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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 8 Apr 2021 15:19:19 +0200
Message-ID: <CAK8P3a2Wu7tT-YajfdXSSVvg5MYMEnEy3APJ83DcLeJdGkkSrQ@mail.gmail.com>
Subject: Re: [PATCH v1 2/2] drivers/gpu/drm: don't select DMA_CMA or CMA from
 aspeed or etnaviv
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     David Hildenbrand <david@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>, Joel Stanley <joel@jms.id.au>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Andrew Jeffery <andrew@aj.id.au>,
        Lucas Stach <l.stach@pengutronix.de>,
        Russell King <linux+etnaviv@armlinux.org.uk>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        Mike Rapoport <rppt@kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Michal Simek <michal.simek@xilinx.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Peter Collingbourne <pcc@google.com>,
        linux-aspeed <linux-aspeed@lists.ozlabs.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        The etnaviv authors <etnaviv@lists.freedesktop.org>,
        Linux Fbdev development list <linux-fbdev@vger.kernel.org>
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On Thu, Apr 8, 2021 at 2:50 PM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Thu, Apr 8, 2021 at 2:01 PM David Hildenbrand <david@redhat.com> wrote:
>
> > > This is something you could do using a hidden helper symbol like
> > >
> > > config DRMA_ASPEED_GFX
> > >         bool "Aspeed display driver"
> > >         select DRM_WANT_CMA
> > >
> > > config DRM_WANT_CMA
> > >         bool
> > >         help
> > >            Select this from any driver that benefits from CMA being enabled
> > >
> > > config DMA_CMA
> > >         bool "Use CMA helpers for DRM"
> > >         default DRM_WANT_CMA
> > >
> > >           Arnd
> > >
> >
> > That's precisely what I had first, with an additional "WANT_CMA" --  but
> > looking at the number of such existing options (I was able to spot 1 !)
>
> If you do this it probably makes sense to fix a few other drivers
> Kconfig in the process. It's not just a problem with your driver.
> "my" drivers:
>
> drivers/gpu/drm/mcde/Kconfig
> drivers/gpu/drm/pl111/Kconfig
> drivers/gpu/drm/tve200/Kconfig
>
> certainly needs this as well, and pretty much anything that is
> selecting DRM_KMS_CMA_HELPER or
> DRM_GEM_CMA_HELPER "wants" DMA_CMA.

Are there any that don't select either of the helpers and
still want CMA? If not, it would be easy to just add

   default  DRM_KMS_CMA_HELPER || DRM_GEM_CMA_HELPER

and skipt the extra symbol.

        Arnd