Re: [PATCH 1/2] xen/kbdif: update protocol documentation

[Stefano Stabellini <sstabellini@kernel.org>]

On Wed, 18 Jan 2017, Oleksandr Andrushchenko wrote:
> On 01/12/2017 08:36 AM, Oleksandr Andrushchenko wrote:
> > On 01/12/2017 12:50 AM, Dario Faggioli wrote:
> > > On Wed, 2017-01-11 at 20:40 +0200, Oleksandr Andrushchenko wrote:
> > > > On 01/11/2017 07:35 PM, Dario Faggioli wrote:
> > > > >   It's indeed a repetition, but a good one, IMO: it helps the reader,
> > > > > as
> > > > > she won't have to go back to figure out how big the struct was, how
> > > > > the
> > > > > macro was call and to what value it was defined).
> > > > I am still not convinced that we should put it.
> > > > Probably we can go the way other RFCs do, like TCP [1], 802.11 [2]
> > > > etc:
> > > > those do not define any reserved fields at the bottom of structures,
> > > > (which are effectively padding?) but are limited to only those fields
> > > > which are defined.
> > > > 
> > > In principle, I like the idea of following the example of those RFCs.
> > > However, I'd say that what we should value most is consistency within
> > > our own source tree.
> > > 
> > > But, TBH, there aren't many binary diagram already committed in
> > > include/public/io, so it's hard to tell.
> > > 
> > > FWIW, I still think that providing a clue to the reader about the size
> > > --even if already specified somewhere else-- would be beneficial, but
> > > it's a rather minor thing, and I certainly can leave with whatever you
> > > and the maintainer(s) agree upon.
> > fair enough
> > > Regards,
> > > Dario
> > Konrad, could you please define what that ASCII box
> > notation should look like?
> > 
> Stefano, Konrad
> As per my understanding this is the only thing blocking multi-touch
> and updated kbdif protocol from being upgraded/extended )
> Could you please make some decision on this any time soon?

I would use something like:
    
            0                 1                 2                 3
  * +-----------------+-----------------+-----------------+-----------------+ 
  * |   _TYPE_MOTION  |                       reserved                      |4
  * +-----------------+-----------------+-----------------+-----------------+
  * |                                 rel_x                                 |8
  * +-----------------+-----------------+-----------------+-----------------+
  * |                                 rel_y                                 |12
  * +-----------------+-----------------+-----------------+-----------------+
  * |                                 rel_z                                 |16
  * +-----------------+-----------------+-----------------+-----------------+
  * |                               reserved                                |20
  * +-----------------+-----------------+-----------------+-----------------+
  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|40
  * +-----------------+-----------------+-----------------+-----------------+

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