[Mesa-dev] [PATCH 2/3] gallium: define the behavior of PIPE_USAGE_* flags properly

[Marek Olšák]

Okay, sounds good.

Marek

On Wed, Feb 5, 2014 at 11:03 PM, Fredrik Höglund <fredrik at kde.org> wrote:
> On Wednesday 05 February 2014, Marek Olšák wrote:
>> On Wed, Feb 5, 2014 at 10:00 PM, Brian Paul <brianp at vmware.com> wrote:
>> > On 02/04/2014 04:26 PM, Marek Olšák wrote:
>> >>
>> >> From: Marek Olšák <marek.olsak at amd.com>
>> >>
>> >> STATIC will be removed in the following commit.
>> >> ---
>> >>   src/gallium/docs/source/screen.rst   | 18 ++++++++++++------
>> >>   src/gallium/include/pipe/p_defines.h | 13 +++++++------
>> >>   2 files changed, 19 insertions(+), 12 deletions(-)
>> >>
>> >> diff --git a/src/gallium/docs/source/screen.rst
>> >> b/src/gallium/docs/source/screen.rst
>> >> index c26f98c..5932e3b 100644
>> >> --- a/src/gallium/docs/source/screen.rst
>> >> +++ b/src/gallium/docs/source/screen.rst
>> >> @@ -343,12 +343,18 @@ PIPE_USAGE_*
>> >>   ^^^^^^^^^^^^
>> >>
>> >>   The PIPE_USAGE enums are hints about the expected usage pattern of a
>> >> resource.
>> >> -
>> >> -* ``PIPE_USAGE_DEFAULT``: Expect many uploads to the resource, intermixed
>> >> with draws.
>> >> -* ``PIPE_USAGE_DYNAMIC``: Expect many uploads to the resource, intermixed
>> >> with draws.
>> >> -* ``PIPE_USAGE_STATIC``: Same as immutable (?)
>> >> -* ``PIPE_USAGE_IMMUTABLE``: Resource will not be changed after first
>> >> upload.
>> >> -* ``PIPE_USAGE_STREAM``: Upload will be followed by draw, followed by
>> >> upload, ...
>> >> +Note that drivers must always support read and write CPU access at any
>> >> time
>> >> +no matter which hint they got.
>> >> +
>> >> +* ``PIPE_USAGE_DEFAULT``: Optimized for fast GPU access.
>> >> +* ``PIPE_USAGE_IMMUTABLE``: Optimized for fast GPU access and the
>> >> resource is
>> >> +  not expected to be mapped after the first upload.
>> >
>> >
>> > How about "mapped or changed"?  For example, an immutable resource probably
>> > shouldn't be the dest of a blit.
>>
>> Isn't it too strict? Who would want to have such a strict flag?
>
> It matches D3D11_USAGE_IMMUTABLE.  But the ARB_buffer_storage spec
> explicitly says that immutable buffers can be updated with calls such as
> glCopyBufferSubData and glClearBuffer.
>
> Fredrik
>