Subject: Re: [PATCH net-next 11/15] net: macb: replace min() with umin() calls

From: David Laight <[email-masked]>
Date: Sun, 19 Oct 2025 15:10:59 +0100

On Tue, 14 Oct 2025 17:25:12 +0200
Théo Lebrun <[email-masked]> wrote:

> Whenever min(a, b) is used with a and b unsigned variables or literals,
> `make W=2` complains. Change four min() calls into umin().

It will, and you'll get the same 'error' all over the place.
Basically -Wtype-limits is broken.

Don't remove valid checks because it bleats.

	David

> 
> stderr extract (GCC 11.2.0, MIPS Codescape):
> 
> ./include/linux/minmax.h:68:57: warning: comparison is always true due
>                           to limited range of data type [-Wtype-limits]
>    68 | #define __is_nonneg(ux) statically_true((long long)(ux) >= 0)
>       |                                                         ^~
> drivers/net/ethernet/cadence/macb_main.c:2299:26: note: in expansion of
>                                                             macro ‘min’
>  2299 |              hdrlen = min(skb_headlen(skb), bp->max_tx_length);
>       |                       ^~~
> 
> Signed-off-by: Théo Lebrun <[email-masked]>
> ---
>  drivers/net/ethernet/cadence/macb_main.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index 98e28d51a6e12c24ef27c939363eb43c0aec1951..6c6bc6aa23c718772b95b398e807f193a38e141a 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -2035,7 +2035,7 @@ static unsigned int macb_tx_map(struct macb *bp,
>  		count++;
>  		tx_head++;
>  
> -		size = min(len, bp->max_tx_length);
> +		size = umin(len, bp->max_tx_length);
>  	}
>  
>  	/* Then, map paged data from fragments */
> @@ -2045,7 +2045,7 @@ static unsigned int macb_tx_map(struct macb *bp,
>  		len = skb_frag_size(frag);
>  		offset = 0;
>  		while (len) {
> -			size = min(len, bp->max_tx_length);
> +			size = umin(len, bp->max_tx_length);
>  			entry = macb_tx_ring_wrap(bp, tx_head);
>  			tx_skb = &queue->tx_skb[entry];
>  
> @@ -2301,7 +2301,7 @@ static netdev_tx_t macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  			return NETDEV_TX_BUSY;
>  		}
>  	} else
> -		hdrlen = min(skb_headlen(skb), bp->max_tx_length);
> +		hdrlen = umin(skb_headlen(skb), bp->max_tx_length);
>  
>  #if defined(DEBUG) && defined(VERBOSE_DEBUG)
>  	netdev_vdbg(bp->dev,
> @@ -4573,8 +4573,8 @@ static int macb_init(struct platform_device *pdev)
>  	 * each 4-tuple define requires 1 T2 screener reg + 3 compare regs
>  	 */
>  	reg = gem_readl(bp, DCFG8);
> -	bp->max_tuples = min((GEM_BFEXT(SCR2CMP, reg) / 3),
> -			GEM_BFEXT(T2SCR, reg));
> +	bp->max_tuples = umin((GEM_BFEXT(SCR2CMP, reg) / 3),
> +			      GEM_BFEXT(T2SCR, reg));
>  	INIT_LIST_HEAD(&bp->rx_fs_list.list);
>  	if (bp->max_tuples > 0) {
>  		/* also needs one ethtype match to check IPv4 */
>