netdev - [PATCH V4 2/8] netdevice.h: Add a new zerocopy device flag

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Date:	Wed, 04 May 2011 00:55:17 -0700
From:	Shirley Ma <mashirle@...ibm.com>
To:	David Miller <davem@...emloft.net>, mst@...hat.com,
	Eric Dumazet <eric.dumazet@...il.com>,
	Avi Kivity <avi@...hat.com>, Arnd Bergmann <arnd@...db.de>
Cc:	netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH V4 2/8] netdevice.h: Add a new zerocopy device flag

Signed-off-by: Shirley Ma <xma@...ibm.com>
---

 include/linux/netdevice.h |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 0249fe7..0808f1e 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1067,6 +1067,16 @@ struct net_device {
 #define NETIF_F_RXHASH		(1 << 28) /* Receive hashing offload */
 #define NETIF_F_RXCSUM		(1 << 29) /* Receive checksumming offload */
 
+/*
+ * Bit 31 is for device to map userspace buffers -- zerocopy
+ * Device can set this flag when it supports HIGHDMA.
+ * Device can't recycle this kind of skb buffers.
+ * There are 256 bytes copied, the rest of buffers are mapped.
+ * The userspace callback should only be called when last reference to this skb
+ * is gone.
+ */
+#define NETIF_F_ZEROCOPY	(1 << 31)
+
 	/* Segmentation offload features */
 #define NETIF_F_GSO_SHIFT	16
 #define NETIF_F_GSO_MASK	0x00ff0000


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