[U-Boot] [RFC PATCH] pxe: add support for FDT overlays

[Neil Armstrong]

This adds support for specicyinf FDT overlays in an extlinux/pxelinux
configuration file.

Without this, there is no simple way to apply overlays when the kernel
and ftd is loaded by the pxe command.

This change adds the 'fdtoverlays' keyword for a label, supporting multiple
overlay files to be applied on top of the fdt specific in the 'fdt' or
'devicetree' keyword.

Cc: Jernej Škrabec <jernej.skrabec at siol.net>
Cc: Jonas Karlman <jonas at kwiboo.se>
Signed-off-by: Neil Armstrong <narmstrong at baylibre.com>
---
 cmd/pxe.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)

diff --git a/cmd/pxe.c b/cmd/pxe.c
index 1dd0a74ea3..8d19e6f99f 100644
--- a/cmd/pxe.c
+++ b/cmd/pxe.c
@@ -13,6 +13,8 @@
 #include <linux/ctype.h>
 #include <errno.h>
 #include <linux/list.h>
+#include <fdt_support.h>
+#include <linux/libfdt.h>
 #include <fs.h>
 #include <splash.h>
 #include <asm/io.h>
@@ -481,6 +483,7 @@ struct pxe_label {
 	char *initrd;
 	char *fdt;
 	char *fdtdir;
+	char *fdtoverlays;
 	int ipappend;
 	int attempted;
 	int localboot;
@@ -561,6 +564,9 @@ static void label_destroy(struct pxe_label *label)
 	if (label->fdtdir)
 		free(label->fdtdir);
 
+	if (label->fdtoverlays)
+		free(label->fdtoverlays);
+
 	free(label);
 }
 
@@ -608,6 +614,92 @@ static int label_localboot(struct pxe_label *label)
 	return run_command_list(localcmd, strlen(localcmd), 0);
 }
 
+/*
+ * Loads fdt overlays specified in 'fdtoverlays'.
+ */
+#ifdef CONFIG_OF_LIBFDT_OVERLAY
+static void label_boot_fdtoverlay(cmd_tbl_t *cmdtp, struct pxe_label *label)
+{
+	char *fdtoverlay = label->fdtoverlays;
+	struct fdt_header *working_fdt;
+	char *fdtoverlay_addr_env;
+	ulong fdtoverlay_addr;
+	ulong fdt_addr;
+	int err;
+
+	/* Get the main fdt and map it */
+	fdt_addr = simple_strtoul(env_get("fdt_addr_r"), NULL, 16);
+	working_fdt = map_sysmem(fdt_addr, 0);
+	err = fdt_check_header(working_fdt);
+	if (err)
+		return;
+
+	/* Get the specific overlay loading address */
+	fdtoverlay_addr_env = env_get("fdtoverlay_addr_r");
+	if (!fdtoverlay_addr_env) {
+		printf("Invalid fdtoverlay_addr_r for loading overlays\n");
+		return;
+	}
+
+	fdtoverlay_addr = simple_strtoul(fdtoverlay_addr_env, NULL, 16);
+
+	/* Cycle over the overlay files and apply them in order */
+	do {
+		struct fdt_header *blob;
+		char *overlayfile;
+		char *end;
+		int len;
+
+		/* Drop leading spaces */
+		while (*fdtoverlay == ' ')
+			++fdtoverlay;
+
+		/* Copy a single filename if multiple provided */
+		end = strstr(fdtoverlay, " ");
+		if (end) {
+			len = (int)(end - fdtoverlay);
+			overlayfile = malloc(len + 1);
+			strncpy(overlayfile, fdtoverlay, len);
+			overlayfile[len] = '\0';
+		} else
+			overlayfile = fdtoverlay;
+
+		if (!strlen(overlayfile))
+			goto skip_overlay;
+
+		/* Load overlay file */
+		err = get_relfile_envaddr(cmdtp, overlayfile,
+					  "fdtoverlay_addr_r");
+		if (err < 0) {
+			printf("Failed loading overlay %s\n", overlayfile);
+			goto skip_overlay;
+		}
+
+		/* Resize main fdt */
+		fdt_shrink_to_minimum(working_fdt, 8192);
+
+		blob = map_sysmem(fdtoverlay_addr, 0);
+		err = fdt_check_header(blob);
+		if (err) {
+			printf("Invalid overlay %s, skipping\n",
+			       overlayfile);
+			goto skip_overlay;
+		}
+
+		err = fdt_overlay_apply_verbose(working_fdt, blob);
+		if (err) {
+			printf("Failed to apply overlay %s, skipping\n",
+			       overlayfile);
+			goto skip_overlay;
+		}
+
+skip_overlay:
+		if (end)
+			free(overlayfile);
+	} while ((fdtoverlay = strstr(fdtoverlay, " ")));
+}
+#endif
+
 /*
  * Boot according to the contents of a pxe_label.
  *
@@ -798,6 +890,11 @@ static int label_boot(cmd_tbl_t *cmdtp, struct pxe_label *label)
 						label->name);
 				goto cleanup;
 			}
+
+#ifdef CONFIG_OF_LIBFDT_OVERLAY
+			if (label->fdtoverlays)
+				label_boot_fdtoverlay(cmdtp, label);
+#endif
 		} else {
 			bootm_argv[3] = NULL;
 		}
@@ -855,6 +952,7 @@ enum token_type {
 	T_INCLUDE,
 	T_FDT,
 	T_FDTDIR,
+	T_FDTOVERLAYS,
 	T_ONTIMEOUT,
 	T_IPAPPEND,
 	T_BACKGROUND,
@@ -889,6 +987,7 @@ static const struct token keywords[] = {
 	{"fdt", T_FDT},
 	{"devicetreedir", T_FDTDIR},
 	{"fdtdir", T_FDTDIR},
+	{"fdtoverlays", T_FDTOVERLAYS},
 	{"ontimeout", T_ONTIMEOUT,},
 	{"ipappend", T_IPAPPEND,},
 	{"background", T_BACKGROUND,},
@@ -1322,6 +1421,11 @@ static int parse_label(char **c, struct pxe_menu *cfg)
 				err = parse_sliteral(c, &label->fdtdir);
 			break;
 
+		case T_FDTOVERLAYS:
+			if (!label->fdtoverlays)
+				err = parse_sliteral(c, &label->fdtoverlays);
+			break;
+
 		case T_LOCALBOOT:
 			label->localboot = 1;
 			err = parse_integer(c, &label->localboot_val);
-- 
2.21.0