[PATCH 1/2] serial: 8250: Use 'hlist_for_each_entry' to simplify code

[PATCH 1/2] serial: 8250: Use 'hlist_for_each_entry' to simplify code

[Christophe JAILLET]

Use 'hlist_for_each_entry' instead of hand writing it.
This saves a few lines of code.

The comment about warning generated by some gcc version is also removed.
The way 'hlist_for_each_entry' is written should prevent such a warning to
be emitted.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Compile tested only
---
 drivers/tty/serial/8250/8250_core.c | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index cae61d1ebec5..081b773a54c9 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -172,7 +172,6 @@ static void serial_do_unlink(struct irq_info *i, struct uart_8250_port *up)
 static int serial_link_irq_chain(struct uart_8250_port *up)
 {
 	struct hlist_head *h;
-	struct hlist_node *n;
 	struct irq_info *i;
 	int ret;
 
@@ -180,13 +179,11 @@ static int serial_link_irq_chain(struct uart_8250_port *up)
 
 	h = &irq_lists[up->port.irq % NR_IRQ_HASH];
 
-	hlist_for_each(n, h) {
-		i = hlist_entry(n, struct irq_info, node);
+	hlist_for_each_entry(i, h, node)
 		if (i->irq == up->port.irq)
 			break;
-	}
 
-	if (n == NULL) {
+	if (i == NULL) {
 		i = kzalloc(sizeof(struct irq_info), GFP_KERNEL);
 		if (i == NULL) {
 			mutex_unlock(&hash_mutex);
@@ -220,25 +217,18 @@ static int serial_link_irq_chain(struct uart_8250_port *up)
 
 static void serial_unlink_irq_chain(struct uart_8250_port *up)
 {
-	/*
-	 * yes, some broken gcc emit "warning: 'i' may be used uninitialized"
-	 * but no, we are not going to take a patch that assigns NULL below.
-	 */
 	struct irq_info *i;
-	struct hlist_node *n;
 	struct hlist_head *h;
 
 	mutex_lock(&hash_mutex);
 
 	h = &irq_lists[up->port.irq % NR_IRQ_HASH];
 
-	hlist_for_each(n, h) {
-		i = hlist_entry(n, struct irq_info, node);
+	hlist_for_each_entry(i, h, node)
 		if (i->irq == up->port.irq)
 			break;
-	}
 
-	BUG_ON(n == NULL);
+	BUG_ON(i == NULL);
 	BUG_ON(i->head == NULL);
 
 	if (list_empty(i->head))
-- 
2.30.2

[PATCH 2/2] serial: 8250: Add an empty line and remove some useless {}

[Christophe JAILLET]

This fixes the following checkpatch.pl warnings:
   WARNING: Missing a blank line after declarations
   WARNING: braces {} are not necessary for any arm of this statement

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/tty/serial/8250/8250_core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 081b773a54c9..1082e76c4d37 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -321,9 +321,9 @@ static int univ8250_setup_irq(struct uart_8250_port *up)
 	 * hardware interrupt, we use a timer-based system.  The original
 	 * driver used to do this with IRQ0.
 	 */
-	if (!port->irq) {
+	if (!port->irq)
 		mod_timer(&up->timer, jiffies + uart_poll_timeout(port));
-	} else
+	else
 		retval = serial_link_irq_chain(up);
 
 	return retval;
@@ -752,6 +752,7 @@ void serial8250_suspend_port(int line)
 	if (!console_suspend_enabled && uart_console(port) &&
 	    port->type != PORT_8250) {
 		unsigned char canary = 0xa5;
+
 		serial_out(up, UART_SCR, canary);
 		if (serial_in(up, UART_SCR) == canary)
 			up->canary = canary;
-- 
2.30.2

Re: [PATCH 1/2] serial: 8250: Use 'hlist_for_each_entry' to simplify code

[Andy Shevchenko]

On Wed, Apr 28, 2021 at 09:30:40AM +0200, Christophe JAILLET wrote:
> Use 'hlist_for_each_entry' instead of hand writing it.
> This saves a few lines of code.
> 
> The comment about warning generated by some gcc version is also removed.
> The way 'hlist_for_each_entry' is written should prevent such a warning to
> be emitted.

I checked the implementation of the macros vs. this usage and below seems legit.
However it indeed needs more test coverage because it's sensitive piece of code.

FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

(with the above caveat)

> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> Compile tested only
> ---
>  drivers/tty/serial/8250/8250_core.c | 18 ++++--------------
>  1 file changed, 4 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index cae61d1ebec5..081b773a54c9 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -172,7 +172,6 @@ static void serial_do_unlink(struct irq_info *i, struct uart_8250_port *up)
>  static int serial_link_irq_chain(struct uart_8250_port *up)
>  {
>  	struct hlist_head *h;
> -	struct hlist_node *n;
>  	struct irq_info *i;
>  	int ret;
>  
> @@ -180,13 +179,11 @@ static int serial_link_irq_chain(struct uart_8250_port *up)
>  
>  	h = &irq_lists[up->port.irq % NR_IRQ_HASH];
>  
> -	hlist_for_each(n, h) {
> -		i = hlist_entry(n, struct irq_info, node);
> +	hlist_for_each_entry(i, h, node)
>  		if (i->irq == up->port.irq)
>  			break;
> -	}
>  
> -	if (n == NULL) {
> +	if (i == NULL) {
>  		i = kzalloc(sizeof(struct irq_info), GFP_KERNEL);
>  		if (i == NULL) {
>  			mutex_unlock(&hash_mutex);
> @@ -220,25 +217,18 @@ static int serial_link_irq_chain(struct uart_8250_port *up)
>  
>  static void serial_unlink_irq_chain(struct uart_8250_port *up)
>  {
> -	/*
> -	 * yes, some broken gcc emit "warning: 'i' may be used uninitialized"
> -	 * but no, we are not going to take a patch that assigns NULL below.
> -	 */
>  	struct irq_info *i;
> -	struct hlist_node *n;
>  	struct hlist_head *h;
>  
>  	mutex_lock(&hash_mutex);
>  
>  	h = &irq_lists[up->port.irq % NR_IRQ_HASH];
>  
> -	hlist_for_each(n, h) {
> -		i = hlist_entry(n, struct irq_info, node);
> +	hlist_for_each_entry(i, h, node)
>  		if (i->irq == up->port.irq)
>  			break;
> -	}
>  
> -	BUG_ON(n == NULL);
> +	BUG_ON(i == NULL);
>  	BUG_ON(i->head == NULL);
>  
>  	if (list_empty(i->head))
> -- 
> 2.30.2
> 

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/2] serial: 8250: Add an empty line and remove some useless {}

[Andy Shevchenko]

On Wed, Apr 28, 2021 at 09:30:52AM +0200, Christophe JAILLET wrote:
> This fixes the following checkpatch.pl warnings:
>    WARNING: Missing a blank line after declarations
>    WARNING: braces {} are not necessary for any arm of this statement

If it makes somebody happier...
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>  drivers/tty/serial/8250/8250_core.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index 081b773a54c9..1082e76c4d37 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -321,9 +321,9 @@ static int univ8250_setup_irq(struct uart_8250_port *up)
>  	 * hardware interrupt, we use a timer-based system.  The original
>  	 * driver used to do this with IRQ0.
>  	 */
> -	if (!port->irq) {
> +	if (!port->irq)
>  		mod_timer(&up->timer, jiffies + uart_poll_timeout(port));
> -	} else
> +	else
>  		retval = serial_link_irq_chain(up);
>  
>  	return retval;
> @@ -752,6 +752,7 @@ void serial8250_suspend_port(int line)
>  	if (!console_suspend_enabled && uart_console(port) &&
>  	    port->type != PORT_8250) {
>  		unsigned char canary = 0xa5;
> +
>  		serial_out(up, UART_SCR, canary);
>  		if (serial_in(up, UART_SCR) == canary)
>  			up->canary = canary;
> -- 
> 2.30.2
> 

-- 
With Best Regards,
Andy Shevchenko