[PATCH] char: xillybus: replace usage of found with dedicated list iterator variable

[PATCH] char: xillybus: replace usage of found with dedicated list iterator variable

[Jakob Koschel]

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@gmail.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
-- 
2.25.1

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

[Eli Billauer]

Thanks.

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