[Mesa-dev] [PATCH] [RFC] egl: propose simple EGL_MESA_image_dma_buf_export v2.2

[Chad Versace]

On 03/03/2015 11:13 AM, Dave Airlie wrote:
> On 4 March 2015 at 05:06, Chad Versace <chad.versace at intel.com> wrote:
>> On 03/03/2015 11:01 AM, Daniel Stone wrote:
>>> Hi,
>>>
>>> On 3 March 2015 at 18:40, Chad Versace <chad.versace at intel.com> wrote:
>>>> On 03/03/2015 12:13 AM, Daniel Stone wrote:
>>>>> On Tuesday, March 3, 2015, Dave Airlie <airlied at gmail.com <mailto:airlied at gmail.com>> wrote:
>>>>>     +    EGLBoolean eglExportDMABUFImageQueryMESA(EGLDisplay dpy,
>>>>>     +                                  EGLImageKHR image,
>>>>>     +                                 int *fourcc,
>>>>>     +                                 int *num_planes);
>>>>>
>>>>>
>>>>> Shouldn't this contain the modifier(s) as well?
>>>>
>>>> What is the motivation for defining two export calls, and exporting
>>>> a subset of information from each call? I don't understand why the
>>>> fourcc values are exported by one call, but the strides exported a
>>>> separate call.
>>>
>>> Querying the image gives you what you need in order to know if you can
>>> actually deal with the image, before you go to all the effort of
>>> exporting it.
>>
>> Thanks. That makes sense.
> 
> Also you need the number of planes to correctly size the arrays for
> the second call to put the results into.

Right, I understood that you needed to know the number of planes before
submitting the array. I was mostly confused by why fourcc was in this call,
not num_planes.

My real feedback: It's probably best to rename num_planes to num_fds,
because you're not guaranteed num_fds != num_planes for interleaved formats.
And, using the name 'num_fds' allows us to avoid awkwardness if we need to
create future layered extensions
that export auxilliary buffers that may not correspond YUV planes. (There's
been a lot of lunch talk about exporting aux buffers at Intel).