linux-kernel - Re: [patch] ALSA: es1968: precedence bug in snd_es1968_tea575x_get

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Date:	Wed, 14 Nov 2012 11:27:39 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Ondrej Zary <linux@...nbow-software.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] ALSA: es1968: precedence bug in
 snd_es1968_tea575x_get_pins()

On Tue, Nov 13, 2012 at 12:03:10AM -0800, Joe Perches wrote:
> On Tue, 2012-11-13 at 10:44 +0300, Dan Carpenter wrote:
> > I don't think this works as intended.  '|' higher precedence than ?: so
> > the bitwize OR "0 | (val & STR_MOST)" is a no-op.
> > 
> > I have re-written it to be more clear.
> []
> > diff --git a/sound/pci/es1968.c b/sound/pci/es1968.c
> []
> > @@ -2581,9 +2581,14 @@ static u8 snd_es1968_tea575x_get_pins(struct snd_tea575x *tea)
> >  	struct es1968 *chip = tea->private_data;
> >  	unsigned long io = chip->io_port + GPIO_DATA;
> >  	u16 val = inw(io);
> > -
> > -	return  (val & STR_DATA) ? TEA575X_DATA : 0 |
> > -		(val & STR_MOST) ? TEA575X_MOST : 0;
> > +	u8 ret;
> > +
> > +	ret = 0;
> > +	if (val & STR_DATA)
> > +		ret |= TEA575X_DATA;
> > +	if (val & STR_MOST)
> > +		ret |= TEA575X_MOST;
> > +	return ret;
> 
> Cute.  smatch I presume?  Tools are useful.

Yep.  This is a smatch thing.

> 
> Moving the close parentheses is a pretty common style too
> 
> 	return  (val & STR_DATA ? TEA575X_DATA : 0) |
> 		(val & STR_MOST ? TEA575X_MOST : 0);

That would work as well, of course.  I don't have a strong
preference either way.

regards,
dan carpenter

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