netdev - [PATCH v4 1/7] via-velocity: Correct 64-byte alignment for rx buffers

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Date:	Thu, 26 Nov 2009 09:09:53 +0100
From:	Simon Kagstrom <simon.kagstrom@...insight.net>
To:	netdev@...r.kernel.org
Cc:	davem@...emloft.net, davej@...hat.com, shemminger@...tta.com,
	romieu@...zoreil.com
Subject: [PATCH v4 1/7] via-velocity: Correct 64-byte alignment for rx
 buffers

(From the VIA driver). The current code does not guarantee 64-byte
alignment since it simply does

        int add = skb->data & 63;

        skb->data += add;

(via skb_reserve). So for example, if the skb->data address would be
0x10, this would result in 32-byte alignment (0x10 + 0x10).

Correct by adding

        64 - (skb->data & 63)

instead.

Signed-off-by: Simon Kagstrom <simon.kagstrom@...insight.net>
---
 drivers/net/via-velocity.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/net/via-velocity.c b/drivers/net/via-velocity.c
index e04e5be..b6cf3b5 100644
--- a/drivers/net/via-velocity.c
+++ b/drivers/net/via-velocity.c
@@ -1483,7 +1483,8 @@ static int velocity_alloc_rx_buf(struct velocity_info *vptr, int idx)
 	 *	Do the gymnastics to get the buffer head for data at
 	 *	64byte alignment.
 	 */
-	skb_reserve(rd_info->skb, (unsigned long) rd_info->skb->data & 63);
+	skb_reserve(rd_info->skb,
+			64 - ((unsigned long) rd_info->skb->data & 63));
 	rd_info->skb_dma = pci_map_single(vptr->pdev, rd_info->skb->data,
 					vptr->rx.buf_sz, PCI_DMA_FROMDEVICE);
 
-- 
1.6.0.4

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