pxe: parse initrd file from append string

For syslinux, the initrd can be set in the append string as
"initrd=<file>", so try to find it there if we haven't already set the
initrd.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>

common/cmd_pxe.c

@@ -999,6 +999,7 @@ static int parse_label_menu(char **c, struct pxe_menu *cfg,
 static int parse_label(char **c, struct pxe_menu *cfg)
 {
 	struct token t;
+	int len;
 	char *s = *c;
 	struct pxe_label *label;
 	int err;
@@ -1033,10 +1034,22 @@ static int parse_label(char **c, struct pxe_menu *cfg)
 
 		case T_APPEND:
 			err = parse_sliteral(c, &label->append);
+			if (label->initrd)
+				break;
+			s = strstr(label->append, "initrd=");
+			if (!s)
+				break;
+			s += 7;
+			len = (int)(strchr(s, ' ') - s);
+			label->initrd = malloc(len + 1);
+			strncpy(label->initrd, s, len);
+			label->initrd[len] = '\0';
+
 			break;
 
 		case T_INITRD:
-			err = parse_sliteral(c, &label->initrd);
+			if (!label->initrd)
+				err = parse_sliteral(c, &label->initrd);
 			break;
 
 		case T_LOCALBOOT:

doc/README.pxe

@@ -224,9 +224,6 @@ PXELINUX and U-boot's pxe support.
 - U-boot's pxe expects U-boot uimg's as kernels.  Anything that would work
   with the 'bootm' command in U-boot could work with the 'pxe boot' command.
 
-- U-boot's pxe doesn't recognize initrd options in the append command - you
-  must specify initrd files using the initrd command.
-
 - U-boot's pxe only recognizes a single file on the initrd command line.  It
   could be extended to support multiple.