linux-kernel - Re: [PATCH v2 2/2] hwmon: sht3x: read out sensor serial number

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Message-ID: <20231211151216.yehwa27daveq57jo@thinkpad>
Date:   Mon, 11 Dec 2023 16:12:16 +0100
From:   Stefan Gloor <code@...fan-gloor.ch>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     jdelvare@...e.com, corbet@....net, linux-hwmon@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] hwmon: sht3x: read out sensor serial number

On Mon, Dec 11, 2023 at 06:31:27AM -0800, Guenter Roeck wrote:
> On Mon, Dec 04, 2023 at 05:50:04PM +0100, Stefan Gloor wrote:
> >  
> > +#ifdef CONFIG_DEBUG_FS
> > +
> > +static void sht3x_debugfs_init(struct sht3x_data *data)
> > +{
> > +	char name[32];
> > +	struct dentry *sensor_dir;
> > +
> > +	data->debugfs = debugfs_lookup("sht3x", NULL);
> > +	if (IS_ERR_OR_NULL(data->debugfs))
> > +		data->debugfs = debugfs_create_dir("sht3x", NULL);
> > +
> > +	snprintf(name, sizeof(name), "i2c%u-%02x",
> > +		 data->client->adapter->nr, data->client->addr);
> > +	sensor_dir = debugfs_create_dir(name, data->debugfs);
> > +	debugfs_create_u32("serial_number", 0444,
> > +			   sensor_dir, &data->serial_number);
> > +}
> > +
> > +#else
> > +
> > +static void sht3x_debugfs_init(struct sht3x_data *data)
> > +{
> > +}
> > +
> > +#endif
> 
> debugfs doesn't need if/else or error handling.
> 
Do you mean the IS_ERR_OR_NULL? I included that to get rid of the
"debugfs directory already exists" message when using multiple sensors.

Will remove #ifdef in V3.

> 
> > +
> > +static int sht3x_serial_number_read(struct sht3x_data *data)
> > +{
> > +	int ret;
> > +	char buffer[SHT3X_RESPONSE_LENGTH];
> > +	struct i2c_client *client = data->client;
> > +
> > +	ret = sht3x_read_from_command(client, data,
> > +				      sht3x_cmd_read_serial_number,
> > +				      buffer,
> > +				      SHT3X_RESPONSE_LENGTH, 0);
> > +	if (ret)
> > +		return ret;
> > +
> > +	data->serial_number = (buffer[0] << 24) | (buffer[1] << 16) |
> > +			      (buffer[3] << 8) | buffer[4];
> > +	return ret;
> > +}
> > +
> >  static const struct hwmon_ops sht3x_ops = {
> >  	.is_visible = sht3x_is_visible,
> >  	.read = sht3x_read,
> > @@ -899,6 +947,13 @@ static int sht3x_probe(struct i2c_client *client)
> >  	if (ret)
> >  		return ret;
> >  
> > +	ret = sht3x_serial_number_read(data);
> > +	if (ret) {
> > +		dev_dbg(dev, "unable to read serial number\n");
> > +		data->serial_number = 0;
> > +	}
> > +	sht3x_debugfs_init(data);
> 
> The debugfs entry should not be created in the first place if the
> serial number can not be read. On top of that, the debugfs entries
> are never removed, meaning the system will crash if the driver or device
> is unloaded and the no longer referenced debugfs file is accessed.

Got it, will fix in V3.
--