Re: [PATCH v1 1/1] gpiolib: cdev: Split line_get_debounce_period() and use

[Kent Gibson]

On Thu, Dec 21, 2023 at 07:55:27PM +0200, Andy Shevchenko wrote:
> Instead of repeating the same code and reduce possible miss
> of READ_ONCE(), split line_get_debounce_period() heler out
> and use in the existing cases.
>

helper


Not a fan of this change.

So using READ_ONCE() is repeating code??
Doesn't providing a wrapper around READ_ONCE() just rename that repitition?
What of all the other uses of READ_ONCE() in cdev (and there are a lot) -
why pick on debounce_period?

The line_set_debounce_period() is necessary as the set is now a
multi-step process as it can impact whether the line is contained
in the supinfo_tree.  The get is just a get.

And you could've included me in the Cc so I didn't just find it by
accident.

Cheers,
Kent.

> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
>  drivers/gpio/gpiolib-cdev.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
> index 744734405912..c573820d5722 100644
> --- a/drivers/gpio/gpiolib-cdev.c
> +++ b/drivers/gpio/gpiolib-cdev.c
> @@ -651,6 +651,16 @@ static struct line *supinfo_find(struct gpio_desc *desc)
>  	return NULL;
>  }
>
> +static unsigned int line_get_debounce_period(struct line *line)
> +{
> +	return READ_ONCE(line->debounce_period_us);
> +}
> +
> +static inline bool line_has_supinfo(struct line *line)
> +{
> +	return line_get_debounce_period(line);
> +}
> +
>  static void supinfo_to_lineinfo(struct gpio_desc *desc,
>  				struct gpio_v2_line_info *info)
>  {
> @@ -665,15 +675,10 @@ static void supinfo_to_lineinfo(struct gpio_desc *desc,
>
>  	attr = &info->attrs[info->num_attrs];
>  	attr->id = GPIO_V2_LINE_ATTR_ID_DEBOUNCE;
> -	attr->debounce_period_us = READ_ONCE(line->debounce_period_us);
> +	attr->debounce_period_us = line_get_debounce_period(line);
>  	info->num_attrs++;
>  }
>
> -static inline bool line_has_supinfo(struct line *line)
> -{
> -	return READ_ONCE(line->debounce_period_us);
> -}
> -
>  /*
>   * Checks line_has_supinfo() before and after the change to avoid unnecessary
>   * supinfo_tree access.
> @@ -846,7 +851,7 @@ static enum hte_return process_hw_ts(struct hte_ts_data *ts, void *p)
>  		line->total_discard_seq++;
>  		line->last_seqno = ts->seq;
>  		mod_delayed_work(system_wq, &line->work,
> -		  usecs_to_jiffies(READ_ONCE(line->debounce_period_us)));
> +				 usecs_to_jiffies(line_get_debounce_period(line)));
>  	} else {
>  		if (unlikely(ts->seq < line->line_seqno))
>  			return HTE_CB_HANDLED;
> @@ -987,7 +992,7 @@ static irqreturn_t debounce_irq_handler(int irq, void *p)
>  	struct line *line = p;
>
>  	mod_delayed_work(system_wq, &line->work,
> -		usecs_to_jiffies(READ_ONCE(line->debounce_period_us)));
> +			 usecs_to_jiffies(line_get_debounce_period(line)));
>
>  	return IRQ_HANDLED;
>  }
> @@ -1215,7 +1220,7 @@ static int edge_detector_update(struct line *line,
>  			gpio_v2_line_config_debounce_period(lc, line_idx);
>
>  	if ((active_edflags == edflags) &&
> -	    (READ_ONCE(line->debounce_period_us) == debounce_period_us))
> +	    (line_get_debounce_period(line) == debounce_period_us))
>  		return 0;
>
>  	/* sw debounced and still will be...*/
> --
> 2.43.0.rc1.1.gbec44491f096
>