Re: [PATCH v11 2/7] rust: debugfs: Add support for read-only files

[Danilo Krummrich <dakr@kernel.org>]

[-- Attachment #1: Type: text/plain, Size: 261 bytes --]

On 9/8/25 6:19 PM, Greg Kroah-Hartman wrote:
> Working code for the simple "foo" example will be good.  Here's my
> horrible (and will not build) example I was trying to get to work.

I think our examples were pretty close already, but here's also your file. :)

[-- Attachment #2: rust_debugfs2.rs --]
[-- Type: text/rust, Size: 2418 bytes --]

// SPDX-License-Identifier: GPL-2.0

// Copyright (C) 2025 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
// Copyright (C) 2025 The Linux Foundation

//! Sample debugfs rust module that emulates soc_info to try to see just how well the api can
//! work...

use core::fmt;
use kernel::c_str;
use kernel::debugfs::{Dir, Scope};
use kernel::prelude::*;

module! {
    type: SocInfo,
    name: "rust_soc_info",
    authors: ["Greg Kroah-Hartman"],
    description: "Rust soc_info sample driver",
    license: "GPL",
}

fn foundry_print(foundry: &u32, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    writeln!(f, "Foundry: {}", foundry)
}

// Fake "hardware SOC info object that ideally would read from the hardware to get the info.
// For now just use some fake data
#[derive(Debug)]
struct HwSocInfo {
    id: u32,
    ver: u32,
    raw_id: u32,
    foundry: u32,
    name: &'static CStr,
}

impl HwSocInfo {
    fn new() -> Self {
        Self {
            id: 123,
            ver: 456,
            raw_id: 789,
            foundry: 0,
            name: c_str!("hw_soc name"),
        }
    }
}

struct SocInfo {
    _debug_dir: Dir,
    _hw_soc_info: Pin<KBox<Scope<HwSocInfo>>>,
}

impl kernel::Module for SocInfo {
    fn init(_this: &'static ThisModule) -> Result<Self> {
        // Read from the hardware and get our structure information
        let hw_soc_info = HwSocInfo::new();

        // Create the root directory
        let root = Dir::new(c_str!("rust_soc_info"));

        let scope = KBox::pin_init(
            // Create directory scope, that contains some data and a bunch of files exporting this
            // data.
            root.scope(hw_soc_info, c_str!("hw_soc_info"), |hw_soc_info, dir| {
                dir.read_only_file(c_str!("id"), &hw_soc_info.id);
                dir.read_only_file(c_str!("ver"), &hw_soc_info.ver);
                dir.read_only_file(c_str!("raw_id"), &hw_soc_info.raw_id);
                dir.read_only_file(c_str!("name"), &hw_soc_info.name);
                dir.read_callback_file(c_str!("foundry"), &hw_soc_info.foundry, &foundry_print);
            }),
            GFP_KERNEL,
        )?;

        let soc_info: &HwSocInfo = &scope;

        // Print the contents of `soc_info` that were moved into `scope`.
        pr_info!("HwSocInfo: {:?}\n", soc_info);

        Ok(Self {
            _debug_dir: root,
            _hw_soc_info: scope,
        })
    }
}