Re: [PATCH net-next v3] xdp: Add helpers for head length, headroom, and metadata length

[Jakub Kicinski <kuba@kernel.org>]

On Thu, 8 May 2025 03:19:42 +0000 Jon Kohler wrote:
> >> I like xdp_linear_len() as it is descriptive/clear.  
> > 
> > FWIW I don't feel strongly but my very weak preference would be 
> > not to merge this. I already know I'll be looking at the definitions
> > every time. Is it obvious to everyone in this thread whether "headroom"
> > includes the metadata length? It's not obvious to me. But the patch
> > seems quite popular so 🤷️  
> 
> Jespers suggestion to have a DOC: on this hopefully will be helpful.
> 
> I’ll try my hand that that and see what sort of trouble I can get into

I hate to dwell since I already said I don't feel strongly :) but the
doc is orthogonal, it helps people who don't understand the geometry
to understand it. My concern was that I understand the geometry, but
now I will also need to remember what we decided to call "headroom"
since (unlike skbs) XDP has all sort of stuff packed in front of the
packet data :)