Re: [PATCH net-next 02/15] net: dsa: sja1105: Remove usage of iterator for list_add() after loop

[Vladimir Oltean]

On Sun, Apr 10, 2022 at 08:24:37PM +0200, Jakob Koschel wrote:
> Btw, I just realized that the if (!pos) is not necessary. This should simply do it:
> 
> diff --git a/drivers/net/dsa/sja1105/sja1105_vl.c b/drivers/net/dsa/sja1105/sja1105_vl.c
> index b7e95d60a6e4..2d59e75a9e3d 100644
> --- a/drivers/net/dsa/sja1105/sja1105_vl.c
> +++ b/drivers/net/dsa/sja1105/sja1105_vl.c
> @@ -28,6 +28,7 @@ static int sja1105_insert_gate_entry(struct sja1105_gating_config *gating_cfg,
>  		list_add(&e->list, &gating_cfg->entries);
>  	} else {
> +		struct list_head *pos = &gating_cfg->entries;
>  		struct sja1105_gate_entry *p;
>  
>  		list_for_each_entry(p, &gating_cfg->entries, list) {
>  			if (p->interval == e->interval) {
> @@ -37,10 +38,12 @@ static int sja1105_insert_gate_entry(struct sja1105_gating_config *gating_cfg,
>  				goto err;
>  			}
>  
> -			if (e->interval < p->interval)
> +			if (e->interval < p->interval) {
> +				pos = &p->list;
>  				break;
> +			}
>  		}
> -		list_add(&e->list, p->list.prev);
> +		list_add(&e->list, pos->prev);
>  	}
>  
>  	gating_cfg->num_entries++;
> -- 
> 2.25.1

I think we can give this a turn that is actually beneficial for the driver.
I've prepared and tested 3 patches on this function, see below.
Concrete improvements:
- that thing with list_for_each_entry() and list_for_each()
- no more special-casing of an empty list
- simplifying the error path
- that thing with list_add_tail()

What do you think about the changes below?