Prev: Kconfig: Enable Kconfig fragments to be used for defconfig
Next: AT91 NOMMU fails to compile 2.6.35-rc5
From: Nicolas Pitre on 16 Jul 2010 14:40
On Fri, 16 Jul 2010, Grant Likely wrote:
> On Fri, Jul 16, 2010 at 12:19 PM, Nicolas Pitre <nico(a)fluxnic.net> wrote:
> > For example, if I want CONFIG_MTD_CMDLINE_PARTS=y, the system may be
> > smart enough to notice and automatically enable CONFIG_MTD and
> > CONFIG_MTD_PARTITIONS without having to carry those in the defconfig.
>
> I fully agree. However, the warnings make the system work now while
> we wait for a full solver to be implemented.

Why can't the tool just _select_ the option it is warning about when a
dependency is not met? That shouldn't require a full solver.


Nicolas
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
From: Nicolas Pitre on 16 Jul 2010 14:50
On Fri, 16 Jul 2010, Russell King - ARM Linux wrote:

> On Fri, Jul 16, 2010 at 02:19:31PM -0400, Nicolas Pitre wrote:
> > For example, if I want CONFIG_MTD_CMDLINE_PARTS=y, the system may be
> > smart enough to notice and automatically enable CONFIG_MTD and
> > CONFIG_MTD_PARTITIONS without having to carry those in the defconfig.
>
> How do you sort out something like this:
>
> config FOO
> bool "Foo"
> depends on (A && B) || C

DOH.


Nicolas
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
From: Catalin Marinas on 16 Jul 2010 16:20
On Fri, 2010-07-16 at 19:46 +0100, Linus Torvalds wrote:
> On Fri, Jul 16, 2010 at 11:40 AM, Nicolas Pitre <nico(a)fluxnic.net> wrote:
> >
> > DOH.
>
> Well, it's possible that the correct approach is a mixture.
>
> Automatically do the trivial cases (recursive selects, dependencies
> that are simple or of the form "x && y" etc), and warn about the cases
> that aren't trivial (where "not trivial" may not necessarily be about
> fundamentally ambiguous ones, but just "complex enough that I won't
> even try").

There is still a risk with this approach when the Kconfig isn't entirely
correct. For example, on ARM we have (I pushed a patch already):

config CPU_32v6K
depends on CPU_V6

config CPU_V7
select CPU_32v6K

In this simple approach, we end up selecting CPU_V6 when we only need
CPU_V7. There other places like this in the kernel.

Of course, kbuild could still warn but if people rely on this feature to
select options automatically I suspect they would ignore the warnings.

--
Catalin

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
From: Nicolas Pitre on 16 Jul 2010 16:30
On Fri, 16 Jul 2010, Grant Likely wrote:

> On Fri, Jul 16, 2010 at 2:09 PM, Catalin Marinas
> <catalin.marinas(a)arm.com> wrote:
> > On Fri, 2010-07-16 at 19:46 +0100, Linus Torvalds wrote:
> >> On Fri, Jul 16, 2010 at 11:40 AM, Nicolas Pitre <nico(a)fluxnic.net> wrote:
> >> >
> >> > DOH.
> >>
> >> Well, it's possible that the correct approach is a mixture.
> >>
> >> Automatically do the trivial cases (recursive selects, dependencies
> >> that are simple or of the form "x && y" etc), and warn about the cases
> >> that aren't trivial (where "not trivial" may not necessarily be about
> >> fundamentally ambiguous ones, but just "complex enough that I won't
> >> even try").
> >
> > There is still a risk with this approach when the Kconfig isn't entirely
> > correct. For example, on ARM we have (I pushed a patch already):
> >
> > config CPU_32v6K
> > � � � �depends on CPU_V6
> >
> > config CPU_V7
> > � � � �select CPU_32v6K
> >
> > In this simple approach, we end up selecting CPU_V6 when we only need
> > CPU_V7. There other places like this in the kernel.
> >
> > Of course, kbuild could still warn but if people rely on this feature to
> > select options automatically I suspect they would ignore the warnings.
>
> In my first patch, I made Kconfig problems errors instead of warnings.
> That would prevent people from ignoring them.

ACK.


Nicolas
From: Catalin Marinas on 16 Jul 2010 16:50
On Fri, 2010-07-16 at 21:17 +0100, Grant Likely wrote:
> On Fri, Jul 16, 2010 at 2:09 PM, Catalin Marinas
> <catalin.marinas(a)arm.com> wrote:
> > On Fri, 2010-07-16 at 19:46 +0100, Linus Torvalds wrote:
> >> On Fri, Jul 16, 2010 at 11:40 AM, Nicolas Pitre <nico(a)fluxnic.net> wrote:
> >> >
> >> > DOH.
> >>
> >> Well, it's possible that the correct approach is a mixture.
> >>
> >> Automatically do the trivial cases (recursive selects, dependencies
> >> that are simple or of the form "x && y" etc), and warn about the cases
> >> that aren't trivial (where "not trivial" may not necessarily be about
> >> fundamentally ambiguous ones, but just "complex enough that I won't
> >> even try").
> >
> > There is still a risk with this approach when the Kconfig isn't entirely
> > correct. For example, on ARM we have (I pushed a patch already):
> >
> > config CPU_32v6K
> > depends on CPU_V6
> >
> > config CPU_V7
> > select CPU_32v6K
> >
> > In this simple approach, we end up selecting CPU_V6 when we only need
> > CPU_V7. There other places like this in the kernel.
> >
> > Of course, kbuild could still warn but if people rely on this feature to
> > select options automatically I suspect they would ignore the warnings.
>
> In my first patch, I made Kconfig problems errors instead of warnings.
> That would prevent people from ignoring them.

My point was that if we allow kbuild to select dependencies
automatically (as per Nico's initial suggestion, followed up by Linus),
in the above situation CPU_V7 would trigger the selection of CPU_V6 and
I don't want this. If we rely on such automatic selection of the
"depends on" options, we can't make the warnings be errors.

--
Catalin

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
First  |  Prev  | 
Pages: 1 2
Prev: Kconfig: Enable Kconfig fragments to be used for defconfig
Next: AT91 NOMMU fails to compile 2.6.35-rc5