[U-Boot] MIPS UHI spec

[Matthew Fortune]

Hi Daniel,

The spec for MIPS Unified Hosting Interface is available here:

http://prplfoundation.org/wiki/MIPS_documentation

As we have previously discussed, this is an ideal place to
define the handover of device tree data from bootloader to
kernel. Using a0 == -2 and defining which register(s) you
need for the actual data will fit nicely. I'll happily
include whatever is decided into the next version of the spec.

This is also the spec I would like to use to implement a syscall
interface. Previous post on the topic:

http://lists.denx.de/pipermail/u-boot/2014-December/198007.html

Only a subset of the operations would be implemented for u-boot
and would be strictly limited to sit on top of the functionality
that is already exposed to standalone applications with GPL
exceptions. Some of the operations need a bit of wrapper code
around the API functions i.e. The write operation would only be
handled for FD 1 and 2 and would be implemented as a loop
sending each byte of the buffer via putc.

UHI also provides a semi-hosting solution for u-boot itself
which it could use to obtain files over the EJTAG interface.

Initial implementation of the syscall interface will be posted
relatively soon.

Thanks,
Matthew