Re: [ptxdist] [RFC PATCH] doc: Add section on creating new layers

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Tue, Sep 03, 2019 at 03:38:31PM +0200, Roland Hieber wrote:
> On Tue, Sep 03, 2019 at 03:08:08PM +0200, Michael Olbrich wrote:
> > On Tue, Sep 03, 2019 at 02:22:04PM +0200, Alexander Dahl wrote:
> > > Hello Roland,
> > > 
> > > Am Dienstag, 3. September 2019, 14:00:17 CEST schrieb Roland Hieber:
> > > > On Tue, Sep 03, 2019 at 01:50:25PM +0200, Alexander Dahl wrote:
> > > > > After discussing these topics in IRC, it seemed reasonable to add some
> > > > > explanation on how to create a new layer from scratch.
> > > > 
> > > > \o/ someone else did a task on my overlong todo list :D
> > > 
> > > Yes, and I just saw you already wrote a piece on that topic, but on your 
> > > website, not in ptxdist documentation:
> > > 
> > > https://pengutronix.de/en/blog/2019-06-18-DistroKitLayer.html
> > > 
> > > o.O
> 
> Uhm. Thanks for reminding me ... ^^ Chris did most of the work though, I
> only proof-read it.
> 
> > > > > +
> > > > > +Creating a new Layer
> > > > > +~~~~~~~~~~~~~~~~~~~~
> > > > > +
> > > > > +Adding new layers on top of an already existing BSP is easy:
> > > > > +
> > > > > +#. Create an empty folder, e.g. next to the existing BSP.
> > > > > +#. The lower layer is just a folder named ``base`` (see layers_ above).
> > > > > You +   may do one of the following (or something else you consider
> > > > > convenient): +
> > > > > +   - Create a symbolic link ``base`` to an outside laying BSP folder. For
> > > > > +     an easy start, you can try this method with DistroKit_ for example:
> > > > > +     ``$ ln -s ../DistroKit base``
> > > > 
> > > > We have done that too sometimes in the past, but if the config files in
> > > > the base layer are not in the right versions, the MD5 sum in the config
> > > > diffs in the inherited layer will not match. I think this should be
> > > > mentioned here.
> > > 
> > > Sorry, I do not understand. :-/
> > > 
> > > > > +   - Use a Git submodule with a BSP in a folder ``base``.
> > > > > +   - Copy over your whole existing BSP to a new subfolder ``base``.
> > > > 
> > > > Subtree merges are another possibility, although I've never done one.
> > > 
> > > Same here.
> > > 
> > > > > +
> > > > > +#. If needed select **ptxconfig** and/or **platformconfig** after copying
> > > > > +   that file from the lower layer to your new layer:
> > > > > +
> > > > > +.. code-block:: text
> > > > > +
> > > > > +   $ mkdir -p configs/platform-v7a
> > > > > +   $ cp base/configs/platform-v7a/platformconfig configs/platform-v7a/
> > > > > +   $ ptxdist platform configs/platform-v7a/platformconfig
> > > > 
> > > > I think you should be able to select the config from base/ directly
> > > > without copying them? mol?
> > > 
> > > I did not try that. What is possible to select would be indeed an interesting 
> > > piece in the docs! That question came up multiple times in IRC in the last 
> > > days. ;-)
> > 
> > If there is just on platform, then ptxdist will just use that on if no
> > selected_platformconfig exists. This is especially useful with layers,
> > because it will then just pick the config from the first layer that has
> > one.
> > 
> > This means, that you can start with just the base link. Then change
> > something with 'ptxdist platformconfig'. PTXdist will create the
> > platformconfig in your new layer and use it automatically.
> > 
> > The same works for the ptxconfig as well.
> 
> Hmm, this explanation does not match my experience...
> 
>     rhi@dude test-bsp $ p version
>     2019.08.0
>     
>     rhi@dude test-bsp $ l
>     lrwxrwxrwx  1 rhi ptx   10 Sep  3 14:58 base -> DistroKit/
>     drwxr-xr-x 11 rhi ptx  232 Sep  3 15:03 DistroKit
>     
>     rhi@dude test-bsp $ l DistroKit/selected_*
>     lrwxrwxrwx 1 rhi ptx  35 Sep  3 15:03 DistroKit/selected_platformconfig -> configs/platform-v7a/platformconfig
>     lrwxrwxrwx 1 rhi ptx 118 Sep  3 15:03 DistroKit/selected_toolchain -> /opt/OSELAS.Toolchain-2018.12.0/arm-v7a-linux-gnueabihf/gcc-8.2.1-glibc-2.28-binutils-2.31.1-kernel-4.19-sanitized/bin
>     
>     rhi@dude test-bsp $ p menuconfig platform
>     configuration written to .config
>     
>     *** End of the configuration.
>     *** Execute 'ptxdist go' to build the project or try 'ptxdist help'.
>     
>     Saving 'test-bsp/DistroKit/configs/platform-v7a/platformconfig'.
> 
> Same for ptxdist menuconfig, which changes test-bsp/DistroKit/configs/ptxconfig
> instead of configs/ptxconfig in the current layer. However, when I copy
> base/configs/ptxconfig to configs/ptxconfig, and then do a menuconfig,
> it is changed in the current layer.

I cannot reproduce this. It works as expected for me. The last log message
may be a clue, I would expect

"Saving 'test-bsp/configs/platform-v7a/platformconfig'."
or
"Saving 'test-bsp/base/configs/platform-v7a/platformconfig'."

but not "test-bsp/DistroKit/....". So maybe the symlink handling does not
work correctly.

What's the output of 'p migrate'?
What happens if 'base' is a symlink to '../DistroKit'?

Michael

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