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

Ryosuke Yasuoka
2025-10-15T04:03:21Z

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
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2.51.0