[Buildroot] Kconfig: "selects" vs. "depends on"
Arnout Vandecappelle
arnout at mind.be
Sun Mar 4 10:53:39 UTC 2012
On Sunday 04 March 2012 10:18:55 Ismael Luceno wrote:
> Which should I use?
>
> Perhaps "selects" for for simple (i.e. non-configurable) dependencies,
> and "depends on" otherwise...?
Actually you have three choices here: "select", "depends on", and "if"
(which is functionally equivalent to "depends on").
I have an opinion on this, but I'm not sure if the others agree (esp.
ThomasDS :-).
- "select" should always be used, except in the cases below.
- "depends on" should be used in the BR2_PACKAGE_<pkgname> config when
* the package requires a certain toolchain config (e.g. WCHAR, CXX)
(in this case there should also be a comment that explains why the
package is not available);
* the package only exists for certain architectures (e.g. for boot
loaders);
* the package is a part of some superpackage (e.g. X11, python)
(it's a bit of a judgement call what can be considered a
superpackage);
* it is deprecated.
- "depends on" should be used in a package's additional config options
when:
* any of the above apply to the additional option;
* to enable an extra sub-sub-config option (cfr. PHP -> PHP_EXT_SQLITE
-> PHP_EXT_SQLITE_UTF8)
* when the suboption requires certain configs of another package and
'select' can't be used reliably (in this case there should also
be a comment);
* in rare cases, when the suboption requires certain configs of the
same package and it would become too complex to resolve all the
dependencies (in this case there should also be a comment)
- "if" should be used:
* to enable a package's additional config options only when the package
is selected;
* around 'source' statements (cfr. x11r7)
Note that the current packages sometimes don't follow these rules.
[Hey, maybe we should add this set of guidelines to the documentation!]
Now, you're probably asking this for the Qt tools for which you just
posted a patch, and I guess those guidelines don't help you much with
that... I would say the dependency of qmlviewer on QtDeclarative falls
under the superpackage category. However, the dependency of qmlviewer
on the SQL module is certainly not a superpackage-type, so it should
preferrably be a select, or a depends on with a comment if the select
is too difficult to get right. So the way you did it is perfect :-)
Regards,
Arnout
--
Arnout Vandecappelle arnout at mind be
Senior Embedded Software Architect +32-16-286540
Essensium/Mind http://www.mind.be
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