Dri2 buffer format

[Jerome Glisse]

On Mon, Nov 8, 2010 at 6:55 PM, Russell Shaw <rjshaw at netspace.net.au> wrote:
> On 09/11/10 04:53, Jerome Glisse wrote:
>>
>> On Mon, Nov 8, 2010 at 10:52 AM, Russell Shaw<rjshaw at netspace.net.au>
>>  wrote:
>>>
>>> Hi,
>>> How should the "format" of a DRI2 buffer be determined?
>>>
>>>
>>> http://www.x.org/releases/current/doc/dri2proto/dri2proto.txt
>>>
>>> DRI2ATTACH_FORMAT { attachment: CARD32
>>>            format:     CARD32 }
>>>
>>>    The DRI2ATTACH_FORMAT describes an attachment and the associated
>>>    format.  'attachment' describes the attachment point for the buffer,
>>>    'format' describes an opaque, device-dependent format for the buffer.
>>>
>>>
>>
>> As the spec says, it's opaque and only the driver understand it, intel,
>> radeon, nouveau all use different things i think. DRI2 is meant to be
>> use btw different driver of same hw which should all understand each
>> others.
>
> If it's opaque, how does one know what bytes are red/green/blue so that
> you can draw a line in the right colour?

This format is intend to be exchanged btw Xorg DDX driver for a given
hw for instance the nouveau ddx and with the mesa or other dri2 driver
like for instance the nouveau gallium driver. Both of this component
understand each others.

DRI2 is not mean to be use by end user application, it's only use by
Xorg to comunicate with library such as opengl that want to provide
direct rendering to X pixmap/window.

Cheers,
Jerome