linux-kernel - Re: [PATCH v4 11/15] rnull: enable configuration via `configfs`

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Message-ID: <CAH5fLggraEP7bwzJ+4ww8-7Ku-Z+d0Em3=NDUpa7r8oTLQy81A@mail.gmail.com>
Date: Wed, 13 Aug 2025 15:54:41 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: Boqun Feng <boqun.feng@...il.com>, 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 <lossin@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 11/15] rnull: enable configuration via `configfs`

On Wed, Aug 13, 2025 at 3:47 PM Andreas Hindborg <a.hindborg@...nel.org> wrote:
>
> "Alice Ryhl" <aliceryhl@...gle.com> writes:
>
> > On Tue, Aug 12, 2025 at 10:44:29AM +0200, Andreas Hindborg wrote:
> >> Allow rust null block devices to be configured and instantiated via
> >> `configfs`.
> >>
> >> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
> >
> > Overall LGTM, but a few comments below:
> >
> >> diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
> >> new file mode 100644
> >> index 000000000000..8d469c046a39
> >> --- /dev/null
> >> +++ b/drivers/block/rnull/configfs.rs
> >> @@ -0,0 +1,218 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +
> >> +use super::{NullBlkDevice, THIS_MODULE};
> >> +use core::fmt::Write;
> >> +use kernel::{
> >> +    block::mq::gen_disk::{GenDisk, GenDiskBuilder},
> >> +    c_str,
> >> +    configfs::{self, AttributeOperations},
> >> +    configfs_attrs, new_mutex,
> >
> > It would be nice to add
> >
> >       pub use configfs_attrs;
> >
> > to the configfs module so that you can import the macro from the
> > configfs module instead of the root.
>
> OK, I'll do that.
>
> >
> >> +            try_pin_init!( DeviceConfig {
> >> +                data <- new_mutex!( DeviceConfigInner {
> >
> > Extra spaces in these macros.
>
> Thanks. I subconsciously like the space in that location, so when
> rustfmt is bailing, I get these things in my code.
>
> >> +        let power_op_str = core::str::from_utf8(page)?.trim();
> >> +
> >> +        let power_op = match power_op_str {
> >> +            "0" => Ok(false),
> >> +            "1" => Ok(true),
> >> +            _ => Err(EINVAL),
> >> +        }?;
> >
> > We probably want kstrtobool here instead of manually parsing the
> > boolean.
>
> Yea, I was debating on this a bit. I did want to consolidate this code,
> but I don't particularly like ktostrbool. But I guess in the name of
> consistency across the kernel it is the right choice.
>
> I'll add it to next spin.

For your convenience, I already wrote a safe wrapper of kstrtobool for
an out-of-tree driver. You're welcome to copy-paste this:

fn kstrtobool(kstr: &CStr) -> Result<bool> {
    let mut res = false;
    to_result(unsafe {
kernel::bindings::kstrtobool(kstr.as_char_ptr(), &mut res) })?;
    Ok(res)
}

Alice