Re: [RFC,libdrm 1/3] tegra: Add stream library

[Arto Merilainen <amerilainen-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 12/28/2012 11:04 AM, Mark Zhang wrote:
> On 12/28/2012 04:50 PM, Arto Merilainen wrote:
>>
>> In my opinion asking tegra_stream_begin() to put a bad fence into the
>> stream is a case we should never be. assert() kills the application
>> immediately (in debug builds) and usually this helps the programmer for
>> 1) finding bugs 2) not doing bad code.
>>
>
> Yep, I agree. But in release builds, assert does nothing. So this
> checking doesn't make sense and also a wrong fence will be pushed into
> command buffer silently. And we always use release version in real
> products, so we can't count on this "assert".

The only pro of using assert is low (=no :-) ) overhead in release builds.

>
>> "Silencing" is not a good solution especially in this case:
>> tegra_stream_flush() returns an invalid fence when flushing fails. If
>> the application chains submits (i.e. do a blit and then do another using
>> the output of the first blit) it is crucial to be sure the first submit
>> has been performed before starting the second one.
>>
>
> Yes. So I suggest doing fence checking at the beginning of the
> "tegra_stream_begin", if invalid fence found, return an error.
>

This sounds reasonable.

- Arto