[Buildroot] [RFC 1/1] infra/pkg-generic: Add rootfs post gen hook

[yann.morin at orange.com]

Vadym, All,

On 2019-04-15 11:42 +0300, Vadym Kochan spake thusly:
> On Mon, Apr 15, 2019 at 09:58:22AM +0200, yann.morin at orange.com wrote:
> > Vadim, All,
> > 
> > On 2019-04-15 10:33 +0300, Vadim Kochan spake thusly:
> > > On Mon, Apr 15, 2019 at 08:58:19AM +0200, Thomas Petazzoni wrote:
> > > > Hello Vadim,
> > > > 
> > > > On Mon, 15 Apr 2019 03:26:35 +0300
> > > > Vadim Kochan <vadim4j at gmail.com> wrote:
> > > > 
> > > > > Add ability to generate image by custom package, and one of the
> > > > > way to do it - is to add new $(PKG)_ROOTFS_POST_GEN_HOOK which will be
> > > > > called after rootfs image is ready. This allows to have easier
> > > > > alternative to post-image script in form of package, which might be
> > > > > just selected by the user (or this package might be automatically
> > > > > selected already already).
> > > > 
> > > > Hum, this description is a bit vague/fuzzy to me. Do you have a
> > > > specific example that requires this rootfs post gen hook ?
> > > > 
> > > 
> > > The use case is simple - allow to generate firmware image by custom
> > > package instead of post-image script. I did not find some dependencies
> > > or other hook to make it installed after rootfs image is ready, so only
> > > option I found is to add yet-another-hook which will be called after
> > > rootfs image is generated.
> > 
> > If you have a custom tool to generate a custom image, why don't you also
> > provide a custom filesystem implementation of your own in fs/your-fs/
> > like any other filesystem ?
> > 
> > Note that a filesystem can also be defined in a br2-external tree.
> > 
> 
> Yes, I understand but this is not for fs image generation but for the
> final firmware image (for flashing, e.g. sdcard image), for example:
> 
> 	https://github.com/vkochan/buildroot-external-rpi/blob/master/package/rpi-image/rpi-image.mk

I perfectly understand what this is about. But now, say that there are
two (or more) packages that must provide a set of tools to run in
sequence on the generated filesystem?

For example, the first is an incantation of genimage or some such, and
the second one does a signature, and so on?

How would your proposal cover this?

This is exactly what post-image is for: to be able to provide whatever
project-specific, board-specific (etc..) tooling to run after filesystems
have been generated.

Besides, your rpi-image stuff does not even solve your (non-)problem,
because your project-specific defconfig still has to enable that package
anyway, so it is not different than having a post-image script listed
in the defconfig.

Regards,
Yann E. MORIN.

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