On Tue, Jul 04, 2017 at 08:08:53PM +0100, Jonathan Cameron wrote:
> On Tue, 4 Jul 2017 12:40:33 +0200
> Geert Uytterhoeven <ge...@linux-m68k.org> wrote:
>
> > Hi Nicholas,
> >
> > On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire <der.h...@hofr.at>
> > wrote:
> > > If the timeout-case prints a warning message then probably the interrupted
> > > case should also. Further, wait_for_completion_interruptible_timeout()
> > > returns long not int.
> > >
> > > Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326 barometer
> > > support")
> > > Signed-off-by: Nicholas Mc Guire <der.h...@hofr.at>
> > > ---
> > >
> > > The original control-flow was technically not wrong just confusing and a
> > > bit
> > > complicated. Not clear if reporting the interrupted case actually is
> > > useful,
> > > but given that the timeout is relatively long (200ms) it is not that
> > > unlikely
> > > so differentiating the cases seems helpful.
> > >
> > > Patch was compile-tested with: x86_64_defconfig + CONFIG_IIO=m,
> > > CONFIG_ZPA2326=m
> > >
> > > Patch is against v4.11 (localversion-next is next-20170512)
> > >
> > > drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
> > > 1 file changed, 10 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/iio/pressure/zpa2326.c
> > > b/drivers/iio/pressure/zpa2326.c
> > > index e58a0ad..617926f 100644
> > > --- a/drivers/iio/pressure/zpa2326.c
> > > +++ b/drivers/iio/pressure/zpa2326.c
> > > @@ -867,12 +867,13 @@ static int zpa2326_wait_oneshot_completion(const
> > > struct iio_dev *indio_dev,
> > > {
> > > int ret;
> > > unsigned int val;
> > > + long timeout;
> > >
> > > zpa2326_dbg(indio_dev, "waiting for one shot completion
> > > interrupt");
> > >
> > > - ret = wait_for_completion_interruptible_timeout(
> > > + timeout = wait_for_completion_interruptible_timeout(
> > > &private->data_ready, ZPA2326_CONVERSION_JIFFIES);
> > > - if (ret > 0)
> > > + if (timeout > 0)
> >
> > Check for strict positive timeout.
> >
> > > /*
> > > * Interrupt handler completed before timeout: return
> > > operation
> > > * status.
> > > @@ -882,13 +883,15 @@ static int zpa2326_wait_oneshot_completion(const
> > > struct iio_dev *indio_dev,
> > > /* Clear all interrupts just to be sure. */
> > > regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
> > >
> > > - if (!ret)
> > > + if (!timeout) {
> >
> > Check for zero timeout.
> >
> > > /* Timed out. */
> > > + zpa2326_warn(indio_dev, "no one shot interrupt occurred
> > > (%ld)",
> > > + timeout);
> > > ret = -ETIME;
> > > -
> > > - if (ret != -ERESTARTSYS)
> > > - zpa2326_warn(indio_dev, "no one shot interrupt occurred
> > > (%d)",
> > > - ret);
> > > + } else if (timeout < 0) {
> >
> > So if we get here, timeout is always strict negative, so the check can
> > be removed.
> >
> > > + zpa2326_warn(indio_dev, "wait for one shot interrupt
> > > canceled");
> > > + ret = -ERESTARTSYS;
> > > + }
> > >
> > > return ret;
> >
> > But gcc-4.1.2 is not smart enough:
> >
> > drivers/iio/pressure/zpa2326.c:868: warning: ???ret??? may be used
> > uninitialized in this function
> Good analysis. Care to send the obvious patch?
>
Thanks Geert for finding that - yes ret needs to be
initialized to 0 here, success case as documented in
the header of zpa2326_wait_oneshot_completion -
interestingly enough gcc gcc (Debian 4.9.2-10) 4.9.2
does not flag this uninitioalized variable !
thx!
hofrat
