On Mon, Mar 9, 2015 at 4:54 AM, Archit Taneja <architt@xxxxxxxxxxxxxx> wrote: > > > On 03/09/2015 01:14 PM, Daniel Vetter wrote: >> >> On Mon, Mar 09, 2015 at 11:27:06AM +0530, Archit Taneja wrote: >>> >>> On 03/05/2015 09:14 PM, Daniel Vetter wrote: >>>> >>>> On Thu, Mar 05, 2015 at 07:10:44AM -0500, Rob Clark wrote: >>>>> >>>>> On Thu, Mar 5, 2015 at 5:06 AM, Archit Taneja <architt@xxxxxxxxxxxxxx> >>>>> wrote: >>>>>> >>>>>> >>>>>> On 02/23/2015 09:09 PM, Daniel Vetter wrote: >>>>>>> >>>>>>> >>>>>>> On Mon, Feb 23, 2015 at 10:03:21AM -0500, Rob Clark wrote: >>>>>> >>>>>> Rather than creating fb helper stub functions, maybe we could help >>>>>> each drm >>>>>> driver create two variants of functions needed by drm core(like >>>>>> output_poll_changed and dev_lastclose), one variant supporting legacy >>>>>> fbdev, >>>>>> and the other not? >>>>> >>>>> >>>>> So one quick thought.. building without fbdev would ideally/eventually >>>>> be a distro level decision, not a driver level decision.. so I think >>>>> it is *eventually* not a problem for it being a global drm level >>>>> decision. The only problem is right now some drivers support no-fbdev >>>>> config, and some do not. Maybe it is worth fixing that? >>>> >>>> >>>> Yeah, if we get fbdev emulation Kconfig option then I think i915 and msm >>>> should remove their own options and just use that. There's really no >>>> need >>>> to have this per-driver, this is a question of what userspace expects >>>> and >>>> so per-distro, independant of the driver. >>>> -Daniel >>>> >>> >>> Okay. If I understand right. We need to do something like this: >>> >>> - Create a new Kconfig option that lets us emulate fbdev >>> >>> - For drivers that already have a config for fbdev emulation, replace it >>> with our new emulation config. >>> >>> - For drivers that assume fbdev emulation by default, select our new >>> emulation config in their respective Kconfigs. >>> >>> Does this sound okay? >>> >>> I suppose this could be the first step. Later we'd need to work on each >>> driver to work with and without the fbdev emulation Kconfig option. >> >> >> See Rob's idea quoted above: Imo you should just do the conditional code >> in the fbdev emulation helper in drm_fb_helper.c, not in drivers. There's >> some additional code in i915 (and maybe also msm) to compile out (mostly >> around taking/dropping console_lock) and we want to keep that. But that >> should also just be using the same new config option. So: >> >> - Add new config option DRM_FBDEV_EMULATION (default y for backwards >> compat). Use that to stub out helpers in drm_fb_helper.c. >> >> - Replace the msm/i915 specific options with the new, i.e. remove it from >> Kconfig and use DRM_FBDEV_EMULATION in the code instead of the msm/i915 >> specific one. >> >> fbdev-less support for all other drivers will just magically happen >> without the need for driver-specific code (except for the special locking >> in i915 and similar things maybe). > > > That sounds good. I wasn't totally sure about fbdev-less support working out > of the box on devices that use the fb CMA helpers. The drm_fbdev_cma_* funcs > internally use the fb helper functions. Stubbing the fb helpers out might > result in some corner cases. > > However, after a quick look at that the cma helpers, it looks like it take > all the necessary precautions to prevent uninitialized accesses. Although, > it would be ideal to stub out the drm_fbdev_cma_* helper functions too since > they don't serve any purpose when fbdev emulation is disabled. > I think for a first pass, I wouldn't worry too much about a little unused code in cma fbdev helpers. If we were going for drm tinyification I suspect there are bigger fish to fry ;-) BR, -R > > 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-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
