linux-kernel - Re: [PATCH v2 3/4] hwmon: Add support for Amphenol ChipCap 2

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Message-ID: <d5692ab7-6d11-41f3-89ec-246a2fc045a8@roeck-us.net>
Date:   Thu, 9 Nov 2023 06:55:23 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Javier Carrasco <javier.carrasco.cruz@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 3/4] hwmon: Add support for Amphenol ChipCap 2

On 11/9/23 00:52, Krzysztof Kozlowski wrote:
> On 08/11/2023 16:37, Javier Carrasco wrote:
>> The Amphenol ChipCap 2 is a capacitive polymer humidity and temperature
>> sensor with an integrated EEPROM and minimum/maximum humidity alarms.
>>
>> All device variants offer an I2C interface and depending on the part
>> number, two different output modes:
>> - CC2D: digital output
>> - CC2A: analog (PDM) output
>>
>> This driver adds support for the digital variant (CC2D part numbers),
>> which is also divided into two subfamilies [1]:
>> - CC2DXX: non-sleep measurement mode
>> - CC2DXXS: sleep measurement mode
> 
> ...
> 
>> +
>> +static int cc2_probe(struct i2c_client *client)
>> +{
>> +	struct cc2_data *data;
>> +	struct device *dev = &client->dev;
>> +	enum cc2_ids chip;
>> +	int ret;
>> +
>> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
>> +		return -EOPNOTSUPP;
>> +
>> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>> +	if (!data)
>> +		return -ENOMEM;
>> +
>> +	i2c_set_clientdata(client, data);
>> +
>> +	mutex_init(&data->i2c_lock);
>> +	mutex_init(&data->alarm_lock);
>> +
>> +	data->client = client;
>> +
>> +	if (client->dev.of_node)
>> +		chip = (uintptr_t)of_device_get_match_data(&client->dev);
>> +	else
>> +		chip = i2c_match_id(cc2_id, client)->driver_data;
>> +
>> +	data->config = &cc2_config[chip];
>> +
>> +	ret = cc2_request_ready_irq(data, dev);
>> +	if (ret)
>> +		return ret;
>> +
>> +	data->regulator = devm_regulator_get_optional(dev, "vdd");
>> +	if (!IS_ERR(data->regulator)) {
>> +		ret = cc2_retrive_alarm_config(data);

fwiw, s/retrive/retrieve/g

>> +		if (ret)
>> +			goto cleanup;
>> +	} else {
>> +		/* No access to EEPROM without regulator: no alarm control */
>> +		goto dev_register;
> 
> Nothing improved here.
> 
> Do not send new version of patchset before discussion finishes.
> 

This driver will take a while to review due to its complexity.

As for the code above: Error handling goes first. Something like
the above, where the error case is just a goto, is unacceptable and
just increases indentation level for the other code and makes it
more difficult to read. Also, the above code _will_ have to handle
error cases other than -ENODEV. Besides deferred probe, it is
completely inappropriate to ignore -EINVAL or -ENOMEM or any other
error codes other than -ENODEV.

>> +	}
>> +
>> +	ret = cc2_request_alarm_irqs(data, dev);
>> +	if (ret)
>> +		goto cleanup;
>> +
>> +dev_register:
>> +	data->hwmon = devm_hwmon_device_register_with_info(dev, client->name,
>> +							   data, &cc2_chip_info,
>> +							   NULL);
>> +	if (IS_ERR(data->hwmon)) {
>> +		ret = PTR_ERR(data->hwmon);
>> +		goto cleanup;
>> +	}
>> +
>> +	return 0;
>> +
>> +cleanup:
>> +	if (cc2_disable(data))
>> +		dev_dbg(dev, "Failed to disable device");
>> +
>> +	return dev_err_probe(dev, ret,
>> +			     "Unable to register hwmon device\n");
> 
> Drop or move to each error path.
> 
This actually follows Documentation/process/coding-style.rst, chapter 7
(Centralized exiting of functions).

Guenter