From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34EF2C433F5 for ; Tue, 4 Oct 2022 10:52:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229548AbiJDKwY (ORCPT ); Tue, 4 Oct 2022 06:52:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229719AbiJDKwV (ORCPT ); Tue, 4 Oct 2022 06:52:21 -0400 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6C51DFF4 for ; Tue, 4 Oct 2022 03:52:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1664880739; x=1696416739; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version:content-transfer-encoding; bh=GsLBEQ+iiyq0tqzhsDbPlBVlnya42aOoxzUP/81MpLo=; b=cmkuQDFm3MY32J55kWLXWypke/KFmcxLfIh8zOGgbAe2KVnQkndCdDsd xS/iLQpJ+m3cocLexId46i2nEOsIBVibVSiH1fxy2QyytyR77w1hFn80B xRfAGhexLXPOTsI5Dr9KLz2fUlIdfM3VogBdDZ0ulXKNaqa8oAGzwKqUU WPmYBa/nKYu1q/Z5xW1hro9NU1n+O/nx8SIvqxN03/r0nEcFd+mv/Yl98 GdhPv0zUGNa8BZTXu+7mL/G3d4F1SyeWmzkdKoA0k4/heSt/YMmclDRqj LQFnvEQyZCyU+QWEdlTcSVJdXpJVPt7ebCkdOi6IPaGxDZhPJHw/e5YBT A==; X-IronPort-AV: E=McAfee;i="6500,9779,10489"; a="282592905" X-IronPort-AV: E=Sophos;i="5.93,367,1654585200"; d="scan'208";a="282592905" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Oct 2022 03:52:14 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10489"; a="686506525" X-IronPort-AV: E=Sophos;i="5.93,367,1654585200"; d="scan'208";a="686506525" Received: from pvarla-mobl4.gar.corp.intel.com (HELO localhost) ([10.252.39.104]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Oct 2022 03:52:11 -0700 From: Jani Nikula To: "Jiri Slaby (SUSE)" Cc: linux-kernel@vger.kernel.org, "Jiri Slaby (SUSE)" , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Martin =?utf-8?Q?Li=C5=A1ka?= Subject: Re: [PATCH 1/2] drm/i915/display: fix randconfig build In-Reply-To: <20221004102837.12181-1-jirislaby@kernel.org> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20221004102837.12181-1-jirislaby@kernel.org> Date: Tue, 04 Oct 2022 13:52:08 +0300 Message-ID: <87mtabuahz.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 04 Oct 2022, "Jiri Slaby (SUSE)" wrote: > When DRM_I915=3Dy and BACKLIGHT_CLASS_DEVICE=3Dm, the build fails: > ld: drivers/gpu/drm/i915/display/intel_backlight.o: in function `intel_ba= cklight_device_register': > intel_backlight.c:(.text+0x5587): undefined reference to `backlight_devic= e_get_by_name' > > ld: drivers/gpu/drm/i915/display/intel_backlight.o: in function `intel_ba= cklight_device_unregister': > intel_backlight.c:(.text+0x576e): undefined reference to `backlight_devic= e_unregister' > > To fix this, use IS_REACHABLE(), not IS_ENABLED() in backlight. That is, > with the above config, backlight support is disabled. So I don't want this. I'll take a patch that fixes the dependencies to block DRM_I915=3Dy and BACKLIGHT_CLASS_DEVICE=3Dm. Nobody wants that combo, and IMO using IS_REACHABLE() is a workaround to hide a broken config under the carpet. The right thing to do is config DRM_I915 depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=3Dn. We're selecting BACKLIGHT_CLASS_DEVICE because almost everyone else is too, and a combo of selecting and depending leads to circular dependencies. But depending is the right fix. Documentation/kbuild/kconfig-language.rst: Note: select should be used with care. select will force a symbol to a value without visiting the dependencies. By abusing select you are able to select a symbol FOO even if FOO depends on BAR that is not set. In general use select only for non-visible symbols (no prompts anywhere) and for symbols with no dependencies. That will limit the usefulness but on the other hand avoid the illegal configurations all over. BR, Jani. > > Cc: Jani Nikula > Cc: Joonas Lahtinen > Cc: Rodrigo Vivi > Cc: Tvrtko Ursulin > Cc: David Airlie > Cc: Daniel Vetter > Cc: intel-gfx@lists.freedesktop.org > Cc: dri-devel@lists.freedesktop.org > Reported-by: Martin Li=C5=A1ka > Signed-off-by: Jiri Slaby (SUSE) > --- > drivers/gpu/drm/i915/display/intel_backlight.c | 2 +- > drivers/gpu/drm/i915/display/intel_backlight.h | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu= /drm/i915/display/intel_backlight.c > index beba39a38c87..c1ba68796b6d 100644 > --- a/drivers/gpu/drm/i915/display/intel_backlight.c > +++ b/drivers/gpu/drm/i915/display/intel_backlight.c > @@ -825,7 +825,7 @@ void intel_backlight_enable(const struct intel_crtc_s= tate *crtc_state, > mutex_unlock(&dev_priv->display.backlight.lock); > } >=20=20 > -#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) > +#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE) > static u32 intel_panel_get_backlight(struct intel_connector *connector) > { > struct drm_i915_private *dev_priv =3D to_i915(connector->base.dev); > diff --git a/drivers/gpu/drm/i915/display/intel_backlight.h b/drivers/gpu= /drm/i915/display/intel_backlight.h > index 339643f63897..207fe1c613d8 100644 > --- a/drivers/gpu/drm/i915/display/intel_backlight.h > +++ b/drivers/gpu/drm/i915/display/intel_backlight.h > @@ -36,7 +36,7 @@ u32 intel_backlight_invert_pwm_level(struct intel_conne= ctor *connector, u32 leve > u32 intel_backlight_level_to_pwm(struct intel_connector *connector, u32 = level); > u32 intel_backlight_level_from_pwm(struct intel_connector *connector, u3= 2 val); >=20=20 > -#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) > +#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE) > int intel_backlight_device_register(struct intel_connector *connector); > void intel_backlight_device_unregister(struct intel_connector *connector= ); > #else /* CONFIG_BACKLIGHT_CLASS_DEVICE */ --=20 Jani Nikula, Intel Open Source Graphics Center