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Date: Thu, 28 Mar 2024 08:20:00 -0700
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Subject: Re: [PATCH RFC 3/7] hwmon: (da9052) Use
 devm_regulator_get_enable_get_voltage()
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To: Jonathan Cameron <jic23@kernel.org>, David Lechner <dlechner@baylibre.com>
Cc: Jonathan Corbet <corbet@lwn.net>, Liam Girdwood <lgirdwood@gmail.com>,
 Mark Brown <broonie@kernel.org>, Jean Delvare <jdelvare@suse.com>,
 Support Opensource <support.opensource@diasemi.com>,
 Cosmin Tanislav <cosmin.tanislav@analog.com>,
 Lars-Peter Clausen <lars@metafoo.de>,
 Michael Hennerich <Michael.Hennerich@analog.com>,
 Antoniu Miclaus <antoniu.miclaus@analog.com>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Dmitry Torokhov <dmitry.torokhov@gmail.com>, linux-doc@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-hwmon@vger.kernel.org,
 linux-iio@vger.kernel.org, linux-staging@lists.linux.dev,
 linux-input@vger.kernel.org
References: <20240327-regulator-get-enable-get-votlage-v1-0-5f4517faa059@baylibre.com>
 <20240327-regulator-get-enable-get-votlage-v1-3-5f4517faa059@baylibre.com>
 <20240328142038.33ad68bc@jic23-huawei>
From: Guenter Roeck <linux@roeck-us.net>
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In-Reply-To: <20240328142038.33ad68bc@jic23-huawei>
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On 3/28/24 07:20, Jonathan Cameron wrote:
> On Wed, 27 Mar 2024 18:18:52 -0500
> David Lechner <dlechner@baylibre.com> wrote:
> 
>> We can reduce boilerplate code by using
>> devm_regulator_get_enable_get_voltage().
>>
>> Signed-off-by: David Lechner <dlechner@baylibre.com>
> 
> A few comments inline, but nothing substantial.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>> ---
>>   drivers/hwmon/da9052-hwmon.c | 33 +++++++--------------------------
>>   1 file changed, 7 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/hwmon/da9052-hwmon.c b/drivers/hwmon/da9052-hwmon.c
>> index 2bd7ae8100d7..70e7bc72e980 100644
>> --- a/drivers/hwmon/da9052-hwmon.c
>> +++ b/drivers/hwmon/da9052-hwmon.c
>> @@ -26,7 +26,6 @@ struct da9052_hwmon {
>>   	struct mutex		hwmon_lock;
>>   	bool			tsi_as_adc;
>>   	int			tsiref_mv;
>> -	struct regulator	*tsiref;
>>   	struct completion	tsidone;
>>   };
>>   
>> @@ -414,32 +413,19 @@ static int da9052_hwmon_probe(struct platform_device *pdev)
>>   		device_property_read_bool(pdev->dev.parent, "dlg,tsi-as-adc");
>>   
>>   	if (hwmon->tsi_as_adc) {
>> -		hwmon->tsiref = devm_regulator_get(pdev->dev.parent, "tsiref");
>> -		if (IS_ERR(hwmon->tsiref)) {
>> -			err = PTR_ERR(hwmon->tsiref);
>> -			dev_err(&pdev->dev, "failed to get tsiref: %d", err);
>> +		err = devm_regulator_get_enable_get_voltage(pdev->dev.parent,
>> +							    "tsiref");
>> +		if (err < 0)
>>   			return err;
>> -		}
>> -
>> -		err = regulator_enable(hwmon->tsiref);
>> -		if (err)
>> -			return err;
>> -
>> -		hwmon->tsiref_mv = regulator_get_voltage(hwmon->tsiref);
>> -		if (hwmon->tsiref_mv < 0) {
>> -			err = hwmon->tsiref_mv;
>> -			goto exit_regulator;
>> -		}
>>   
>>   		/* convert from microvolt (DT) to millivolt (hwmon) */
>> -		hwmon->tsiref_mv /= 1000;
>> +		hwmon->tsiref_mv = err / 1000;
>>
> 
> Using a variable called err for a good value is a bit ugly but fair enough if that
> is precedence in this driver.
> 

It isn't. The existing code assigns the return value from regulator_get_voltage()
to hwmon->tsiref_mv and then evaluates it. I would not oppose introducing a variable
such as tsiref_uv, but not the misuse of 'err'. I am not going to accept the code
as suggested. It is bad style, and it would invite others to use it as precedent
when trying to introduce similar code.

>>   }
>> @@ -483,10 +466,8 @@ static void da9052_hwmon_remove(struct platform_device *pdev)
>>   {
>>   	struct da9052_hwmon *hwmon = platform_get_drvdata(pdev);
>>   
>> -	if (hwmon->tsi_as_adc) {
>> +	if (hwmon->tsi_as_adc)
>>   		da9052_free_irq(hwmon->da9052, DA9052_IRQ_TSIREADY, hwmon);
> Superficially looks like devm_da9052_request_irq could be added that
> uses devm_request_threaded_irq() to allow dropping this remaining handling.
> 

That should be a separate series of patches. A local solution might be
to use devm_add_action_or_reset(), but that should also be a separate patch.

Thanks,
Guenter