On 05/23/2014 05:41 PM, Kevin Hilman wrote:
By default, add some padding to the DT blobs to facilitate later patching.
An example need for DTB patching is the need to modifiy the command line on platforms where ATAGS are not (or cannot) be used to pass the commandline. For example, we do not support a big-endian kernel reading ATAGS from a little-endian u-boot, so the only way to pass a command line in the DT.
Also, without ATAG support (or if u-boot was built without CONFIG_INITRD_TAG) the only way to pass an initrd is by adding an initrd= option to command line (in the DT).
Therefore, to facilitate adding to the DT command line directly in the DTB, add some padding.
Cc: Nicolas Pitre nico@linaro.org Cc: Stephen Warren swarren@wwwdotorg.org Cc: Thomas Petazzoni thomas.petazzoni@free-electrons.com Signed-off-by: Kevin Hilman khilman@linaro.org
I kinda pulled 64 bytes out of the air here since it's enough to add some common things to the commandline like debug, earlyprink initrd=<addr>,<size>, etc., but I'm certainlly not opposed to more padding.
Conceptually, Acked-by: Stephen Warren swarren@nvidia.com
But I would expect a pad of something like 4KB to be more future-proof. U-Boot appears to use 4KB on ARM at least:
./arch/arm/dts/Makefile:37:DTC_FLAGS += -R 4 -p 0x1000