[patch][rfc]flattened device tree: Passing a dtb (blob) to Linux.

[Jimi Xenidis <jimix@watson.ibm.com>]

A devtree compiler (dtc) generated devtree blob is "relocatable" and  
so does not contain a reserved_map entry for the blob itself.
This means that if passed to Linux, Linux will not get lmb_reserve()  
the blob and it could be over.
The following patch will explicitly reserve the "blob" as it was  
given to us and stops prom_init.c from creating a reserved mapping  
for the blob.

NOTE: that the dtc must also not generate the blob reservation  
entry.  Should we try to detect this redundant entry? Should we bump  
the DT version number?


Signed-off-by:  <jimix@watson.ibm.com>
--
diff -r eb0990a251a9 arch/powerpc/kernel/prom.c
--- a/arch/powerpc/kernel/prom.c	Thu Mar 30 22:05:40 2006 -0500
+++ b/arch/powerpc/kernel/prom.c	Wed Apr 12 22:00:27 2006 -0400
@@ -1132,6 +1132,11 @@ static void __init early_reserve_mem(voi
	reserve_map = (u64 *)(((unsigned long)initial_boot_params) +
					initial_boot_params->off_mem_rsvmap);
+
+	/* before we do anything, lets reserve the dt blob */
+	lmb_reserve(__pa((unsigned long)initial_boot_params),
+		    initial_boot_params->totalsize);
+
#ifdef CONFIG_PPC32
	/*
	 * Handle the case where we might be booting from an old kexec
diff -r eb0990a251a9 arch/powerpc/kernel/prom_init.c
--- a/arch/powerpc/kernel/prom_init.c	Thu Mar 30 22:05:40 2006 -0500
+++ b/arch/powerpc/kernel/prom_init.c	Wed Apr 12 22:00:27 2006 -0400
@@ -1909,11 +1909,7 @@ static void __init flatten_device_tree(v
	/* Version 16 is not backward compatible */
	hdr->last_comp_version = 0x10;
-	/* Reserve the whole thing and copy the reserve map in, we
-	 * also bump mem_reserve_cnt to cause further reservations to
-	 * fail since it's too late.
-	 */
-	reserve_mem(RELOC(dt_header_start), hdr->totalsize);
+	/* Copy the reserve map in */
	memcpy(rsvmap, RELOC(mem_reserve_map), sizeof(mem_reserve_map));
#ifdef DEBUG_PROM
@@ -1926,6 +1922,9 @@ static void __init flatten_device_tree(v
				    RELOC(mem_reserve_map)[i].size);
	}
#endif
+	/* Bump mem_reserve_cnt to cause further reservations to fail
+	 * since it's too late.
+	 */
	RELOC(mem_reserve_cnt) = MEM_RESERVE_MAP_SIZE;
	prom_printf("Device tree strings 0x%x -> 0x%x\n",