linux-kernel - Re: [PATCH v7.1 2/4] gpu: nova-core: bitfield: Move bitfield-specific code from register! into new macro

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Message-ID: <e4f5ca12-bf67-4b48-97a1-7ab2c771056e@nvidia.com>
Date: Thu, 16 Oct 2025 12:39:31 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Danilo Krummrich <dakr@...nel.org>, Joel Fernandes <joelagnelf@...dia.com>
Cc: Yury Norov <yury.norov@...il.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "rust-for-linux@...r.kernel.org" <rust-for-linux@...r.kernel.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 Alexandre Courbot <acourbot@...dia.com>, Alistair Popple
 <apopple@...dia.com>, Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
 Gary Guo <gary@...yguo.net>,
 "bjorn3_gh@...tonmail.com" <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>,
 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>,
 Timur Tabi <ttabi@...dia.com>,
 "joel@...lfernandes.org" <joel@...lfernandes.org>,
 Elle Rhumsaa <elle@...thered-steel.dev>,
 Daniel Almeida <daniel.almeida@...labora.com>,
 "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
 Edwin Peer <epeer@...dia.com>
Subject: Re: [PATCH v7.1 2/4] gpu: nova-core: bitfield: Move bitfield-specific
 code from register! into new macro

On 10/16/25 12:34 PM, Danilo Krummrich wrote:
> On Thu Oct 16, 2025 at 9:28 PM CEST, Joel Fernandes wrote:
>>> On Oct 16, 2025, at 1:48 PM, Yury Norov <yury.norov@...il.com> wrote:
>>> On Thu, Oct 16, 2025 at 11:13:21AM -0400, Joel Fernandes wrote:
...
> While I'm not super opinionated for general bitfields, for the register!()
> infrastructure I very much prefer the hi:lo notation, as this is the common
> notation in datasheets and TRMs.
> 
> However, if we use hi:lo, we should use it decending, i.e.:
> 

Sure, descending works.

> 	bitfield! {
> 	    struct ControlReg {
> 	        7:5 state as u8 => State;
> 	        3:0 mode as u8 ?=> Mode;

And hi:lo matches our HW reference manuals. And if you're dealing
with bitfields, you are often also dealing with HW, so this is
a reasonable place in the SW to use hi:lo.

Looks good to me.

thanks,
-- 
John Hubbard