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

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Message-ID: <CAA8EJpokxcO2qXgZ=+f=J+6EhAS_7KkrNJ_oZgk=RMHfv8riog@mail.gmail.com>
Date:   Thu, 16 Nov 2023 13:11:00 +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, 16 Nov 2023 at 12:29, Sui Jingfeng <sui.jingfeng@...ux.dev> wrote:
>
> Hi,
>
>
> On 2023/11/15 00:30, Dmitry Baryshkov wrote:
> >> @@ -703,14 +704,32 @@ static int it66121_bridge_attach(struct drm_bridge *bridge,
> >>                                   enum drm_bridge_attach_flags flags)
> >>   {
> >>          struct it66121_ctx *ctx = bridge_to_it66121(bridge);
> >> +       struct drm_bridge *next_bridge = ctx->next_bridge;
> >> +       struct drm_encoder *encoder = bridge->encoder;
> >>          int ret;
> >>
> >> -       if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> >> -               return -EINVAL;
> >> +       if (next_bridge) {
> >> +               if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
> >> +                       WARN_ON(1);
> > Why? At least use WARN() instead
>
> If (next_bridge) is true, it says that the driver *already* known that
> it66121 have a next bridges attached. Then it66121 driver should certainly
> attach it, no matter what it is. Either a connector or another display bridge.
> It also says that this is a DT-based system on such a case. CallingWARN_ON(1) here helps to see(print) which DC driver is doing the wired
> things. Ok, I will remove the WARN_ON(1)  on the next version.

That's why I pointed you to WARN(). WARN_ON(1) gives no information to
the user. WARN() allows you to add a message.

-- 
With best wishes
Dmitry