This is checked in, not currently enabled in the autobuild.
One minor note:
If vid_get_viewport_fb_d is in platform lib.c (as opposed to the sub lib.c used in older ports), it should use the variable output by the sig finder (viewport_fb_d) rather than the function that directly references the address.
The platform lib.c shouldn't refer to things like variable or ROM addresses that might vary between firmware versions. I made that change in r5128.
Hardware addresses (like raw_image_addr, bitmap_fb, MMIOs) are fine in platform lib.c, since they are not expected to vary between subs.