linux-kernel - Re: [PATCH v11 04/33] counter: 104-quad-8: Return error when invalid mode during ceiling

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Date:   Thu, 10 Jun 2021 00:48:12 +0900
From:   William Breathitt Gray <vilhelm.gray@...il.com>
To:     syednwaris@...il.com, Jonathan Cameron <jic23@...nel.org>
Cc:     linux-stm32@...md-mailman.stormreply.com, kernel@...gutronix.de,
        a.fatoum@...gutronix.de, kamel.bouhara@...tlin.com,
        gwendal@...omium.org, alexandre.belloni@...tlin.com,
        david@...hnology.com, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        patrick.havelange@...ensium.com, fabrice.gasnier@...com,
        mcoquelin.stm32@...il.com, alexandre.torgue@...com,
        o.rempel@...gutronix.de, jarkko.nikula@...ux.intel.com
Subject: Re: [PATCH v11 04/33] counter: 104-quad-8: Return error when invalid
 mode during ceiling_write

On Wed, Jun 09, 2021 at 04:12:36PM +0100, Jonathan Cameron wrote:
> On Wed,  9 Jun 2021 10:31:07 +0900
> William Breathitt Gray <vilhelm.gray@...il.com> wrote:
> 
> > The 104-QUAD-8 only has two count modes where a ceiling value makes
> > sense: Range Limit and Modulo-N. Outside of these two modes, setting a
> > ceiling value is an invalid operation -- so let's report it as such by
> > returning -EINVAL.
> > 
> > Fixes: fc069262261c ("counter: 104-quad-8: Add lock guards - generic interface")
> > Acked-by: Syed Nayyar Waris <syednwaris@...il.com>
> > Signed-off-by: William Breathitt Gray <vilhelm.gray@...il.com>
> 
> We seem to have some inconsistency in the driver about whether
> we hold the priv->lock when calling quad8_preset_register_set()
> 
> Can we look to make that consistent?

We do need to hold the lock when calling quad8_preset_register_set()
lest priv->preset goes out of sync with the device state.

Syed, if you have no objections I'll adjust this in the next version.

William Breathitt Gray

> > ---
> >  drivers/counter/104-quad-8.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
> > index 4bb9abffae48..233a3acc1377 100644
> > --- a/drivers/counter/104-quad-8.c
> > +++ b/drivers/counter/104-quad-8.c
> > @@ -714,13 +714,14 @@ static ssize_t quad8_count_ceiling_write(struct counter_device *counter,
> >  	switch (priv->count_mode[count->id]) {
> >  	case 1:
> >  	case 3:
> > +		mutex_unlock(&priv->lock);
> 
> Probably swap this line and the next one...]
> 
> >  		quad8_preset_register_set(priv, count->id, ceiling);
> > -		break;
> > +		return len;
> >  	}
> >  
> >  	mutex_unlock(&priv->lock);
> >  
> > -	return len;
> > +	return -EINVAL;
> >  }
> >  
> >  static ssize_t quad8_count_preset_enable_read(struct counter_device *counter,
> 

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