libfdt queries

[David Gibson]

On Tue, Oct 25, 2011 at 11:28:51AM +0530, Varun Wadekar wrote:
> Hi,
> 
> I am using libfdt v1.3.0 for modifying the dtb file from the bootloader
> (not U-Boot). I have a .dtb file whose bootargs have to be modified
> before passing over to the kernel. This is the sequence that I am following:
> 
> <snip>
> 
> newlen = fdt_totalsize(blob) + 512;
> fdt_open_into(blob, blob, newlen)
> 
> node = fdt_path_offset(blob, "/chosen");
> if (node < 0)
>     <error handling code>
> 
> fdt_setprop_string(blob, node, "bootargs", cmdline)
> 
> <snip>
> 
> Now with the above code the serial console on my board does not come up
> with the default bootargs that are present in the .dts file. If I
> manipulate the bootargs string in the .dts file with some additional
> garbage characters and then run the above code then I see that the
> serial console comes up. I suspect that the dtb is not getting updated
> properly with the above apis.

That seems a bit unlikely, but maybe.  Is there any way you can dump
out the dtb after processing by your bootloader?

> Somehow the dtb contents are getting
> overwritten and the serial console info is getting overwritten I think.
> 
> If I add a partial command line to my dts, then modifying the bootargs
> from fastboot does not corrupt the dtb file and I can see the kernel
> console come up.
> 
> Any pointers or ideas where I might have screwed up?

First thing would be to check if fdt_setprop_string() is returning an
error code.

Also, is that the only dtb manipulation you do, or do you make other
changes to the dtb?

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson