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Date: Wed, 18 Mar 2026 01:21:59 +0100
Message-Id: <DH5H95R3ZKJK.3SMHG8B4JP051@kernel.org>
To: "John Hubbard" <jhubbard@nvidia.com>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH v7 18/31] gpu: nova-core: add MCTP/NVDM protocol types
 for firmware communication
Cc: "Alexandre Courbot" <acourbot@nvidia.com>, "Joel Fernandes"
 <joelagnelf@nvidia.com>, "Timur Tabi" <ttabi@nvidia.com>, "Alistair Popple"
 <apopple@nvidia.com>, "Eliot Courtney" <ecourtney@nvidia.com>, "Shashank
 Sharma" <shashanks@nvidia.com>, "Zhi Wang" <zhiw@nvidia.com>, "David
 Airlie" <airlied@gmail.com>, "Simona Vetter" <simona@ffwll.ch>, "Bjorn
 Helgaas" <bhelgaas@google.com>, "Miguel Ojeda" <ojeda@kernel.org>, "Alex
 Gaynor" <alex.gaynor@gmail.com>, "Boqun Feng" <boqun.feng@gmail.com>, "Gary
 Guo" <gary@garyguo.net>, =?utf-8?q?Bj=C3=B6rn_Roy_Baron?=
 <bjorn3_gh@protonmail.com>, "Benno Lossin" <lossin@kernel.org>, "Andreas
 Hindborg" <a.hindborg@kernel.org>, "Alice Ryhl" <aliceryhl@google.com>,
 "Trevor Gross" <tmgross@umich.edu>, <rust-for-linux@vger.kernel.org>,
 "LKML" <linux-kernel@vger.kernel.org>
References: <20260317225355.549853-1-jhubbard@nvidia.com>
 <20260317225355.549853-19-jhubbard@nvidia.com>
 <b6d58cbe-a375-40f4-ae70-a3d7344160e5@nvidia.com>
In-Reply-To: <b6d58cbe-a375-40f4-ae70-a3d7344160e5@nvidia.com>

On Wed Mar 18, 2026 at 1:01 AM CET, John Hubbard wrote:
> On 3/17/26 3:53 PM, John Hubbard wrote:
> ...
>> +bitfield! {
>> +    pub(crate) struct MctpHeader(u32), "MCTP transport header for NVIDI=
A firmware messages." {
>> +        31:31 som as bool, "Start-of-message bit.";
>> +        30:30 eom as bool, "End-of-message bit.";
>> +        29:28 seq as u8, "Packet sequence number.";
>> +        23:16 seid as u8, "Source endpoint ID.";
>
> hmmm, I seem to remember my very slightly younger self insisting
> that fields be listed from lowest to highest bits. And now I've
> violated that in both headers in this patch. arghh

My now slightly older self still thinks that what you have above is actuall=
y the
way to go. So, I think your current self intuitively did the right thing. :=
P

It should be either

	31:16
	15:0

or it should be

	0:15
	16:31

with a strong preference for the former, but this

	15:0
	31:16

still looks pretty odd to me.