linux-kernel - Re: [PATCH] rust/drm: tyr: Convert to the register!() macro

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Message-Id: <1EF6A3B7-216F-47C3-8631-25C38994BAC1@collabora.com>
Date: Fri, 16 Jan 2026 09:26:55 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Dirk Behme <Dirk.Behme@...bosch.com>
Cc: Dirk Behme <dirk.behme@...il.com>,
 Danilo Krummrich <dakr@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>,
 Miguel Ojeda <ojeda@...nel.org>,
 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>,
 Trevor Gross <tmgross@...ch.edu>,
 Steven Price <steven.price@....com>,
 dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org,
 Alexandre Courbot <acourbot@...dia.com>
Subject: Re: [PATCH] rust/drm: tyr: Convert to the register!() macro

+cc Alex,


>>> +    31:0    l2_pwractive_hi as u32, "Bitmap of L2 caches active (higher 32 bits)";
>>> +});
>>> +
>>>  pub(crate) const MCU_CONTROL_ENABLE: u32 = 1;
>>>  pub(crate) const MCU_CONTROL_AUTO: u32 = 2;
>>>  pub(crate) const MCU_CONTROL_DISABLE: u32 = 0;
>>>  -pub(crate) const MCU_STATUS: Register<0x704> = Register;
>>> +register!(McuControl @ 0x700, "Controls the execution state of the MCU subsystem" {
>>> +    1:0     req as u32, "Request state change";
>>> +});
>> Any reason why req is a u32 and not a u8? Same for some other places.
>> And would it be an option to move the const MCU_CONTROL* to an ìmpl
>> McuControl Same for STATUS below.
> 
> Just fyi something like [1] builds for me.
> 
> This is inspired by
> 
> https://lore.kernel.org/rust-for-linux/20251003154748.1687160-6-joelagnelf@nvidia.com/
> 
> Best regards
> 
> Dirk
> 
> [1]
> 
> #[repr(u32)]
> #[derive(Debug, Default, Clone, Copy, PartialEq)]
> enum McuControl {
>    #[default]
>    Disable = 0,
>    Enable = 1,
>    Auto = 2,
> }
> 
> impl From<McuControl> for u8 {
>    fn from(ctrl: McuControl) -> Self {
>        ctrl as u8
>    }
> }
> 
> impl From<u8> for McuControl {
>    fn from(req: u8) -> Self {
>        match req & 0x3 {
>            0 => McuControl::Disable,
>            1 => McuControl::Enable,
>            2 => McuControl::Auto,
>            _ => McuControl::Disable,
>        }
>    }
> }
> 
> register!(MCUCONTROL @ 0x700, "Controls the execution state of the MCU subsystem" {
>    1:0     req as u8 => McuControl, "Request state change";
> });

Alex, looking at the above, I wonder if a “as Foo” would be a good
addition to the macro? That would then invoke a TryFrom implementation, i.e.:


register!(MCUCONTROL @ 0x700, "Controls the execution state of the MCU subsystem" {
   1:0     req as McuControl => McuControl, "Request state change";
});