[PATCH v2] hwmon: (tps53679) Fix device ID comparison and printing in tps53676_identify()

["Pradhan, Sanman" <sanman.pradhan@hpe.com>]

From: Sanman Pradhan <psanman@juniper.net>

tps53676_identify() uses strncmp() to compare the device ID buffer
against a byte sequence containing embedded non-printable bytes
(\x53\x67\x60). strncmp() is semantically wrong for binary data
comparison; use memcmp() instead.

Additionally, the buffer from i2c_smbus_read_block_data() is not
NUL-terminated, so printing it with "%s" in the error path is
undefined behavior and may read past the buffer. Use "%*ph" to
hex-dump the actual bytes returned.

Per the datasheet, the expected device ID is the 6-byte sequence
54 49 53 67 60 00 ("TI\x53\x67\x60\x00"), so compare all 6 bytes
including the trailing NUL.

Fixes: cb3d37b59012 ("hwmon: (pmbus/tps53679) Add support for TI TPS53676")
Signed-off-by: Sanman Pradhan <psanman@juniper.net>
---
v2:
 - Compare full 6-byte datasheet device ID including trailing NUL
 - Return -ENODEV for any mismatch
---
 drivers/hwmon/pmbus/tps53679.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/pmbus/tps53679.c b/drivers/hwmon/pmbus/tps53679.c
index 1a6abc32afe2..94258e8cfd90 100644
--- a/drivers/hwmon/pmbus/tps53679.c
+++ b/drivers/hwmon/pmbus/tps53679.c
@@ -175,8 +175,8 @@ static int tps53676_identify(struct i2c_client *client,
 	ret = i2c_smbus_read_block_data(client, PMBUS_IC_DEVICE_ID, buf);
 	if (ret < 0)
 		return ret;
-	if (strncmp("TI\x53\x67\x60", buf, 5)) {
-		dev_err(&client->dev, "Unexpected device ID: %s\n", buf);
+	if (ret != 6 || memcmp(buf, "TI\x53\x67\x60\x00", 6)) {
+		dev_err(&client->dev, "Unexpected device ID: %*ph\n", ret, buf);
 		return -ENODEV;
 	}
 
-- 
2.34.1