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

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Cc: Xuanhao Shi <X15000177@gmail.com>,
	buildroot@buildroot.org, Romain Naour <romain.naour@smile.fr>,
	michael@amarulasolutions.com, linux-amarula@amarulasolutions.com,
	"Yann E. MORIN" <yann.morin.1998@free.fr>,
	Anand Gadiyar <gadiyar@ti.com>
Subject: Re: [Buildroot] [RFC PATCH 1/2] support/scripts/genimage.sh: support creating a bmap image
Date: Fri, 10 May 2024 21:54:42 +0200	[thread overview]
Message-ID: <20240510215442.3475120a@windsurf> (raw)
In-Reply-To: <20240421095353.208034-2-dario.binacchi@amarulasolutions.com>

Hello Dario,

On Sun, 21 Apr 2024 11:53:52 +0200
Dario Binacchi <dario.binacchi@amarulasolutions.com> wrote:

> The patch adds an option to create, in addition to the usual image, an
> image of type bmap that drastically reduces the amount of data that
> needs to be written to an SD card, resulting in time savings.
> 
> This makes it possible to activate this option easily and maintain
> backward compatibility for all configurations already using the genimage
> tool for creating the image to be written to the SD card:
> 
> BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
> +BR2_ROOTFS_POST_IMAGE_SCRIPT_ARGS="-c board/<manufacturer>/<boardname>/genimage.cfg -b"
> +BR2_PACKAGE_HOST_BMAP_TOOLS=y
> 
> It follows that the script now assumes a broader functionality that
> extends beyond just being an interface for the genimage tool.
> 
> An alternative implementation could have been to create another script,
> such as support/scripts/bmap.sh, capable of creating the bmap image
> using the same parameters passed to support/scripts/genimage.sh (i. e.
> -c board/<manufacturer>/<boardname>/genimage.cfg). However, in this case,
> the script would also need to know that the image is located in the
> ${BINARIES} directory. This could be achieved by adding an additional
> parameter, but it might cause genimage.sh to fail due to an unrecognized
> parameter.
> 
> Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

Thanks for this proposal! Actually, I very much like the idea of
extending the usage of bmap-tools in Buildroot. I think it's a great
tool, and it makes a lot of sense to encourage more of its use.

Now the question is how to do this. To me your proposal looks
reasonable, though some people had the feedback that bmap-tools will
not work in all cases (should we then gracefully handle this failure
case?).

Arnout, Yann, Peter, Romain, what do you think? Do you see other
approaches to easily allow generating bmap-compatible images?

Another question, perhaps for Dario, or other people familiar with
genimage: if the rootfs.ext4 generated by Buildroot is sparse, is
genimage able to preserve the "holes" when generating the sdcard.img
that includes the rootfs.ext4 ?

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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