linux-kernel - Re: [PATCH] USB: gtco: remove unnecessary variable assignments

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Message-ID: <20170615192517.4giikw5z7etu56a6@beacon.debie>
Date:   Thu, 15 Jun 2017 21:25:18 +0200
From:   ulrik.debie-os@...ig.org
To:     Joe Perches <joe@...ches.com>
Cc:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: gtco: remove unnecessary variable assignments

Hi Joe, Gustavo,

On Wed, Jun 14, 2017 at 10:00:48PM -0700, Joe Perches wrote:
> On Wed, 2017-06-14 at 20:50 -0500, Gustavo A. R. Silva wrote:
> > Remove unnecessary variable assignments.
> > Variable _val_ is overwritten before the value stored in it can be used.
> > 
> > Addresses-Coverity-ID: 1397695
> > Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> > ---
> >  drivers/input/tablet/gtco.c | 2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/drivers/input/tablet/gtco.c b/drivers/input/tablet/gtco.c
> > index b796e89..d9de13c 100644
> > --- a/drivers/input/tablet/gtco.c
> > +++ b/drivers/input/tablet/gtco.c
> > @@ -652,8 +652,6 @@ static void gtco_urb_callback(struct urb *urbinfo)
> >  		switch (device->buffer[0]) {
> >  		case 5:
> >  			/* Pressure is 9 bits */
> > -			val = ((u16)(device->buffer[8]) << 1);
> > -			val |= (u16)(device->buffer[7] >> 7);
> >  			input_report_abs(inputdev, ABS_PRESSURE,
> >  					 device->buffer[8]);
> 
> Perhaps more likely to be
> 
> 			input_report_abs(inputdev, ABS_PRESSURE, val);

Probably that was the original intention but changing it that way now
would give a shift of factor 2 to userspace.

But if the 2 lines are deleted, I would update the comment above it so it
is clear the lowest significant bit in buffer[7] is not included in the
report call.

Kind regards,
Ulrik