linux-kernel - Re: [PATCH 1/2] rust: Add initial interconnect framework abstractions

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Message-ID: <4c9e4399-7337-43dd-9efc-c530d0989bbb@oss.qualcomm.com>
Date: Wed, 23 Jul 2025 13:36:08 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Daniel Sedlak <daniel@...lak.dev>, Konrad Dybcio
 <konradybcio@...nel.org>,
        Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron
 <bjorn3_gh@...tonmail.com>,
        Benno Lossin <lossin@...nel.org>,
        Andreas Hindborg <a.hindborg@...nel.org>,
        Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
        Danilo Krummrich <dakr@...nel.org>, Georgi Djakov <djakov@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Bjorn Andersson <bjorn.andersson@....qualcomm.com>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH 1/2] rust: Add initial interconnect framework abstractions

On 7/23/25 12:44 PM, Daniel Sedlak wrote:
> Hi Konrad,

[...]

>> +    /// Create a new instance from bits (b) per second
>> +    pub const fn from_bits_per_sec(_bps: u32) -> Self {
>> +        Self(1)
>> +    }
> 
> This is a very shady API. If I were to call
> 
>     let bw = IccBwUnit::from_bits_per_sec(16);
> 
> I would expect.
> 
>     assert_eq!(bw.as_bytes_per_sec(), 2);
> 
> But it would fail (assuming that 8 bits = 1 byte), since IccBwUnit::from_bits_per_sec(), always assigns 1.

I followed the C api:

include/linux/interconnect.h
18:#define bps_to_icc(x)        (1)

But indeed, something like bw.div_ceil(8) makes more logical sense


>> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
>> index 87bcaa1c6b8a6291e71905e8dde60d945b654b98..60f6ac6e79cce57a8538ea0ad48f34f51af91731 100644
>> --- a/rust/kernel/lib.rs
>> +++ b/rust/kernel/lib.rs
>> @@ -89,6 +89,7 @@
>>   pub mod fmt;
>>   pub mod fs;
>>   pub mod init;
>> +pub mod icc;
> 
> Nit: formatting/missing space?

No, it's actually fine.. git decided that context lines shall begin
with a space

Konrad