The glXChooseFBConfig implementation from libGL.so Not relevant documentation.
SGI TPL View (glxchoosefbconfig)
Pass null to third argument get crash in __glXInitializeVisualConfigFromTags+0x50
on instruction
LDR R3, [R4]
The registry is R4 value of the third argument.
If attribList is NULL then glXChooseFBConfig returns an array of GLX frame
buffer configurations that are available on the specified screen.