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 >>> <[email protected]> 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?
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