On Tue, Sep 11, 2012 at 01:30:05PM +0900, Simon Horman wrote:
> From: Isaku Yamahata <yamah...@valinux.co.jp>
>
> Signed-off-by: Isaku Yamahata <yamah...@valinux.co.jp>
> Signed-off-by: Simon Horman <ho...@verge.net.au>
There are two reasons that a field is currently marked read-only:
1. It doesn't make sense, in my opinion, to modify the field.
For example, modifying the Ethernet type means that you'd
lose all the L3 and L4 information and is probably a
mistake. (I don't remember ever seeing a request for that,
actually, even though people ask for all kinds of crazy
things.)
2. We haven't implemented setting that field in the kernel
module yet, e.g. IPv6 label.
I can only guess why oxm_writable is sometimes different in this patch,
but I'd guess:
a. Some fields are marked read-only because they're from NXM,
not OXM. I don't see any benefit to that; it doesn't hurt to
allow it. (Also, the point of OXM/NXM is extensibility. I
don't think that disallowing it fits that intent.)
b. Fields in category 2 above are marked writable. That won't
be too useful. (But if you know of some hardware provider
implementation that can write to these fields, I'm happy to
mark those fields writable across the board.)
So I'd rather just use the 'writable' member instead of introducing a
new one.
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