Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754128AbdCaGib (ORCPT ); Fri, 31 Mar 2017 02:38:31 -0400 Received: from mail-wr0-f194.google.com ([209.85.128.194]:34159 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751347AbdCaGia (ORCPT ); Fri, 31 Mar 2017 02:38:30 -0400 Date: Fri, 31 Mar 2017 08:35:09 +0200 From: Tobias Regnery To: Jani Nikula Cc: daniel.vetter@intel.com, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/i915: fix build error without CONFIG_BACKLIGHT_CLASS_DEVICE Message-ID: <20170331063509.a54qi5firzpau4xb@builder> References: <20170329092722.6352-1-tobias.regnery@gmail.com> <87a88345u6.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87a88345u6.fsf@intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1897 Lines: 55 On 30.03.17, Jani Nikula wrote: > On Wed, 29 Mar 2017, Tobias Regnery wrote: > > With CONFIG_ACPI=n and CONFIG_BACKLIGHT_CLASS_DEVICE=n we see the following > > link error in the i915 driver: > > > > drivers/built-in.o: In function 'intel_backlight_device_register': > > (.text+0x2a921d): undefined reference to 'backlight_device_register' > > > > Fix this by removing the condition on ACPI from the appropriate select > > statement. > > The right fix for the build problem is to add empty stub functions for > BACKLIGHT_CLASS_DEVICE=n in include/linux/backlight.h. I'm frankly > surprised nobody's done that yet. Thanks for the advice, I will try to come up with a patch. -- Tobias > > It's another question whether we should support and select backlight for > ACPI=n, and yet another question whether we should support ACPI=n. > > Also, selecting BACKLIGHT_CLASS_DEVICE is fundamentally broken, but > people aren't interested [1]. > > > BR, > Jani. > > [1] http://mid.mail-archive.com/1413580403-16225-1-git-send-email-jani.nikula@intel.com > > > > > Signed-off-by: Tobias Regnery > > --- > > 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 a5cd5dacf055..532df4bb9283 100644 > > --- a/drivers/gpu/drm/i915/Kconfig > > +++ b/drivers/gpu/drm/i915/Kconfig > > @@ -15,7 +15,7 @@ config DRM_I915 > > # i915 depends on ACPI_VIDEO when ACPI is enabled > > # but for select to work, need to select ACPI_VIDEO's dependencies, ick > > select BACKLIGHT_LCD_SUPPORT if ACPI > > - 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 Technology Center