[PATCH 02/02] dri2: Add DRI2GetParam request

[Chad Versace]

On 05/14/2012 08:51 AM, Kristian Høgsberg wrote:
> On Thu, May 10, 2012 at 3:04 AM, Chad Versace
> <chad.versace at linux.intel.com> wrote:
>> Bump dri2proto dependency to 2.7.
>> Bump DRI2INFOREC_VERSION to 7.
>>
>> This new protocol request effectively allows clients to perform feature
>> detection on the DDX. The request was added in DRI2 protocol 1.4.
>>
>> If I had DRI2GetParam in June 2011, when I was implementing support in the
>> Intel DDX and Mesa for new hardware that required a new DRI2 attachment
>> format, then I could have avoided a week of pain caused by the necessity
>> of writing a horrid feature detection hack [1] in Mesa. In the future, when
>> the work begins to add MSAA support to the Intel DDX, having a clean way
>> to do feature detection will allow us to avoid revisiting and expanding
>> that hack.
> 
> Yeah, that looks fine, should make things simpler than trying to infer
> from version numbers.  If we expect to add many parameters or query
> them often (per frame), we should think about how to query a batch of
> parameters at a time to avoid multiple roundtrips.  EGL uses xcb, so
> it's not a big deal there, and for GLX, the protocol code is in mesa,
> so we could just pipeline the request/reply code by hand if we have
> to.
> 
> Also, if I was painting this bikeshed I'd just drop the namespace arg,
> and have a CARD32 be the param and put driver params above 0x1000 or
> whatever.  CARD64 for the value makes sense, at least some of the
> crazy swap parameters are 64 bit.
> 
> Kristian

You threw some paint on the bikeshed, and it stuck. I never liked
the namespace argument, but it was only solution I arrived at; I
like the idea of enum ranges better. And, if we really need 2^64
parameter names, something is terribly wrong.

Let's let the high byte determine which component owns the paramter
name. Parameter names 0x00------ are reserved for the server. Names
0x01------ are owned by the DDX. Other names are reserved for future use.

I'll resubmit the patch series with the changes.

Chad