linux-kernel - Re: [PATCH] hwmon: (tmp108) Add basic regulator support

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Message-ID: <be920ecb-7aa9-4222-a909-41d6c0f27463@roeck-us.net>
Date: Wed, 4 Dec 2024 06:15:12 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Stanislav Jakubek <stano.jakubek@...il.com>
Cc: Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
 linux-kernel@...r.kernel.org, Frank Li <Frank.Li@....com>
Subject: Re: [PATCH] hwmon: (tmp108) Add basic regulator support

On 12/4/24 00:57, Stanislav Jakubek wrote:
> On Sat, Nov 30, 2024 at 09:58:17AM -0800, Guenter Roeck wrote:
>> On 11/26/24 00:40, Stanislav Jakubek wrote:
>>> TMP108/P3T1085 are powered by the V+/VCC regulator, add support for it.
>>>
>>> Signed-off-by: Stanislav Jakubek <stano.jakubek@...il.com>
>>> ---
>>>    drivers/hwmon/tmp108.c | 5 +++++
>>>    1 file changed, 5 insertions(+)
>>>
>>> diff --git a/drivers/hwmon/tmp108.c b/drivers/hwmon/tmp108.c
>>> index 1f36af2cd2d9..85e4466259a3 100644
>>> --- a/drivers/hwmon/tmp108.c
>>> +++ b/drivers/hwmon/tmp108.c
>>> @@ -17,6 +17,7 @@
>>>    #include <linux/init.h>
>>>    #include <linux/jiffies.h>
>>>    #include <linux/regmap.h>
>>> +#include <linux/regulator/consumer.h>
>>>    #include <linux/slab.h>
>>>    #define	DRIVER_NAME "tmp108"
>>> @@ -331,6 +332,10 @@ static int tmp108_common_probe(struct device *dev, struct regmap *regmap, char *
>>>    	u32 config;
>>>    	int err;
>>> +	err = devm_regulator_get_enable(dev, "vcc");
>>> +	if (err)
>>> +		return dev_err_probe(dev, err, "Failed to enable regulator\n");
>>> +
>>
>> Problem with this is that existing devicetree bindings do not provide
>> a reference to the regulator. Those would now fail to instantiate,
>> which would be unacceptable. I think you'll need something like
> 
> Doesn't devm_regulator_get_enable fallback to a dummy regulator when
> a reference to the regulator isn't provided?
> 
> lm90 does it this way too.
> 

Ah yes, you are correct. I misinterpreted the code. I'll apply the patch.

Thanks,
Guenter

> Regards,
> Stanislav
> 
>>
>> 	err = devm_regulator_get_enable_optional(dev, "vcc");
>> 	if (err && err != -ENODEV)
>> 		return dev_err_probe(dev, err, "Failed to enable regulator\n");
>>
>> Even though the regulator is now mandatory, existing devicetree bindings
>> don't know that.
>>
>> Guenter
>>