Patchwork [1/7] docs/manual: update 'adding packages' with the new _AVAILABLE symbol

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Submitter Yann E. MORIN
Date Sept. 9, 2012, 11:40 p.m.
Message ID <1347234052-10527-2-git-send-email-yann.morin.1998@free.fr>
Download mbox | patch
Permalink /patch/182756/
State Rejected
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Yann E. MORIN - Sept. 9, 2012, 11:40 p.m.
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
---
 docs/manual/adding-packages-autotools.txt |   48 ++++++--
 docs/manual/adding-packages-directory.txt |  190 +++++++++++++++--------------
 docs/manual/adding-packages-generic.txt   |   85 ++++++++-----
 3 files changed, 191 insertions(+), 132 deletions(-)
Arnout Vandecappelle - Nov. 1, 2012, 1:30 a.m.
On 09/10/12 01:40, Yann E. MORIN wrote:
> Signed-off-by: "Yann E. MORIN"<yann.morin.1998@free.fr>
> ---
>   docs/manual/adding-packages-autotools.txt |   48 ++++++--
>   docs/manual/adding-packages-directory.txt |  190 +++++++++++++++--------------
>   docs/manual/adding-packages-generic.txt   |   85 ++++++++-----
>   3 files changed, 191 insertions(+), 132 deletions(-)
>
> diff --git a/docs/manual/adding-packages-autotools.txt b/docs/manual/adding-packages-autotools.txt
> index 9fb0918..0f14489 100644
> --- a/docs/manual/adding-packages-autotools.txt
> +++ b/docs/manual/adding-packages-autotools.txt
> @@ -20,10 +20,24 @@ package, with an example :
>   08: LIBFOO_SITE = http://www.foosoftware.org/download
>   09: LIBFOO_INSTALL_STAGING = YES
>   10: LIBFOO_INSTALL_TARGET = YES
> -11: LIBFOO_CONF_OPT = --enable-shared
> -12: LIBFOO_DEPENDENCIES = libglib2 host-pkg-config
> -13:
> -14: $(eval $(autotools-package))
> +11: LIBFOO_DEPENDENCIES = host-libaaa libbbb

  In the Config.in example, it's libbar, not libbb.

> +12:
> +13: ifeq ($(BR2_PACKAGE_LIBFOO_FROBBLE),y)
> +14: LIBFOO_CONF_OPT += --enable-frobble
> +15: else
> +16: LIBFOO_CONF_OPT += --disable-frobble
> +17: endif
> +18:
> +19: LIBFOO_CONF_OPT += --with-gazzle-level=$(BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL)

  This one is going a bit too far...  And if you keep it, it should
probably have a qstrip.

> +20:
> +21: ifeq ($(BR2_PACKAGE_LIBFOO_GOO),y)
> +22: LIBFOO_DEPENDENCIES += goo
> +23: LIBFOO_CONF_OPT += --enable-goo
> +24: else
> +25: LIBFOO_CONF_OPT += --disable-goo
> +26: endif

  While you're at it, an automatic enable/disable example would
be nice too.

> +27:
> +28: $(eval $(autotools-package))
>   ------------------------
>
>   On line 6, we declare the version of the package.
> @@ -50,16 +64,26 @@ installation is enabled, so in fact, this line is not strictly
>   necessary. Also by default, packages are installed in this location
>   using the +make install+ command.
>
> -On line 11, we tell Buildroot to pass a custom configure option, that
> -will be passed to the +./configure+ script before configuring
> -and building the package.
> +On line 11, we declare our dependencies, so that they are built before the
> +build process of our package starts.
>
> -On line 12, we declare our dependencies, so that they are built
> -before the build process of our package starts.
> +On lines 13 to 17, if the user selected the option 'frobble'
> ++BR2_PACKAGE_LIBFOO_FROBBLE+, we add the corresponding configure option
> +to enable 'frobble' (line 14), or disable it (line 16), that will be
> +passed to the +./configure+ script before configuring and building the
> +package.

  "before configuring and building the package" is redundant.

>
> -Finally, on line line 14, we invoke the +autotools-package+
> -macro that generates all the Makefile rules that actually allows the
> -package to be built.
> +Similarly, on line 19, we add the configure option that defines the
> +'bazzle level' +BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL+.

  bazzle -> gazzle.

> +
> +On lines 21 to 26, if user selected the option 'goo' +BR2_PACKAGE_LIBFOO_GOO+,
> +we add a dependency on the package +goo+ (line 22), and add the corresponding
> +configure option to enable 'goo' (line 23); or if 'goo' support is not
> +selected, we pass the configure option to disable it (line 25).
> +
> +Finally, on line line 28, we invoke the +autotools-package+ macro that
> +generates all the Makefile rules that actually allows the package to be
> +built.
>
>   [[autotools-package-reference]]
>
> diff --git a/docs/manual/adding-packages-directory.txt b/docs/manual/adding-packages-directory.txt
> index 4a96415..4863332 100644
> --- a/docs/manual/adding-packages-directory.txt
> +++ b/docs/manual/adding-packages-directory.txt
> @@ -12,30 +12,37 @@ one of these categories, then create your package directory in these.
>   +Config.in+ file
>   ~~~~~~~~~~~~~~~~
>
> -Then, create a file named +Config.in+. This file will contain the
> -option descriptions related to our +libfoo+ software that will be used
> -and displayed in the configuration tool. It should basically contain:
> +Then, create a file named +Config.in+. This file will contain the option
> +descriptions related to our +libfoo+ software that will be used and
> +displayed in the configuration tool. It should basically contain:
>
>   ---------------------------
> +config BR2_PACKAGE_LIBFOO_AVAILABLE
> +	def_bool y
> +
>   config BR2_PACKAGE_LIBFOO
>   	bool "libfoo"
> +	depends on BR2_PACKAGE_LIBFOO_AVAILABLE
>   	help
>   	  This is a comment that explains what libfoo is.
>
>   	  http://foosoftware.org/libfoo/
>   ---------------------------
>
> -The +bool+ line, +help+ line and other meta-informations about the
> -configuration option must be indented with one tab. The help text
> -itself should be indented with one tab and two spaces, and it must
> -mention the upstream URL of the project.
> +*Notes*
> +
> +* This is a very simple example, not really complete, for a very simple
> +  package with no dependency.
> +
> +* The syntax of the +Config.in+ file is the same as the one for the kernel
> +  Kconfig file. The documentation for this syntax is available at:
> +  https://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=Documentation/kbuild/kconfig-language.txt[]

  http://kernel.org/doc/Documentation/kbuild/kconfig-language.txt

> +
> +* The +bool+ line, +help+ line and other meta-informations about the
> +  configuration option must be indented with one tab. The help text
> +  itself should be indented with one tab and two spaces, and it must
> +  mention the upstream URL of the project.
>
> -Of course, you can add other sub-options into a +if
> -BR2_PACKAGE_LIBFOO...endif+ statement to configure particular things
> -in your software. You can look at examples in other packages. The
> -syntax of the +Config.in+ file is the same as the one for the kernel
> -Kconfig file. The documentation for this syntax is available at
> -http://lxr.free-electrons.com/source/Documentation/kbuild/kconfig-language.txt[]
>
>   Finally you have to add your new +libfoo/Config.in+ to
>   +package/Config.in+ (or in a category subdirectory if you decided to
> @@ -47,103 +54,108 @@ supposed to contain anything but the 'bare' name of the package.
>   source "package/libfoo/Config.in"
>   --------------------------
>
> -The +Config.in+ file of your package must also ensure that
> -dependencies are enabled. Typically, Buildroot uses the following
> -rules:
> +The +Config.in+ file for your package must also ensure that its
> +dependencies are available. This is done in four steps:
>
> -* Use a +select+ type of dependency for dependencies on
> -  libraries. These dependencies are generally not obvious and it
> -  therefore make sense to have the kconfig system ensure that the
> -  dependencies are selected. For example, the _libgtk2_ package uses
> -  +select BR2_PACKAGE_LIBGLIB2+ to make sure this library is also
> -  enabled.
> +1. The +BR2_PACKAGE_LIBFOO_AVAILABLE+ symbol shall +depends on+ any
> +other package's +_AVAILABLE+ symbol. It may also depend on any other
> +symbol, such as toolchain features, but should not directly depend on
> +any package's main symbol.

  ... except for _XORG7, _PYTHON, etc.

>
> -* Use a +depends on+ type of dependency when the user really needs to
> -  be aware of the dependency. Typically, Buildroot uses this type of
> -  dependency for dependencies on toolchain options (large file
> -  support, RPC support, IPV6 support), or for dependencies on "big"
> -  things, such as the X.org system. In some cases, especially
> -  dependency on toolchain options, it is recommended to add a
> -  +comment+ displayed when the option is not enabled, so that the user
> -  knows why the package is not available.
> +1. The main +BR2_PACKAGE_LIBFOO+ symbol should directly +depends
> +on+ it's own +_AVAILABLE+ symbol, +BR2_PACKAGE_LIBFOO_AVAILABLE+, and
> +should not depend on any other symbol.
>
> -An example illustrates both the usage of +select+ and +depends on+.
> +1. For each +_AVAILABLE+ symbol your package's own +_AVAILABLE+
> +symbol depends on, your package's main symbol should +select+ the
> +corresponding package's main symbol.
> +
> +1. Add a +comment+ briefly explaining why your package is not
> +available. That +comment+ shall have a single negative dependency on
> +your package's +_AVAILABLE+ symbol.
> +
> +The example below illustrates this mechanism for our libfoo package:
>
>   --------------------------
> -config BR2_PACKAGE_ACL
> -        bool "acl"
> -        select BR2_PACKAGE_ATTR
> -        depends on BR2_LARGEFILE
> -        help
> -          POSIX Access Control Lists, which are used to define more
> -          fine-grained discretionary access rights for files and
> -          directories.
> -          This package also provides libacl.
> -
> -          http://savannah.nongnu.org/projects/acl
> -
> -comment "acl requires a toolchain with LARGEFILE support"
> -        depends on !BR2_LARGEFILE
> +config BR2_PACKAGE_LIBFOO_AVAILABLE
> +	def_bool y
> +	depends on BR2_LARGEFILE
> +	depends on BR2_PACKAGE_LIBBAR
> +
> +comment "libfoo requires libbar, and a toolchain with support for LARGEFILEs"
> +	depends on !BR2_PACKAGE_LIBFOO_AVAILABLE
> +
> +config BR2_PACKAGE_LIBFOO
> +	bool "libfoo"
> +	depends on BR2_PACKAGE_LIBFOO_AVAILABLE
> +	select BR2_PACKAGE_LIBBAR
> +	help
> +	  This is a comment that explains what libfoo is.
> +
> +	  http://foosoftware.org/libfoo/
>   --------------------------
>
> +*Notes*
> +
> +* Even if your package does not have any dependency, you should anyway
> +  add the corresponding +_AVAILABLE+ symbol. This way, other packages can
> +  safely use the mechanism above to select your package, even if it is later
> +  updated and dependencies are added (eg. a new version of the package is
> +  released; or features, initially disabled, are now enabled...)
> +
> +* The symbols and the comment should be in this order, so that the
> +  +menuconfig+ will be properly laid out.
> +
> +* The dependencies in +Config.in+ will make sure that your package's
> +  dependencies options are also enabled, but they will not necessarily be
> +  built before your package. To do so, these dependencies also need to be
> +  expressed in the +.mk+ file of the package (see below).
>
> -Note that these two dependency types are only transitive with the
> -dependencies of the same kind.
> +If your package can be fine-tuned, you can add sub-options, enclosed inside
> +an +if BR2_PACKAGE_LIBFOO ... endif+ block. You can even have each option
> +depend on other packages, using the +_AVAILABLE+ and main symbols for
> +those pacakges.
>
> -This means, in the following example:
> +Finally, here's our now-complete example package:
>
>   --------------------------
> -config BR2_PACKAGE_A
> -        bool "Package A"
> +config BR2_PACKAGE_LIBFOO_AVAILABLE
> +	def_bool y
> +	depends on BR2_LARGEFILE
> +	depends on BR2_PACKAGE_LIBBAR
>
> -config BR2_PACKAGE_B
> -        bool "Package B"
> -        depends on BR2_PACKAGE_A
> +comment "libfoo requires libbar"

  And largefile.  Copy the comment from above.

> +	depends on !BR2_PACKAGE_LIBFOO_AVAILABLE
>
> -config BR2_PACKAGE_C
> -        bool "Package C"
> -        depends on BR2_PACKAGE_B
> +config BR2_PACKAGE_LIBFOO
> +	bool "libfoo"
> +	depends on BR2_PACKAGE_LIBFOO_AVAILABLE
> +	select BR2_PACKAGE_LIBBAR
> +	help
> +	  This is a comment that explains what libfoo is.
>
> -config BR2_PACKAGE_D
> -        bool "Package D"
> -        select BR2_PACKAGE_B
> +	  http://foosoftware.org/libfoo/
>
> -config BR2_PACKAGE_E
> -        bool "Package E"
> -        select BR2_PACKAGE_D
> ---------------------------
> +if BR2_PACKAGE_LIBFOO
>
> -* Selecting +Package C+ will be visible if +Package B+ has been
> -  selected, which in turn is only visible if +Package A+ has been
> -  selected.
> +config BR2_PACKAGE_LIBFOO_FROBBLE
> +	bool "Frobble the foo"
>
> -* Selecting +Package E+ will select +Package D+, which will select
> -  +Package B+, it will not check for the dependencies of +Package B+,
> -  so it will not select +Package A+.
> +config BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL
> +	int "Gazzle level"
> +	range 0 10

  We currently don't have a single range config option, and only one int.
So the example is a bit contrived...  If you add an extra example, a string
option that is qstripped in the .mk file is more appropriate.

>
> -* Since +Package B+ is selected but +Package A+ is not, this violates
> -  the dependency of +Package B+ on +Package A+.  Therefore, in such a
> -  situation, the transitive dependency has to be added explicitly:
> +comment "goo option requires package goo"
> +	depends on !BR2_PACKAGE_GOO_AVAILABLE
>
> ---------------------------
> -config BR2_PACKAGE_D
> -	bool "Package D"
> -	select BR2_PACKAGE_B
> -	depends on BR2_PACKAGE_A
> -
> -config BR2_PACKAGE_E
> -	bool "Package E"
> -	select BR2_PACKAGE_D
> -	depends on BR2_PACKAGE_A
> ---------------------------
> +config BR2_PACKAGE_LIBFOO_GOO
> +	bool "goo"
> +	depends on BR2_PACKAGE_GOO_AVAILABLE
> +	select BR2_PACKAGE_GOO
>
> -Overall, for package library dependencies, +select+ should be
> -preferred.
> +endif
> +--------------------------
>
> -Note that such dependencies will make sure that the dependency option
> -is also enabled, but not necessarily built before your package. To do
> -so, the dependency also needs to be expressed in the +.mk+ file of the
> -package.
>
>   The +.mk+ file
>   ~~~~~~~~~~~~~~
> diff --git a/docs/manual/adding-packages-generic.txt b/docs/manual/adding-packages-generic.txt
> index d3a4abb..3e4c864 100644
> --- a/docs/manual/adding-packages-generic.txt
> +++ b/docs/manual/adding-packages-generic.txt
> @@ -23,30 +23,45 @@ system is based on hand-written Makefiles or shell scripts.
>   09: LIBFOO_INSTALL_STAGING = YES
>   10: LIBFOO_DEPENDENCIES = host-libaaa libbbb

  libbar

>   11:
> -12: define LIBFOO_BUILD_CMDS
> -13: 	$(MAKE) CC="$(TARGET_CC)" LD="$(TARGET_LD)" -C $(@D) all
> -14: endef
> +12: ifeq ($(BR2_PACKAGE_LIBFOO_FROBBLE),y)
> +13: LIBFOO_CFLAGS += -DFROBBLE
> +14: endif
>   15:
> -16: define LIBFOO_INSTALL_STAGING_CMDS
> -17: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.a $(STAGING_DIR)/usr/lib/libfoo.a
> -18: 	$(INSTALL) -D -m 0644 $(@D)/foo.h $(STAGING_DIR)/usr/include/foo.h
> -19: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.so* $(STAGING_DIR)/usr/lib
> -20: endef
> -21:
> -22: define LIBFOO_INSTALL_TARGET_CMDS
> -23: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.so* $(TARGET_DIR)/usr/lib
> -24: 	$(INSTALL) -d -m 0755 $(TARGET_DIR)/etc/foo.d
> -25: endef
> -26:
> -27: define LIBFOO_DEVICES
> -28: 	/dev/foo  c  666  0  0  42  0  -  -  -
> +16: LIBFOO_CFLAGS += -DGAZZLE_LEVEL=$(BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL)
> +17:
> +18: ifeq ($(BR2_PACKAGE_LIBFOO_GOO),y)
> +19: LIBFOO_DEPENDENCIES += goo
> +20: LIBFOO_CFLAGS       += -DGOO
> +21: LIBFOO_LDFLAGS      += -lgoo
> +22: endif
> +23:
> +24: define LIBFOO_BUILD_CMDS
> +25: 	$(MAKE) -C $(@D)                                        \
> +26: 	        CC="$(TARGET_CC)" CFLAGS="$(LIBFOO_CFLAGS)"     \
> +27: 	        LD="$(TARGET_LD)" LDFLAGS="$(LIBFOO_LDFLAGS)"   \
> +28: 	        all
>   29: endef
>   30:
> -31: define LIBFOO_PERMISSIONS
> -32: 	/bin/foo  f  4755  0  0  -  -  -  -  -
> -33: endef
> -34:
> -35: $(eval $(generic-package))
> +31: define LIBFOO_INSTALL_STAGING_CMDS
> +32: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.a $(STAGING_DIR)/usr/lib/libfoo.a
> +33: 	$(INSTALL) -D -m 0644 $(@D)/foo.h $(STAGING_DIR)/usr/include/foo.h
> +34: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.so* $(STAGING_DIR)/usr/lib
> +35: endef
> +36:
> +37: define LIBFOO_INSTALL_TARGET_CMDS
> +38: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.so* $(TARGET_DIR)/usr/lib
> +39: 	$(INSTALL) -d -m 0755 $(TARGET_DIR)/etc/foo.d
> +40: endef
> +41:
> +42: define LIBFOO_DEVICES
> +43: 	/dev/foo  c  666  0  0  42  0  -  -  -
> +44: endef
> +45:
> +46: define LIBFOO_PERMISSIONS
> +47: 	/bin/foo  f  4755  0  0  -  -  -  -  -
> +48: endef
> +49:
> +50: $(eval $(generic-package))
>   --------------------------------
>
>   The Makefile begins on line 6 to 8 with metadata information: the
> @@ -64,12 +79,20 @@ install header files and other development files in the staging space.
>   This will ensure that the commands listed in the
>   +LIBFOO_INSTALL_STAGING_CMDS+ variable will be executed.
>
> -On line 10, we specify the list of dependencies this package relies
> -on. These dependencies are listed in terms of lower-case package names,
> -which can be packages for the target (without the +host-+
> -prefix) or packages for the host (with the +host-+) prefix).
> -Buildroot will ensure that all these packages are built and installed
> -'before' the current package starts its configuration.
> +On line 10, we specify the list of dependencies this package relies on.
> +These dependencies are listed in terms of lower-case package names, which
> +can be packages for the target (without the +host-+ prefix) or packages
> +for the host (with the +host-+ prefix). Buildroot will ensure that all
> +these packages are built and installed 'before' the current package starts
> +its configuration.
> +
> +On lines 12 to 14, if the user did select the option
> ++BR2_PACKAGE_LIBFOO_FROBBLE+ (see above, in the +Config.in+), we
> +conditionnally add a value to the +CFLAGS+. On line 16, we add the 'gazzle

  conditionally

> +level' +BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL+ to the +CFLAGS+. And on lines 18
> +to 22, if the user selected 'goo' support, +BR2_PACKAGE_LIBFOO_GOO+, we
> +add a dependency on the package +goo+, and add appropriate +CFLAGS+ and
> ++LDFLAGS+.
>
>   The rest of the Makefile defines what should be done at the different
>   steps of the package configuration, compilation and installation.
> @@ -79,11 +102,11 @@ steps should be performed to install the package in the staging space.
>   +LIBFOO_INSTALL_TARGET_CMDS+ tells what steps should be
>   performed to install the package in the target space.

  Shouldn't _DEVICES and _PERMISSIONS be explained?

>
> -All these steps rely on the +$(@D)+ variable, which
> -contains the directory where the source code of the package has been
> -extracted.
> +All these steps rely on the +$(@D)+ variable, which contains the directory
> +where the source code of the package has been extracted, and where the
> +package is being built.
>
> -Finally, on line 35, we call the +generic-package+ which
> +Finally, on line 50, we call the +generic-package+ which
>   generates, according to the variables defined previously, all the
>   Makefile code necessary to make your package working.
>


  Overall, a very good addition to the doc, regardless of the _AVAILABLE stuff!

  Regards,
  Arnout
Yann E. MORIN - Nov. 1, 2012, 4:21 p.m.
Arnout, All,

On Thursday 01 November 2012 Arnout Vandecappelle wrote:
> On 09/10/12 01:40, Yann E. MORIN wrote:
> > --- a/docs/manual/adding-packages-autotools.txt
> > +++ b/docs/manual/adding-packages-autotools.txt
> > +12:
> > +13: ifeq ($(BR2_PACKAGE_LIBFOO_FROBBLE),y)
> > +14: LIBFOO_CONF_OPT += --enable-frobble
> > +15: else
> > +16: LIBFOO_CONF_OPT += --disable-frobble
> > +17: endif
> > +18:
> > +19: LIBFOO_CONF_OPT += --with-gazzle-level=$(BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL)
> 
>   This one is going a bit too far...  And if you keep it, it should
> probably have a qstrip.

It's an 'int', so is not quoted in the .config.
(but I'll use a 'string' to address your other comment, so
I'll qstrip it.)

> > +20:
> > +21: ifeq ($(BR2_PACKAGE_LIBFOO_GOO),y)
> > +22: LIBFOO_DEPENDENCIES += goo
> > +23: LIBFOO_CONF_OPT += --enable-goo
> > +24: else
> > +25: LIBFOO_CONF_OPT += --disable-goo
> > +26: endif
> 
>   While you're at it, an automatic enable/disable example would
> be nice too.

What do you mean by "automatic"?

> > --- a/docs/manual/adding-packages-directory.txt
> > +++ b/docs/manual/adding-packages-directory.txt
> > +* The syntax of the +Config.in+ file is the same as the one for the kernel
> > +  Kconfig file. The documentation for this syntax is available at:
> > +  https://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=Documentation/kbuild/kconfig-language.txt[]
> 
>   http://kernel.org/doc/Documentation/kbuild/kconfig-language.txt

Does this URL always match the latest version in the git tree?

> > +1. The +BR2_PACKAGE_LIBFOO_AVAILABLE+ symbol shall +depends on+ any
> > +other package's +_AVAILABLE+ symbol. It may also depend on any other
> > +symbol, such as toolchain features, but should not directly depend on
> > +any package's main symbol.
> 
>   ... except for _XORG7, _PYTHON, etc.

Well, my opinion (FWIW) is those packages should not be treated
differently just because they are /big/.

(One of) the goal(s) of _AVAILABLE is to allow the user to say either:
  - I want this package, enable whatever dependencies are required.
or:
  - I need this package, but I have to provide a toolchain that has
    such and such feature

_AVAILABLE makes that easy.

Then, it's up to the user to understand what pulling-in a package implies.

> > +config BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL
> > +	int "Gazzle level"
> > +	range 0 10
> 
>   We currently don't have a single range config option, and only one int.
> So the example is a bit contrived...  If you add an extra example, a string
> option that is qstripped in the .mk file is more appropriate.

OK.

> > --- a/docs/manual/adding-packages-generic.txt
> > +++ b/docs/manual/adding-packages-generic.txt
> > @@ -79,11 +102,11 @@ steps should be performed to install the package in the staging space.
> >   +LIBFOO_INSTALL_TARGET_CMDS+ tells what steps should be
> >   performed to install the package in the target space.
> 
>   Shouldn't _DEVICES and _PERMISSIONS be explained?

Da, tovarich!

Thank you!

Regards,
Yann E. MORIN.
Arnout Vandecappelle - Nov. 1, 2012, 10:40 p.m.
On 11/01/12 17:21, Yann E. MORIN wrote:
> Arnout, All,
>
> On Thursday 01 November 2012 Arnout Vandecappelle wrote:
>> On 09/10/12 01:40, Yann E. MORIN wrote:
[snip]
>>> +21: ifeq ($(BR2_PACKAGE_LIBFOO_GOO),y)
>>> +22: LIBFOO_DEPENDENCIES += goo
>>> +23: LIBFOO_CONF_OPT += --enable-goo
>>> +24: else
>>> +25: LIBFOO_CONF_OPT += --disable-goo
>>> +26: endif
>>
>>    While you're at it, an automatic enable/disable example would
>> be nice too.
>
> What do you mean by "automatic"?

ifeq ($(BR2_PACKAGE_OPENSSL),y)
LIBFOO_DEPENDENCIES += openssl
LIBFOO_CONF_OPT += --enable-openssl
else
LIBFOO_CONF_OPT += --disable-openssl
endif

>
>>> --- a/docs/manual/adding-packages-directory.txt
>>> +++ b/docs/manual/adding-packages-directory.txt
>>> +* The syntax of the +Config.in+ file is the same as the one for the kernel
>>> +  Kconfig file. The documentation for this syntax is available at:
>>> +  https://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=Documentation/kbuild/kconfig-language.txt[]
>>
>>    http://kernel.org/doc/Documentation/kbuild/kconfig-language.txt
>
> Does this URL always match the latest version in the git tree?

  I'm not sure, but anyway we don't sync with the upstream kconfig very
often either.

>
>>> +1. The +BR2_PACKAGE_LIBFOO_AVAILABLE+ symbol shall +depends on+ any
>>> +other package's +_AVAILABLE+ symbol. It may also depend on any other
>>> +symbol, such as toolchain features, but should not directly depend on
>>> +any package's main symbol.
>>
>>    ... except for _XORG7, _PYTHON, etc.
>
> Well, my opinion (FWIW) is those packages should not be treated
> differently just because they are /big/.
>
> (One of) the goal(s) of _AVAILABLE is to allow the user to say either:
>    - I want this package, enable whatever dependencies are required.
> or:
>    - I need this package, but I have to provide a toolchain that has
>      such and such feature
>
> _AVAILABLE makes that easy.
>
> Then, it's up to the user to understand what pulling-in a package implies.

  I actually agree, but that's not the current reality.

  OTOH, it makes sense to promote the wanted reality in the documentation.

  Regards,
  Arnout

[snip]
Thomas Petazzoni - Nov. 2, 2012, 8:59 a.m.
On Thu, 01 Nov 2012 23:40:21 +0100, Arnout Vandecappelle wrote:

> >>> +1. The +BR2_PACKAGE_LIBFOO_AVAILABLE+ symbol shall +depends on+
> >>> any +other package's +_AVAILABLE+ symbol. It may also depend on
> >>> any other +symbol, such as toolchain features, but should not
> >>> directly depend on +any package's main symbol.
> >>
> >>    ... except for _XORG7, _PYTHON, etc.
> >
> > Well, my opinion (FWIW) is those packages should not be treated
> > differently just because they are /big/.
> >
> > (One of) the goal(s) of _AVAILABLE is to allow the user to say
> > either:
> >    - I want this package, enable whatever dependencies are required.
> > or:
> >    - I need this package, but I have to provide a toolchain that has
> >      such and such feature
> >
> > _AVAILABLE makes that easy.
> >
> > Then, it's up to the user to understand what pulling-in a package
> > implies.
> 
>   I actually agree, but that's not the current reality.
> 
>   OTOH, it makes sense to promote the wanted reality in the
> documentation.

Except that even with the _AVAILABLE feature, I don't know if we want
to change how we handle things like Python modules, X.org and so on. We
will pretty likely still want to hide all of the Python modules behind
a global Python option.

Best regards,

Thomas

Patch

diff --git a/docs/manual/adding-packages-autotools.txt b/docs/manual/adding-packages-autotools.txt
index 9fb0918..0f14489 100644
--- a/docs/manual/adding-packages-autotools.txt
+++ b/docs/manual/adding-packages-autotools.txt
@@ -20,10 +20,24 @@  package, with an example :
 08: LIBFOO_SITE = http://www.foosoftware.org/download
 09: LIBFOO_INSTALL_STAGING = YES
 10: LIBFOO_INSTALL_TARGET = YES
-11: LIBFOO_CONF_OPT = --enable-shared
-12: LIBFOO_DEPENDENCIES = libglib2 host-pkg-config
-13:
-14: $(eval $(autotools-package))
+11: LIBFOO_DEPENDENCIES = host-libaaa libbbb
+12:
+13: ifeq ($(BR2_PACKAGE_LIBFOO_FROBBLE),y)
+14: LIBFOO_CONF_OPT += --enable-frobble
+15: else
+16: LIBFOO_CONF_OPT += --disable-frobble
+17: endif
+18:
+19: LIBFOO_CONF_OPT += --with-gazzle-level=$(BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL)
+20:
+21: ifeq ($(BR2_PACKAGE_LIBFOO_GOO),y)
+22: LIBFOO_DEPENDENCIES += goo
+23: LIBFOO_CONF_OPT += --enable-goo
+24: else
+25: LIBFOO_CONF_OPT += --disable-goo
+26: endif
+27:
+28: $(eval $(autotools-package))
 ------------------------
 
 On line 6, we declare the version of the package.
@@ -50,16 +64,26 @@  installation is enabled, so in fact, this line is not strictly
 necessary. Also by default, packages are installed in this location
 using the +make install+ command.
 
-On line 11, we tell Buildroot to pass a custom configure option, that
-will be passed to the +./configure+ script before configuring
-and building the package.
+On line 11, we declare our dependencies, so that they are built before the
+build process of our package starts.
 
-On line 12, we declare our dependencies, so that they are built
-before the build process of our package starts.
+On lines 13 to 17, if the user selected the option 'frobble'
++BR2_PACKAGE_LIBFOO_FROBBLE+, we add the corresponding configure option
+to enable 'frobble' (line 14), or disable it (line 16), that will be
+passed to the +./configure+ script before configuring and building the
+package.
 
-Finally, on line line 14, we invoke the +autotools-package+
-macro that generates all the Makefile rules that actually allows the
-package to be built.
+Similarly, on line 19, we add the configure option that defines the
+'bazzle level' +BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL+.
+
+On lines 21 to 26, if user selected the option 'goo' +BR2_PACKAGE_LIBFOO_GOO+,
+we add a dependency on the package +goo+ (line 22), and add the corresponding
+configure option to enable 'goo' (line 23); or if 'goo' support is not
+selected, we pass the configure option to disable it (line 25).
+
+Finally, on line line 28, we invoke the +autotools-package+ macro that
+generates all the Makefile rules that actually allows the package to be
+built.
 
 [[autotools-package-reference]]
 
diff --git a/docs/manual/adding-packages-directory.txt b/docs/manual/adding-packages-directory.txt
index 4a96415..4863332 100644
--- a/docs/manual/adding-packages-directory.txt
+++ b/docs/manual/adding-packages-directory.txt
@@ -12,30 +12,37 @@  one of these categories, then create your package directory in these.
 +Config.in+ file
 ~~~~~~~~~~~~~~~~
 
-Then, create a file named +Config.in+. This file will contain the
-option descriptions related to our +libfoo+ software that will be used
-and displayed in the configuration tool. It should basically contain:
+Then, create a file named +Config.in+. This file will contain the option
+descriptions related to our +libfoo+ software that will be used and
+displayed in the configuration tool. It should basically contain:
 
 ---------------------------
+config BR2_PACKAGE_LIBFOO_AVAILABLE
+	def_bool y
+
 config BR2_PACKAGE_LIBFOO
 	bool "libfoo"
+	depends on BR2_PACKAGE_LIBFOO_AVAILABLE
 	help
 	  This is a comment that explains what libfoo is.
 
 	  http://foosoftware.org/libfoo/
 ---------------------------
 
-The +bool+ line, +help+ line and other meta-informations about the
-configuration option must be indented with one tab. The help text
-itself should be indented with one tab and two spaces, and it must
-mention the upstream URL of the project.
+*Notes*
+
+* This is a very simple example, not really complete, for a very simple
+  package with no dependency.
+
+* The syntax of the +Config.in+ file is the same as the one for the kernel
+  Kconfig file. The documentation for this syntax is available at:
+  https://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=Documentation/kbuild/kconfig-language.txt[]
+
+* The +bool+ line, +help+ line and other meta-informations about the
+  configuration option must be indented with one tab. The help text
+  itself should be indented with one tab and two spaces, and it must
+  mention the upstream URL of the project.
 
-Of course, you can add other sub-options into a +if
-BR2_PACKAGE_LIBFOO...endif+ statement to configure particular things
-in your software. You can look at examples in other packages. The
-syntax of the +Config.in+ file is the same as the one for the kernel
-Kconfig file. The documentation for this syntax is available at
-http://lxr.free-electrons.com/source/Documentation/kbuild/kconfig-language.txt[]
 
 Finally you have to add your new +libfoo/Config.in+ to
 +package/Config.in+ (or in a category subdirectory if you decided to
@@ -47,103 +54,108 @@  supposed to contain anything but the 'bare' name of the package.
 source "package/libfoo/Config.in"
 --------------------------
 
-The +Config.in+ file of your package must also ensure that
-dependencies are enabled. Typically, Buildroot uses the following
-rules:
+The +Config.in+ file for your package must also ensure that its
+dependencies are available. This is done in four steps:
 
-* Use a +select+ type of dependency for dependencies on
-  libraries. These dependencies are generally not obvious and it
-  therefore make sense to have the kconfig system ensure that the
-  dependencies are selected. For example, the _libgtk2_ package uses
-  +select BR2_PACKAGE_LIBGLIB2+ to make sure this library is also
-  enabled.
+1. The +BR2_PACKAGE_LIBFOO_AVAILABLE+ symbol shall +depends on+ any
+other package's +_AVAILABLE+ symbol. It may also depend on any other
+symbol, such as toolchain features, but should not directly depend on
+any package's main symbol.
 
-* Use a +depends on+ type of dependency when the user really needs to
-  be aware of the dependency. Typically, Buildroot uses this type of
-  dependency for dependencies on toolchain options (large file
-  support, RPC support, IPV6 support), or for dependencies on "big"
-  things, such as the X.org system. In some cases, especially
-  dependency on toolchain options, it is recommended to add a
-  +comment+ displayed when the option is not enabled, so that the user
-  knows why the package is not available.
+1. The main +BR2_PACKAGE_LIBFOO+ symbol should directly +depends
+on+ it's own +_AVAILABLE+ symbol, +BR2_PACKAGE_LIBFOO_AVAILABLE+, and
+should not depend on any other symbol.
 
-An example illustrates both the usage of +select+ and +depends on+.
+1. For each +_AVAILABLE+ symbol your package's own +_AVAILABLE+
+symbol depends on, your package's main symbol should +select+ the
+corresponding package's main symbol.
+
+1. Add a +comment+ briefly explaining why your package is not
+available. That +comment+ shall have a single negative dependency on
+your package's +_AVAILABLE+ symbol.
+
+The example below illustrates this mechanism for our libfoo package:
 
 --------------------------
-config BR2_PACKAGE_ACL
-        bool "acl"
-        select BR2_PACKAGE_ATTR
-        depends on BR2_LARGEFILE
-        help
-          POSIX Access Control Lists, which are used to define more
-          fine-grained discretionary access rights for files and
-          directories.
-          This package also provides libacl.
-
-          http://savannah.nongnu.org/projects/acl
-
-comment "acl requires a toolchain with LARGEFILE support"
-        depends on !BR2_LARGEFILE
+config BR2_PACKAGE_LIBFOO_AVAILABLE
+	def_bool y
+	depends on BR2_LARGEFILE
+	depends on BR2_PACKAGE_LIBBAR
+
+comment "libfoo requires libbar, and a toolchain with support for LARGEFILEs"
+	depends on !BR2_PACKAGE_LIBFOO_AVAILABLE
+
+config BR2_PACKAGE_LIBFOO
+	bool "libfoo"
+	depends on BR2_PACKAGE_LIBFOO_AVAILABLE
+	select BR2_PACKAGE_LIBBAR
+	help
+	  This is a comment that explains what libfoo is.
+
+	  http://foosoftware.org/libfoo/
 --------------------------
 
+*Notes*
+
+* Even if your package does not have any dependency, you should anyway
+  add the corresponding +_AVAILABLE+ symbol. This way, other packages can
+  safely use the mechanism above to select your package, even if it is later
+  updated and dependencies are added (eg. a new version of the package is
+  released; or features, initially disabled, are now enabled...)
+
+* The symbols and the comment should be in this order, so that the
+  +menuconfig+ will be properly laid out.
+
+* The dependencies in +Config.in+ will make sure that your package's
+  dependencies options are also enabled, but they will not necessarily be
+  built before your package. To do so, these dependencies also need to be
+  expressed in the +.mk+ file of the package (see below).
 
-Note that these two dependency types are only transitive with the
-dependencies of the same kind.
+If your package can be fine-tuned, you can add sub-options, enclosed inside
+an +if BR2_PACKAGE_LIBFOO ... endif+ block. You can even have each option
+depend on other packages, using the +_AVAILABLE+ and main symbols for
+those pacakges.
 
-This means, in the following example:
+Finally, here's our now-complete example package:
 
 --------------------------
-config BR2_PACKAGE_A
-        bool "Package A"
+config BR2_PACKAGE_LIBFOO_AVAILABLE
+	def_bool y
+	depends on BR2_LARGEFILE
+	depends on BR2_PACKAGE_LIBBAR
 
-config BR2_PACKAGE_B
-        bool "Package B"
-        depends on BR2_PACKAGE_A
+comment "libfoo requires libbar"
+	depends on !BR2_PACKAGE_LIBFOO_AVAILABLE
 
-config BR2_PACKAGE_C
-        bool "Package C"
-        depends on BR2_PACKAGE_B
+config BR2_PACKAGE_LIBFOO
+	bool "libfoo"
+	depends on BR2_PACKAGE_LIBFOO_AVAILABLE
+	select BR2_PACKAGE_LIBBAR
+	help
+	  This is a comment that explains what libfoo is.
 
-config BR2_PACKAGE_D
-        bool "Package D"
-        select BR2_PACKAGE_B
+	  http://foosoftware.org/libfoo/
 
-config BR2_PACKAGE_E
-        bool "Package E"
-        select BR2_PACKAGE_D
---------------------------
+if BR2_PACKAGE_LIBFOO
 
-* Selecting +Package C+ will be visible if +Package B+ has been
-  selected, which in turn is only visible if +Package A+ has been
-  selected.
+config BR2_PACKAGE_LIBFOO_FROBBLE
+	bool "Frobble the foo"
 
-* Selecting +Package E+ will select +Package D+, which will select
-  +Package B+, it will not check for the dependencies of +Package B+,
-  so it will not select +Package A+.
+config BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL
+	int "Gazzle level"
+	range 0 10
 
-* Since +Package B+ is selected but +Package A+ is not, this violates
-  the dependency of +Package B+ on +Package A+.  Therefore, in such a
-  situation, the transitive dependency has to be added explicitly:
+comment "goo option requires package goo"
+	depends on !BR2_PACKAGE_GOO_AVAILABLE
 
---------------------------
-config BR2_PACKAGE_D
-	bool "Package D"
-	select BR2_PACKAGE_B
-	depends on BR2_PACKAGE_A
-
-config BR2_PACKAGE_E
-	bool "Package E"
-	select BR2_PACKAGE_D
-	depends on BR2_PACKAGE_A
---------------------------
+config BR2_PACKAGE_LIBFOO_GOO
+	bool "goo"
+	depends on BR2_PACKAGE_GOO_AVAILABLE
+	select BR2_PACKAGE_GOO
 
-Overall, for package library dependencies, +select+ should be
-preferred.
+endif
+--------------------------
 
-Note that such dependencies will make sure that the dependency option
-is also enabled, but not necessarily built before your package. To do
-so, the dependency also needs to be expressed in the +.mk+ file of the
-package.
 
 The +.mk+ file
 ~~~~~~~~~~~~~~
diff --git a/docs/manual/adding-packages-generic.txt b/docs/manual/adding-packages-generic.txt
index d3a4abb..3e4c864 100644
--- a/docs/manual/adding-packages-generic.txt
+++ b/docs/manual/adding-packages-generic.txt
@@ -23,30 +23,45 @@  system is based on hand-written Makefiles or shell scripts.
 09: LIBFOO_INSTALL_STAGING = YES
 10: LIBFOO_DEPENDENCIES = host-libaaa libbbb
 11:
-12: define LIBFOO_BUILD_CMDS
-13: 	$(MAKE) CC="$(TARGET_CC)" LD="$(TARGET_LD)" -C $(@D) all
-14: endef
+12: ifeq ($(BR2_PACKAGE_LIBFOO_FROBBLE),y)
+13: LIBFOO_CFLAGS += -DFROBBLE
+14: endif
 15:
-16: define LIBFOO_INSTALL_STAGING_CMDS
-17: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.a $(STAGING_DIR)/usr/lib/libfoo.a
-18: 	$(INSTALL) -D -m 0644 $(@D)/foo.h $(STAGING_DIR)/usr/include/foo.h
-19: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.so* $(STAGING_DIR)/usr/lib
-20: endef
-21:
-22: define LIBFOO_INSTALL_TARGET_CMDS
-23: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.so* $(TARGET_DIR)/usr/lib
-24: 	$(INSTALL) -d -m 0755 $(TARGET_DIR)/etc/foo.d
-25: endef
-26:
-27: define LIBFOO_DEVICES
-28: 	/dev/foo  c  666  0  0  42  0  -  -  -
+16: LIBFOO_CFLAGS += -DGAZZLE_LEVEL=$(BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL)
+17:
+18: ifeq ($(BR2_PACKAGE_LIBFOO_GOO),y)
+19: LIBFOO_DEPENDENCIES += goo
+20: LIBFOO_CFLAGS       += -DGOO
+21: LIBFOO_LDFLAGS      += -lgoo
+22: endif
+23:
+24: define LIBFOO_BUILD_CMDS
+25: 	$(MAKE) -C $(@D)                                        \
+26: 	        CC="$(TARGET_CC)" CFLAGS="$(LIBFOO_CFLAGS)"     \
+27: 	        LD="$(TARGET_LD)" LDFLAGS="$(LIBFOO_LDFLAGS)"   \
+28: 	        all
 29: endef
 30:
-31: define LIBFOO_PERMISSIONS
-32: 	/bin/foo  f  4755  0  0  -  -  -  -  -
-33: endef
-34:
-35: $(eval $(generic-package))
+31: define LIBFOO_INSTALL_STAGING_CMDS
+32: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.a $(STAGING_DIR)/usr/lib/libfoo.a
+33: 	$(INSTALL) -D -m 0644 $(@D)/foo.h $(STAGING_DIR)/usr/include/foo.h
+34: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.so* $(STAGING_DIR)/usr/lib
+35: endef
+36:
+37: define LIBFOO_INSTALL_TARGET_CMDS
+38: 	$(INSTALL) -D -m 0755 $(@D)/libfoo.so* $(TARGET_DIR)/usr/lib
+39: 	$(INSTALL) -d -m 0755 $(TARGET_DIR)/etc/foo.d
+40: endef
+41:
+42: define LIBFOO_DEVICES
+43: 	/dev/foo  c  666  0  0  42  0  -  -  -
+44: endef
+45:
+46: define LIBFOO_PERMISSIONS
+47: 	/bin/foo  f  4755  0  0  -  -  -  -  -
+48: endef
+49:
+50: $(eval $(generic-package))
 --------------------------------
 
 The Makefile begins on line 6 to 8 with metadata information: the
@@ -64,12 +79,20 @@  install header files and other development files in the staging space.
 This will ensure that the commands listed in the
 +LIBFOO_INSTALL_STAGING_CMDS+ variable will be executed.
 
-On line 10, we specify the list of dependencies this package relies
-on. These dependencies are listed in terms of lower-case package names,
-which can be packages for the target (without the +host-+
-prefix) or packages for the host (with the +host-+) prefix).
-Buildroot will ensure that all these packages are built and installed
-'before' the current package starts its configuration.
+On line 10, we specify the list of dependencies this package relies on.
+These dependencies are listed in terms of lower-case package names, which
+can be packages for the target (without the +host-+ prefix) or packages
+for the host (with the +host-+ prefix). Buildroot will ensure that all
+these packages are built and installed 'before' the current package starts
+its configuration.
+
+On lines 12 to 14, if the user did select the option
++BR2_PACKAGE_LIBFOO_FROBBLE+ (see above, in the +Config.in+), we
+conditionnally add a value to the +CFLAGS+. On line 16, we add the 'gazzle
+level' +BR2_PACKAGE_LIBFOO_GAZZLE_LEVEL+ to the +CFLAGS+. And on lines 18
+to 22, if the user selected 'goo' support, +BR2_PACKAGE_LIBFOO_GOO+, we
+add a dependency on the package +goo+, and add appropriate +CFLAGS+ and
++LDFLAGS+.
 
 The rest of the Makefile defines what should be done at the different
 steps of the package configuration, compilation and installation.
@@ -79,11 +102,11 @@  steps should be performed to install the package in the staging space.
 +LIBFOO_INSTALL_TARGET_CMDS+ tells what steps should be
 performed to install the package in the target space.
 
-All these steps rely on the +$(@D)+ variable, which
-contains the directory where the source code of the package has been
-extracted.
+All these steps rely on the +$(@D)+ variable, which contains the directory
+where the source code of the package has been extracted, and where the
+package is being built.
 
-Finally, on line 35, we call the +generic-package+ which
+Finally, on line 50, we call the +generic-package+ which
 generates, according to the variables defined previously, all the
 Makefile code necessary to make your package working.