Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752678AbbF3HKa (ORCPT ); Tue, 30 Jun 2015 03:10:30 -0400 Received: from mail-oi0-f45.google.com ([209.85.218.45]:34942 "EHLO mail-oi0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750698AbbF3HKU (ORCPT ); Tue, 30 Jun 2015 03:10:20 -0400 MIME-Version: 1.0 X-Originating-IP: [212.51.149.109] In-Reply-To: <20150325092111.GT1349@phenom.ffwll.local> References: <20150310094756.GE3800@phenom.ffwll.local> <54FEBEF1.5000103@codeaurora.org> <20150310100547.GG3800@phenom.ffwll.local> <54FEC5F1.90208@codeaurora.org> <20150310121702.GO3800@phenom.ffwll.local> <54FFFAEE.3020301@codeaurora.org> <20150311151731.GJ3800@phenom.ffwll.local> <550282C3.10903@codeaurora.org> <20150313090651.GZ3800@phenom.ffwll.local> <55126F32.90404@codeaurora.org> <20150325092111.GT1349@phenom.ffwll.local> Date: Tue, 30 Jun 2015 09:10:19 +0200 X-Google-Sender-Auth: Zmi-4BDOU2gKL1YOpoiZqkRGUPM Message-ID: Subject: Re: [RFC 1/6] drm: Add top level Kconfig option for DRM fbdev emulation From: Daniel Vetter To: Archit Taneja , "Clark, Rob" , Dave Airlie , Thierry Reding , Philipp Zabel , Benjamin Gaignard , dri-devel , Linux Kernel Mailing List , linux-arm-msm , Jani Nikula , Linux Fbdev development list , Tomi Valkeinen Cc: Daniel Vetter Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5873 Lines: 152 Any updates on this or too much distractions? I really think doing this would be awesome for the drm subsystem, instead of reinventing this wheel for each driver. -Daniel On Wed, Mar 25, 2015 at 10:21 AM, Daniel Vetter wrote: > On Wed, Mar 25, 2015 at 01:47:54PM +0530, Archit Taneja wrote: >> Hi, >> >> On 03/13/2015 02:36 PM, Daniel Vetter wrote: >> >On Fri, Mar 13, 2015 at 11:55:07AM +0530, Archit Taneja wrote: >> >> >> >> >> >>On 03/11/2015 08:47 PM, Daniel Vetter wrote: >> >>>On Wed, Mar 11, 2015 at 01:51:02PM +0530, Archit Taneja wrote: >> >>>> >> >>>> >> >>>>On 03/10/2015 05:47 PM, Daniel Vetter wrote: >> >>>>>On Tue, Mar 10, 2015 at 03:52:41PM +0530, Archit Taneja wrote: >> >>>>>>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: >> >>>>>>>>>>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. >> >>>>> >> >>>>>But with the stubbed out functions that should work, right? Why doesn't >> >>>>>it? >> >>>> >> >>>>There are still calls to functions from fb core like fb_set_suspend and >> >>>>register_framebuffer which aren't covered by the drm fb helper functions. >> >>> >> >>>Hm, sounds like we need another patch to stub out fb_set_suspend when >> >>>fbdev isn't enabled. Is there anything else? >> >> >> >>There are a handful of fb core functions which are called by drm drivers: >> >> >> >>fb_alloc_cmap/fb_dealloc_cmap >> >> >> >>fb_sys_read/fb_sys_write >> >> >> >>register_framebuffer/unregister_framebuffer/unlink_framebuffer/ >> >>remove_conflicting_framebuffers >> >> >> >>fb_set_suspend >> >> >> >>fb_deferred_io_init/fb_deferred_io_cleanup >> >> >> >>framebuffer_alloc/framebuffer_release >> > >> >Hm yeah that's somewhat annoying indeed. What about the following: >> >1. We move all the #include from drivers into drm_fb_helper.h >> > >> >2. Then we add stubs for these functions in drm_fb_helper.h, like this >> > >> >#if defined(CONFIG_FB) >> >#include >> >#else >> > >> >/* static inline stubs for all the fb stuff used by kms drivers */ >> >#endif >> > >> >Imo this makes sense since kms drivers really have a bit a special >> >situation with fbdev. They're not full-blown fbdev drivers and can be >> >useful fully without fbdev. >> > >> >> I was trying this out. Removing 'linux/fb.h' and replacing stub fb funcs >> won't really work because struct declarations(like fb_info) also get >> removed. >> >> I considered placing '#if IS_ENABLED(CONFIG_FB)' within linux/fb.h itself, >> but that seemed a bit too intrusive. >> >> This is what I'm currently doing: >> >> - Some funcs, like framebufer_alloc/release, alloc_cmap/dealloc_cmap would >> actually benefit if we have drm fb helpers for them. They are used in >> exactly the same manner by all the drivers. >> >> - For the rest of the functions that are sparsely used, I was considering >> making very simple drm_fb_* wrapper functions. Something like: >> >> void drm_fb_helper_deferred_io_init(struct drm_fb_helper *helper) >> { >> if (helper->fbdev) >> fb_deferred_io_init(helper->fbdev); >> } >> >> We could have all fb calls called within drm_fb_helper.c, creating >> drm_fb_helper_* stub functions would then be an easier task. What do you >> think? > > That's actually an option I considered, but I hoped we could do it with > less work. If this indeed works and you can create the patch that would be > awesome. > > Thanks, Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/