On Mon, Mar 24, 2014 at 09:07:32AM +1000, Dave Airlie wrote: > On Sat, Mar 8, 2014 at 12:13 AM, Pohjolainen, Topi > <topi.pohjolai...@intel.com> wrote: > > On Mon, Mar 03, 2014 at 01:19:48PM +1000, Dave Airlie wrote: > >> There is a comment and two checks in the i965 dma-buf importer, > >> > >> * Images originating via EGL_EXT_image_dma_buf_import can be used only > >> * with GL_OES_EGL_image_external only. > >> > >> however I can't find any reference to this in the spec txt, and > >> removing the checks make my test app run fine using TEXTURE_2D. > > > > You are correct that there is nothing in the spec about this, but it also > > leaves > > it open for the driver to choose on which buffers it allows the external > > sampling. > > After quite a bit of debate on when/where it would be safe to use > > dma-buffers, > > it was decided that we simply allow dma-buffers for external sampling only - > > that extension already restricts the use for single-miplevel and read-only > > which is exactly what we wanted. > > The same time it wasn't clear what kind of sources we should allow for > > external > > sampling (besides dma), and hence we simply kept things as they were before > > - > > none other. Note that before the introduction of dma-buffers the image > > external > > extension wasn't enabled at all on i965. > > > > This is a really bad idea, since it means you can't use dma-buf > imported things with standard shader programs, if I want to import a > dma-buf I shouldn't have to write specific shader programs or use > special bindings, unless the spec says so.
Bringing your request to its logical conclusion... > Either the spec should be more restrictive, or the implementation > shouldn't have arbitrary differences from what other implementations > could do. ...leads to disaster. It's naive to expect each implementation to support what other implementations *could*, or even *currently* do. Are you prepared to impelement support for these horrorshows? A. Import a YUV EGLImage backed by two dma_bufs (Y in the first, UV in the second) as a GL_TEXTURE_EXTERNAL_OES and transparently handle the YUV->RGB transcode in your shader code generator? Because, iirc, ARM's EGL/GLES2 stack supports that for Chrome. B. Same idea as A, but support importing the image as a GL_TEXTURE_2D and again transparently handle the YUV->RGB transcode. Because, for all we know, ARM's stack may support that too. An implementation has to draw the line somewhere. And Topi, Anholt, and I carefully decided where that line would initially lie for i965. If real users demand more features from dma-buf-images, then it makes sense to implement them. Until then, supporting them leads to a maintenance burden. Frankly, the Intel guys did not want to deal with headache of correctly orphaning 2d textures backed by dma-buf-EGLImages. (FYI. The only real world user of EGL_EXT_image_dma_buf_import I'm aware of is Chrome on ARM. If iirc, it exclusively uses the extension to import YUV data). -Chad _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
