netdev - Re: [RFC 5/6] drm/rcar-du: fix selection of CMM driver

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Date:   Wed, 15 Apr 2020 21:07:14 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nicolas Pitre <nico@...xnic.net>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        "David S. Miller" <davem@...emloft.net>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        linux-rdma <linux-rdma@...r.kernel.org>
Subject: Re: [RFC 5/6] drm/rcar-du: fix selection of CMM driver

On Wed, Apr 15, 2020 at 5:18 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Wed, Apr 15, 2020 at 4:13 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Wed, Apr 15, 2020 at 3:47 PM Arnd Bergmann <arnd@...db.de> wrote:
> > > On Tue, Apr 14, 2020 at 10:52 PM Laurent Pinchart <laurent.pinchart@...asonboard.com> wrote:
> > > > Doesn't "imply" mean it gets selected by default but can be manually
> > > > disabled ?
> > >
> > > That may be what it means now (I still don't understand how it's defined
> > > as of v5.7-rc1), but traditionally it was more like a 'select if all
> > > dependencies are met'.
> >
> > That's still what it is supposed to mean right now ;-)
> > Except that now it should correctly handle the modular case, too.
>
> Then there is a bug. If I run 'make menuconfig' now on a mainline kernel
> and enable CONFIG_DRM_RCAR_DU, I can set
> DRM_RCAR_CMM and DRM_RCAR_LVDS to 'y', 'n' or 'm' regardless
> of whether CONFIG_DRM_RCAR_DU is 'm' or 'y'. The 'implies'
> statement seems to be ignored entirely, except as reverse 'default'
> setting.

Here is another version that should do what we want and is only
half-ugly. I can send that as a proper patch if it passes my testing
and nobody hates it too much.

       Arnd

diff --git a/drivers/gpu/drm/rcar-du/Kconfig b/drivers/gpu/drm/rcar-du/Kconfig
index 0919f1f159a4..d2fcec807dfa 100644
--- a/drivers/gpu/drm/rcar-du/Kconfig
+++ b/drivers/gpu/drm/rcar-du/Kconfig
@@ -4,8 +4,6 @@ config DRM_RCAR_DU
        depends on DRM && OF
        depends on ARM || ARM64
        depends on ARCH_RENESAS || COMPILE_TEST
-       imply DRM_RCAR_CMM
-       imply DRM_RCAR_LVDS
        select DRM_KMS_HELPER
        select DRM_KMS_CMA_HELPER
        select DRM_GEM_CMA_HELPER
@@ -14,13 +12,17 @@ config DRM_RCAR_DU
          Choose this option if you have an R-Car chipset.
          If M is selected the module will be called rcar-du-drm.

-config DRM_RCAR_CMM
-       tristate "R-Car DU Color Management Module (CMM) Support"
-       depends on DRM && OF
+config DRM_RCAR_USE_CMM
+       bool "R-Car DU Color Management Module (CMM) Support"
        depends on DRM_RCAR_DU
+       default DRM_RCAR_DU
        help
          Enable support for R-Car Color Management Module (CMM).

+config DRM_RCAR_CMM
+       def_tristate DRM_RCAR_DU
+       depends on DRM_RCAR_USE_CMM
+
 config DRM_RCAR_DW_HDMI
        tristate "R-Car DU Gen3 HDMI Encoder Support"
        depends on DRM && OF
@@ -28,15 +30,20 @@ config DRM_RCAR_DW_HDMI
        help
          Enable support for R-Car Gen3 internal HDMI encoder.

-config DRM_RCAR_LVDS
-       tristate "R-Car DU LVDS Encoder Support"
-       depends on DRM && DRM_BRIDGE && OF
+config DRM_RCAR_USE_LVDS
+       bool "R-Car DU LVDS Encoder Support"
+       depends on DRM_BRIDGE && OF
+       default DRM_RCAR_DU
        select DRM_PANEL
        select OF_FLATTREE
        select OF_OVERLAY
        help
          Enable support for the R-Car Display Unit embedded LVDS encoders.

+config DRM_RCAR_LVDS
+       def_tristate DRM_RCAR_DU
+       depends on DRM_RCAR_USE_LVDS
+
 config DRM_RCAR_VSP
        bool "R-Car DU VSP Compositor Support" if ARM
        default y if ARM64