On 16.02.2017 09:21, Tapani Pälli wrote:
On 02/16/2017 10:11 AM, Timothy Arceri wrote:
On 16/02/17 18:58, Timothy Arceri wrote:
On 16/02/17 17:55, Tapani Pälli wrote:
On 02/16/2017 04:52 AM, Timothy Arceri wrote:
In order add functionality to ARB_get_program_binary we need
binary format enums.
I've understood that this is a driver internal enumeration. When
application gets the binary it also receives enum (integer value) what
format we gave. Then when loading application needs to query what
formats are supported by the implementation and load the correct
binary.
We just need to internally make agreement on format list and return
correct one matching the current driver in use?
Not that it's actually likely to happen but if we were to only have a
single MESA enum an application could only distribute a single binary.
e.g either for AMD, INTEL or NVIDIA but not one for each. That is unless
we were to compile and pack all gpu vendor binarys at the same time
which seems overly complicated and expensive.
I could see an intenal id being used for gpu generations from hardware
vendors.
Or are you saying we don't need to define the enums? If so I don't think
that is correct. The ARB_get_program_binary extension says:
"A vendor extension must also be present in order
to define one or more binary formats, thereby populating the list of
PROGRAM_BINARY_FORMATS. The <binaryFormat> returned by
GetProgramBinary is always one of the binary formats in this list.
...
The beauty of this extension, however, is that an application does
not need
to be aware of the vendor extension on any given implementation. It
only
needs to retrieve a program binary with an anonymous
<binaryFormat> and
resupply that same <binaryFormat> when loading the program binary."
OK, I did not spot this one. At same time we have to supply extension
where values defined (which makes it hard to make changes later) but
then from application POV the values are still considered anonymous and
it will likely not use the extension. This is a bit strange requirement ..
We can still internally put more data in to the blob about exact backend
and version requirements and so on so I guess single enum value per
vendor is enough.
So the question is what the use case of this extension really is. Keep
in mind that the driver can always decide to fail loading a binary.
If the purpose is to allow games to cache shaders for a second run, then
I think even a single Mesa enum is sufficient -- the local driver is
always going to be the same.
If the purpose is to distribute pre-compiled binaries via the internet,
then assigning enums that need to be registered with Khronos is clearly
not scalable. We can't have an enum for each build ID, so it's all
unworkable anyway, and we'd need some way of querying a build ID string.
I think this points towards us registering a single enum for Mesa only.
Still, a bit more information about how this extension is actually used
in the wild could change my mind.
Cheers,
Nicolai
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