netdev - Re: [patch] net/fec: "u32" is more explicit than "unsigned long"

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Date:	Fri, 23 Aug 2013 13:44:29 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	"David S. Miller" <davem@...emloft.net>,
	"Fabio Estevam" <fabio.estevam@...escale.com>,
	Frank Li <Frank.Li@...escale.com>,
	Jim Baxter <jim_baxter@...tor.com>,
	Fugang Duan <B38611@...escale.com>, <netdev@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <kernel-janitors@...r.kernel.org>
Subject: Re: [patch] net/fec: "u32" is more explicit than "unsigned long"

On Fri, 2013-08-23 at 12:49 +0300, Dan Carpenter wrote:
> tmpaddr[] is a six byte array.  We want to set the first four bytes on
> the first line and the remaining two on the next line.  The code assumes
> that "unsigned long" is 32 bits and obviously that's not true on 64 bit
> arches.  It's better to just use u32 instead.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
> This is a static checker thing and I can't compile this file.
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index fdf9307..422b125 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -1100,9 +1100,9 @@ static void fec_get_mac(struct net_device *ndev)
>  	 * 4) FEC mac registers set by bootloader
>  	 */
>  	if (!is_valid_ether_addr(iap)) {
> -		*((unsigned long *) &tmpaddr[0]) =
> +		*((u32 *) &tmpaddr[0]) =
>  			be32_to_cpu(readl(fep->hwp + FEC_ADDR_LOW));
> -		*((unsigned short *) &tmpaddr[4]) =
> +		*((u16 *) &tmpaddr[4]) =
>  			be16_to_cpu(readl(fep->hwp + FEC_ADDR_HIGH) >> 16);
>  		iap = &tmpaddr[0];
>  	}

This code also seems to have CPU vs big-endian byte order the wrong way
round.  readl() returns bytes in native order whereas we always store
MAC addresses in network (big-endian) order.  So I think it should be
doing:

		*((__be32 *) &tmpaddr[0]) =
			cpu_to_be32(readl(fep->hwp + FEC_ADDR_LOW));
		*((__be16 *) &tmpaddr[4]) =
			cpu_to_be16(readl(fep->hwp + FEC_ADDR_HIGH) >> 16);

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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