[Mesa-dev] [PATCH 09/21] mesa: remove legacy TCL dri config options

[Roland Scheidegger]

Am 15.08.2018 um 20:47 schrieb Ian Romanick:
> On 08/15/2018 04:09 AM, Timothy Arceri wrote:
>> On 15/08/18 20:26, Michel Dänzer wrote:
>>> On 2018-08-15 12:13 PM, Timothy Arceri wrote:
>>>> Use enviroment var overrides in legacy drivers instead.
>>>
>>> This could break existing user configurations using the driconf tcl_mode
>>> option.
>>>
>>> Apart from this, I like the idea of this series.
>>
>> I assumed this was a debug like option. If you think I should keep the
>> dri config entry I can move it to the driver.
> 
> I have some vague recollection that at least at one time there were
> applications that didn't work with HW TNL on at least R100 cards... or
> maybe they just had rubbish performance.  The memories are pretty fuzzy.
>  Moving it to the driver and deleting the duplicate envvar seems like
> the safest option.
> 

I suspect there might be issues with z-fighting if the app renders
something which causes tcl fallbacks and something which doesn't. Albeit
I don't think the state changes causing fallbacks or not would be
covered under the GL invariance guarantee, apps wouldn't care about such
details. So just forcing it off always would prevent this. Can't
remember neither though if it was an actual problem with some apps.

Roland