Re: [PATCH net 2/2] net: macb: reject an unknown link speed in the taprio setup

[Andrew Lunn <andrew@lunn.ch>]

On Wed, Sep 02, 2026 at 08:05:28AM +0000, Aleksei Sviridkin wrote:
> speed is a u32, so SPEED_UNKNOWN arrives as 0xffffffff and passes the
> "speed <= 0" check. A taprio schedule installed while the link is down
> then has its hardware interval limit derived from that value, a limit
> that rounds to 1 ns, and the first entry fails with a misleading
> "exceeds hardware limit". Name the case instead of relying on the
> sign.
> 
> Fixes: 89934dbf169e ("net: macb: Add TAPRIO traffic scheduling support")
> Assisted-by: LLM
> Signed-off-by: Aleksei Sviridkin <f@lex.la>
> ---
>  drivers/net/ethernet/cadence/macb_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index a43855db1e45..81530b9257b2 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -4324,7 +4324,7 @@ static int macb_taprio_setup_replace(struct net_device *netdev,
>  	}
>  
>  	speed = kset.base.speed;
> -	if (unlikely(speed <= 0)) {
> +	if (unlikely(speed == SPEED_UNKNOWN || !speed)) {

Can ethtool_validate_speed() be used?

    Andrew

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