Hi Daniel,

thanks, I got it to work - almost. I am running this on the i.MX6 with etnaviv. I do get some flickering, however.


To test if something is wrong with the page flipping, I call drmGetCap() with DRM_CAP_ASYNC_PAGE_FLIP , and it returns me 0, indicating that async page flipping is not supported. But this is odd - is this really not implemented yet for the i.MX6? And why does drmModePageFlip() still work with DRM_MODE_PAGE_FLIP_EVENT ?



On 2018-02-09 17:05, Daniel Stone wrote:
Hi Carlos,

On 9 February 2018 at 08:33, Carlos Rafael Giani <d...@pseudoterminal.org> 
wrote:
I want to implement triple buffering instead of double buffering for a
program that uses EGL on GBM on a KMS-enabled platform. So far, I used
kmscube as an example.

However, I do not see where I can specify that I want to have 3 buffers
allocated instead of 2. From what I saw, I could try to call
gbm_dri_surface_lock_front_buffer() to produce 3 BOs over time, but there's
a chance that gbm_dri_surface_has_free_buffers() will return 0 after getting
2 BOs already.
You're correct that there is no explicit control available. On the
other hand, having three buffers is pretty much guaranteed for GBM:
since your last buffer won't be released until after vblank, only
having double buffering is likely to give you very badly reduced
performance. (In practice, Mesa makes four buffers available.)

And, does gbm_dri_surface_lock_front_buffer() internally allocate the buffer
itself too (not just the BO structure)? Or are the flippable pages
preallocated by the implementation?
This is an implementation detail. Usually buffer allocation is
deferred to the first draw call of a frame: if there are no buffers
available, then the implementation will allocate a new one.

Cheers,
Daniel

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