[PATCH] i2c-mxs: fix compile warning in mxs_i2c_xfer()

[Dong Aisheng-B29396]

> -----Original Message-----
> From: Uwe Kleine-König [mailto:u.kleine-koenig at pengutronix.de]
> Sent: Thursday, November 24, 2011 5:07 PM
> To: Dong Aisheng-B29396
> Cc: Wolfram Sang; Shawn Guo; linux-arm-kernel at lists.infradead.org; Ben
> Dooks; linux-i2c at vger.kernel.org
> Subject: Re: [PATCH] i2c-mxs: fix compile warning in mxs_i2c_xfer()
> 
> Hello,
> 
> On Thu, Nov 24, 2011 at 09:02:21AM +0000, Dong Aisheng-B29396 wrote:
> > > > > diff --git a/drivers/i2c/busses/i2c-mxs.c
> > > > > b/drivers/i2c/busses/i2c-mxs.c index 7e78f7c..00f098f 100644
> > > > > --- a/drivers/i2c/busses/i2c-mxs.c
> > > > > +++ b/drivers/i2c/busses/i2c-mxs.c
> > > > > @@ -193,7 +193,7 @@ static int mxs_i2c_wait_for_data(struct
> > > > > mxs_i2c_dev *i2c)
> > > > >
> > > > >  static int mxs_i2c_finish_read(struct mxs_i2c_dev *i2c, u8
> > > > > *buf, int len)  {
> > > > > -	u32 data;
> > > > > +	u32 data = 0;
> > > > >  	int i;
> > > > >
> > > > >  	for (i = 0; i < len; i++) {
> > > > Looks like a stupid compiler. Then better use
> > > >
> > > > 	u32 uninitialized_var(data);
> > >
> > > Leave it as it is and fix the compiler? Will do another test later
> > > to make sure.
> > >
> >
> > Compiler is wrong?
> > Just from the code that it seems to be right the 'data' might be used
> > uninitialized.
> >
> > Something I missed?
> >
> > static int mxs_i2c_finish_read(struct mxs_i2c_dev *i2c, u8 *buf, int
> > len) {
> >         u32 data;
> >         int i;
> >
> >         for (i = 0; i < len; i++) {
> >                 if ((i & 3) == 0) {
> >                         if (mxs_i2c_wait_for_data(i2c))
> >                                 return -ETIMEDOUT;
> >                         data = readl(i2c->regs + MXS_I2C_QUEUEDATA);
> >                 }
> >                 buf[i] = data & 0xff;
> >                 data >>= 8;
> >         }
> When data is used the first time, i is 0, so it went through the body of
> the if above before which assigned data. So no, data is initialized when
> used to assign buf[i].
> 
Ok, Thanks for the info.
So the compiler should do intelligent checking.

Regards
Dong Aisheng