netdev - Re: hardware time stamping with extra skb->hwtstamp

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Message-Id: <1228149086.16263.626.camel@ecld0pohly>
Date:	Mon, 01 Dec 2008 17:31:26 +0100
From:	Patrick Ohly <patrick.ohly@...el.com>
To:	Octavian Purdila <opurdila@...acom.com>
Cc:	Oliver Hartkopp <oliver@...tkopp.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: hardware time stamping with extra skb->hwtstamp

On Mon, 2008-12-01 at 10:37 +0000, Patrick Ohly wrote:
> Oliver suggested:
> > What about just creating a new pointer in the struct skbuff that points 
> > to a struct hwstamp when it is available OR the pointer is NULL when no 
> > hwstamps are available.
[...]
> So it seems to me that we need the additional 32 bit offset (or pointer,
> on 32 bit architectures) in skb which points towards the struct
> hwtstamp. But that's actually less than the additional 64 bit which hold
> the time stamp value, as in the current patch.

It doesn't even need a 32 bit offset. If it is always at the same
location in the buffer (e.g., directly after skb_shared_info), then a
single bit is sufficient. The same mechanism could be used to also store
other optional structs/fields.

-- 
Best Regards, Patrick Ohly

The content of this message is my personal opinion only and although
I am an employee of Intel, the statements I make here in no way
represent Intel's position on the issue, nor am I authorized to speak
on behalf of Intel on this matter.

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