On Thu, 06 May 2010 09:17:24 EDT, James Bottomley said: > On Thu, 2010-05-06 at 08:47 +0200, Geert Uytterhoeven wrote: > > On Wed, May 5, 2010 at 23:49, James Bottomley > > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > [Sam: I know you don't maintain kbuild anymore, but since you have the > > > most experience, if you could find time to comment, I'd be grateful] > > > > > > The select problem is that the kbuild select directive will turn a > > > symbol on without reference to its dependencies. This, in turn, means > > > that either selected symbols must select their dependencies, or that > > > people using select have to be aware of the selected symbol's dependency > > > and build those dependencies into their symbol (leading to duplication > > > and the possibility of getting the dependencies out of sync). We use > > > select for the scsi transport classes, so we run into this problem in > > > SCSI quite a lot. > > > > > > I think the correct fix is to make a symbol that selects another symbol > > > automatically inherit all of the selected symbol's dependencies. > > > > What if there's a good reason the selected symbol has this dependency? > > E.g. it depends on a critical feature not available? Like CONFIG_HAS_IOMEM? > > I don't quite understand the question. If a selected symbol has a > critical dependency which is config'd to N then the build usually > breaks ... that's what I'm calling the select problem. I thought > CONFIG_HAS_IOMEM was usually selected by the architecture, though. In > the new proposal, we wouldn't be able to generate the invalid > configuration in the first place. I think Geert is asking "If the arch says CONFIG_HAS_IOMEM=n, but some driver does a 'select CONFIG_FOO' which then (under your proposal) forces the value CONFIG_BAR=y, which eventually ends up with CONFIG_HAS_IOMEM=y, what should the behavior be?" (I suspect the right answer here is "one of the symbols is buggy and its 'select' should be a 'depends' instead", but somebody else better double-check that conclusion - I'm hardly a Kconfig expert).
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