[Buildroot] [PATCH 2/2] manual: add virtual package tutorial.

[Arnout Vandecappelle <arnout@mind.be>]

On 24/02/14 20:01, Yann E. MORIN wrote:
> Eric, All,
> 
> I think you should base this on master, since we think it would be very
> interesting to have it in this release.

 I don't think it's that important. I don't think people will be adding
virtual packages for their custom stuff, so this documentation is
targeted towards people that will upstream packages. And for these, we
can assume that they read the documentation of master and not that of
whatever release they happen to be working with.

 And of course, if the $(virtual-package) infrastructure gets added, then
this piece of documentation has to be entirely rewritten.

> 
> On 2014-02-24 10:50 +0100, Eric Le Bihan spake thusly:
>> The manual now features a new section with instructions about how to add a
>> virtual package.
>>
>> Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
>> ---
>>  docs/manual/adding-packages-virtual.txt |  102 +++++++++++++++++++++++++++++++
>>  docs/manual/adding-packages.txt         |    2 +
>>  2 files changed, 104 insertions(+)
>>  create mode 100644 docs/manual/adding-packages-virtual.txt
>>
>> diff --git a/docs/manual/adding-packages-virtual.txt b/docs/manual/adding-packages-virtual.txt
>> new file mode 100644
>> index 0000000..6cccc4e
>> --- /dev/null
>> +++ b/docs/manual/adding-packages-virtual.txt
>> @@ -0,0 +1,102 @@
>> +// -*- mode:doc; -*-
>> +// vim: set syntax=asciidoc:
>> +
>> +Infrastructure for virtual packages
>> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> +
>> +[[virtual-package-tutorial]]
>> +
>> ++virtual-package+ tutorial
>> +^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> 'virtual-package' is not an infrastructure [ie. you can't use:
> $(eval $(virtual-package)) ], 

 Well, soon you will be able to! :-)


 Regards,
 Arnout

> so I would suggest to just use:
> 
>     Virtual package tutorial
>     ^^^^^^^^^^^^^^^^^^^^^^^^
> 
> [--SNIP--]
>> +First, let's create the virtual package.
>> +
>> +.Virtual package +Config.in+ file
>> +=================================
> 
> The formatting of the title is weird. Here's what I've changed:
> 
>     Virtual package +Config.in+ file
>     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> 
> (notice: no leading dot, and an empty line after the ^^^ line)
> 
>> +The +Config.in+ file of virtual package 'something-virtual' should contain:
>> +
>> +---------------------------
>> +01: config BR2_PACKAGE_HAS_SOMETHING_VIRTUAL
>> +02:	bool
>> +03:
>> +04: config BR2_PACKAGE_PROVIDES_SOMETHING_VIRTUAL
>> +05:	depends on BR2_PACKAGE_HAS_SOMETHING_VIRTUAL
>> +06:	string
>> +---------------------------
>> +=================================
> 
> Remove this === line.
> 
>> +In this file, we declare two options, +BR2_PACKAGE_HAS_SOMETHING_VIRTUAL+ and
>> ++BR2_PACKAGE_PROVIDES_SOMETHING_VIRTUAL+, whose values will be used by the
>> +providers.
>> +
>> +.Virtual package +*.mk+ file
>> +============================
> 
> Ditto title.
> 
>> +The Makefile +package/something-virtual/something-virtual.mk+ should contain:
>> +
>> +---------------------------
>> +01: ################################################################################
>> +02: #
>> +03: # something-virtual
>> +04: #
>> +05: ################################################################################
>> +06:
>> +07: SOMETHING_VIRTUAL_SOURCE =
>> +08: SOMETHING_VIRTUAL_DEPENDENCIES = $(call qstrip,$(BR2_PACKAGE_PROVIDES_SOMETHING_VIRTUAL))
>> +09:
>> +10: ifeq ($(BR2_PACKAGE_HAS_SOMETHING_VIRTUAL),y)
>> +11: ifeq ($(SOMETHING_VIRTUAL_DEPENDENCIES),)
>> +12: $(error No something-virtual implementation selected. Configuration error.)
>> +13: endif
>> +14: endif
>> +15:
>> +16: $(eval $(generic-package))
>> +---------------------------
>> +============================
> 
> Ditto ===.
> 
>> +The Makefile is quite small as it will only check if a provider for the
>> +virtual package has been selected.
>> +
>> +When adding a package as a provider, only the +Config.in+ file requires some
>> +modifications. The +*.mk+ file should follow the Buildroot infrastructure with
>> +no change at all.
>> +
>> +.Provider +Config.in+ file
>> +==========================
> 
> Ditto title.
> 
>> +The +Config.in+ file of the package 'some-provider', which provides the
>> +functionalities of 'something-virtual', should contain:
>> +
>> +---------------------------
>> +01: config BR2_PACKAGE_SOME_PROVIDER
>> +02:	bool "some-provider"
>> +03:	select BR2_PACKAGE_HAS_SOMETHING_VIRTUAL
>> +04:	help
>> +05:	  This is a comment that explains what some-provider is.
>> +06:
>> +07:	  http://foosoftware.org/some-provider/
>> +08:
>> +09: if BR2_PACKAGE_SOME_PROVIDER
>> +10: config BR2_PACKAGE_PROVIDES_SOMETHING_VIRTUAL
>> +11:	default "some-provider"
>> +12: endif
>> +---------------------------
>> +==========================
> 
> Ditto ===.
> 
> With those changes, the manual looks better, IMHO.
> 
> Regards,
> Yann E. MORIN.
> 


-- 
Arnout Vandecappelle                          arnout at mind be
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