Re: [PATCH v7 2/2] arm64: boot: Support Flat Image Tree

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hi,

a few more comments after decompiling the FIT image:

On 29.11.23 18:21, Simon Glass wrote:
> +    with fsw.add_node('kernel'):
> +        fsw.property_string('description', args.name)
> +        fsw.property_string('type', 'kernel_noload')

The specification only says no loading done, but doesn't explain what it
means for a bootloader to _not_ load an image. Looking into the U-Boot commit
b9b50e89d317 ("image: Implement IH_TYPE_KERNEL_NOLOAD") that introduces this,
apparently no loading means ignoring load and entry address?

I presume missing load and entry is something older U-Boot versions
were unhappy about? Please let me know if the semantics are as I understood,
so I can prepare a barebox patch supporting it.

> +        fsw.property_string('arch', args.arch)
> +        fsw.property_string('os', args.os)
> +        fsw.property_string('compression', args.compress)
> +        fsw.property('data', data)
> +        fsw.property_u32('load', 0)
> +        fsw.property_u32('entry', 0)
> +
> +
> +def finish_fit(fsw, entries):
> +    """Finish the FIT ready for use
> +
> +    Writes the /configurations node and subnodes
> +
> +    Args:
> +        fsw (libfdt.FdtSw): Object to use for writing
> +        entries (list of tuple): List of configurations:
> +            str: Description of model
> +            str: Compatible stringlist
> +    """
> +    fsw.end_node()
> +    seq = 0
> +    with fsw.add_node('configurations'):
> +        for model, compat in entries:
> +            seq += 1
> +            with fsw.add_node(f'conf-{seq}'):
> +                fsw.property('compatible', bytes(compat))

The specification says that this is the root U-Boot compatible,
which I presume to mean the top-level compatible, which makes sense to me.

The code here though adds all compatible strings from the device tree though,
is this intended?

> +        fsw.property_string('description', model)
> +        fsw.property_string('type', 'flat_dt')
> +        fsw.property_string('arch', arch)
> +        fsw.property_string('compression', compress)
> +        fsw.property('compatible', bytes(compat))

I think I've never seen a compatible for a fdt node before.
What use does this serve?

Cheers,
Ahmad

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