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Date:   Thu, 8 Apr 2021 12:56:02 +0300
From:   Mike Rapoport <rppt@kernel.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org, 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>,
        Arnd Bergmann <arnd@arndb.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Michal Simek <michal.simek@xilinx.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Peter Collingbourne <pcc@google.com>,
        linux-aspeed@lists.ozlabs.org, dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org,
        etnaviv@lists.freedesktop.org, linux-fbdev@vger.kernel.org
Subject: Re: [PATCH v1 1/2] drivers/video/fbdev: don't select DMA_CMA
Message-ID: <YG7TMt0cgGucCPUX@kernel.org>
References: <20210408092011.52763-1-david@redhat.com>
 <20210408092011.52763-2-david@redhat.com>
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On Thu, Apr 08, 2021 at 11:20:10AM +0200, David Hildenbrand wrote:
> Random drivers should not override a user configuration of core knobs
> (e.g., CONFIG_DMA_CMA=n). Use "imply" instead, to still respect
> dependencies and manual overrides.
> 
> "This is similar to "select" as it enforces a lower limit on another
>  symbol except that the "implied" symbol's value may still be set to n
>  from a direct dependency or with a visible prompt."
> 
> Implying DRM_CMA should be sufficient, as that depends on CMA.

	  ^ DMA_CMA ?

> Note: If this is a real dependency, we should use "depends on DMA_CMA"
> instead -  but I assume the driver can work without CMA just fine --
> esp. when we wouldn't have HAVE_DMA_CONTIGUOUS or CMA right now.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  drivers/video/fbdev/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
> index 4f02db65dede..d37cd5341e1b 100644
> --- a/drivers/video/fbdev/Kconfig
> +++ b/drivers/video/fbdev/Kconfig
> @@ -2186,7 +2186,7 @@ config FB_HYPERV
>  	select FB_CFB_COPYAREA
>  	select FB_CFB_IMAGEBLIT
>  	select FB_DEFERRED_IO
> -	select DMA_CMA if HAVE_DMA_CONTIGUOUS && CMA
> +	imply DMA_CMA
>  	help
>  	  This framebuffer driver supports Microsoft Hyper-V Synthetic Video.
>  
> -- 
> 2.30.2
> 

-- 
Sincerely yours,
Mike.