Subject: [PATCH] ARM: /proc/atags: Export also for DT

From: [email-masked] (Pali Rohár)
Date: Mon, 26 Jan 2015 20:16:52 +0100

This patch will cause that decompressor store full ATAG structure into DT tree ("/atags"):

diff --git a/arch/arm/boot/compressed/atags_to_fdt.c b/arch/arm/boot/compressed/atags_to_fdt.c
index e7e1cc9..1975d7c 100644
--- a/arch/arm/boot/compressed/atags_to_fdt.c
+++ b/arch/arm/boot/compressed/atags_to_fdt.c
@@ -112,7 +112,7 @@ int atags_to_fdt(void *atag_list, void *fdt, int total_space)
 	 * address and size for each bank */
 	uint32_t mem_reg_property[2 * 2 * NR_BANKS];
 	int memcount = 0;
-	int ret, memsize;
+	int ret, memsize, atag_size;
 
 	/* make sure we've got an aligned pointer */
 	if ((u32)atag_list & 0x3)
@@ -184,6 +184,10 @@ int atags_to_fdt(void *atag_list, void *fdt, int total_space)
 		}
 	}
 
+	/* include the terminating ATAG_NONE */
+	atag_size = (char *)atag - (char *)atag_list + sizeof(struct tag_header);
+	setprop(fdt, "/", "atags", atag_list, atag_size);
+
 	if (memcount) {
 		setprop(fdt, "/memory", "reg", mem_reg_property,
 			4 * memcount * memsize);

And this patch will export ATAG structure from DT tree ("/atags") into /proc/atags file:

diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
index 9946c1b..0f249a3 100644
--- a/arch/arm/kernel/devtree.c
+++ b/arch/arm/kernel/devtree.c
@@ -29,6 +29,7 @@
 #include <asm/mach-types.h>
 #include <asm/system_info.h>
 
+#include "atags.h"
 
 #ifdef CONFIG_SMP
 extern struct of_cpu_method __cpu_method_of_table[];
@@ -254,5 +255,10 @@ const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
 	if (prop)
 		system_rev = fdt32_to_cpu(*prop);
 
+	/* Save atags */
+	prop = of_get_flat_dt_prop(dt_root, "atags", NULL);
+	if (prop)
+		save_atags((void *)prop);
+
 	return mdesc;
 }

Some userspace applications needs access to ATAG structure where can be stored some information passed 
from bootloader to kernel. Example is Nokia N900 device and NOLO bootloader which provides information 
about bootreason (device was started by power button or by alarm or restarted...) and bootmode (normal 
mode or device update mode).

-- 
Pali Roh?r
pali.rohar at gmail.com
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