On 2017-06-22 08:36, Daniel Vetter wrote: > On Wed, Jun 21, 2017 at 11:40:52AM +0200, Peter Rosin wrote: >> On 2017-06-21 09:38, Daniel Vetter wrote: >>> On Tue, Jun 20, 2017 at 09:25:25PM +0200, Peter Rosin wrote: >>>> This makes the redundant fb helpers .load_lut, .gamma_set and .gamma_get >>>> totally obsolete. >>>> >>>> I think the gamma_store can end up invalid on error. But the way I read >>>> it, that can happen in drm_mode_gamma_set_ioctl as well, so why should >>>> this pesky legacy fbdev stuff be any better? >>>> >>>> drm_fb_helper_save_lut_atomic justs saves the gamma lut for later. However, >>>> it saves it to the gamma_store which should already be up to date with what >>>> .gamma_get would return and is thus a nop. So, zap it. >>> >>> Removing drm_fb_helper_save_lut_atomic should be a separate patch I >>> think. >> >> Then 3 patches would be needed, first some hybrid thing that does it the >> old way, but also stores the lut in .gamma_store, then the split-out that >> removes drm_fb_helper_save_lut_atomic, then whatever is needed to get >> to the desired code. I can certainly do that, but do you want me to? > > Explain that in the commit message and it's fine. I did the split in v2, I assume that's ok too. Better in case anyone ever needs to run a bisect on this... >>> It's a pre-existing bug, but should we also try to restore the fbdev lut >>> in drm_fb_helper_restore_fbdev_mode_unlocked()? Would be yet another bug, >>> but might be relevant for your use-case. Just try to run both an fbdev >>> application and some kms-native thing, and then SIGKILL the native kms >>> app. >>> >>> But since pre-existing not really required, and probably too much effort. >> >> Good thing too, because I don't really know my way around this code... > > Btw I cc'ed you on one of my patches in the fbdev locking series, we might > need to do the same legacy vs. atomic split for the new lut code as I did > for dpms. The rule with atomic is that you can't do multiple commits under > drm_modeset_lock_all, you either have to do one overall atomic commit > (preferred) or drop&reacquire locks again. This matters for LUT since > you're updating the LUT on all CRTCs, which when using the gamma_set > atomic helper would be multiple commits :-/ Ahh, ok, I see the problem. > Using the dpms patch as template it shouldn't be too hard to address that > for your patch here too. Hmm, in that patch you handle the legacy case in a separate function, and doing that for the lut case looks difficult when the atomic commit happens inside the helper (typically drm_atomic_helper_legacy_gamma_set which could perhaps be handled, but a real drag to handle for drivers that have a custom crtc .gamma_set). So, I'm aiming for the drop&reacquire approach... However, I don't have all of that series, and I suspect that is why I do not have any fb_helper->lock. I'll send my best guess as a follow-up to patch 3/14 in v2. Cheers, peda
