[Mesa-dev] Why are we using server-side GLX fbconfigs?

[Kristian Høgsberg]

On Fri, Jun 30, 2017 at 2:49 AM, Thomas Hellstrom <thellstrom at vmware.com> wrote:
> On 06/29/2017 07:30 PM, Kristian Høgsberg wrote:
>>
>> On Thu, Jun 29, 2017 at 7:36 AM, Thomas Hellstrom <thellstrom at vmware.com>
>> wrote:
>>>
>>> Hi!
>>>
>>> I was spending some time going through the GLX code to try to fix up the
>>> GLX_OML_swap_method extension implementation.
>>>
>>> I then stumbled across the fact that when we, for direct rendering
>>> connections, construct the list of fbconfigs, we start out with the
>>> server
>>> provided fbconfigs from the AIGLX driver and then try to match each
>>> fbconfig
>>> with a corresponding client driver driconfig. Effectively making us use
>>> the
>>> intersection of the server AIGLX capabilities and the client Direct
>>> rendering capabilities.
>>>
>>> Wouldn't it be more correct, or at least "better" if we, for direct
>>> rendering, took a list of client driver driconfigs, matched each with a
>>> server provided visual and if we have a match, built an fbconfig from
>>> that
>>> driconfig? That would make us essentialy exposing all client driver
>>> capabilities regardless of what the server is using, as long as we have a
>>> matching visual?
>>>
>>> Any insights into this would be greatly appreciated.
>>
>> I'm largely to blame for that. Historically it was part me trying to
>> keep things working they did before as well as having to pay more
>> attention to server side configs as DRI2 tried to share aux buffers
>> (not just color) between clients. I think mesa today only shares color
>> buffers with DRI2 and DRI3 is obviously fine, so what you're proposing
>> sounds like a nice simplification of the code as well as something
>> that might expose more configs to the client.
>>
>> Kristian
>
>
> OK. Thanks Kristian.
>
> FWIW, from what I can tell, dri3 only shares the real front. Has dri2 been
> modified to also allocate local buffers?

No, DRI2 still uses DRI2GetBuffers or DRI2GetBuffersWithFormat to ask
the X server to allocate buffers, which then shares the buffers with
the client by sending the gem name back in the reply.

Kristian

> Thanks,
> Thomas
>
>
>
>
>
>>> Thanks,
>>>
>>> Thomas
>>>
>>>
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