linux-kernel - Re: [PATCH v6 2/8] scripts/make_fit: Support an initial ramdisk

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Message-ID: <7fdf869d-d2c8-4694-8f06-db1a32e817da@pengutronix.de>
Date: Wed, 26 Nov 2025 11:56:54 +0100
From: Ahmad Fatoum <a.fatoum@...gutronix.de>
To: Simon Glass <sjg@...omium.org>, linux-arm-kernel@...ts.infradead.org
Cc: Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
 Masahiro Yamada <masahiroy@...nel.org>, Tom Rini <trini@...sulko.com>,
 J . Neuschäfer <j.ne@...teo.net>,
 Chen-Yu Tsai <wenst@...omium.org>, Nicolas Schier <nsc@...nel.org>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/8] scripts/make_fit: Support an initial ramdisk



On 11/19/25 7:13 PM, Simon Glass wrote:
> FIT (Flat Image Tree) allows a ramdisk to be included in each
> configuration. Add support for this to the script.
> 
> This feature is not available via 'make image.fit' since the ramdisk
> likely needs to be built separately anyway, e.g. using modules from
> the kernel build. A later patch in this series provides support for
> doing that.
> 
> Note that the uncompressed size is not correct when a ramdisk is used,
> since it is too expensive to decompress the ramdisk.
> 
> Signed-off-by: Simon Glass <sjg@...omium.org>
> Reviewed-by: Nicolas Schier <nsc@...nel.org>

With load address removed:

Reviewed-by: Ahmad Fatoum <a.fatoum@...gutronix.de>

> +    with fsw.add_node('ramdisk'):> +
fsw.property_string('description', 'Ramdisk')
> +        fsw.property_string('type', 'ramdisk')
> +        fsw.property_string('arch', args.arch)
> +        fsw.property_string('os', args.os)
> +        fsw.property('data', data)

The spec reads as if a compression = "none" is mandatory for ramdisks:

If the data is compressed but it should not be uncompressed by the
loader (e.g. compressed ramdisk <pair: ramdisk; compressed), this should
also be set to “none”.

Thoughts?

> +        fsw.property_u32('load', 0)

0 is a valid SDRAM address on many SoCs. I think this should be dropped.

> +
> +
> +def finish_fit(fsw, entries, has_ramdisk=False):
>      """Finish the FIT ready for use
>  
>      Writes the /configurations node and subnodes
> @@ -143,6 +168,7 @@ def finish_fit(fsw, entries):
>          entries (list of tuple): List of configurations:
>              str: Description of model
>              str: Compatible stringlist
> +        has_ramdisk (bool): True if a ramdisk is included in the FIT
>      """
>      fsw.end_node()
>      seq = 0
> @@ -154,6 +180,8 @@ def finish_fit(fsw, entries):
>                  fsw.property_string('description', model)
>                  fsw.property('fdt', bytes(''.join(f'fdt-{x}\x00' for x in files), "ascii"))
>                  fsw.property_string('kernel', 'kernel')
> +                if has_ramdisk:
> +                    fsw.property_string('ramdisk', 'ramdisk')
>      fsw.end_node()
>  
>  
> @@ -274,6 +302,14 @@ def build_fit(args):
>      size += os.path.getsize(args.kernel)
>      write_kernel(fsw, comp_data, args)
>  
> +    # Handle the ramdisk if provided. Compression is not supported as it is
> +    # already compressed.
> +    if args.ramdisk:
> +        with open(args.ramdisk, 'rb') as inf:
> +            data = inf.read()
> +        size += len(data)
> +        write_ramdisk(fsw, data, args)
> +
>      for fname in args.dtbs:
>          # Ignore non-DTB (*.dtb) files
>          if os.path.splitext(fname)[1] != '.dtb':
> @@ -296,12 +332,12 @@ def build_fit(args):
>  
>          entries.append([model, compat, files_seq])
>  
> -    finish_fit(fsw, entries)
> +    finish_fit(fsw, entries, bool(args.ramdisk))
>  
>      # Include the kernel itself in the returned file count
>      fdt = fsw.as_fdt()
>      fdt.pack()
> -    return fdt.as_bytearray(), seq + 1, size
> +    return fdt.as_bytearray(), seq + 1 + bool(args.ramdisk), size
>  
>  
>  def run_make_fit():

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