linux-kernel - Re: [PATCH v2] 3c59x: fix bad split of cpu_to_le32(pci_map

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Message-ID: <20140925160230.GF32725@hmsreliant.think-freely.org>
Date:	Thu, 25 Sep 2014 12:02:30 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Sylvain 'ythier' Hitier <sylvain.hitier@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Meelis Roos <mroos@...ux.ee>
Subject: Re: [PATCH v2] 3c59x: fix bad split of cpu_to_le32(pci_map_single())

On Thu, Sep 25, 2014 at 03:15:19PM +0000, Sylvain 'ythier' Hitier wrote:
> Hello,
> 
> When: 2014-09-24_3@...16-47 -0400
> Who:  Neil Horman
> What:
> > You do probably want to fixup
> > the changelog to be a bit more clear as to whats going on here.
> 
> Date:   Wed Sep 24 09:22:16 2014 +0000
> 
> 3c59x: fix bad split of cpu_to_le32(pci_map_single())
> 
> In commit 6f2b6a3005b2c34c39f207a87667564f64f2f91a,
>   # 3c59x: Add dma error checking and recovery
> the intent is to split out the mapping from the byte-swapping in order to
> insert a dma_mapping_error() check.
> 
> Kinda this semantic patch:
> 
>     // See http://coccinelle.lip6.fr/
>     //
>     // Beware, grouik-and-dirty!
>     @@
>     expression DEV, X, Y, Z;
>     @@
>     -   cpu_to_le32(pci_map_single(DEV, X, Y, Z))
>     +   dma_addr_t addr = pci_map_single(DEV, X, Y, Z);
>     +   if (dma_mapping_error(&DEV->dev, addr))
>     +       /* snip */;
>     +   cpu_to_le32(addr)
> 
> However, the #else part (of the #if DO_ZEROCOPY test) is changed this way:
> 
>     -   cpu_to_le32(pci_map_single(DEV, X, Y, Z))
>     +   dma_addr_t addr = cpu_to_le32(pci_map_single(DEV, X, Y, Z));
>     //                    ^^^^^^^^^^^
>     //                    That mismatches the 3 other changes!
>     +   if (dma_mapping_error(&DEV->dev, addr))
>     +       /* snip */;
>     +   cpu_to_le32(addr)
> 
> Let's remove the leftover cpu_to_le32() for coherency.
> 
> v2: Better changelog.
> 
> Fixes: 6f2b6a3005b2c34c39f207a87667564f64f2f91a
>   # 3c59x: Add dma error checking and recovery
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Meelis Roos <mroos@...ux.ee>
> Cc: Neil Horman <nhorman@...driver.com>
> Signed-off-by: Sylvain "ythier" Hitier <sylvain.hitier@...il.com>
> ---
>  drivers/net/ethernet/3com/3c59x.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/3com/3c59x.c b/drivers/net/ethernet/3com/3c59x.c
> index 8ca49f04..0a3108b3 100644
> --- a/drivers/net/ethernet/3com/3c59x.c
> +++ b/drivers/net/ethernet/3com/3c59x.c
> @@ -2214,7 +2214,7 @@ boomerang_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  		}
>  	}
>  #else
> -	dma_addr = cpu_to_le32(pci_map_single(VORTEX_PCI(vp), skb->data, skb->len, PCI_DMA_TODEVICE));
> +	dma_addr = pci_map_single(VORTEX_PCI(vp), skb->data, skb->len, PCI_DMA_TODEVICE);
>  	if (dma_mapping_error(&VORTEX_PCI(vp)->dev, dma_addr))
>  		goto out_dma_err;
>  	vp->tx_ring[entry].addr = cpu_to_le32(dma_addr);
> 
> Regards,
> Sylvain "ythier" Hitier
> 
> -- 
> Business is about being busy, not being rich...
> Lived 777 days in a Debian package => http://en.wikipedia.org/wiki/Apt,_Vaucluse
> There's THE room for ideals in this mechanical place!
> 
Acked-by: Neil Horman <nhorman@...driver.com>
Thanks!
Neil

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