linux-kernel - Re: [PATCH] drivers: iio: proximity: This patch fix the following checkpatch warning.

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Date:   Mon, 22 Apr 2019 11:48:21 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Matt Ranostay <matt.ranostay@...sulko.com>
Cc:     Mohan Kumar <mohankumar718@...il.com>,
        Andreas Klinger <ak@...klinger.de>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: iio: proximity: This patch fix the following
 checkpatch warning.

On Thu, 18 Apr 2019 16:23:51 -0700
Matt Ranostay <matt.ranostay@...sulko.com> wrote:

> See comments inline
> 
> On Wed, Apr 17, 2019 at 11:15 AM Mohan Kumar <mohankumar718@...il.com> wrote:
> >
> > As per Documentation/timers/timers-howto.txt Msleep < 20ms can sleep for
> > up to 20ms. so use usleep_range.
> >
> > Signed-off-by: Mohan Kumar <mohankumar718@...il.com>
> > ---
> >  drivers/iio/proximity/mb1232.c | 2 +-
> >  drivers/iio/proximity/srf08.c  | 4 ++--
> >  2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/iio/proximity/mb1232.c b/drivers/iio/proximity/mb1232.c
> > index 166b3e6..74f7eae 100644
> > --- a/drivers/iio/proximity/mb1232.c
> > +++ b/drivers/iio/proximity/mb1232.c
> > @@ -81,7 +81,7 @@ static s16 mb1232_read_distance(struct mb1232_data *data)
> >                 }
> >         } else {
> >                 /* use simple sleep if announce irq is not connected */
> > -               msleep(15);
> > +               usleep_range(15000, 20000);  
> 
> This is actually less than ideal.. because usleep_range uses the
> hrtimers which forces an interrupt.
> 
> Unless you actually need to read between 15ms and 20ms it is best just
> to leave the msleep() as it is, and let it take a bit longer
> if required.
Good response.  Perhaps Mohan could follow up with a patch to add
a comment to this effect to save anyone else trying to 'fix' this
issue in future?

Thanks,

Jonathan
> 
> - Matt
> 
> >         }
> >
> >         ret = i2c_master_recv(client, (char *)&buf, sizeof(buf));
> > diff --git a/drivers/iio/proximity/srf08.c b/drivers/iio/proximity/srf08.c
> > index f2bf783..605a582 100644
> > --- a/drivers/iio/proximity/srf08.c
> > +++ b/drivers/iio/proximity/srf08.c
> > @@ -150,7 +150,7 @@ static int srf08_read_ranging(struct srf08_data *data)
> >          * polling for not more than 20 ms should be enough
> >          */
> >         waittime = 1 + data->range_mm / 172;
> > -       msleep(waittime);
> > +       usleep_range(waittime * 1000, (waittime * 1000) + 2000);
> >         for (i = 0; i < 4; i++) {
> >                 ret = i2c_smbus_read_byte_data(data->client,
> >                                                 SRF08_READ_SW_REVISION);
> > @@ -158,7 +158,7 @@ static int srf08_read_ranging(struct srf08_data *data)
> >                 /* check if a valid version number is read */
> >                 if (ret < 255 && ret > 0)
> >                         break;
> > -               msleep(5);
> > +               usleep_range(5000, 15000);
> >         }
> >
> >         if (ret >= 255 || ret <= 0) {
> > --
> > 2.7.4
> >