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GBM ES2 Demo

  • Example OpenGL ES2 demo using GBM and DRM (KMS) modesetting
  • This shows how ChromeOS renders GLES2 contents on the screen.
  • It uses OpenGL ES2/3 without X11 dependency, so it fits pretty good with the embedded devices world.

Alt text

Build

  • If you are on Ubuntu, first make sure you have the dependencies installed
> sudo apt-get install libgles2-mesa-dev libgbm-dev

> mkdir build; cd build
> cmake ../
> make

Run

  • I have successfully ran it on Ubuntu, ChromeOS and Yocto.

Ubuntu

  • Go to tty1 with Ctrl + Alt + F1
  • Kill gdm or lightdm because they are DRM master now. This demo has to be DRM master.
> sudo service lightdm stop
  • Run the demo
> gbm_es2_demo
or
> gbm_es2_demo -M # mmap test

Yocto

  • The easiest way to build embedded linux image is to use Yocto.
  • I make Yocto recipes to make standalone emebeded OpenGL ES2 demo image.
  • Check Yocto GBM ES2 Demo
  • Enjoy building Linux image from the scratch.

Android

Build

  • Clone gbm_es2_demo code in vendor/intel/external
git clone https://github.com/yugang/gbm_es2_demo.git
  • Update minigbm .mk file for minigbm static build
cp gbm_es2_demo/Android.mk.minigbm hardware/intel/external/minigbm-intel/Android.mk
  • Add a line "gbm_es2_demo" in section PRODUCT_PACKAGES of device/intel/mixins/groups/graphics/mesa/product.mk to build gbm_es2_demo to final image.
  • Build the Android image.

Run

adb shell
su
stop
stop vendor.hwcomposer-2-1
/vendor/bin/gbm_es2_demo

Demo detail

gbm_es2_demo

  • Show how to glue DRM, GBM and EGL
  • Show how to swap buffer and vsync
  • Show how to implement GLES2 app

gbm_es2_demo -M

  • Same to gbm_es2_demo except for updating cube surface using dma_buf mmap
  • It's very nice demo to show how Chromium zero-copy texture upload works. Chromium doesn't use glTexImage2D to update texture thank to new dma_buf mmap API. For more Chromium detail, check the chrome issue
  • After Linux kernel v4.6, you can use following code. (currently only Intel Architecture supports it)
  • Tiago Vignatti made this change in kernel.
  void* data = mmap(dma_buf_fd)
  update contents on |data|
  munmap(data)

Code style

> clang-format-5.0 -i `find . -name "*.cpp" -o -name "*.h"`

Reference