cmd_bootm: Add command line arguments to Plan 9

This patch introduces support for command line arguments to Plan 9.
Plan 9 generally dedicates a small region of kernel memory (known
as CONFADDR) for runtime configuration.  A new environment variable
named confaddr was introduced to indicate this location when copying
arguments.

Signed-off-by: Steven Stallion <sstallion@gmail.com>
[trini: Adapt for Simon's changes about correcting argc, no need to bump
by 2 now]
Signed-off-by: Tom Rini <trini@ti.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/README.plan9 b/doc/README.plan9
new file mode 100644
index 0000000000..2d3d0e0cf6
--- /dev/null
+++ b/doc/README.plan9
@@ -0,0 +1,18 @@
+Plan 9 from Bell Labs kernel images require additional setup to pass
+configuration information to the kernel.  An environment variable named
+confaddr must be defined with the same value as CONFADDR (see mem.h).
+Use of this facility is optional, but should be preferable to manual
+configuration.
+
+When booting an image, arguments supplied to the bootm command will be
+copied to CONFADDR.  If no arguments are specified, the contents of the
+bootargs environment variable will be copied.
+
+If no command line arguments or bootargs are defined, CONFADDR is left
+uninitialized to permit manual configuration.  For example, PC-style
+configuration could be simulated by issuing a fatload in bootcmd:
+
+  # setenv bootcmd fatload mmc 0 $confaddr plan9.ini; ...; bootm
+
+Steven Stallion
+June 2013