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@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 3856032a0628 ("w1: ds2413: when the slave is not responding during read, select it again")
Signed-off-by: Mariusz Bialonczyk <manio@skyboo.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files 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 @@ next:
         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);