[PATCH 1/2] glamor: add support for allocating linear buffers

[Michel Dänzer]

On 20.06.2015 07:32, Dave Airlie wrote:
>>
>>> at which point you'd want to continue
>>> the versioning from the mesa point to avoid epochs. So I don't
>>> take your argument, the API version is what we ship in the gbm.pc
>>> file, compatible implementations should make the same API changes
>>> in their same versions.
>>>
>> Other companies may use different versionning schemes (YYYY/MM/DD) and
>> which they cannot shift away from for whatever reason. Based on that
>> (plus the libEGL <> libgbm ABI mentioned above) sticking with "use
>> mesa's version" seems a bit impossible/narrow minded imho. I think we
>> can all agree things are less than perfect and checking the version in
>> the pc file is not a good idea.
> 
> gbm.pc is the gbm API version number. It isn't the Mesa version number,
> it just happens at the moment they are the same thing because nobody
> has split them, and because there isn't much value to Mesa in doing so.
> 
> Other projects implementing the gbm API need to use the same version
> number for their gbm.pc file. it sucks but otherwise they are not API
> compatible. This doesn't mean they cannot use other versioning schemes
> for their project, but their gbm.pc needs to be compatible with Mesa.
> 
> But yes checking the version sucks and I'd rather not do it, but it doesn't
> escape the fact that other gbm implementations are currently doing it
> wrong if they want to be API compatible.

I think one fundamental issue is that we're trying to determine the GBM
runtime ABI from compile time constants. One possible solution might be
to add something like

 enum gbm_bo_flags gbm_bo_get_supported_flags(struct gbm_device *gbm)

which returns the mask of flags supported by the implementation.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer