On Thu, 13 Feb 2020 02:01:58 +0500 "Alexander E. Patrakov" <patra...@gmail.com> said:
> On Thu, Feb 13, 2020 at 1:12 AM Carsten Haitzler <ras...@rasterman.com> wrote: > > > > On Wed, 12 Feb 2020 16:45:50 +0100 Michel Dänzer <mic...@daenzer.net> said: > > > > > On 2020-02-12 4:34 p.m., Carsten Haitzler wrote: > > > > On Wed, 12 Feb 2020 15:36:06 +0100 Michel Dänzer <mic...@daenzer.net> > > > > said: > > > > > > > >> On 2020-02-12 2:06 p.m., Carsten Haitzler wrote: > > > >>> On Wed, 12 Feb 2020 13:23:28 +0200 Pekka Paalanen > > > >>> <ppaala...@gmail.com> said: > > > >>> > > > >>>> On Wed, 12 Feb 2020 11:07:56 +0000 > > > >>>> Carsten Haitzler <ras...@rasterman.com> wrote: > > > >>>> > > > >>>>> On Wed, 12 Feb 2020 12:40:15 +0200 Pekka Paalanen > > > >>>>> <ppaala...@gmail.com> said: > > > >>>>> > > > >>>>>> On Wed, 12 Feb 2020 10:21:02 +0000 > > > >>>>>> Carsten Haitzler (The Rasterman) <ras...@rasterman.com> wrote: > > > >>>>>> > > > >>>>>>> even better - if the /dev/dri/card0 > > > >>>>>>> device exists, dlopen libdrm and get some symbols from it and ... > > > >>>>>>> use it to request the drm device sent you vsync events so you can > > > >>>>>>> use the vsync interrupt as your frame event. this will be another > > > >>>>>>> fd to listen on in select() and of course you can turn this > > > >>>>>>> vblank event stream on and off. > > > >>>>>> > > > >>>>>> Please don't. Talk to the X server instead. > > > >>>>> > > > >>>>> and what vsync events does the xserver provide? > > > >>>> > > > >>>> You don't want vsync events. You have no idea what they > > > >>>> correspond to, or even if you opened the right device. > > > >>>> > > > >>>> https://gitlab.freedesktop.org/xorg/proto/xorgproto/blob/master/presentproto.txt > > > >>> > > > >>> I wrote the drm support before the present extension existed. The drm > > > >>> path is easy to support - only open if a single card exists (if > > > >>> multiple > > > >>> - don't do it and fall back to timer based animation) and you can > > > >>> filter for multiple screens as you get events for all screens. Yes - > > > >>> you end up syncing with a single chosen screen if you filter for just > > > >>> one of the vblank events, but it's better than using the system clock. > > > >> > > > >> You only get an event for the CRTC you ask for in the > > > >> DRM_IOCTL_WAIT_VBLANK ioctl. How do yo know which CRTC to pick? > > > > > > > > drmVBlank vbl; > > > > vbl.request.type = DRM_VBLANK_RELATIVE | DRM_VBLANK_EVENT; > > > > vbl.request.sequence = 1; > > > > vbl.request.signal = 0; > > > > drmWaitVBlank(drm_fd, &vbl); > > > > > > > > has worked a charm for maybe give or take close to a decade (as i said - > > > > before present existed). > > > > > > That selects the first CRTC. It'll work most of the time, except when > > > the first CRTC isn't enabled for some reason. > > > > I've seen it select multiple crtc's as I get multiple vblank events with the > > same frame number... (thus filter out the dups to only get one). > > > > > >>> I have found x present XPresentNotifyMSC() to be unreliable where the > > > >>> drm back-door above is far more reliable. For example - on my amdgpu > > > >>> driver here it just refuses to produce any events (yes - extension is > > > >>> there), [...] > > > >> > > > >> I haven't seen any such reports, so I'm not aware of such issues with > > > >> xf86-video-amdgpu. > > > > > > > > i'm staring at it not working :) admittedly it's a slightly older rx550 > > > > with amdgpu on an aarch64 host... :) i did play with xpresent in the > > > > early days it came out and found it to be iffy and stuck to the > > > > solution we already had (above) which is more reliable. > > > > > > A proper issue report with all the needed information will be needed to > > > do anything about this. > > > > It hasn't been something I've needed to do as I have the other method above > > and no xpresent one to have to support and make work :) > > > > > To be clear, even the Present extension is really too low level to be > > > used directly for this by a compositor (unless it also uses it directly > > > for the actual presentation). The DRM vblank ioctl even more so, it's > > > for the display server. > > > > > > A compositor which uses GLX/EGL for presentation should use > > > corresponding GLX/EGL (extension) APIs for this. > > > > Aaaah therein lies the rub. I need this to work with our without EGL/GLX. I > > need it work for compositors and clients - the whole shebang as the same > > library, infra etc. is used on both sides. There already is an "animator" > > infra where you request a callback to be called whenever a frame needs to be > > produced. The idea is that you just modify objects in the scene graph and > > this then percolates down to there being changes that then results in a > > render that may or may not use GL. at once point I had an xrender engine I > > gave up on so i'm down to just software and GL (GLX or EGL and mostly a > > gles2 susbset of GL). The animation is far removed from the rendering. In > > the end the pipeline depends on their being some event to say "wake-up! > > time to render!". The vblank events are just that. That means there is an > > entire frame worth of budget to go set up the changes, render them and get > > a swap or xshmputimage queued up and ready to go. The GL infra for this is > > certainly not ideal and in most cases just hasn't been able to do this in > > my experience in the past. I need this event even though I have not > > actually rendered anything previously. > > Please also consider the corner case of Xvfb, xf86-video-dummy, or > maybe (untested) rendering on a headless GPU on a EC2 instance and > displaying the result via VNC. In these cases, there will be no vblank > events at all. I know. That's why there is also a timeout if code has asked for vblank interrupts and none come in within that timeout - it'll hiccup a bit then switch over to timer based ticking, so it works regardless. -- ------------- Codito, ergo sum - "I code, therefore I am" -------------- Carsten Haitzler - ras...@rasterman.com _______________________________________________ xorg-devel@lists.x.org: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: https://lists.x.org/mailman/listinfo/xorg-devel
