cmd/fdt: support single value replacement within an array

With this commit we can modify single values within an array of a dts
property.

This is useful if we have for example a pwm-backlight where we want to
modifiy the pwm frequency per u-boot script.

The pwm is described in dts like this:

backlight {
	pwms = <0x0000002b 0x00000000 0x004c4b40>;
};

For changing the frequency, here the 3rd parameter, we simply type:

fdt set /backlight pwms <? ? 0x1E8480>;

For doing all this we:
- backup the property content into our 'SCRATCHPAD'
- only modify the array-cell if the new content doesn't start with '?'

Signed-off-by: Hannes Schmelzer <hannes.schmelzer@br-automation.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/cmd/fdt.c b/cmd/fdt.c
index a21415d..e55102a 100644 (file)
--- a/cmd/fdt.c
+++ b/cmd/fdt.c
@@ -257,6 +257,7 @@ static int do_fdt(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
                char *prop;             /* property */
                int  nodeoffset;        /* node offset from libfdt */
                static char data[SCRATCHPAD];   /* storage for the property */
+               const void *ptmp;
                int  len;               /* new length of the property */
                int  ret;               /* return value */
 
@@ -268,13 +269,6 @@ static int do_fdt(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 
                pathp  = argv[2];
                prop   = argv[3];
-               if (argc == 4) {
-                       len = 0;
-               } else {
-                       ret = fdt_parse_prop(&argv[4], argc - 4, data, &len);
-                       if (ret != 0)
-                               return ret;
-               }
 
                nodeoffset = fdt_path_offset (working_fdt, pathp);
                if (nodeoffset < 0) {
@@ -286,6 +280,21 @@ static int do_fdt(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
                        return 1;
                }
 
+               if (argc == 4) {
+                       len = 0;
+               } else {
+                       ptmp = fdt_getprop(working_fdt, nodeoffset, prop, &len);
+                       if (len > SCRATCHPAD) {
+                               printf("prop (%d) doesn't fit in scratchpad!\n",
+                                      len);
+                               return 1;
+                       }
+                       memcpy(data, ptmp, len);
+                       ret = fdt_parse_prop(&argv[4], argc - 4, data, &len);
+                       if (ret != 0)
+                               return ret;
+               }
+
                ret = fdt_setprop(working_fdt, nodeoffset, prop, data, len);
                if (ret < 0) {
                        printf ("libfdt fdt_setprop(): %s\n", fdt_strerror(ret));
@@ -766,7 +775,11 @@ static int fdt_parse_prop(char * const *newval, int count, char *data, int *len)
 
                        cp = newp;
                        tmp = simple_strtoul(cp, &newp, 0);
-                       *(fdt32_t *)data = cpu_to_fdt32(tmp);
+                       if (*cp != '?')
+                               *(fdt32_t *)data = cpu_to_fdt32(tmp);
+                       else
+                               newp++;
+
                        data  += 4;
                        *len += 4;