of/fdt: Rework early_init_dt_scan_chosen() to call directly

Use of the of_scan_flat_dt() function predates libfdt and is discouraged
as libfdt provides a nicer set of APIs. Rework
early_init_dt_scan_chosen() to be called directly and use libfdt.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Frank Rowand <frank.rowand@sony.com>
Link: https://lore.kernel.org/r/20211118181213.1433346-2-robh@kernel.org

arch/powerpc/kernel/prom.c

@@ -402,7 +402,7 @@ static int __init early_init_dt_scan_chosen_ppc(unsigned long node,
 	const unsigned long *lprop; /* All these set by kernel, so no need to convert endian */
 
 	/* Use common scan routine to determine if this is the chosen node */
-	if (early_init_dt_scan_chosen(node, uname, depth, data) == 0)
+	if (early_init_dt_scan_chosen(data) < 0)
 		return 0;
 
 #ifdef CONFIG_PPC64

arch/powerpc/mm/nohash/kaslr_booke.c

@@ -44,9 +44,7 @@ struct regions __initdata regions;
 
 static __init void kaslr_get_cmdline(void *fdt)
 {
-	int node = fdt_path_offset(fdt, "/chosen");
-
-	early_init_dt_scan_chosen(node, "chosen", 1, boot_command_line);
+	early_init_dt_scan_chosen(boot_command_line);
 }
 
 static unsigned long __init rotate_xor(unsigned long hash, const void *area,

drivers/of/fdt.c

@@ -1124,18 +1124,18 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
 	return 0;
 }
 
-int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
-				     int depth, void *data)
+int __init early_init_dt_scan_chosen(char *cmdline)
 {
-	int l;
+	int l, node;
 	const char *p;
 	const void *rng_seed;
+	const void *fdt = initial_boot_params;
 
-	pr_debug("search \"chosen\", depth: %d, uname: %s\n", depth, uname);
-
-	if (depth != 1 || !data ||
-	    (strcmp(uname, "chosen") != 0 && strcmp(uname, "chosen@0") != 0))
-		return 0;
+	node = fdt_path_offset(fdt, "/chosen");
+	if (node < 0)
+		node = fdt_path_offset(fdt, "/chosen@0");
+	if (node < 0)
+		return -ENOENT;
 
 	early_init_dt_check_for_initrd(node);
 	early_init_dt_check_for_elfcorehdr(node);
@@ -1144,7 +1144,7 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 	/* Retrieve command line */
 	p = of_get_flat_dt_prop(node, "bootargs", &l);
 	if (p != NULL && l > 0)
-		strlcpy(data, p, min(l, COMMAND_LINE_SIZE));
+		strlcpy(cmdline, p, min(l, COMMAND_LINE_SIZE));
 
 	/*
 	 * CONFIG_CMDLINE is meant to be a default in case nothing else
@@ -1153,18 +1153,18 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 	 */
 #ifdef CONFIG_CMDLINE
 #if defined(CONFIG_CMDLINE_EXTEND)
-	strlcat(data, " ", COMMAND_LINE_SIZE);
-	strlcat(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+	strlcat(cmdline, " ", COMMAND_LINE_SIZE);
+	strlcat(cmdline, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
 #elif defined(CONFIG_CMDLINE_FORCE)
-	strlcpy(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+	strlcpy(cmdline, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
 #else
 	/* No arguments from boot loader, use kernel's  cmdl*/
-	if (!((char *)data)[0])
-		strlcpy(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+	if (!((char *)cmdline)[0])
+		strlcpy(cmdline, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
 #endif
 #endif /* CONFIG_CMDLINE */
 
-	pr_debug("Command line is: %s\n", (char *)data);
+	pr_debug("Command line is: %s\n", (char *)cmdline);
 
 	rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l);
 	if (rng_seed && l > 0) {
@@ -1178,8 +1178,7 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 				fdt_totalsize(initial_boot_params));
 	}
 
-	/* break now */
-	return 1;
+	return 0;
 }
 
 #ifndef MIN_MEMBLOCK_ADDR
@@ -1261,14 +1260,14 @@ bool __init early_init_dt_verify(void *params)
 
 void __init early_init_dt_scan_nodes(void)
 {
-	int rc = 0;
+	int rc;
 
 	/* Initialize {size,address}-cells info */
 	of_scan_flat_dt(early_init_dt_scan_root, NULL);
 
 	/* Retrieve various information from the /chosen node */
-	rc = of_scan_flat_dt(early_init_dt_scan_chosen, boot_command_line);
-	if (!rc)
+	rc = early_init_dt_scan_chosen(boot_command_line);
+	if (rc)
 		pr_warn("No chosen node found, continuing without\n");
 
 	/* Setup memory, calling early_init_dt_add_memory_arch */

include/linux/of_fdt.h

@@ -58,8 +58,7 @@ extern int of_flat_dt_is_compatible(unsigned long node, const char *name);
 extern unsigned long of_get_flat_dt_root(void);
 extern uint32_t of_get_flat_dt_phandle(unsigned long node);
 
-extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
-				     int depth, void *data);
+extern int early_init_dt_scan_chosen(char *cmdline);
 extern int early_init_dt_scan_memory(unsigned long node, const char *uname,
 				     int depth, void *data);
 extern int early_init_dt_scan_chosen_stdout(void);