[U-Boot] Support for reading GPIO's in boot scripts?

Hi folks,

I'm wondering if there is any support in u-boot for reading the state of a GPIO input (i.e. button) to control the sequence of boot events?

i.e. my board has a reset button, can I read its state to determine whether to try to TFTP-boot a new kernel, or to boot the existing one in flash?

I did try to grep the sources for any hints, but did not find anything. I may have been looking in the wrong place, of course!

Thanks,

Rogan