On Thu, May 29, 2014 at 8:55 AM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: > 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@xxxxxxxxxx> >> Cc: Stephen Warren <swarren@xxxxxxxxxxxxx> >> Cc: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx> >> Signed-off-by: Kevin Hilman <khilman@xxxxxxxxxx> >> --- >> 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@xxxxxxxxxx> > > 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 Great. As I mentioned above, I'm certainly not opposed to more padding, and agree that it would be more future proof. I was simply being rather conservative in case folks didn't want to see every .dtb grow by 4k. I'll wait a bit to see if there are any other opinions, and the respin with 4k padding. Kevin -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
