linux-kernel - Re: [PATCH v4 05/13] serial: max3100: Replace open-coded parity calculation with parity

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Message-ID: <Z_atODqZDkff5sjj@yury>
Date: Wed, 9 Apr 2025 13:24:08 -0400
From: Yury Norov <yury.norov@...il.com>
To: Kuan-Wei Chiu <visitorckw@...il.com>
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	Yu-Chun Lin <eleanor15x@...il.com>
Subject: Re: [PATCH v4 05/13] serial: max3100: Replace open-coded parity
 calculation with parity_odd()

On Wed, Apr 09, 2025 at 11:43:48PM +0800, Kuan-Wei Chiu wrote:
> Refactor parity calculations to use the standard parity_odd() helper.
> This change eliminates redundant implementations.
> 
> Co-developed-by: Yu-Chun Lin <eleanor15x@...il.com>
> Signed-off-by: Yu-Chun Lin <eleanor15x@...il.com>
> Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>
> ---
>  drivers/tty/serial/max3100.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/max3100.c b/drivers/tty/serial/max3100.c
> index f2dd83692b2c..36ed41eef7b1 100644
> --- a/drivers/tty/serial/max3100.c
> +++ b/drivers/tty/serial/max3100.c
> @@ -16,6 +16,7 @@
>  /* 4 MAX3100s should be enough for everyone */
>  #define MAX_MAX3100 4
>  
> +#include <linux/bitops.h>
>  #include <linux/container_of.h>
>  #include <linux/delay.h>
>  #include <linux/device.h>
> @@ -133,7 +134,7 @@ static int max3100_do_parity(struct max3100_port *s, u16 c)
>  	else
>  		c &= 0xff;
>  
> -	parity = parity ^ (hweight8(c) & 1);
> +	parity = parity ^ parity_odd(c);

This can be simplified for more unless I misunderstand something...

From: Yury Norov <yury.norov@...il.com>
Date:   Wed Apr 9 13:22:04 2025 -0400

serial: max3100: Replace open-coded parity

diff --git a/drivers/tty/serial/max3100.c b/drivers/tty/serial/max3100.c
index f2dd83692b2c..07d332b8e87d 100644
--- a/drivers/tty/serial/max3100.c
+++ b/drivers/tty/serial/max3100.c
@@ -121,20 +121,12 @@ static DEFINE_MUTEX(max3100s_lock);		   /* race on probe */
 
 static int max3100_do_parity(struct max3100_port *s, u16 c)
 {
-	int parity;
-
-	if (s->parity & MAX3100_PARITY_ODD)
-		parity = 1;
-	else
-		parity = 0;
-
 	if (s->parity & MAX3100_7BIT)
 		c &= 0x7f;
 	else
 		c &= 0xff;
 
-	parity = parity ^ (hweight8(c) & 1);
-	return parity;
+	return s->parity & MAX3100_PARITY_ODD ? !parity(c) : parity(c);
 }
 
 static int max3100_check_parity(struct max3100_port *s, u16 c)