From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH] [V3] Add non-Virtex5 support for LL TEMAC driver
Date: Mon, 05 Apr 2010 23:29:53 +0200
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Cc: netdev@vger.kernel.org, linuxppc-dev@ozlabs.org,
	grant.likely@secretlab.ca, jwboyer@linux.vnet.ibm.com,
	john.williams@petalogix.com, michal.simek@petalogix.com,
	John Tyner <jtyner@cs.ucr.edu>
To: John Linn <john.linn@xilinx.com>
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Le lundi 05 avril 2010 =C3=A0 15:11 -0600, John Linn a =C3=A9crit :
> This patch adds support for using the LL TEMAC Ethernet driver on
> non-Virtex 5 platforms by adding support for accessing the Soft DMA
> registers as if they were memory mapped instead of solely through the
> DCR's (available on the Virtex 5).
>=20
> The patch also updates the driver so that it runs on the MicroBlaze.
> The changes were tested on the PowerPC 440, PowerPC 405, and the
> MicroBlaze platforms.
>=20
> Signed-off-by: John Tyner <jtyner@cs.ucr.edu>
> Signed-off-by: John Linn <john.linn@xilinx.com>
>=20
> ---

> +/* Align the IP data in the packet on word boundaries as MicroBlaze
> + * needs it.
> + */
> +
>  #define XTE_ALIGN       32
> -#define BUFFER_ALIGN(adr) ((XTE_ALIGN - ((u32) adr)) % XTE_ALIGN)
> +#define BUFFER_ALIGN(adr) ((34 - ((u32) adr)) % XTE_ALIGN)
> =20

Very interesting way of doing this, but why such convoluted thing ?

Because of the % 32, this is equivalent to :

#define BUFFER_ALIGN(adr) ((2 - ((u32) adr)) % XTE_ALIGN)

But wait, dont we recognise the magic constant NET_IP_ALIGN ?

So, I ask, cant you use netdev_alloc_skb_ip_align() in this driver ?