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From 0d685fe90ab92ccb9f15b7d79b1063f5b79b2dd5 Mon Sep 17 00:00:00 2001
From: Frans Meulenbroeks <fransmeulenbroeks@gmail.com>
Date: Thu, 25 Feb 2010 11:05:31 +0100
Subject: [PATCH 7/7] cmd_setexpr: allow memory addresses and env vars in expressions
This patch add functionality to use memory addresses and environment variables in
expressions. This increases the power of expressions substantially
It adheres to the standard convemtions: memory addresses can be given in the format
*address (e.g. *1000), environment variables as $this_var.
environment variables are not processed recursively but can contain both constants
and memory addresses.
Rationale for this change is that it allows masking off bits from a byte that is
obtained by reading data from e.g. i2c.
Signed-off-by: Frans Meulenbroeks <fransmeulenbroeks@gmail.com>
---
If recursive environment vars is desired: this can be added easily by changing the
if statement into a while statement.
I figured that would be somewhat over the top though (and, unless you take
special precautions you can run into an endless loop if an env var contains
its own name.
If it is desired, please let me know and I happily will add it.
---
common/cmd_setexpr.c | 31 ++++++++++++++++++++++++++++---
1 files changed, 28 insertions(+), 3 deletions(-)
diff --git a/common/cmd_setexpr.c b/common/cmd_setexpr.c
index f8b5d4d..a7c6f53 100644
--- a/common/cmd_setexpr.c
+++ b/common/cmd_setexpr.c
@@ -28,10 +28,32 @@
#include <config.h>
#include <command.h>
+static ulong get_arg(char *s, int w)
+{
+ ulong *p;
+
+ /* if the parameter starts with a $ replace it with the environment value */
+ if (s[0] == '$') {
+ s = getenv(&s[1]);
+ }
+ /* if the parameter starts with a * then assume is a pointer to the value we want */
+ if (s[0] == '*') {
+ p = (ulong *)simple_strtoul(&s[1], NULL, 16);
+ switch (w) {
+ case 1: return((ulong)(*(uchar *)p));
+ case 2: return((ulong)(*(ushort *)p));
+ case 4: return(*p);
+ }
+ } else {
+ return simple_strtoul(s, NULL, 16);
+ }
+}
+
int do_setexpr(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
ulong a, b;
char buf[16];
+ int w;
/* Validate arguments */
if ((argc != 5) || (strlen(argv[3]) != 1)) {
@@ -39,8 +61,10 @@ int do_setexpr(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
return 1;
}
- a = simple_strtoul(argv[2], NULL, 16);
- b = simple_strtoul(argv[4], NULL, 16);
+ w = cmd_get_data_size(argv[0], 4);
+
+ a = get_arg(argv[2], w);
+ b = get_arg(argv[4], w);
switch (argv[3][0]) {
case '|': sprintf(buf, "%lx", (a | b)); break;
@@ -64,7 +88,8 @@ int do_setexpr(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
U_BOOT_CMD(
setexpr, 5, 0, do_setexpr,
"set environment variable as the result of eval expression",
- "name value1 <op> value2\n"
+ "[.b, .w, .l] name value1 <op> value2\n"
" - set environment variable 'name' to the result of the evaluated\n"
" express specified by <op>. <op> can be &, |, ^, +, -, *, /, %"
+ " size argument is only meaningful if value1 and/or value2 are memory addresses"
);
--
1.7.0
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