netdev - RE: [PATCH net-next v1] net: mvneta: Avoid the misuse of the '

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Message-ID: <d1709ca244ac45cd8a7361d7cbd0ea66@AcuMS.aculab.com>
Date: Thu, 5 Sep 2024 08:30:59 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Yan Zhen' <yanzhen@...o.com>, "marcin.s.wojtas@...il.com"
	<marcin.s.wojtas@...il.com>, "davem@...emloft.net" <davem@...emloft.net>,
	"edumazet@...gle.com" <edumazet@...gle.com>, "kuba@...nel.org"
	<kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"openkernel.kernel@...o.com" <openkernel.kernel@...o.com>, "horms@...nel.org"
	<horms@...nel.org>
Subject: RE: [PATCH net-next v1] net: mvneta: Avoid the misuse of the '_t'
 variants

From: Yan Zhen
> Sent: 05 September 2024 07:37
> 
> Type conversions (especially when narrowing down types) can lead to
> unexpected behavior and should be done with extreme caution.
> 
> In this case if someone tries to set the tx_pending to 65536(0x10000),
> after forcing it to convert to u16, it becomes 0x0000, they will get
> the minimum supported size and not the maximum.
> 
> Based on previous discussions [1], such behavior may confuse users or even
> create unexpected errors.
> 
> [1] https://lore.kernel.org/netdev/d23dfbf563714d7090d163a075ca9a51@AcuMS.aculab.com/
> 
> Signed-off-by: Yan Zhen <yanzhen@...o.com>

Reviewed-by: david.laight@...lab.com

> ---
>  drivers/net/ethernet/marvell/mvneta.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index d72b2d5f96db..b41de182cc88 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -4753,8 +4753,8 @@ mvneta_ethtool_set_ringparam(struct net_device *dev,
>  	pp->rx_ring_size = ring->rx_pending < MVNETA_MAX_RXD ?
>  		ring->rx_pending : MVNETA_MAX_RXD;
> 
> -	pp->tx_ring_size = clamp_t(u16, ring->tx_pending,
> -				   MVNETA_MAX_SKB_DESCS * 2, MVNETA_MAX_TXD);
> +	pp->tx_ring_size = clamp(ring->tx_pending,
> +				 MVNETA_MAX_SKB_DESCS * 2, MVNETA_MAX_TXD);
>  	if (pp->tx_ring_size != ring->tx_pending)
>  		netdev_warn(dev, "TX queue size set to %u (requested %u)\n",
>  			    pp->tx_ring_size, ring->tx_pending);
> --
> 2.34.1

-
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