linux-kernel - Re: [PATCH] net: nixge: fix warnings on 32-bit platforms

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Date:   Wed, 26 Sep 2018 09:03:29 -0700
From:   Moritz Fischer <mdf@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Moritz Fischer <mdf@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: nixge: fix warnings on 32-bit platforms

Hi Arnd,

On Wed, Sep 26, 2018 at 02:47:24PM +0200, Arnd Bergmann wrote:
> Making it work on 64-bit caused 32-bit builds to regress:
> 
> drivers/net/ethernet/ni/nixge.c: In function 'nixge_hw_dma_bd_release':
> drivers/net/ethernet/ni/nixge.c:254:9: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>    skb = (struct sk_buff *)
>          ^
> In file included from include/linux/skbuff.h:17,
>                  from include/linux/if_ether.h:23,
>                  from include/linux/etherdevice.h:25,
>                  from drivers/net/ethernet/ni/nixge.c:7:
> drivers/net/ethernet/ni/nixge.c: In function 'nixge_hw_dma_bd_init':
> drivers/net/ethernet/ni/nixge.c:130:37: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    (bd)->field##_lo = lower_32_bits(((u64)addr)); \
>                                      ^
> include/linux/kernel.h:234:33: note: in definition of macro 'lower_32_bits'
>  #define lower_32_bits(n) ((u32)(n))
>                                  ^
> 
> Casting to a uintptr_t avoids all these warnings.
> 
> Fixes: 7e8d5755be0e ("net: nixge: Add support for 64-bit platforms")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/ethernet/ni/nixge.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ni/nixge.c b/drivers/net/ethernet/ni/nixge.c
> index 74cf52e3fb09..2e132f6a7c36 100644
> --- a/drivers/net/ethernet/ni/nixge.c
> +++ b/drivers/net/ethernet/ni/nixge.c
> @@ -127,8 +127,8 @@ struct nixge_hw_dma_bd {
>  #ifdef CONFIG_PHYS_ADDR_T_64BIT
>  #define nixge_hw_dma_bd_set_addr(bd, field, addr) \
>  	do { \
> -		(bd)->field##_lo = lower_32_bits(((u64)addr)); \
> -		(bd)->field##_hi = upper_32_bits(((u64)addr)); \
> +		(bd)->field##_lo = lower_32_bits(((uintptr_t)addr)); \
> +		(bd)->field##_hi = upper_32_bits(((uintptr_t)addr)); \
>  	} while (0)
>  #else
>  #define nixge_hw_dma_bd_set_addr(bd, field, addr) \
> @@ -251,7 +251,7 @@ static void nixge_hw_dma_bd_release(struct net_device *ndev)
>  				 NIXGE_MAX_JUMBO_FRAME_SIZE,
>  				 DMA_FROM_DEVICE);
>  
> -		skb = (struct sk_buff *)
> +		skb = (struct sk_buff *)(uintptr_t)
>  			nixge_hw_dma_bd_get_addr(&priv->rx_bd_v[i],
>  						 sw_id_offset);
>  		dev_kfree_skb(skb);
> @@ -601,8 +601,8 @@ static int nixge_recv(struct net_device *ndev, int budget)
>  		tail_p = priv->rx_bd_p + sizeof(*priv->rx_bd_v) *
>  			 priv->rx_bd_ci;
>  
> -		skb = (struct sk_buff *)nixge_hw_dma_bd_get_addr(cur_p,
> -								 sw_id_offset);
> +		skb = (struct sk_buff *)(uintptr_t)
> +			nixge_hw_dma_bd_get_addr(cur_p, sw_id_offset);
>  
>  		length = cur_p->status & XAXIDMA_BD_STS_ACTUAL_LEN_MASK;
>  		if (length > NIXGE_MAX_JUMBO_FRAME_SIZE)
> -- 
> 2.18.0
> 

I had submitted a similar patch https://lkml.org/lkml/2018/9/24/1719
here. I should probably add the Fixes tag yours has but other than that
they look largely equivalent. Comments?

Thanks,

Moritz