[yocto] RFC: User configurable recipe features

[Koen Kooi]

Op 12 okt. 2011, om 17:41 heeft Darren Hart het volgende geschreven:

> 
> 
> On 10/11/2011 05:18 PM, Philip Balister wrote:
>> On 10/11/2011 07:51 PM, Khem Raj wrote:
>>> On Tue, Oct 11, 2011 at 3:15 PM, Richard Purdie
>>> <richard.purdie at linuxfoundation.org> wrote:
>>>> On Mon, 2011-10-10 at 11:41 -0700, Darren Hart wrote:
>>>>> As part of working on meta-tiny, I've come across a need (want?) to
>>>>> present users with the ability to select some set of features in a local
>>>>> configuration file that will impact the build of the image and a set of
>>>>> recipes.
>>>>> 
>>>>> It is currently possible to affect which packages are installed in an
>>>>> image with variables like POKY_EXTRA_INSTALL. What I'm not finding a way
>>>>> to do is specify some set of features that will impact how a recipe is
>>>>> built.
>>>>> 
>>>>> For example, a user may or may not want networking support or virtual
>>>>> terminal support in their image. This impacts both the kernel and
>>>>> busybox (at least). The linux-yocto infrastructure provides us with
>>>>> config fragment functionality, something similar will need to be added
>>>>> to busybox. Access to that is still bound to the machine config by means
>>>>> of the SRC_URI machine override mechanism, but it would be useful to be
>>>>> able to influence it from the image config or the user's local config.
>>>>> 
>>>>> For example, when building a tiny image I may decide I do not want VT
>>>>> nor INET support. I might wish to specify this like this (by removing
>>>>> them from the default features):
>>>>> 
>>>>> local.conf:
>>>>> #CORE_IMAGE_TINY_FEATURES = "VT INET MDEV"
>>>>> CORE_IMAGE_TINY_FEATURES = "MDEV"
>>>>> 
>>>>> I would want this to affect linux-yocto-tiny by dropping the vt.cfg and
>>>>> inet.cfg fragments from the SRC_URI (or from the .scc descriptor files
>>>>> assembled by the linux-yocto meta indrastructure).
>>>>> 
>>>>> Busybox would need a similar configuration mechanism, and would also
>>>>> need to add a "no-vt-support.patch" patch to the SRC_URI to avoid a
>>>>> bug/oversight in the busybox init routine.
>>>>> 
>>>>> I'd appreciate some help determining the proper bitbake way of doing
>>>>> this. I want to avoid having to create a new machine.conf and/or recipes
>>>>> for every possible combination of features that a user may want to turn
>>>>> on or off.
>>>> 
>>>> We have a few mechanisms around for this but its a difficult problem to
>>>> do totally generically since everyone has their own ideas about what
>>>> should/shouldn't happen.
>>>> 
>>>> One tricky aspect is that some people care about package feeds and the
>>>> output into those needs to be deterministic. This is why DISTRO_FEATURES
>>>> exist which state things like "does x11 make sense"? This means dbus may
>>>> or may not be compiled with X but given a set of policy decisions by the
>>>> distro, the output is determined.
>>>> 
>>>> Recently we've taken the idea of PACKAGECONFIG on board. This is recipe
>>>> level policy which can enable/disable features in a given recipe (e.g.
>>>> does gsteamer depend on and build flac or not?). Whilst we have a high
>>>> level setup for this for autotools recipes, this is probably something
>>>> we need to do a more custom implementation of for busybox and the
>>>> features you mention above would map well to this. It would be good to
>>>> have a standardised way of representing this (and we may also want to
>>>> look at moving the kernel feature control towards this variable name
>>>> too).
>>>> 
>>>> What we need to be really really careful about is getting the
>>>> namespacing right and your CORE_IMAGE_TINY_FEATURES = "VT INET MDEV"
>>>> example above scares me as it mixes up several different things. My
>>>> worry is for example trying to build two different versions of busybox
>>>> in the same tmpdir depending on what image you build, for example what
>>>> does "bitbake core-image-tiny core-image-sato" do?
>>>> 
>>>> Contrast this to some settings:
>>>> 
>>>> PACKAGECONFIG_pn-linux-yocto = "vt inet"
>>>> PACKAGECONFIG_pn-busybox = "mdev"
>>>> 
>>>> which then mean you have one set of configuration for these recipes and
>>>> its clear what the bitbake command above would result in.
>>>> 
>>>> One of the bigger problems we're going to have with tiny is its
>>>> effectively a different set of distro settings to our normal builds. The
>>>> side effect of that is that you couldn't share a tmpdir with a "big"
>>>> build but I'm not sure that is an issue in practise, we just need to do
>>>> it in a way which doesn't give us the nasty configuration corner cases.
>>>> 
>>>> So I guess what I'm saying is the end result of your work is likely a
>>>> "poky-tiny" distro setting which would take the "poky" distro but tweak
>>>> some pieces for really small images. It would need a separate tmpdir and
>>>> we should look in the PACKAGECONFIG variable direction for handling
>>>> recipe specific customisations...
>>>> 
>>> 
>>> FWIW I agree it seems like a new distro to me. I think if we add more to mix
>>> it just will complicate the customizations and may even make it
>>> difficult to share
>>> things.
>> 
>> Along the same line of thought, does this overlap with the micro distro?
>> 
> 
> Hrm... the micro distro? What's this?

http://cgit.openembedded.org/meta-micro/