Re: [PATCH 21/22] Input: rotary_encoder - use guard notation when acquiring mutex

[Javier Carrasco]

On 04/09/2024 06:49, 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@xxxxxxxxx>
> ---
>  drivers/input/misc/rotary_encoder.c | 23 ++++++++---------------
>  1 file changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/input/misc/rotary_encoder.c b/drivers/input/misc/rotary_encoder.c
> index 6628fe540834..52761da9f999 100644
> --- a/drivers/input/misc/rotary_encoder.c
> +++ b/drivers/input/misc/rotary_encoder.c
> @@ -113,7 +113,7 @@ static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
>  	struct rotary_encoder *encoder = dev_id;
>  	unsigned int state;
>  
> -	mutex_lock(&encoder->access_mutex);
> +	guard(mutex)(&encoder->access_mutex);
>  
>  	state = rotary_encoder_get_state(encoder);
>  
> @@ -136,8 +136,6 @@ static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
>  		break;
>  	}
>  
> -	mutex_unlock(&encoder->access_mutex);
> -
>  	return IRQ_HANDLED;
>  }
>  
> @@ -146,7 +144,7 @@ static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
>  	struct rotary_encoder *encoder = dev_id;
>  	unsigned int state;
>  
> -	mutex_lock(&encoder->access_mutex);
> +	guard(mutex)(&encoder->access_mutex);
>  
>  	state = rotary_encoder_get_state(encoder);
>  
> @@ -159,8 +157,6 @@ static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
>  		}
>  	}
>  
> -	mutex_unlock(&encoder->access_mutex);
> -
>  	return IRQ_HANDLED;
>  }
>  
> @@ -169,22 +165,19 @@ static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
>  	struct rotary_encoder *encoder = dev_id;
>  	unsigned int state;
>  
> -	mutex_lock(&encoder->access_mutex);
> +	guard(mutex)(&encoder->access_mutex);
>  
>  	state = rotary_encoder_get_state(encoder);
>  
> -	if ((encoder->last_stable + 1) % 4 == state)
> +	if ((encoder->last_stable + 1) % 4 == state) {
>  		encoder->dir = 1;
> -	else if (encoder->last_stable == (state + 1) % 4)
> +		rotary_encoder_report_event(encoder);
> +	} else if (encoder->last_stable == (state + 1) % 4) {
>  		encoder->dir = -1;
> -	else
> -		goto out;
> -
> -	rotary_encoder_report_event(encoder);
> +		rotary_encoder_report_event(encoder);
> +	}
>  
> -out:
>  	encoder->last_stable = state;
> -	mutex_unlock(&encoder->access_mutex);
>  
>  	return IRQ_HANDLED;
>  }

Reviewed-by: Javier Carrasco <javier.carrasco.cruz@xxxxxxxxx>