linux-kernel - Re: [RFC] drm/msm/dp: Allow attaching a drm

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Date:   Thu, 26 Aug 2021 13:29:32 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Kuogee Hsieh <khsieh@...eaurora.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Vara Reddy <varar@...eaurora.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Chandan Uddaraju <chandanu@...eaurora.org>
Subject: Re: [RFC] drm/msm/dp: Allow attaching a drm_panel

Hi,

On Mon, Jul 26, 2021 at 4:15 PM Bjorn Andersson
<bjorn.andersson@...aro.org> wrote:
>
> +static int dp_parser_find_panel(struct dp_parser *parser)
> +{
> +       struct device_node *np = parser->pdev->dev.of_node;
> +       int rc;
> +
> +       rc = drm_of_find_panel_or_bridge(np, 2, 0, &parser->drm_panel, NULL);
> +       if (rc == -ENODEV)
> +               rc = 0;
> +       else if (rc)
> +               DRM_ERROR("failed to acquire DRM panel: %d\n", rc);
> +
> +       return rc;

So rather than storing the drm_panel, I suggest that you actually wrap
it with a "panel_bridge". Follow the ideas from commit 4e5763f03e10
("drm/bridge: ti-sn65dsi86: Wrap panel with panel-bridge") and the fix
in commit c7782443a889 ("drm/bridge: ti-sn65dsi86: Avoid creating
multiple connectors").

If you do that then actually a bunch of your patch becomes
unnecessary. You basically just have to attach the "next" bridge in
the right place and you're good, right?

-Doug