linux-kernel - Re: [PATCH v1 3/5] iio: accel: bma400: Add triggered buffer support

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Message-ID: <20220322154047.GA3677@jagath-PC>
Date:   Tue, 22 Mar 2022 21:10:49 +0530
From:   Jagath Jog J <jagathjog1996@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Dan Robertson <dan@...obertson.com>,
        Jonathan Cameron <jic23@...nel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 3/5] iio: accel: bma400: Add triggered buffer support

Hello Andy,

On Tue, Mar 22, 2022 at 10:54:53AM +0200, Andy Shevchenko wrote:
> On Tue, Mar 22, 2022 at 12:21 AM Jagath Jog J <jagathjog1996@...il.com> wrote:
> > On Mon, Mar 21, 2022 at 10:39:22AM +0200, Andy Shevchenko wrote:
> > > On Sat, Mar 19, 2022 at 8:10 PM Jagath Jog J <jagathjog1996@...il.com> wrote:
> 
> First of all, you left many uncommented comments. I assume you agree
> with my comments and are going to address them. If it's not the case,
> please elaborate.

Yes Andy, I agree with your comments and I will address them in the next v2 series.

> 
> ...
> 
> > > > +out:
> >
> > Just to skip the below "if()" if error occurs in previous regmap read,
> > I used this label.
> >        if (status & BMA400_INT_DRDY_MSK)
> >              iio_trigger_poll_chained(data->trig);
> >
> > I will remove the label in next patch
> 
> Just return directly.
> 
> ...
> 
> > > A useless label. Moreover this raises a question: why is it okay to
> > > always mark IRQ as handled?
> > >
> > > > +       return IRQ_HANDLED;
> >
> > Since I was not using top-half of the interrupt so I marked IRQ as handled
> > even for error case in the handler.
> 
> Yes, but why? Isn't it an erroneous state? Does it mean spurious
> interrupt? Does it mean interrupt is unserviced?

Sorry, even for erroneous state I was returning IRQ_HANDLED.
As shown below, now for erroneous state and spurious interrupt I will return
IRQ_NONE and for valid interrupt IRQ_HANDLED will be returned.

Is below method is correct?

static irqreturn_t bma400_interrupt(int irq, void *private)
{
       struct iio_dev *indio_dev = private;
       struct bma400_data *data = iio_priv(indio_dev);
       int ret;
       __le16 status;

       mutex_lock(&data->mutex);
       ret = regmap_bulk_read(data->regmap, BMA400_INT_STAT0_REG, &status,
                              sizeof(status));
       mutex_unlock(&data->mutex);
       if (ret)
               return IRQ_NONE;

       if (le16_to_cpu(status) & BMA400_INT_DRDY_MSK) {
               iio_trigger_poll_chained(data->trig);
	       return IRQ_HANDLED;
	}

        return IRQ_NONE;
}

> 
> -- 
> With Best Regards,
> Andy Shevchenko