linux-kernel - Re: [PATCH v2] video: exynos: fix modular build

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Date:	Mon, 29 Feb 2016 18:12:45 +0200
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	Paul Bolle <pebolle@...cali.nl>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Inki Dae <inki.dae@...sung.com>,
	Donghwa Lee <dh09.lee@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	<linux-fbdev@...r.kernel.org>, <linux-samsung-soc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] video: exynos: fix modular build

Hi,

On 26/02/16 14:38, Arnd Bergmann wrote:
> The s6e8ax0 driver has a dependency on BACKLIGHT_CLASS_DEVICE,
> which can be configured as a loadable module, so we have to
> make the driver a tristate symbol as well, to avoid this error:
> 
> drivers/built-in.o: In function `s6e8ax0_probe':
> :(.text+0x23a48): undefined reference to `devm_backlight_device_register'

If a 'bool' Kconfig option depends on BACKLIGHT_CLASS_DEVICE, shouldn't
the Kconfig dependency take care of having BACKLIGHT_CLASS_DEVICE as
built-in?

> This also means we get another error from a missing export, which
> this fixes as well:
> 
> ERROR: "exynos_mipi_dsi_register_lcd_driver" [drivers/video/fbdev/exynos/s6e8ax0.ko] undefined!
> 
> The drivers are all written to be loadable modules already,
> except the Kconfig options for that are missing, which makes
> the patch really easy.

Looks and sound fine, except doesn't this tell that the drivers have
never been tested as modules? Did you or someone else actually test these?

> diff --git a/drivers/video/fbdev/exynos/Makefile b/drivers/video/fbdev/exynos/Makefile
> index b5b1bd228abb..02d8dc522fea 100644
> --- a/drivers/video/fbdev/exynos/Makefile
> +++ b/drivers/video/fbdev/exynos/Makefile
> @@ -2,6 +2,8 @@
>  # Makefile for the exynos video drivers.
>  #
>  
> -obj-$(CONFIG_EXYNOS_MIPI_DSI)		+= exynos_mipi_dsi.o exynos_mipi_dsi_common.o \
> -				     	exynos_mipi_dsi_lowlevel.o
> +obj-$(CONFIG_EXYNOS_MIPI_DSI)		+= exynos-mipi-dsi-mod.o
> +
> +exynos-mipi-dsi-mod-objs		+= exynos_mipi_dsi.o exynos_mipi_dsi_common.o \
> +					   exynos_mipi_dsi_lowlevel.o

Hmm, why is this makefile change needed?

 Tomi



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