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Date: Fri, 13 Mar 2015 16:30:06 +0530 From: Archit Taneja <architt@...eaurora.org> To: treding@...dia.com, p.zabel@...gutronix.de, benjamin.gaignard@...aro.org, daniel@...ll.ch CC: linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, Jani Nikula <jani.nikula@...ux.intel.com>, robdclark@...il.com, airlied@...ux.ie, dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org, tomi.valkeinen@...com Subject: Re: [RFC 1/6] drm: Add top level Kconfig option for DRM fbdev emulation 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 <linux/fb.h> 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 <linux/fb.h> > #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. > > What do you think? This looks good! I'll give it a try. Archit -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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