linux-kernel - Re: [PATCH] drm/virtio: fix building without CONFIG

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Message-ID: <20160802135838.GQ6232@phenom.ffwll.local>
Date:	Tue, 2 Aug 2016 15:58:38 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	David Airlie <airlied@...ux.ie>, Gerd Hoffmann <kraxel@...hat.com>,
	Archit Taneja <architt@...eaurora.org>,
	Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Emil Velikov <emil.l.velikov@...il.com>,
	dri-devel@...ts.freedesktop.org,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/virtio: fix building without CONFIG_FBDEV

On Tue, Aug 02, 2016 at 12:09:15PM +0200, Arnd Bergmann wrote:
> Removing the build-time dependency on DRM_KMS_FB_HELPER means
> we can now build with CONFIG_FB disabled or as a loadable module,
> leading to a link error:
> 
> ERROR: "remove_conflicting_framebuffers" [drivers/gpu/drm/virtio/virtio-gpu.ko] undefined!
> 
> There is no need to call remove_conflicting_framebuffers() if
> CONFIG_FB is disabled, or if the virtio-gpu driver is built-in
> and CONFIG_FB=m, as there won't be any prior consoles that
> are registered at that point.
> 
> This adds a compile-time check in the driver to ensure we only
> attempt to call that function if either CONFIG_FB=y or
> both subsystems are configured as loadable modules.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Fixes: 0b6320dfdfea ("drm/virtio: make fbdev support really optional")

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

Dave, can you pls pick this one up directly?
-Daniel

> ---
>  drivers/gpu/drm/virtio/virtgpu_drm_bus.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drm_bus.c b/drivers/gpu/drm/virtio/virtgpu_drm_bus.c
> index 7f0e93f87a55..2087569ae8d7 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drm_bus.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drm_bus.c
> @@ -65,7 +65,7 @@ int drm_virtio_init(struct drm_driver *driver, struct virtio_device *vdev)
>  		DRM_INFO("pci: %s detected\n",
>  			 vga ? "virtio-vga" : "virtio-gpu-pci");
>  		dev->pdev = pdev;
> -		if (vga)
> +		if (IS_REACHABLE(CONFIG_FB) && vga)
>  			virtio_pci_kick_out_firmware_fb(pdev);
>  	}
>  
> -- 
> 2.9.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch