On 30 August 2018 at 11:41, Eric Engestrom <eric.engest...@intel.com> wrote:
> On Thursday, 2018-08-30 17:55:14 +0900, Tomasz Figa wrote:
>> Hi Erik, Emil, Eric,
>>
>> On Tue, Jul 10, 2018 at 12:41 AM Erik Faye-Lund <kusmab...@gmail.com> wrote:
>> >
>> > On Thu, Jul 5, 2018 at 7:02 PM Emil Velikov <emil.l.veli...@gmail.com> 
>> > wrote:
>> > >
>> > > On 5 July 2018 at 17:17, Eric Engestrom <eric.engest...@intel.com> wrote:
>> > > > On Thursday, 2018-07-05 14:43:02 +0100, Emil Velikov wrote:
>> > > >> On 5 July 2018 at 10:53, Eric Engestrom <eric.engest...@intel.com> 
>> > > >> wrote:
>> > > >> > On Monday, 2018-07-02 14:12:44 +0530, samiuddi wrote:
>> > > >> >> This fixes crash due to NULL window when swap interval is set
>> > > >> >> for pbuffer surface.
>> > > >> >>
>> > > >> >> Test: CtsDisplayTestCases pass
>> > > >> >>
>> > > >> >> Signed-off-by: samiuddi <sami.uddin.moham...@intel.com>
>> > > >> >> ---
>> > > >> >>
>> > > >> >> Kindly ignore this patch
>> > > >> >> https://lists.freedesktop.org/archives/mesa-dev/2018-July/199098.html
>> > > >> >>
>> > > >> >>  src/egl/drivers/dri2/platform_android.c | 2 +-
>> > > >> >>  1 file changed, 1 insertion(+), 1 deletion(-)
>> > > >> >>
>> > > >> >> diff --git a/src/egl/drivers/dri2/platform_android.c 
>> > > >> >> b/src/egl/drivers/dri2/platform_android.c
>> > > >> >> index ca8708a..b5b960a 100644
>> > > >> >> --- a/src/egl/drivers/dri2/platform_android.c
>> > > >> >> +++ b/src/egl/drivers/dri2/platform_android.c
>> > > >> >> @@ -485,7 +485,7 @@ droid_swap_interval(_EGLDriver *drv, 
>> > > >> >> _EGLDisplay *dpy,
>> > > >> >>     struct dri2_egl_surface *dri2_surf = dri2_egl_surface(surf);
>> > > >> >>     struct ANativeWindow *window = dri2_surf->window;
>> > > >> >>
>> > > >> >> -   if (window->setSwapInterval(window, interval))
>> > > >> >> +   if (window && window->setSwapInterval(window, interval))
>> > > >> >>        return EGL_FALSE;
>> > > >> >
>> > > >> > Shouldn't we return false if we couldn't set the swap interval?
>> > > >> >
>> > > >> > I think this should be:
>> > > >> >    if (!window || window->setSwapInterval(window, interval))
>> > > >> >       return EGL_FALSE;
>> > > >> >
>> > > >> Changing the patch as above will lead to eglSwapInterval consistently
>> > > >> failing for pbuffer surfaces.
>> > > >
>> > > > I'm not that familiar with pbuffers, but does SwapInterval really make
>> > > > sense for them? I thought you couldn't swap a pbuffer.
>> > > >
>> > > > If so, failing an invalid op seems like the right thing to do.
>> > > > Otherwise, I guess sure, no-op returning success is fine.
>> > > >
>> > > Looking at eglSwapInterval manpage [1] (with my annotation):
>> > > "eglSwapInterval — specifies the minimum number of video frame periods
>> > > per buffer swap for the _window_ associated with the current context."
>> > > While the spec does not mention window/pbuffer/pixmap at all - it
>> > > extensively refers to eglSwapBuffers.
>> > >
>> > > Wrt eglSwapBuffers manpage [2] and spec are consistent:
>> > >
>> > > "If surface is a pixel buffer or a pixmap, eglSwapBuffers has no
>> > > effect, and no error is generated."
>> > >
>> > > Perhaps it's wrong to set eglSwapInterval for !window surfaces, but
>> > > its sibling (eglSwapBuffers) does not error out.
>> > > Hence I doubt many users make a distinction between window and pbuffer
>> > > surfaces for eglSwap*.
>> > >
>> > > Worth bringing to the WG meeting - it' planned for 1st August.
>> > >
>> >
>> > As I pointed out when I proposed this variant here:
>> > https://patchwork.freedesktop.org/patch/219313/
>> >
>> > "Also, I don't think EGL_FALSE is the right return-value, as it doesn't
>> > seem the EGL 1.5 spec defines any such error. Also, for instance
>> > dri2_swap_interval returns EGL_TRUE when there's no driver-function,
>> > which further backs the "silent failure" in this case IMO."
>> >
>> > So I think EGL_TRUE is the correct return-value for now. If the spec
>> > gets changed, we can of course update our implementation.
>>
>> What happens to this patch in the end? It looks like we're observing a
>> similar problem in Chrome OS.
>>
>> Emil, was there any follow-up on the WG meeting?
>
> Meeting was cancelled, but I raised the issue here:
> https://gitlab.khronos.org/egl/API/merge_requests/17
>
> Right now we have ARM saying they return false + error and NVIDIA saying
> they return true + no error and that ARM has a bug.
> I think another party adding their opinion might nudge it forward :)
>
Fwiw I put forward a suggestion to add a workaround in the
Android/CrOS libEGL wrapper for the ARM drivers.
Although one could also consider the Nvidia/Mesa drivers as
non-compliant and add a workaround for those instead.

I have to admit it's not pretty, but it seems consistent with all the
other workarounds in the wrapper.

As Eric said - input from another party should, would be great.

HTH
Emil
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