linux-kernel - Re: [PATCH v3 12/16] rnull: enable configuration via `configfs`

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Message-ID: <87sei3795e.fsf@kernel.org>
Date: Thu, 07 Aug 2025 11:50:37 +0200
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Alice Ryhl <aliceryhl@...gle.com>
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 v3 12/16] rnull: enable configuration via `configfs`

"Alice Ryhl" <aliceryhl@...gle.com> writes:

> On Fri, Jul 11, 2025 at 01:43:13PM +0200, Andreas Hindborg wrote:

..

>> +#[vtable]
>> +impl configfs::AttributeOperations<0> for DeviceConfig {
>> +    type Data = DeviceConfig;
>> +
>> +    fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        let mut writer = kernel::str::Formatter::new(page);
>> +
>> +        if this.data.lock().powered {
>> +            writer.write_fmt(fmt!("1\n"))?;
>> +        } else {
>> +            writer.write_fmt(fmt!("0\n"))?;
>
> I think these can just be
> writer.write_str("1\n")?;

Cool 👍

>
>> +        }
>> +
>> +        Ok(writer.bytes_written())
>> +    }
>> +
>> +    fn store(this: &DeviceConfig, page: &[u8]) -> Result {
>> +        let power_op: bool = core::str::from_utf8(page)?
>> +            .trim()
>> +            .parse::<u8>()
>> +            .map_err(|_| kernel::error::code::EINVAL)?
>> +            != 0;
>
> So if I write 27, that's treated as true, but if I write 300, that's an
> EINVAL?

Yea. Let's do this instead:

        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),
        }?;

It is closer to `kstrtobool`.


Best regards,
Andreas Hindborg