linux-kernel - Re: iomux-mx3.h: possible macro precedence issue

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Message-ID: <1474438379.15981.1.camel@perches.com>
Date:   Tue, 20 Sep 2016 23:12:59 -0700
From:   Joe Perches <joe@...ches.com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Sascha Hauer <kernel@...gutronix.de>,
        Julia Lawall <julia.lawall@...6.fr>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Shawn Guo <shawnguo@...nel.org>
Subject: Re: iomux-mx3.h: possible macro precedence issue

On Wed, 2016-09-21 at 08:06 +0200, Uwe Kleine-König wrote:\
> On Tue, Sep 20, 2016 at 01:02:24PM -0700, Joe Perches wrote:
> > Julia Lawall wrote a script
> > 
> > Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1609201503260.2914@hadrien
> > 
> > that found a possible issue with macro argument precedence.
> > 
> > 
> > diff -u -p a/arch/arm/mach-imx/iomux-mx3.h b/arch/arm/mach-imx/iomux-mx3.h
> > --- a/arch/arm/mach-imx/iomux-mx3.h
> > +++ b/arch/arm/mach-imx/iomux-mx3.h
> > @@ -529,7 +529,7 @@ enum iomux_pins {
> >  #define MX31_PIN_DCD_DTE1__DCD_DTE2	IOMUX_MODE(MX31_PIN_DCD_DTE1, IOMUX_CONFIG_ALT1)
> >  #define MX31_PIN_RI_DTE1__RI_DTE2	IOMUX_MODE(MX31_PIN_RI_DTE1, IOMUX_CONFIG_ALT1)
> >  #define MX31_PIN_DSR_DTE1__DSR_DTE2	IOMUX_MODE(MX31_PIN_DSR_DTE1, IOMUX_CONFIG_ALT1)
> > -#define MX31_PIN_DTR_DTE1__DTR_DTE2	IOMUX_MODE(MX31_PIN_DTR_DTE1, IOMUX_OCONFIG_ALT3 | IOMUX_ICONFIG_NONE)
> > +#define MX31_PIN_DTR_DTE1__DTR_DTE2	IOMUX_MODE(MX31_PIN_DTR_DTE1, (IOMUX_OCONFIG_ALT3 | IOMUX_ICONFIG_NONE))
> >  #define MX31_PIN_PC_RST__CTS5		IOMUX_MODE(MX31_PIN_PC_RST, IOMUX_CONFIG_ALT2)
> >  #define MX31_PIN_PC_VS2__RTS5		IOMUX_MODE(MX31_PIN_PC_VS2, IOMUX_CONFIG_ALT2)
> >  #define MX31_PIN_PC_BVD2__TXD5		IOMUX_MODE(MX31_PIN_PC_BVD2, IOMUX_CONFIG_ALT2)
> 
> 
> I assume this is the only problematic definition?

yes..

> If so, there is a
> single affected platform: arch/arm/mach-imx/mach-kzm_arm11_01.c
>  
> > this may be intentional, but perhaps a solution
> > would be to use parentheses in the #define IOMUX_MODE 
> > 
> > ---
> > 
> > diff --git a/arch/arm/mach-imx/iomux-mx3.h b/arch/arm/mach-imx/iomux-mx3.h
> > index 368667b..3f9ede2 100644
> > --- a/arch/arm/mach-imx/iomux-mx3.h
> > +++ b/arch/arm/mach-imx/iomux-mx3.h
> > @@ -156,7 +156,7 @@ void mxc_iomux_mode(unsigned int pin_mode);
> > > >  	(((gpionum << IOMUX_GPIONUM_SHIFT) & IOMUX_GPIONUM_MASK) | \
> > > >  	 (padnum & IOMUX_PADNUM_MASK))
> >  
> > -#define IOMUX_MODE(pin, mode) (pin | mode << IOMUX_MODE_SHIFT)
> > +#define IOMUX_MODE(pin, mode) ((pin) | ((mode) << IOMUX_MODE_SHIFT))
> >  
> >  #define IOMUX_TO_GPIO(iomux_pin) \
> >  	((iomux_pin & IOMUX_GPIONUM_MASK) >> IOMUX_GPIONUM_SHIFT)
> 
> 
> My preference is to fix IOMUX_MODE instead of adding the parents to
> MX31_PIN_DTR_DTE1__DTR_DTE2.

Mine too.

> Joe, do you create a proper patch?

I just don't have the hardware and don't know what was intended
by the existing code.  It does appear to be a defect though.