linux-kernel - Re: [PATCH] mfd: SM501 core driver

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Message-Id: <20070207085225.c2371cfd.akpm@linux-foundation.org>
Date:	Wed, 7 Feb 2007 08:52:25 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ben Dooks <ben-linux@...ff.org>
Cc:	linux-kernel@...r.kernel.org,
	linux-fbdev-devel@...ts.sourceforge.net, Greg KH <greg@...ah.com>
Subject: Re: [PATCH] mfd: SM501 core driver

On Wed, 7 Feb 2007 11:48:25 +0000 Ben Dooks <ben-linux@...ff.org> wrote:

> On Tue, Feb 06, 2007 at 09:09:30PM -0800, Andrew Morton wrote:
> > On Tue, 6 Feb 2007 19:26:28 +0000 Ben Dooks <ben-linux@...ff.org> wrote:
> > 
> > > This patch is an update patch, ready for merging
> > > for the Silicon Motion SM501 multi-function device
> > > core.
> > > 
> > > This driver handles the core function of the chip,
> > > including the clock, power control and allocation
> > > of resources for drivers. It also exports a series
> > > of platform devices for the function drivers to
> > > attach to.
> > > 
> > > This patch supports both platform and PCI bus
> > > attached devices.
> > > 
> > > Signed-off-by: Ben Dooks <ben-linux@...ff.org>
> > 
> > Can we get Vincent's signoff here?
> > 
> > > +#ifdef CONFIG_DEBUG
> > 
> > This doesn't appear to be defined anywhere, and nor should it be. 
> > Something subsystem-specific should be used here?
> 
> This protects the code being used by dev_dbg() only from being
> warned as not being used.

I know what is does, but I query the use of "CONFIG_DEBUG".  I don't think
there's a CONFIG_DEBUG defined in existing Kconfig, and your patch doesn't
add a CONFIG_DEBUG and nor should it, because that would be an
inappropriate identifier to use.

So I'd suggest you just use DEBUG, as many other drivers do.  Or call it
CONFIG_SM501_DEBUG and add the Kconfig record to enable it.

> > > +#define fmt_freq(x) ((x) / MHZ), ((x) % MHZ), (x)
> > 
> > eww.
> 
> Do you have a better way of printing a nice formatted MHz with
> fractional parts?

Nope.

>  Is it going to be necessary to remove this?

Nope.  But ewww.

> > > +		(void)readl(sm->regs);
> > 
> > Is there any benefit in all those casts?  Generally we prefer to avoid
> > them.
> 
> I thoguht they where necessary to stop the compiler optimising
> away the readl() ?

No, that shuldn't be necessary.  If it was, the compiler would optimise
away the first readl() in 

	my_local = readl(foo);
	my_local = readl(bar);

which would break stuff.  readl() implementations use volatile to prevent
this.


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