linux-kernel - Re: [PATCH v14 03/10] drm/display: Add Type-C switch helpers

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Message-ID: <ZBxJz4ESBocICA/L@smile.fi.intel.com>
Date:   Thu, 23 Mar 2023 14:45:03 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jani Nikula <jani.nikula@...el.com>
Cc:     Pin-yen Lin <treapking@...omium.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Prashant Malani <pmalani@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Xin Ji <xji@...logixsemi.com>, linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-acpi@...r.kernel.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Lyude Paul <lyude@...hat.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Allen Chen <allen.chen@....com.tw>,
        dri-devel@...ts.freedesktop.org, Marek Vasut <marex@...x.de>,
        Stephen Boyd <swboyd@...omium.org>,
        chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org,
        Andi Shyti <andi.shyti@...ux.intel.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Imre Deak <imre.deak@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        YueHaibing <yuehaibing@...wei.com>
Subject: Re: [PATCH v14 03/10] drm/display: Add Type-C switch helpers

On Wed, Mar 22, 2023 at 06:27:56PM +0200, Jani Nikula wrote:
> On Wed, 22 Mar 2023, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> > On Wed, Mar 22, 2023 at 06:46:32PM +0800, Pin-yen Lin wrote:
> >> +#ifdef CONFIG_DRM_DISPLAY_DP_TYPEC_HELPER
> >
> > Ah, maybe this should use IS_REACHABLE() ?
> 
> Personally, I think IS_REACHABLE() is a build-time band-aid solution to
> a problem that should be solved in Kconfig. :p
> 
> I think it always means there's a configuration combo that shouldn't
> exist, and it's a surprise to the user when they've configured
> something, Kconfig has deemed it a valid configuration, but they don't
> get the feature they want.
> 
> As a user, how would they even debug that case? Double check configs,
> don't see anything wrong.

Usual pairing is 'imply FOO' in Kconfig & 'IS_REACHEABLE(CONFIG_FOO)' in the
code. And I believe it's not an abnormal.

-- 
With Best Regards,
Andy Shevchenko