RPi: Autodetect when we are on a Raspberry Pi 4

[Lauszus]

Do NOT use the proprietary Broadcom video core drivers, as they are not available on the Raspberry Pi 4.

I'll also like to update the documentation with my instructions here: #6474 (comment), so new users should be able to get it up and running on a Pi 4 easily :)

For anyone that wants to try this, you can install it like so:

export VIDEOCOREMESA=1; pip3 install --verbose git+https://github.com/Lauszus/kivy.git@rpi4_auto#egg=kivy

[Lauszus]

I'll like to test this with VIDEOCOREMESA=0 and VIDEOCOREMESA=1 and see if there is any performance difference.

In case VIDEOCOREMESA=1 works better I'll enable it by default for the Raspberry Pi 4.

[Lauszus]

@matham I found another issue, as VIDEOCOREMESA=0 does actually select the mesa drivers:

>>> print(True if '0' else False)
True

Instead one should use:

unset VIDEOCOREMESA; pip3 install --verbose git+https://github.com/Lauszus/kivy.git@rpi4_auto#egg=kivy

I've pushed another commit, so it checks if VIDEOCOREMESA is equal to 1: cef99e4.

[Lauszus]

I have now compared VIDEOCOREMESA=0 and VIDEOCOREMESA=1 and I can't really tell any difference in performance.

FYI here's the Kivy log for VIDEOCOREMESA=0:

[INFO   ] Window: Provider: sdl2(['window_egl_rpi'] ignored)
[INFO   ] GL: Using the "OpenGL" graphics system
[INFO   ] GL: Backend used <sdl2>
[INFO   ] GL: OpenGL version <b'2.1 Mesa 19.2.0-rc1'>
[INFO   ] GL: OpenGL vendor <b'Broadcom'>
[INFO   ] GL: OpenGL renderer <b'V3D 4.2'>
[INFO   ] GL: OpenGL parsed version: 2, 1
[INFO   ] GL: Shading version <b'1.20'>
[INFO   ] GL: Texture max size <4096>
[INFO   ] GL: Texture max units <16>

and VIDEOCOREMESA=1:

[INFO   ] Window: Provider: sdl2(['window_egl_rpi'] ignored)
[INFO   ] GL: Using the "OpenGL ES 2" graphics system
[INFO   ] GL: Backend used <sdl2>
[INFO   ] GL: OpenGL version <b'2.1 Mesa 19.2.0-rc1'>
[INFO   ] GL: OpenGL vendor <b'Broadcom'>
[INFO   ] GL: OpenGL renderer <b'V3D 4.2'>
[INFO   ] GL: OpenGL parsed version: 2, 1
[INFO   ] GL: Shading version <b'1.20'>
[INFO   ] GL: Texture max size <4096>
[INFO   ] GL: Texture max units <16>

From what I can tell from the output it seems like it is always using Mesa, so the VIDEOCOREMESA flag does not make any difference.

[tshirtman]

Thanks! Didn't test, but LGTM, if it's enough to be able to use kivy on the pi4, then i'm all for it, do we need some documentation update btw ? doc/sources/installation/installation-rpi.rst (can be done in a different PR).

[Lauszus]

@tshirtman yes that is all that is needed. Please see my comment here: #6474 (comment) on how to get it up and running on a Raspberry Pi 4 when using Raspbian Lite, as it needs X.

[tshirtman]

Great, merging then, thanks a lot!

[Lauszus]

@tshirtman installtion instructions are added in #6568