linux-kernel - Re: [PATCH net-next 1/6] tools: ynl-gen: bitshift the flag values in the generated code

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Message-ID: <d3f1427f-e8bc-4ab0-bf15-171b701325b9@fiberby.net>
Date: Tue, 14 Oct 2025 16:49:22 +0000
From: Asbjørn Sloth Tønnesen <ast@...erby.net>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 Alexei Starovoitov <ast@...nel.org>, Andrew Lunn <andrew+netdev@...n.ch>,
 Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
 Daniel Borkmann <daniel@...earbox.net>, Daniel Zahka
 <daniel.zahka@...il.com>, Donald Hunter <donald.hunter@...il.com>,
 Jacob Keller <jacob.e.keller@...el.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>, Jiri Pirko <jiri@...nulli.us>,
 Joe Damato <jdamato@...tly.com>, John Fastabend <john.fastabend@...il.com>,
 Jonathan Corbet <corbet@....net>, Simon Horman <horms@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>,
 Toke Høiland-Jørgensen <toke@...hat.com>,
 Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
 Willem de Bruijn <willemb@...gle.com>, bpf@...r.kernel.org,
 netdev@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/6] tools: ynl-gen: bitshift the flag values in
 the generated code

On 10/14/25 12:53 AM, Jakub Kicinski wrote:
> On Mon, 13 Oct 2025 16:49:58 +0000 Asbjørn Sloth Tønnesen wrote:
>> Instead of pre-computing the flag values within the code generator,
>> then move the bitshift operation into the generated code.
>>
>> This IMHO makes the generated code read more like handwritten code.
> 
> I like it the way it is. The values are irrelevant.

Bit-shifting seams like the preferred way across the uAPI headers.

Would you be open to hexadecimal notation, if not bit-shifting?

Currently NLA_POLICY_MASK() is generated with a hexadecimal mask, and
with these patches, if render-max is not set. If using literal values
then we should properly consistently generate them as either decimal
or hexadecimal. I prefer hexadecimal over decimal.

> And returning a string from user_value() is quite ugly.
It only returns a string, when as_c is set, I am happy to duplicate
some code instead, and add a dedicated method always returning a string,
but can we please agree on the generated output, before implementation?