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Date: Wed, 11 Mar 2015 13:51:02 +0530 From: Archit Taneja <architt@...eaurora.org> To: robdclark@...il.com, airlied@...ux.ie, treding@...dia.com, p.zabel@...gutronix.de, benjamin.gaignard@...aro.org, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, Jani Nikula <jani.nikula@...ux.intel.com> Subject: Re: [RFC 1/6] drm: Add top level Kconfig option for DRM fbdev emulation 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. > >> 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. > > The problem with the patch as-is the massive amounts of selects the FB > helper still has. We need to get rid of them so that when you disable > fbdev emulation you can indeed disable fbcon and the entire fbdev > subsystem. I've thought that remove the hidden symbol DRM_KMS_FB_HELPER > and moving all the selects to DRM_FBDEV_EMULATION should work out? If that > doesn't work we need to look again how to better stub things out I think. That's true. Also, as Jani pointed out, maybe it isn't the best idea to make every kms driver select DRM_FBDEV_EMULATION? Maybe the drivers that are currently built with fbdev emulation by default can add a 'depends on DRM_FBDEV_EMULATION'? Since the config defaults to y, the drivers should run as is. Later, we could take up each driver and build the fb stuff only when DRM_FBDEV_EMULATION is set, like how we do for i915 and msm? 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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