Date:	Mon, 14 Apr 2008 11:54:45 +0200
From:	Uwe Kleine-König <Uwe.Kleine-Koenig@...i.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	"Hans J. Koch" <hjk@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Re: [PATCH 4/4 v2] [RFC] UIO: generic platform driver

Hi Russell,

Russell King - ARM Linux wrote:
> On Mon, Apr 14, 2008 at 09:48:58AM +0200, Uwe Kleine-König wrote:
> > > > > > > But what about this:
> > > > > > > 
> > > > > > > ERROR: "clk_get" [drivers/uio/uio_pdrv.ko] undefined!
> > > > > > > ERROR: "clk_enable" [drivers/uio/uio_pdrv.ko] undefined!
> > > > > > > ERROR: "clk_disable" [drivers/uio/uio_pdrv.ko] undefined!
> > > > > > > ERROR: "clk_put" [drivers/uio/uio_pdrv.ko] undefined!
> > > > > > > 
> > > > > > > Do you have any extra patches applied?
> > > > > > Yes I have, but nothing special.  This is part of a generic API defined
> > > > > > in include/linux/clk.h.  One of it's use it to abstract away some
> > > > > > platform dependencies.  There are several architectures that define
> > > > > > it[1].
> > > > > 
> > > > > I know. Unfortunately, I tested on x86_64, and it doesn't compile.
> > > > > If it's depending on something, then this dependency should be added in
> > > > > Kconfig. If it can be selected in the configuration, I expect it to
> > > > > compile (and work).
> > > > Maybe adding a dummy implementation that is compiled for machines that
> > > > don't provide a native one.  Currently there is no cpp symbol that tells
> > > > if an machine supports the API.
> > > > 
> > > > @Russell: Do you have an opinion regarding this!?
> > > 
> > > Only that the kernels Kconfig is turning into a real complicated mess
> > > of dependencies IMHO.
> > > 
> > > We could add a HAVE_CLK and add that to the dependency of all the drivers
> > > which use linux/clk.h.  The problem will be finding all those drivers and
> > > their corresponding Kconfig entries.
> > > 
> > > My feeling is that we're just going to end up creating another Kconfig
> > > symbol which folk half-heartedly use.
> >
> > I don't like that either.  What do you think about the patch below?
> > It doesn't introduce a new symbol that needs much care and attention.
> > This way the clk API is available on all configurations provided that 
> > CONFIG_DUMMY_CLK is set correctly.  If CONFIG_DUMMY_CLK is set wrong it
> > should result in a compile error.  Either because there are two
> > implementations of clk_get or none.
> 
> Hang on.  I'm lost.  What are we talking about here?  I thought the
> thread was about the one liner patch for UIO to arch/arm/Kconfi
> (which still hasn't hit the patch system so is still on target for
> being missed...)
No, the topic here is a generic uio platform driver.  It uses the clk
API and Hans criticised that is doesn't compile on x86 (because there is
no implementation of the clk API).  So I suggested to implement a dummy
for that.

This is completly independant of the inclusion of drivers/uio/Kconfig in
arch/arm/Kconfig.  I will send a patch for that.

> What's this drivers/uio/uio_pdrv.ko module, and why doesn't it appear
> in the LKML archive of this thread?
Don't know why lkml.org didn't link these.  The start of the thread can
be found at

	http://lkml.org/lkml/2008/4/10/110

gmane managed to link these mails:

	http://thread.gmane.org/gmane.linux.kernel/663884

Best regards
Uwe

-- 
Uwe Kleine-König, Software Engineer
Digi International GmbH Branch Breisach, Küferstrasse 8, 79206 Breisach, Germany
Tax: 315/5781/0242 / VAT: DE153662976 / Reg. Amtsgericht Dortmund HRB 13962
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