linux-kernel - Re: [PATCH 8/8] drm/bridge: it66121: Allow link this driver as a lib

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Date:   Thu, 23 Nov 2023 19:39:08 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Sui Jingfeng <sui.jingfeng@...ux.dev>
Cc:     Phong LE <ple@...libre.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Maxime Ripard <mripard@...nel.org>,
        Sui Jingfeng <suijingfeng@...ngson.cn>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: Re: [PATCH 8/8] drm/bridge: it66121: Allow link this driver as a lib

On Thu, 23 Nov 2023 at 19:04, Sui Jingfeng <sui.jingfeng@...ux.dev> wrote:
>
> Hi,
>
>
> On 2023/11/23 16:08, Dmitry Baryshkov wrote:
> >>> The host can not specify the
> >>> DRM_BRIDGE_ATTACH_NO_CONNECTOR flag, it will cause a warning here. And
> >>> it can not omit the flag (as otherwise the first bridge will create a
> >>> connector, without consulting the second bridge).
> >> The semantics of DRM_BRIDGE_ATTACH_NO_CONNECTOR flagare implement-defined,
> > No, they are not. Semantics are pretty simple: do not create the
> > drm_connector instance. Pass the flag to the next bridge in the chain.
> >
> >> for our case, I could just ignore it if their
> >> don't have a signal(DT or ACPI) tell me that there are multiple bridges
> >> in the chain. This depend on community's attitude.
> > Ignoring a flag is a bad idea.
>
>
> Can you also read the code in the bridge/lontium-lt8912.c please?
> when flags == 0 is true, the lt8912 driver will just create
> a drm_connector instance in the drm bridge drivers. The behavior
> is similar with this patch in the perspective of spirit.
>
> And the most important thing is that no matter what the flag the upstream
> port is passed, lt8912 just always pass the DRM_BRIDGE_ATTACH_NO_CONNECTOR
> flags to the next bridge. Does this count as a kind of ignore? or
>
> This is to say that both the lt8912 and the tfp410 drm bridge drivers are
> allowing create a drm_connector manually in drm bridge drivers. They didn't
> being asked to move the drm_connector related code to display controller
> driver. I don't know why I can't follow this way?

This is called 'legacy'.

>
> Do you really read the code before do comments or I failed to understand something?


-- 
With best wishes
Dmitry