Synchronization between a crtc mode_set and page_flip?

[Archit Taneja]

Hi,

I was trying to figure out how we are supposed to manage synchronization 
between a mode_set and a page_flip called on a crtc.

Say, if a mode_set is immediately followed by a page_flip. The driver 
can't process the page_flip straight away since the hardware is still 
completing the mode_set.

What is the driver supposed to do? Should it return -EBUSY? Or should it 
somehow queue the page_flip task internally?

A lot of libdrm applications seem to call mode_set, and call a page_flip 
soon after it. They tend to bail out if page_flip returns an error, they 
don't try to do another page_flip if it fails the first time. Is this 
okay behaviour?

Thanks,
Archit