netdev - Re: [PATCH net-next 6/7] drivers: net: smc911x: Fix cast from pointer to integer of different size

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Message-ID: <20201102154745.39cd54ef@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
Date:   Mon, 2 Nov 2020 15:47:45 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev <netdev@...r.kernel.org>, Nicolas Pitre <nico@...xnic.net>
Subject: Re: [PATCH net-next 6/7] drivers: net: smc911x: Fix cast from
 pointer to integer of different size

On Sat, 31 Oct 2020 01:49:57 +0100 Andrew Lunn wrote:
> drivers/net/ethernet/smsc/smc911x.c: In function ‘smc911x_hardware_send_pkt’:
> drivers/net/ethernet/smsc/smc911x.c:471:11: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
>   471 |  cmdA = (((u32)skb->data & 0x3) << 16) |
> 
> When built on 64bit targets, the skb->data pointer cannot be cast to a
> u32 in a meaningful way. Use long instead.
> 
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> ---
>  drivers/net/ethernet/smsc/smc911x.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/smsc/smc911x.c b/drivers/net/ethernet/smsc/smc911x.c
> index 4ec292563f38..f37832540364 100644
> --- a/drivers/net/ethernet/smsc/smc911x.c
> +++ b/drivers/net/ethernet/smsc/smc911x.c
> @@ -466,9 +466,9 @@ static void smc911x_hardware_send_pkt(struct net_device *dev)
>  			TX_CMD_A_INT_FIRST_SEG_ | TX_CMD_A_INT_LAST_SEG_ |
>  			skb->len;
>  #else
> -	buf = (char*)((u32)skb->data & ~0x3);
> -	len = (skb->len + 3 + ((u32)skb->data & 3)) & ~0x3;
> -	cmdA = (((u32)skb->data & 0x3) << 16) |
> +	buf = (char *)((long)skb->data & ~0x3);
> +	len = (skb->len + 3 + ((long)skb->data & 3)) & ~0x3;
> +	cmdA = (((long)skb->data & 0x3) << 16) |

Probably best if you swap the (long) for something unsigned here as
well.