linux-kernel - [PATCH] w1: ds2413: fix state byte comparision

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Message-Id: <20190530075125.27379-1-manio@skyboo.net>
Date:   Thu, 30 May 2019 09:51:25 +0200
From:   Mariusz Bialonczyk <manio@...boo.net>
To:     linux-kernel@...r.kernel.org, Greg Kroah-Hartman <greg@...ah.com>
Cc:     Mariusz Bialonczyk <manio@...boo.net>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH] w1: ds2413: fix state byte comparision

This commit is fixing a smatch warning:
drivers/w1/slaves/w1_ds2413.c:61 state_read() warn: impossible condition '(*buf == 255) => ((-128)-127 == 255)'
by creating additional u8 variable for the bus reading and comparision

Reported-by: kbuild test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Fixes: 3856032a0628 ("w1: ds2413: when the slave is not responding during read, select it again")
Signed-off-by: Mariusz Bialonczyk <manio@...boo.net>
---
 drivers/w1/slaves/w1_ds2413.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/w1/slaves/w1_ds2413.c b/drivers/w1/slaves/w1_ds2413.c
index 21f08ac8a4e0..3364ad276b15 100644
--- a/drivers/w1/slaves/w1_ds2413.c
+++ b/drivers/w1/slaves/w1_ds2413.c
@@ -33,6 +33,7 @@ static ssize_t state_read(struct file *filp, struct kobject *kobj,
 	struct w1_slave *sl = kobj_to_w1_slave(kobj);
 	unsigned int retries = W1_F3A_RETRIES;
 	ssize_t bytes_read = -EIO;
+	u8 state;
 
 	dev_dbg(&sl->dev,
 		"Reading %s kobj: %p, off: %0#10x, count: %zu, buff addr: %p",
@@ -53,12 +54,13 @@ static ssize_t state_read(struct file *filp, struct kobject *kobj,
 	while (retries--) {
 		w1_write_8(sl->master, W1_F3A_FUNC_PIO_ACCESS_READ);
 
-		*buf = w1_read_8(sl->master);
-		if ((*buf & 0x0F) == ((~*buf >> 4) & 0x0F)) {
+		state = w1_read_8(sl->master);
+		if ((state & 0x0F) == ((~state >> 4) & 0x0F)) {
 			/* complement is correct */
+			*buf = state;
 			bytes_read = 1;
 			goto out;
-		} else if (*buf == W1_F3A_INVALID_PIO_STATE) {
+		} else if (state == W1_F3A_INVALID_PIO_STATE) {
 			/* slave didn't respond, try to select it again */
 			dev_warn(&sl->dev, "slave device did not respond to PIO_ACCESS_READ, " \
 					    "reselecting, retries left: %d\n", retries);
-- 
2.19.0.rc1