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authorDavid Gibson <david@gibson.dropbear.id.au>2007-03-13 20:50:40 -0400
committerPaul Mackerras <paulus@samba.org>2007-03-16 01:38:19 -0400
commit0e0293c898c424c52e5d4e7f6923a203d06b9c4b (patch)
tree54078533f47d45c0840095901e416dfa543393ba /Documentation/powerpc
parenta782a9e3a12bcea4916117b0832016c24fffeb85 (diff)
[POWERPC] Update documentation for flat device tree format v17
This patch updates booting-without-of.txt to describe version 17 of the flattened device tree format. Version 17 is a small, backwards compatible change from version 16, adding an extra field giving the size of the device tree's structure block. At this time, the kernel has no use for the extra information, however its presence can make life easier for bootloaders or other software manipulating the tree. In addition this patch adds information on the size_dt_strings field of the device tree header, present since version 3 of the flattened tree format, but omitted from the documentation. It also makes changes to consistently refer to versions 16 and 17 as versions 16 and 17 in decimal, rather than version 0x10 which was occasionally used for version 16 previously. Finally, we also add the new field to the definition of the device tree header structure in prom.h Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Acked-by: Jon Loeliger <jdl@freescale.com> Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'Documentation/powerpc')
-rw-r--r--Documentation/powerpc/booting-without-of.txt29
1 files changed, 23 insertions, 6 deletions
diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
index 6d5a5a0fa5e8..a1f83f1c24c9 100644
--- a/Documentation/powerpc/booting-without-of.txt
+++ b/Documentation/powerpc/booting-without-of.txt
@@ -265,6 +265,9 @@ struct boot_param_header {
265 booting on */ 265 booting on */
266 /* version 3 fields below */ 266 /* version 3 fields below */
267 u32 size_dt_strings; /* size of the strings block */ 267 u32 size_dt_strings; /* size of the strings block */
268
269 /* version 17 fields below */
270 u32 size_dt_struct; /* size of the DT structure block */
268}; 271};
269 272
270 Along with the constants: 273 Along with the constants:
@@ -335,10 +338,13 @@ struct boot_param_header {
335 to reallocate it easily at boot and free up the unused flattened 338 to reallocate it easily at boot and free up the unused flattened
336 structure after expansion. Version 16 introduces a new more 339 structure after expansion. Version 16 introduces a new more
337 "compact" format for the tree itself that is however not backward 340 "compact" format for the tree itself that is however not backward
338 compatible. You should always generate a structure of the highest 341 compatible. Version 17 adds an additional field, size_dt_struct,
339 version defined at the time of your implementation. Currently 342 allowing it to be reallocated or moved more easily (this is
340 that is version 16, unless you explicitly aim at being backward 343 particularly useful for bootloaders which need to make
341 compatible. 344 adjustments to a device tree based on probed information). You
345 should always generate a structure of the highest version defined
346 at the time of your implementation. Currently that is version 17,
347 unless you explicitly aim at being backward compatible.
342 348
343 - last_comp_version 349 - last_comp_version
344 350
@@ -347,7 +353,7 @@ struct boot_param_header {
347 is backward compatible with version 1 (that is, a kernel build 353 is backward compatible with version 1 (that is, a kernel build
348 for version 1 will be able to boot with a version 2 format). You 354 for version 1 will be able to boot with a version 2 format). You
349 should put a 1 in this field if you generate a device tree of 355 should put a 1 in this field if you generate a device tree of
350 version 1 to 3, or 0x10 if you generate a tree of version 0x10 356 version 1 to 3, or 16 if you generate a tree of version 16 or 17
351 using the new unit name format. 357 using the new unit name format.
352 358
353 - boot_cpuid_phys 359 - boot_cpuid_phys
@@ -360,6 +366,17 @@ struct boot_param_header {
360 point (see further chapters for more informations on the required 366 point (see further chapters for more informations on the required
361 device-tree contents) 367 device-tree contents)
362 368
369 - size_dt_strings
370
371 This field only exists on version 3 and later headers. It
372 gives the size of the "strings" section of the device tree (which
373 starts at the offset given by off_dt_strings).
374
375 - size_dt_struct
376
377 This field only exists on version 17 and later headers. It gives
378 the size of the "structure" section of the device tree (which
379 starts at the offset given by off_dt_struct).
363 380
364 So the typical layout of a DT block (though the various parts don't 381 So the typical layout of a DT block (though the various parts don't
365 need to be in that order) looks like this (addresses go from top to 382 need to be in that order) looks like this (addresses go from top to
@@ -417,7 +434,7 @@ root node who has no parent.
417A node has 2 names. The actual node name is generally contained in a 434A node has 2 names. The actual node name is generally contained in a
418property of type "name" in the node property list whose value is a 435property of type "name" in the node property list whose value is a
419zero terminated string and is mandatory for version 1 to 3 of the 436zero terminated string and is mandatory for version 1 to 3 of the
420format definition (as it is in Open Firmware). Version 0x10 makes it 437format definition (as it is in Open Firmware). Version 16 makes it
421optional as it can generate it from the unit name defined below. 438optional as it can generate it from the unit name defined below.
422 439
423There is also a "unit name" that is used to differentiate nodes with 440There is also a "unit name" that is used to differentiate nodes with