Date: Wed, 31 Jan 2007 09:20:35 -0500 (EST)
From: "Robert P. J. Day" <rpjday@mindspring.com>
To: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
cc: Linux kernel mailing list <linux-kernel@vger.kernel.org>,
       dhowells@redhat.com, rth@twiddle.net
Subject: Re: [PATCH] Centralize the selection for debugging semaphores.
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On Wed, 31 Jan 2007, Michal Piotrowski wrote:

> On 31/01/07, Robert P. J. Day <rpjday@mindspring.com> wrote:
> > On Wed, 31 Jan 2007, Michal Piotrowski wrote:
> >
> > > On 31/01/07, Robert P. J. Day <rpjday@mindspring.com> wrote:
> > > >
> > > >   Centralize the kernel config option for debugging semaphores and
> > > > modify the macro for frv to use that config option instead.
> > > >
> > > > Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
> > > [..]
> > > > +config DEBUG_SEMAPHORE
> > > > +       bool "Semaphore debugging"
> > > > +       depends on DEBUG_KERNEL
> > > > +       default n
> > > > +       help
> > > > +         If you say Y here then semaphore processing will issue lots of
> > > > +         verbose debugging messages.  If you suspect a semaphore
> > problem or
> > > > a
> > > > +         kernel hacker asks for this option then say Y.  Otherwise say
> > N.
> > > > +
> > > > +         At the moment, this is implemented only by alpha and frv.
> > >
> > > IMHO this option should stay in arch/{alpha,frv}/Kconfig.debug
> >
> > any particular reason?
>
> Only this
> "At the moment, this is implemented only by alpha and frv."
>
> It depends on architecture.

  yes, i realize that, but surely there's a cleaner way to implement
something that's supported by only *some* of the architectures rather
than duplicating the code for every one of those architectures.

  one possibility is to have the global config option look like this:

config DEBUG_SEMAPHORE
	bool "Semaphore debugging"
	depends on DEBUG_KERNEL && HAVE_SEMAPHORE_DEBUGGING
				   ^^^^^^^^^^^^^^^^^^^^^^^^
        default n
	...

  at that point, any architecture that implements semaphore debugging
and wants to advertise that simply needs to add this at the top of its
Kconfig.debug file:

config HAVE_SEMAPHORE_DEBUGGING
        def_bool y

  that was just off the top of my head, but it seems to work.  more
generally, though, surely this sort of thing has come up before --
wanting to advertise an identical user-configurable option only for
certain architectures.  how is that done *now* without rampant code
duplication?  or is it?

rday

-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel
Pedantry Waterloo, Ontario, CANADA

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