linux-kernel - Re: [PATCH RFC] iio: pressure: zpa2326: report interrupted case as failure

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Message-ID: <CAMuHMdXdcY1fsZsdgUe7=gNUaKannGe==4BvQTwren898QXPfw@mail.gmail.com>
Date:   Tue, 4 Jul 2017 12:40:33 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Nicholas Mc Guire <der.herr@...r.at>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        simran singhal <singhalsimran0@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Gregor Boirie <gregor.boirie@...rot.com>,
        linux-iio@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] iio: pressure: zpa2326: report interrupted case as failure

Hi Nicholas,

On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire <der.herr@...r.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.herr@...r.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

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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