access qualifier and kernel launch

In OpenCL 2.0, it seems reasonable to want to pass, say, a write_only image or pipe from a parent kernel to be used as a read_only pipe or image in a child kernel. However, the spec gives no indication that an access qualifier changing cast is permitted, and so one may assume that such scenarios are illegal.

But should it be illegal (if it is)? It seems useful to me.

Begin with the OpenCL 2.0 access-qualifier and kernel-launch rules referenced in the issue. Done means reaching a specification decision and documenting whether changing access qualifiers for image or pipe arguments passed to child kernels is permitted.

Written by the indexing model from the issue text.