From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752652AbbCJKWu (ORCPT ); Tue, 10 Mar 2015 06:22:50 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:34846 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751945AbbCJKWr (ORCPT ); Tue, 10 Mar 2015 06:22:47 -0400 Message-ID: <54FEC5F1.90208@codeaurora.org> Date: Tue, 10 Mar 2015 15:52:41 +0530 From: Archit Taneja User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: robdclark@gmail.com, airlied@linux.ie, treding@nvidia.com, p.zabel@pengutronix.de, benjamin.gaignard@linaro.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, daniel@ffwll.ch Subject: Re: [RFC 1/6] drm: Add top level Kconfig option for DRM fbdev emulation References: <1425980493-27533-1-git-send-email-architt@codeaurora.org> <1425980493-27533-2-git-send-email-architt@codeaurora.org> <20150310094756.GE3800@phenom.ffwll.local> <54FEBEF1.5000103@codeaurora.org> <20150310100547.GG3800@phenom.ffwll.local> In-Reply-To: <20150310100547.GG3800@phenom.ffwll.local> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/10/2015 03:35 PM, Daniel Vetter wrote: > On Tue, Mar 10, 2015 at 03:22:49PM +0530, Archit Taneja wrote: >> >> >> On 03/10/2015 03:17 PM, Daniel Vetter wrote: >>> On Tue, Mar 10, 2015 at 03:11:28PM +0530, Archit Taneja wrote: >>>> Legacy fbdev emulation support via DRM is achieved through KMS FB helpers. >>>> Most modesetting drivers enable provide fbdev emulation by default by selecting >>>> KMS FB helpers. A few provide a separate Kconfig option for the user to enable >>>> or disbale fbdev emulation. >>>> >>>> Enabling fbdev emulation is finally a distro-level decision. Having a top level >>>> Kconfig option for fbdev emulation helps by providing a uniform way to >>>> enable/disable fbdev emulation for any modesetting driver. It also lets us >>>> remove unnecessary driver specific Kconfig options that causes bloat. >>>> >>>> With a top level Kconfig in place, we can stub out the fb helper functions when >>>> not needed without breaking functionality. Having stub functions also prevents >>>> drivers to require wrapping fb helper function calls with #ifdefs. >>>> >>>> DRM_FBDEV_EMULATION defaults to y since many drivers enable fbdev emulation by >>>> default and majority of distributions expect the fbdev interface in the kernel. >>>> >>>> For now, this config selects both FB_SYS_* and FB_CFB_* configs as some >>>> modesetting drivers use the former and other the later. This needs to be taken >>>> care of in a better way. >>>> >>>> Signed-off-by: Archit Taneja >>>> --- >>>> drivers/gpu/drm/Kconfig | 18 +++++++ >>>> drivers/gpu/drm/Makefile | 4 ++ >>>> include/drm/drm_fb_helper.h | 120 ++++++++++++++++++++++++++++++++++++++++++++ >>>> 3 files changed, 142 insertions(+) >>>> >>>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig >>>> index 151a050..38f83a0 100644 >>>> --- a/drivers/gpu/drm/Kconfig >>>> +++ b/drivers/gpu/drm/Kconfig >>>> @@ -40,6 +40,24 @@ config DRM_KMS_FB_HELPER >>>> help >>>> FBDEV helpers for KMS drivers. >>>> >>>> +config DRM_FBDEV_EMULATION >>>> + bool "Enable legacy fbdev support for your modesetting driver" >>>> + depends on DRM >>>> + select DRM_KMS_HELPER >>>> + select DRM_KMS_FB_HELPER >>>> + select FB_SYS_FILLRECT >>>> + select FB_SYS_COPYAREA >>>> + select FB_SYS_IMAGEBLIT >>>> + select FB_SYS_FOPS >>>> + select FB_CFB_FILLRECT >>>> + select FB_CFB_COPYAREA >>>> + select FB_CFB_IMAGEBLIT >>>> + default y >>>> + help >>>> + Choose this option if you have a need for the legacy fbdev >>>> + support. Note that this support also provide the linux console >>>> + support on top of your modesetting driver. >>> >>> Maybe clarify that for linux console support you also need >>> CONFIG_FRAMEBUFFER_CONSOLE? fbdev alone isn't enough. >> >> DRM_KMS_FB_HELPER selects that for us, right? > > Hm right I've missed that. Reminds me that you need one more patch at the > end to remove all the various select DRM_KMS_FB_HELPER from all drm > drivers. Otherwise this knob here won't work by default if you e.g. select > radeon. In general we can't mix explicit options with menu entries with a > select. I was trying that out. Removing DRM_KMS_FB_HELPER and having DRM_FBDEV_EMULATION disabled breaks drivers which use FB stuff internally in their respective xyz_fbdev.c files. Are you saying that we should remove DRM_KMS_FB_HELPER for such drivers and replace them with 'select DRM_FBDEV_EMULATION'? Another option would be to provide #ifdef DRM_FBDEV_EMULATION wrap-arounds for fb related function calls/declarations in each driver, something that's already done for i915 and msm drivers. Archit -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project