linux-kernel - Re: [PATCH] char: xillybus: replace usage of found with dedicated list iterator variable

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Date:   Thu, 24 Mar 2022 17:41:43 +0200
From:   Eli Billauer <eli.billauer@...il.com>
To:     Jakob Koschel <jakobkoschel@...il.com>
CC:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...nel.org>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: Re: [PATCH] char: xillybus: replace usage of found with dedicated
 list iterator variable

Thanks.

Acked-by: Eli Billauer <eli.billauer@...il.com>

On 24/03/22 09:09, Jakob Koschel wrote:
> To move the list iterator variable into the list_for_each_entry_*()
> macro in the future it should be avoided to use the list iterator
> variable after the loop body.
>
> To *never* use the list iterator variable after the loop it was
> concluded to use a separate iterator variable instead of a
> found boolean [1].
>
> This removes the need to use a found variable and simply checking if
> the variable was set, can determine if the break/goto was hit.
>
> Link:https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
> Signed-off-by: Jakob Koschel<jakobkoschel@...il.com>
> ---
>   drivers/char/xillybus/xillybus_class.c | 26 ++++++++++++--------------
>   1 file changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/char/xillybus/xillybus_class.c b/drivers/char/xillybus/xillybus_class.c
> index 5046486011c8..0f238648dcfe 100644
> --- a/drivers/char/xillybus/xillybus_class.c
> +++ b/drivers/char/xillybus/xillybus_class.c
> @@ -174,18 +174,17 @@ void xillybus_cleanup_chrdev(void *private_data,
>   			     struct device *dev)
>   {
>   	int minor;
> -	struct xilly_unit *unit;
> -	bool found = false;
> +	struct xilly_unit *unit = NULL, *iter;
>
>   	mutex_lock(&unit_mutex);
>
> -	list_for_each_entry(unit,&unit_list, list_entry)
> -		if (unit->private_data == private_data) {
> -			found = true;
> +	list_for_each_entry(iter,&unit_list, list_entry)
> +		if (iter->private_data == private_data) {
> +			unit = iter;
>   			break;
>   		}
>
> -	if (!found) {
> +	if (!unit) {
>   		dev_err(dev, "Weird bug: Failed to find unit\n");
>   		mutex_unlock(&unit_mutex);
>   		return;
> @@ -216,22 +215,21 @@ int xillybus_find_inode(struct inode *inode,
>   {
>   	int minor = iminor(inode);
>   	int major = imajor(inode);
> -	struct xilly_unit *unit;
> -	bool found = false;
> +	struct xilly_unit *unit = NULL, *iter;
>
>   	mutex_lock(&unit_mutex);
>
> -	list_for_each_entry(unit,&unit_list, list_entry)
> -		if (unit->major == major&&
> -		    minor>= unit->lowest_minor&&
> -		    minor<  (unit->lowest_minor + unit->num_nodes)) {
> -			found = true;
> +	list_for_each_entry(iter,&unit_list, list_entry)
> +		if (iter->major == major&&
> +		    minor>= iter->lowest_minor&&
> +		    minor<  (iter->lowest_minor + iter->num_nodes)) {
> +			unit = iter;
>   			break;
>   		}
>
>   	mutex_unlock(&unit_mutex);
>
> -	if (!found)
> +	if (!unit)
>   		return -ENODEV;
>
>   	*private_data = unit->private_data;
>
> base-commit: f443e374ae131c168a065ea1748feac6b2e76613
>