +0900
From: Ryosuke Yasuoka <ryasuoka@...hat.com>
To: arnd@...db.de,
	gregkh@...uxfoundation.org,
	ojeda@...nel.org,
	alex.gaynor@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	lossin@...nel.org,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu,
	dakr@...nel.org,
	viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz
Cc: Ryosuke Yasuoka <ryasuoka@...hat.com>,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH rust-next v2 0/3] rust: miscdevice: add llseek support

Hi all,

This patch series add support for the llseek file operation to misc
devices written in Rust.

The first patch introduces pos()/pos_mut() methods to LocalFile and
File. These helpers allow to refer to the file's position, which is
required for implementing lseek in misc_device.

The second patch adds the llseek hook to the MiscDevice trait, enabling
Rust drivers to implement the seeking logic.

The last one updates the rust_misc_device sample to demonstrate the
usage of the new llseek hook, including a C test program that verifies
the functionality.

history of this patch:

v2:
- Introduce pos() and pos_mut() methods to get file positions,
and use them in sample programs.
- Add read, write and lseek in the userspace sample program. 
- Remove unsafe block from the sample program. 
- In this v2 patch, remove SEEK_END related codes from
a sample program because it needs inode->i_size which has not
implemented yet. The purpose of this patch is to introduce
lseek(). Since implementing an 'inode wrap' requires more
extensive discussion than adding llseek hook(), I just
exclude it from this patch series. I believe that whether
SEEK_END is supported or not has no impact on adding lseek()
to MiscDevice.

v1:
https://lore.kernel.org/rust-for-linux/20250818135846.133722-1-ryasuoka@redhat.com/


Ryosuke Yasuoka (3):
  rust: fs: add pos/pos_mut methods for LocalFile struct
  rust: miscdevice: add llseek support
  rust: samples: miscdevice: add lseek samples

 rust/kernel/fs/file.rs           | 61 ++++++++++++++++++++++++++++
 rust/kernel/miscdevice.rs        | 36 +++++++++++++++++
 samples/rust/rust_misc_device.rs | 68 ++++++++++++++++++++++++++++++++
 3 files changed, 165 insertions(+)


base-commit: 98906f9d850e4882004749eccb8920649dc98456
-- 
2.51.0