envreg documentation

Hello,

Is there any documentation for environment registers, ie envreg. In the PTX ISA it says they are documented in the driver documentation, but they are not. It is also mentioned that the driver initializes them before the context is setup.

Secondly, if they are initialized in different ways with different versions of CUDA, I guess programmers are not supposed to use them, is it possible to let me know if this is the case as in that case I will drop the idea of using them

Thanks,
Anil