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From:   Jani Nikula <jani.nikula@linux.intel.com>
To:     Arnd Bergmann <arnd@kernel.org>, dri-devel@lists.freedesktop.org,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>
Cc:     linux-fbdev@vger.kernel.org, intel-gfx@lists.freedesktop.org,
        Arnd Bergmann <arnd@arndb.de>,
        Matthew Auld <matthew.auld@intel.com>,
        Zhenyu Wang <zhenyuw@linux.intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] [v2] i915: fix backlight configuration issue
In-Reply-To: <20211027132732.3993279-3-arnd@kernel.org>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
References: <20211027132732.3993279-1-arnd@kernel.org> <20211027132732.3993279-3-arnd@kernel.org>
Date:   Wed, 27 Oct 2021 16:41:55 +0300
Message-ID: <87r1c6h9ek.fsf@intel.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Wed, 27 Oct 2021, Arnd Bergmann <arnd@kernel.org> wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> The i915 driver can use the backlight subsystem as an option, and usually
> selects it when CONFIG_ACPI is set. However it is possible to configure
> a kernel with modular backlight classdev support and a built-in i915
> driver, which leads to a linker error:
>
> drivers/gpu/drm/i915/display/intel_panel.o: In function `intel_backlight_device_register':
> intel_panel.c:(.text+0x2f58): undefined reference to `backlight_device_register'
> drivers/gpu/drm/i915/display/intel_panel.o: In function `intel_backlight_device_unregister':
> intel_panel.c:(.text+0x2fe4): undefined reference to `backlight_device_unregister'
>
> Change i915 to just 'depends on' for both BACKLIGHT_CLASS_DEVICE
> and ACPI_VIDEO, which avoids a lot of the problems.
>
> Link: https://lore.kernel.org/all/20200108140227.3976563-1-arnd@arndb.de/
> Link: https://lore.kernel.org/all/20200417155553.675905-1-arnd@arndb.de/
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> This change depends on cleaning up drivers/video/fbdev to no longer
> 'select' I2C and BACKLIGHT_CLASS_DEVICE, otherwise it causes
> dependency loops.
> ---
>  drivers/gpu/drm/i915/Kconfig | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
> index 84b6fc70cbf5..f427e6d50d9b 100644
> --- a/drivers/gpu/drm/i915/Kconfig
> +++ b/drivers/gpu/drm/i915/Kconfig
> @@ -3,6 +3,8 @@ config DRM_I915
>  	tristate "Intel 8xx/9xx/G3x/G4x/HD Graphics"
>  	depends on DRM
>  	depends on X86 && PCI
> +	depends on ACPI_VIDEO || !ACPI
> +	depends on BACKLIGHT_CLASS_DEVICE || !BACKLIGHT_CLASS_DEVICE
>  	select INTEL_GTT
>  	select INTERVAL_TREE
>  	# we need shmfs for the swappable backing store, and in particular
> @@ -16,10 +18,6 @@ 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

The comment needs updating as well.

Other than that,

Acked-by: Jani Nikula <jani.nikula@intel.com>

on the series.

> -	select BACKLIGHT_CLASS_DEVICE if ACPI
> -	select INPUT if ACPI
> -	select ACPI_VIDEO if ACPI
> -	select ACPI_BUTTON if ACPI
>  	select SYNC_FILE
>  	select IOSF_MBI
>  	select CRC32

-- 
Jani Nikula, Intel Open Source Graphics Center