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From:   Jani Nikula <jani.nikula@linux.intel.com>
To:     Chen Zhou <chenzhou10@huawei.com>, airlied@linux.ie,
        daniel@ffwll.ch
Cc:     dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        chenzhou10@huawei.com, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH next] drm/i915: fix build error without ACPI
In-Reply-To: <20200113132724.143687-1-chenzhou10@huawei.com>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
References: <20200113132724.143687-1-chenzhou10@huawei.com>
Date:   Mon, 13 Jan 2020 15:57:10 +0200
Message-ID: <874kwzmpc9.fsf@intel.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, 13 Jan 2020, Chen Zhou <chenzhou10@huawei.com> wrote:
> If CONFIG_ACPI=n and CONFIG_BACKLIGHT_CLASS_DEVICE=m, compilation complains
> with undefined references:
>
> drivers/gpu/drm/i915/display/intel_panel.o: In function `intel_backlight_device_register':
> intel_panel.c:(.text+0x4dd9): undefined reference to `backlight_device_register'
> drivers/gpu/drm/i915/display/intel_panel.o: In function `intel_backlight_device_unregister':
> intel_panel.c:(.text+0x4e96): undefined reference to `backlight_device_unregister'
>
> This patch select BACKLIGHT_CLASS_DEVICE directly.

i915 does not unconditionally require backlight.

See e.g. [1] for the details.

BR,
Jani.


[1] http://lore.kernel.org/r/87o8veotf9.fsf@intel.com

>
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
> ---
>  drivers/gpu/drm/i915/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
> index ba95959..6b69dab 100644
> --- a/drivers/gpu/drm/i915/Kconfig
> +++ b/drivers/gpu/drm/i915/Kconfig
> @@ -16,7 +16,7 @@ config DRM_I915
>  	select IRQ_WORK
>  	# i915 depends on ACPI_VIDEO when ACPI is enabled
>  	# but for select to work, need to select ACPI_VIDEO's dependencies, ick
> -	select BACKLIGHT_CLASS_DEVICE if ACPI
> +	select BACKLIGHT_CLASS_DEVICE
>  	select INPUT if ACPI
>  	select ACPI_VIDEO if ACPI
>  	select ACPI_BUTTON if ACPI

-- 
Jani Nikula, Intel Open Source Graphics Center