[PATCH] arm: use /sys/firmware/fdt in case without --atags and --dtb

[Dave Young]

Latest linux kernel will create /sys/firmware/fdt file. It will be convenient
to use it in case one does not specify --atags and --dtb options.

Signed-off-by: Dave Young <dyoung at redhat.com>
---
 kexec/arch/arm/kexec-arm.c        |    7 +++++++
 kexec/arch/arm/kexec-arm.h        |    2 ++
 kexec/arch/arm/kexec-zImage-arm.c |    8 ++++++++
 3 files changed, 17 insertions(+)

--- kexec-tools.orig/kexec/arch/arm/kexec-arm.c
+++ kexec-tools/kexec/arch/arm/kexec-arm.c
@@ -12,6 +12,7 @@
 #include <stdint.h>
 #include <string.h>
 #include <getopt.h>
+#include <unistd.h>
 #include "../../kexec.h"
 #include "../../kexec-syscall.h"
 #include "kexec-arm.h"
@@ -137,3 +138,9 @@ int arch_compat_trampoline(struct kexec_
 void arch_update_purgatory(struct kexec_info *UNUSED(info))
 {
 }
+
+/* return 1 if /sys/firmware/fdt exists, otherwise return 0 */
+int have_sysfs_fdt(void)
+{
+	return !access(SYSFS_FDT, F_OK);
+}
--- kexec-tools.orig/kexec/arch/arm/kexec-arm.h
+++ kexec-tools/kexec/arch/arm/kexec-arm.h
@@ -3,6 +3,7 @@
 
 #include <sys/types.h>
 
+#define SYSFS_FDT "/sys/firmware/fdt"
 #define BOOT_BLOCK_VERSION 17
 #define BOOT_BLOCK_LAST_COMP_VERSION 16
 
@@ -16,5 +17,6 @@ void zImage_arm_usage(void);
 int uImage_arm_probe(const char *buf, off_t len);
 int uImage_arm_load(int argc, char **argv, const char *buf, off_t len,
 		        struct kexec_info *info);
+extern int have_sysfs_fdt(void);
 
 #endif /* KEXEC_ARM_H */
--- kexec-tools.orig/kexec/arch/arm/kexec-zImage-arm.c
+++ kexec-tools/kexec/arch/arm/kexec-zImage-arm.c
@@ -358,6 +358,14 @@ int zImage_arm_load(int argc, char **arg
 		return -1;
 	}
 
+	if (!use_atags && !dtb_file) {
+		int f;
+
+		f = have_sysfs_fdt();
+		if (f)
+			dtb_file = SYSFS_FDT;
+	}
+
 	if (command_line) {
 		command_line_len = strlen(command_line) + 1;
 		if (command_line_len > COMMAND_LINE_SIZE)