x86: use FDT accessors for FDT blob header data

Remove the direct accesses to FDT header data using accessor
function instead. This makes the code more readable and makes the FDT
blob structure more opaque to the arch code. This also prepares for
removing struct boot_param_header completely.

Signed-off-by: Rob Herring <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Tested-by: Grant Likely <[email protected]>

Author: robherring

arch/x86/kernel/devicetree.c

@@ -206,23 +206,21 @@ static void __init dtb_apic_setup(void)
 static void __init x86_flattree_get_config(void)
 {
 	u32 size, map_len;
-	struct boot_param_header *dt;
+	void *dt;
 
 	if (!initial_dtb)
 		return;
 
-	map_len = max(PAGE_SIZE - (initial_dtb & ~PAGE_MASK),
-			(u64)sizeof(struct boot_param_header));
+	map_len = max(PAGE_SIZE - (initial_dtb & ~PAGE_MASK), (u64)128);
 
-	dt = early_memremap(initial_dtb, map_len);
-	size = be32_to_cpu(dt->totalsize);
+	initial_boot_params = dt = early_memremap(initial_dtb, map_len);
+	size = of_get_flat_dt_size();
 	if (map_len < size) {
 		early_iounmap(dt, map_len);
-		dt = early_memremap(initial_dtb, size);
+		initial_boot_params = dt = early_memremap(initial_dtb, size);
 		map_len = size;
 	}
 
-	initial_boot_params = dt;
 	unflatten_and_copy_device_tree();
 	early_iounmap(dt, map_len);
 }