linux-kernel - Re: [PATCH 12/22] Input: iqs269a - use guard notation when acquiring mutex

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Message-ID: <ZtilRLKICDSXKyEp@google.com>
Date: Wed, 4 Sep 2024 11:21:56 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>
Cc: linux-input@...r.kernel.org,
	Michael Hennerich <michael.hennerich@...log.com>,
	Ville Syrjala <syrjala@....fi>,
	Support Opensource <support.opensource@...semi.com>,
	Eddie James <eajames@...ux.ibm.com>,
	Andrey Moiseev <o2g.org.ru@...il.com>,
	Hans de Goede <hdegoede@...hat.com>,
	Jeff LaBundy <jeff@...undy.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/22] Input: iqs269a - use guard notation when acquiring
 mutex

Hi Javier,

On Wed, Sep 04, 2024 at 03:53:40PM +0200, Javier Carrasco wrote:
> On 04/09/2024 06:47, Dmitry Torokhov wrote:
> > Using guard notation makes the code more compact and error handling
> > more robust by ensuring that mutexes are released in all code paths
> > when control leaves critical section.
> > 
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > ---
> >  drivers/input/misc/iqs269a.c | 46 +++++++++++++-----------------------
> >  1 file changed, 16 insertions(+), 30 deletions(-)
> > 
> > diff --git a/drivers/input/misc/iqs269a.c b/drivers/input/misc/iqs269a.c
> > index 843f8a3f3410..c34d847fa4af 100644
> > --- a/drivers/input/misc/iqs269a.c
> > +++ b/drivers/input/misc/iqs269a.c
> 
> ...
> 
> > @@ -453,9 +449,9 @@ static int iqs269_ati_base_get(struct iqs269_private *iqs269,
> >  	if (ch_num >= IQS269_NUM_CH)
> >  		return -EINVAL;
> >  
> > -	mutex_lock(&iqs269->lock);
> > +	guard(mutex)(&iqs269->lock);
> > +
> >  	engine_b = be16_to_cpu(ch_reg[ch_num].engine_b);
> 
> maybe scoped_guard() to keep the scope of the mutex as it used to be?

Thank you for looking over patches.

It is just a few computations extra, so I decided not to use
scoped_guard(). Note that original code was forced to release mutex
early to avoid having to unlock it in all switch branches.

> 
> > -	mutex_unlock(&iqs269->lock);
> >  
> >  	switch (engine_b & IQS269_CHx_ENG_B_ATI_BASE_MASK) {
> >  	case IQS269_CHx_ENG_B_ATI_BASE_75:
> > @@ -491,7 +487,7 @@ static int iqs269_ati_target_set(struct iqs269_private *iqs269,
> >  	if (target > IQS269_CHx_ENG_B_ATI_TARGET_MAX)
> >  		return -EINVAL;
> >  
> > -	mutex_lock(&iqs269->lock);
> > +	guard(mutex)(&iqs269->lock);
> >  
> >  	engine_b = be16_to_cpu(ch_reg[ch_num].engine_b);
> >  
> > @@ -501,8 +497,6 @@ static int iqs269_ati_target_set(struct iqs269_private *iqs269,
> >  	ch_reg[ch_num].engine_b = cpu_to_be16(engine_b);
> >  	iqs269->ati_current = false;
> >  
> > -	mutex_unlock(&iqs269->lock);
> > -
> >  	return 0;
> >  }
> >  
> > @@ -515,10 +509,9 @@ static int iqs269_ati_target_get(struct iqs269_private *iqs269,
> >  	if (ch_num >= IQS269_NUM_CH)
> >  		return -EINVAL;
> >  
> > -	mutex_lock(&iqs269->lock);
> > -	engine_b = be16_to_cpu(ch_reg[ch_num].engine_b);
> > -	mutex_unlock(&iqs269->lock);
> > +	guard(mutex)(&iqs269->lock);
> 
> same here?
> 
> >  
> > +	engine_b = be16_to_cpu(ch_reg[ch_num].engine_b);
> >  	*target = (engine_b & IQS269_CHx_ENG_B_ATI_TARGET_MASK) * 32;

Same here, calculating the line above will take no time at all...

Thanks.

-- 
Dmitry