netdev - Re: [PATCH V5 2/6 net-next] netdevice.h: Add zero-copy flag in netdevice

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Date:	Mon, 16 May 2011 20:35:18 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Shirley Ma <mashirle@...ibm.com>
Cc:	David Miller <davem@...emloft.net>, mst@...hat.com,
	Eric Dumazet <eric.dumazet@...il.com>,
	Avi Kivity <avi@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V5 2/6 net-next] netdevice.h: Add zero-copy flag in
 netdevice

On Mon, 2011-05-16 at 12:28 -0700, Shirley Ma wrote:
> 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 a134d80..2646251 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1066,6 +1066,16 @@ struct net_device {
>  #define NETIF_F_NOCACHE_COPY	(1 << 30) /* Use no-cache copyfromuser */
>  #define NETIF_F_LOOPBACK	(1 << 31) /* Enable loopback */
>  
> +/*
> + * 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)

Sorry, bit 31 is taken.  You get the job of turning features into a
wider bitmap.

Ben.

-- 
Ben Hutchings, Senior Software 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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