Hi Nicholas,
On Wed, Jul 5, 2017 at 9:37 AM, Nicholas Mc Guire <der.h...@hofr.at> wrote:
> 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:
>> > 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 -
No, ret does not need to be initialized to 0, as it would prevent the warning
from reappearing in case of future logic errors.
Instead the last "if" should be removed, as it's always true.
Will send a patch, as requested by Jonathan.
> interestingly enough gcc gcc (Debian 4.9.2-10) 4.9.2
> does not flag this uninitioalized variable !
Only very old or very new versions of gcc do that.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
