netdev - Re: [PATCH v6 net-next 1/6] net: fec: use a member variable for maximum buffer size

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Message-ID: <20250909170053.6d0eb1b7@kernel.org>
Date: Tue, 9 Sep 2025 17:00:53 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Shenwei Wang <shenwei.wang@....com>
Cc: Wei Fang <wei.fang@....com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
 Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel
 Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>, Clark Wang
 <xiaoning.wang@....com>, Stanislav Fomichev <sdf@...ichev.me>,
 imx@...ts.linux.dev, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-imx@....com, Andrew Lunn <andrew@...n.ch>, Frank Li
 <frank.li@....com>
Subject: Re: [PATCH v6 net-next 1/6] net: fec: use a member variable for
 maximum buffer size

On Mon,  8 Sep 2025 11:17:50 -0500 Shenwei Wang wrote:
> -#define	OPT_FRAME_SIZE	(PKT_MAXBUF_SIZE << 16)
> -#else
> -#define	OPT_FRAME_SIZE	0
> +#define	OPT_ARCH_HAS_MAX_FL
>  #endif

> +#ifdef OPT_ARCH_HAS_MAX_FL
> +	rcntl |= fep->max_buf_size << 16;
> +#endif

We try to avoid ifdefs inside C functions, they make compilation
coverage harder. Could you define OPT_ARCH_HAS_MAX_FL to 0 or 1
depending on the platform, and then use:

	if (OPT_ARCH_HAS_MAX_FL)
		rcntl |= fep->max_buf_size << 16;

The compiler will eliminate the condition if it's a constant,
but its slightly easier to read and lets the compiler see the code
regardless of the arch.