linux-kernel - Re: [PATCH v4 08/20] gpu: nova-core: allow register aliases

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Message-ID: <aC2Quag3HYN70D8p@pollux>
Date: Wed, 21 May 2025 10:37:13 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Alexandre Courbot <acourbot@...dia.com>
Cc: 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 <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	John Hubbard <jhubbard@...dia.com>, Ben Skeggs <bskeggs@...dia.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Timur Tabi <ttabi@...dia.com>, Alistair Popple <apopple@...dia.com>,
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
	nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v4 08/20] gpu: nova-core: allow register aliases

On Wed, May 21, 2025 at 03:45:03PM +0900, Alexandre Courbot wrote:
> Some registers (notably scratch registers) don't have a definitive
> purpose, but need to be interpreted differently depending on context.
> 
> Expand the register!() macro to support a syntax indicating that a
> register type should be at the same offset as another one, but under a
> different name, and with different fields and documentation.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
>  drivers/gpu/nova-core/regs/macros.rs | 40 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 38 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/regs/macros.rs b/drivers/gpu/nova-core/regs/macros.rs
> index 7cd013f3c90bbd8ca437d4072cae8f11d7946fcd..64dda1d4d93d3c7022ef02b6f6fb81b58e90dd44 100644
> --- a/drivers/gpu/nova-core/regs/macros.rs
> +++ b/drivers/gpu/nova-core/regs/macros.rs
> @@ -71,6 +71,20 @@
>  /// pr_info!("CPU CTL: {:#x}", cpuctl);
>  /// cpuctl.set_start(true).write(&bar, CPU_BASE);
>  /// ```
> +///
> +/// It is also possible to create a alias register by using the `=> PARENT` syntax. This is useful
> +/// for cases where a register's interpretation depends on the context:
> +///
> +/// ```no_run
> +/// register!(SCRATCH_0 @ 0x0000100, "Scratch register 0" {
> +///    31:0     value as u32, "Raw value";
> +///
> +/// register!(SCRATCH_0_BOOT_STATUS => SCRATCH_0, "Boot status of the firmware" {

NIT: I'd put the arrow the other way around, i.e. SCRATCH_0_BOOT_STATUS is
derived from SCRATCH_0, not the other way around.