linux-kernel - Re: [PATCH] drm/bridge: ti-sn65dsi86: Implement lane reordering + polarity

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Date:   Tue, 5 May 2020 17:18:48 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <seanpaul@...omium.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Jonas Karlman <jonas@...boo.se>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/bridge: ti-sn65dsi86: Implement lane reordering + polarity

Hi,

On Tue, May 5, 2020 at 2:24 PM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Tue, May 5, 2020 at 2:14 PM Laurent Pinchart
> <laurent.pinchart@...asonboard.com> wrote:
> >
> > > I'll add this documentation into the comments of the yaml, but I'm not
> > > going to try to implement enforcement at the yaml level.
> >
> > Why not ? :-)
>
> Because trying to describe anything in the yaml bindings that doesn't
> fit in the exact pattern of things that the yaml bindings are designed
> to check is like constructing the empire state building with only
> toothpicks.
>
> If you want to suggest some syntax that would actually make this
> doable without blowing out the yaml bindings then I'm happy to add it.
> Me being naive would assume that we'd need to do an exhaustive list of
> the OK combinations.  That would be fine for the 1-land and 2-lane
> cases, but for 4 lanes that means adding 256 entries to the bindings.
>
> I think the correct way to do this would require adding code in the
> <https://github.com/devicetree-org/dt-schema> project but that's
> really only done for generic subsystem-level concepts and not for a
> single driver.

OK.  Looked at your review of the .yaml and the "uniqueItems" is
probably the bit I didn't think of.  With that I can limit this but
it's still a little awkward.  I still haven't figured out how to force
data-lanes and lane-polarities to have the same number of items, too.
I'll add this as an add-on patch to my v2 and folks can decide if they
like it or hate it.

# See ../../media/video-interface.txt for details.
data-lanes:
  oneOf:
    - minItems: 1
      maxItems: 1
      uniqueItems: true
      items:
        enum:
          - 0
          - 1
      description:
        If you have 1 logical lane it can go to either physical
        port 0 or port 1.  Port 0 is suggested.

    - minItems: 2
      maxItems: 2
      uniqueItems: true
      items:
        enum:
          - 0
          - 1
      description:
        If you have 2 logical lanes they can be reordered on
        physical ports 0 and 1.

    - minItems: 4
      maxItems: 4
      uniqueItems: true
      items:
        enum:
          - 0
          - 1
          - 2
          - 3
      description:
        If you have 4 logical lanes they can be reordered on
        in any way.

-Doug