Re: [Buildroot] [RFC PATCH 1/2] support/scripts/genimage.sh: support creating a bmap image

From: "Yann E. MORIN" <yann.morin.1998@free.fr>
To: Michael Nazzareno Trimarchi <michael@amarulasolutions.com>
Cc: Xuanhao Shi <X15000177@gmail.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	buildroot@buildroot.org, Romain Naour <romain.naour@smile.fr>,
	Dario Binacchi <dario.binacchi@amarulasolutions.com>,
	linux-amarula@amarulasolutions.com,
	Anand Gadiyar <gadiyar@ti.com>
Subject: Re: [Buildroot] [RFC PATCH 1/2] support/scripts/genimage.sh: support creating a bmap image
Date: Tue, 21 May 2024 19:44:24 +0200	[thread overview]
Message-ID: <ZkzdeFeoYMkyGv7w@landeda> (raw)
In-Reply-To: <CAOf5uwnVbowN6GCYUxFL0xh2YV9AvG2JTkuyQR6rk+56J=3DLQ@mail.gmail.com>

Michael, All,

On 2024-05-21 11:28 +0200, Michael Nazzareno Trimarchi spake thusly:
> On Tue, May 21, 2024 at 7:25 AM Yann E. MORIN <yann.morin.1998@free.fr> wrote:
> > I think the question by Thomas was whether, given an input sparse file,
> > genimage will keep the generated image sparse in the same places the
> > input file was (only shifted by the offset that input file was copied
> > at in the image).
[--SNIP--]
> Seems I did not understand the question. My idea on the topic is how
> we can generate
> images that we can easily flash. Now I understand the question of
> Thomas and thank you.
> 
> Yann can I ask how we can use an image generated as you describe before?

    $ make pc_x86_64_efi_defconfig
    $ make
    $ ls -sl output/images/{rootfs.ext2,disk.img}

I tried a bit earlier, and the genimage file is indeed sparse, but I
could not find a tool that would report the list of holes/non-holes in a
file, and their offset, e.g. something like:

                size    offset
    non-hole    2MiB    @0
    hole        1MiB    @2MiB
    non-hole    16MiB   @3MiB
 and so on...

So I could not validate whether the hole/non-hole structure is the same
in the generated disk.img and the rootfs.ext2. If you have any idea how
to do that, I'm all eyes.

Regards,
Yann E. MORIN.

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