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 <architt at codeaurora.org> >>>> --- >>>> 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
