linux-kernel - Re: [PATCH v2] hwmon: lm75: Handle broken device nodes gracefully

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Date:   Tue, 2 Feb 2021 07:08:51 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Matwey V. Kornilov" <matwey@....msu.ru>,
        Jean Delvare <jdelvare@...e.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        "open list:HARDWARE MONITORING" <linux-hwmon@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Cc:     matwey.kornilov@...il.com
Subject: Re: [PATCH v2] hwmon: lm75: Handle broken device nodes gracefully

On 2/2/21 6:21 AM, Matwey V. Kornilov wrote:
> 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
> found. This is the case when OF node exists but has unknown

is found.

> 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>
> ---
>  drivers/hwmon/lm75.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
> index e447febd121a..130ad5042107 100644
> --- a/drivers/hwmon/lm75.c
> +++ b/drivers/hwmon/lm75.c
> @@ -561,9 +561,15 @@ 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;
>  

else needs to be in { } to match if.

Guenter

>  	if (!i2c_check_functionality(client->adapter,
>