Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933512AbcJLO2y (ORCPT ); Wed, 12 Oct 2016 10:28:54 -0400 Received: from mga09.intel.com ([134.134.136.24]:35948 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932751AbcJLO2r (ORCPT ); Wed, 12 Oct 2016 10:28:47 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,482,1473145200"; d="scan'208";a="771777253" From: Jani Nikula To: Emil Velikov Cc: "Sun\, Jing A" , Takashi Iwai , "airlied\@linux.ie" , "Vetter\, Daniel" , "linux-kernel\@vger.kernel.org" , "dri-devel\@lists.freedesktop.org" , "a.hajda\@samsung.com" , Thierry Reding Subject: Re: [PATCH]"drm: change DRM_MIPI_DSI module type from "bool" to "tristate". In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <87h98ktxow.fsf@intel.com> <87lgxvqlg3.fsf@intel.com> Date: Wed, 12 Oct 2016 17:28:38 +0300 Message-ID: <877f9dd4kp.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2121 Lines: 46 On Wed, 12 Oct 2016, Emil Velikov wrote: > On 11 October 2016 at 10:33, Jani Nikula wrote: >> On Tue, 11 Oct 2016, "Sun, Jing A" wrote: >>> It's needed that DRM Driver module could be removed and reloaded after >>> kernel booting on the projects that I have been working on, and I hope >>> such module type change could be accepted. Looks like Iwai has similar >>> change request as well. Would you please review it and let us know if >>> any concerns? >> >> Looking at the Kconfig, selecting CONFIG_DRM_MIPI_DSI is against the >> recommendations of Documentation/kbuild/kconfig-language.txt: >> >> 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. >> >> Indeed, you may end up with CONFIG_DRM_MIPI_DSI=y and CONFIG_DRM=m, >> which violates DRM_MIPI_DSI dependency on CONFIG_DRM. This is broken and >> should be fixed. The suggested patch does *not* fix this issue. >> > Jani, git log suggests you as the unfortunate author of the select > DRM_MIPI_DSI/select DRM_PANEL hunks in i915 ;-) /o\ As much as my present self would like to scold my past self for all his mistakes, I have to remind myself that it is the mistakes that have given me invaluable experience that my past self didn't have. I can only hope my future self will have time to fix even a fraction of the mistakes. Anyway, as Andrzej pointed out, all configs that select DRM_MIPI_DSI also depend on DRM, so this problem can't currently occur. Once dsi bus un-registration gets addressed, we can turn DRM_MIPI_DSI into a tristate config (i.e. a loadable module). BR, Jani. -- Jani Nikula, Intel Open Source Technology Center