linux-kernel - Re: [PATCH] drm: pl111: add CONFIG_VEXPRESS

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Message-ID: <CAK8P3a2k2qPOdREo-+AwOL8JVcO2VFoouAFyx6-fr1UnpavwLA@mail.gmail.com>
Date:   Wed, 27 May 2020 17:47:21 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Eric Anholt <eric@...olt.net>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Rob Herring <robh@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm: pl111: add CONFIG_VEXPRESS_CONFIG dependency

On Wed, May 27, 2020 at 4:52 PM Sam Ravnborg <sam@...nborg.org> wrote:
>
> Hi Arnd.
>
> On Wed, May 27, 2020 at 03:31:42PM +0200, Arnd Bergmann wrote:
> > The vexpress_config code fails to link in some configurations:
> >
> > drivers/gpu/drm/pl111/pl111_versatile.o: in function `pl111_versatile_init':
> > (.text+0x1f0): undefined reference to `devm_regmap_init_vexpress_config'
> >
> > Add a dependency that links to this only if the dependency is there,
> > and prevent the configuration where the drm driver is built-in but
> > the config is a loadable module.
> >
> > Fixes: 826fc86b5903 ("drm: pl111: Move VExpress setup into versatile init")
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> Could this be another way to fix it:
>
> diff --git a/drivers/gpu/drm/pl111/pl111_versatile.c b/drivers/gpu/drm/pl111/pl111_versatile.c
> index 64f01a4e6767..1c38d3bd2e84 100644
> --- a/drivers/gpu/drm/pl111/pl111_versatile.c
> +++ b/drivers/gpu/drm/pl111/pl111_versatile.c
> @@ -379,7 +379,7 @@ static int pl111_vexpress_clcd_init(struct device *dev, struct device_node *np,
>         u32 val;
>         int ret;
>
> -       if (!IS_ENABLED(CONFIG_VEXPRESS_CONFIG))
> +       if (!IS_REACHABLE(CONFIG_VEXPRESS_CONFIG))
>                 return -ENODEV;
>
>         /*
>
>
> Then we no longer have the whole driver depending on
> the value of VEXPRESS_CONFIG.
> Not that I like IS_REACHABLE() but we already had
> IS_ENABLED() to cover up here, and that was not enough.
>
> With your patch would we then need the IS_ENABLED()
> check?

The IS_ENABLED() check is what I'm adding, not removing. I'd still
the Kconfig dependency combined with that check over
IS_REACHABLE(), which is more likely to silently not work.

       Arnd