linux-kernel - [PATCH v3] hwmon: lm75: Handle broken device nodes gracefully

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Date:   Tue,  2 Feb 2021 21:37:37 +0300
From:   "Matwey V. Kornilov" <matwey@....msu.ru>
To:     Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Javier Martinez Canillas <javier@....samsung.com>,
        linux-hwmon@...r.kernel.org (open list:HARDWARE MONITORING),
        linux-kernel@...r.kernel.org (open list)
Cc:     matwey.kornilov@...il.com,
        "Matwey V. Kornilov" <matwey@....msu.ru>,
        linux-hwmon@...r.kernel.org (open list:HARDWARE MONITORING),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v3] hwmon: lm75: Handle broken device nodes gracefully

There is a logical flaw in lm75_probe() function introduced in

    commit e97a45f1b460 ("hwmon: (lm75) Add OF device ID table")

Note, that of_device_get_match_data() returns NULL when no match
is found. This is the case when OF node exists but has unknown
compatible line, while the module is still loaded via i2c
detection.

arch/powerpc/boot/dts/fsl/p2041rdb.dts:

    lm75b@48 {
    	compatible = "nxp,lm75a";
    	reg = <0x48>;
    };

In this case, the sensor is mistakenly considered as ADT75 variant.

Fixes: e97a45f1b460 ("hwmon: (lm75) Add OF device ID table")
Signed-off-by: Matwey V. Kornilov <matwey@....msu.ru>
---
 Changes since v2:
 * fixed typo in the message
 * fixed brackets

 drivers/hwmon/lm75.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
index e447febd121a..53882c334a0d 100644
--- a/drivers/hwmon/lm75.c
+++ b/drivers/hwmon/lm75.c
@@ -561,10 +561,17 @@ static int lm75_probe(struct i2c_client *client)
 	int status, err;
 	enum lm75_type kind;
 
-	if (client->dev.of_node)
-		kind = (enum lm75_type)of_device_get_match_data(&client->dev);
-	else
+	if (dev->of_node) {
+		const struct of_device_id *match =
+			of_match_device(dev->driver->of_match_table, dev);
+
+		if (!match)
+			return -ENODEV;
+
+		kind = (enum lm75_type)(match->data);
+	} else {
 		kind = i2c_match_id(lm75_ids, client)->driver_data;
+	}
 
 	if (!i2c_check_functionality(client->adapter,
 			I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA))
-- 
2.26.2