linux-kernel - Re: [PATCH] drivers/w1/masters/w1-gpio.c: fix read

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Message-Id: <20090310150059.ce64548a.akpm@linux-foundation.org>
Date:	Tue, 10 Mar 2009 15:00:59 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Daniel Mack <daniel@...aq.de>
Cc:	linux-kernel@...r.kernel.org, syrjala@....fi, johnpol@....mipt.ru,
	david-b@...bell.net
Subject: Re: [PATCH] drivers/w1/masters/w1-gpio.c: fix read_bit()

On Tue, 10 Mar 2009 10:18:00 +0100
Daniel Mack <daniel@...aq.de> wrote:

> On Mon, Mar 09, 2009 at 07:14:19PM -0700, Andrew Morton wrote:
> > > --- a/drivers/w1/masters/w1-gpio.c
> > > +++ b/drivers/w1/masters/w1-gpio.c
> > > @@ -39,7 +39,7 @@ static u8 w1_gpio_read_bit(void *data)
> > >  {
> > >  	struct w1_gpio_platform_data *pdata = data;
> > >  
> > > -	return gpio_get_value(pdata->pin);
> > > +	return gpio_get_value(pdata->pin) ? 1 : 0;
> > >  }
> > >  
> > >  static int __init w1_gpio_probe(struct platform_device *pdev)
> > 
> > We recently merged a patch (I forget where) which fixed one
> > gpio_get_value() implementation so that it always returns 0 or 1.
> > 
> > From which I deduce that the correct fix for <whatever problem you're
> > seeing> is to fix <whichever driver that is>?
> 
> I agree those functions should return 0 and 1 only, but my patch fixes
> the w1-gpio driver for all platforms at once, so people can use it.
> 
> On the other hand, I will submit a patch which modifies PXA's
> gpio_get_value() and see what the maintainers say, but I can't go thru
> all the implemenations of all architectures to do this.
> 
> So for the time being, the above patch helps many users of that driver.
> 

Problem is, the patch will just conceal bugs.

How about this?

--- a/drivers/w1/masters/w1-gpio.c~a
+++ a/drivers/w1/masters/w1-gpio.c
@@ -38,8 +38,12 @@ static void w1_gpio_write_bit_val(void *
 static u8 w1_gpio_read_bit(void *data)
 {
 	struct w1_gpio_platform_data *pdata = data;
+	u8 ret;
 
-	return gpio_get_value(pdata->pin);
+	ret = gpio_get_value(pdata->pin);
+	if (WARN_ONCE(ret > 1, "gpio_get_value(): invalid return: %u\n", ret))
+		ret = !!ret
+	return ret;
 }
 
 static int __init w1_gpio_probe(struct platform_device *pdev)
_

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