Re: [PATCH] Input: bcm5974.c initialize raw_w, raw_x and raw_y before it get used

[Jaswinder Singh Rajput <jaswinder@kernel.org>]

On Sun, 2009-09-13 at 01:24 +0200, Henrik Rydberg wrote:
> Jaswinder Singh Rajput wrote:
> > raw_w, raw_x and raw_y is used uninitialized for !raw_n
> 
> Thanks for the heads up, but actually not, since !raw_n also implies
> !(ptest > PRESSURE_LOW).
> 

Then can we move 'if (ptest > PRESSURE_LOW && origin)' stuff to 'if
(raw_n)'. If not then my patch is correct.

> > This also fixed these compilation warnings :
> > 
> >  CC [M]  drivers/input/mouse/bcm5974.o
> > drivers/input/mouse/bcm5974.c: In function ‘report_tp_state’:
> > drivers/input/mouse/bcm5974.c:319: warning: ‘raw_y’ may be used uninitialized in this function
> > drivers/input/mouse/bcm5974.c:319: warning: ‘raw_x’ may be used uninitialized in this function
> > drivers/input/mouse/bcm5974.c:319: warning: ‘raw_w’ may be used uninitialized in this function
> > 
> > Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
> > ---
> >  drivers/input/mouse/bcm5974.c |    3 ++-
> >  1 files changed, 2 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/input/mouse/bcm5974.c b/drivers/input/mouse/bcm5974.c
> > index 2d8fc0b..171f345 100644
> > --- a/drivers/input/mouse/bcm5974.c
> > +++ b/drivers/input/mouse/bcm5974.c
> > @@ -345,7 +345,8 @@ static int report_tp_state(struct bcm5974 *dev, int size)
> >  		/* set the integrated button if applicable */
> >  		if (c->tp_type == TYPE2)
> >  			ibt = raw2int(dev->tp_data[BUTTON_TYPE2]);
> > -	}
> > +	} else
> > +		raw_w = raw_x = raw_y = 0;
> >  
> >  	/* while tracking finger still valid, count all fingers */
> >  	if (ptest > PRESSURE_LOW && origin) {
> 
> I would prefer treating raw_p on the same footing here, completing the set of
> non-obviously initialized variables. It might also make sense to utilize the
> same initialization technique already used in the code, thus:
> 

No, then you are wasting cpu cycles and doing double initialization for
some cases.

> diff --git a/drivers/input/mouse/bcm5974.c b/drivers/input/mouse/bcm5974.c
> index 2d8fc0b..2f85876 100644
> --- a/drivers/input/mouse/bcm5974.c
> +++ b/drivers/input/mouse/bcm5974.c
> @@ -316,7 +316,7 @@ static int report_tp_state(struct bcm5974 *dev, int size)
>  	const struct bcm5974_config *c = &dev->cfg;
>  	const struct tp_finger *f;
>  	struct input_dev *input = dev->input;
> -	int raw_p, raw_w, raw_x, raw_y, raw_n;
> +	int raw_p = 0, raw_w = 0, raw_x = 0, raw_y = 0, raw_n;
>  	int ptest = 0, origin = 0, ibt = 0, nmin = 0, nmax = 0;
>  	int abs_p = 0, abs_w = 0, abs_x = 0, abs_y = 0;
> 
> 
> I wonder how many cpu cycles in the world are spent making compilers happy.
> 

It is not compiler mistake it is programming/logic mistakes. We should
be thankful to compiler to pointing mistakes made by us.

Thanks,
--
JSR

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