linux-kernel - Re: [PATCH 1/2] hwmon: shtc1: add support for device tree bindings

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Message-ID: <83ed44a9-179e-f8c7-a712-e81302dd5d42@gtsys.com.hk>
Date:   Sun, 5 Jul 2020 08:34:33 +0800
From:   Chris Ruehl <chris.ruehl@...ys.com.hk>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Jack Lo <jack.lo@...ys.com.hk>, devicetree@...r.kernel.org,
        Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] hwmon: shtc1: add support for device tree bindings

Hi Guenter,

On 3/7/2020 1:48 pm, Guenter Roeck wrote:
> On 7/2/20 8:48 PM, Chris Ruehl wrote:
>> Add support for DTS bindings to the shtc driver, use CONFIG_OF
>> to compile in the code if needed.
>>
> 
> Ah, here it is. The introducing patch should say something like "[PATCH 0/2]".
> 
>> Signed-off-by: Chris Ruehl <chris.ruehl@...ys.com.hk>
>> ---
>>   drivers/hwmon/shtc1.c | 30 ++++++++++++++++++++++++++++++
>>   1 file changed, 30 insertions(+)
>>
>> diff --git a/drivers/hwmon/shtc1.c b/drivers/hwmon/shtc1.c
>> index a0078ccede03..3bcabc1cbce8 100644
>> --- a/drivers/hwmon/shtc1.c
>> +++ b/drivers/hwmon/shtc1.c
>> @@ -14,6 +14,9 @@
>>   #include <linux/err.h>
>>   #include <linux/delay.h>
>>   #include <linux/platform_data/shtc1.h>
>> +#ifdef CONFIG_OF
> 
> No. Please no conditional includes.

OK, will be fixed and same for below.

> 
>> +#include <linux/of.h>
>> +#endif
>>   
>>   /* commands (high precision mode) */
>>   static const unsigned char shtc1_cmd_measure_blocking_hpm[]    = { 0x7C, 0xA2 };
>> @@ -196,6 +199,10 @@ static int shtc1_probe(struct i2c_client *client,
>>   	enum shtcx_chips chip = id->driver_data;
>>   	struct i2c_adapter *adap = client->adapter;
>>   	struct device *dev = &client->dev;
>> +#ifdef CONFIG_OF
>> +	struct device_node *np = dev->of_node;
>> +	u8 value;
>> +#endif
>>   
>>   	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
>>   		dev_err(dev, "plain i2c transactions not supported\n");
>> @@ -235,6 +242,20 @@ static int shtc1_probe(struct i2c_client *client,
>>   
>>   	if (client->dev.platform_data)
>>   		data->setup = *(struct shtc1_platform_data *)dev->platform_data;
>> +
>> +#ifdef CONFIG_OF
> 
> Unnecessary ifdef. Selection of devicetree data or not can be made
> based on np != NULL. Also, if devictree data is available, platform
> data should be ignored to avoid confusion.

Ok, I wasn't aware this rule. Will change it.

> 
>> +	if (np) {
>> +		if (of_property_read_bool(np, "sensirion,blocking_io")) {
>> +			of_property_read_u8(np, "sensirion,blocking_io", &value);
>> +			data->setup.blocking_io = (value > 0) ? true : false;
>> +		}
> Why this complexity, and why not just make the property a boolean ?
> 
>> +		if (of_property_read_bool(np, "sensicon,high_precision")) {
>> +			of_property_read_u8(np, "sensirion,high_precision", &value);
>> +			data->setup.high_precision = (value > 0) ? true : false;
> 
> "sensicon,high_precision" should also be a boolean.
> 
>> +		}
>> +	}
>> +#endif
>> +
>>   	shtc1_select_command(data);
>>   	mutex_init(&data->update_lock);
>>   
>> @@ -257,6 +278,15 @@ static const struct i2c_device_id shtc1_id[] = {
>>   };
>>   MODULE_DEVICE_TABLE(i2c, shtc1_id);
>>   
>> +#ifdef CONFIG_OF
>> +static const struct of_device_id shtc1_of_match[] = {
>> +	{ .compatible = "sensirion,shtc1" },
>> +	{ .compatible = "sensirion,shtw1" },
>> +	{ .compatible = "sensirion,shtc3" },
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(of, shtc1_of_match);
>> +#endif
>>   static struct i2c_driver shtc1_i2c_driver = {
>>   	.driver.name  = "shtc1",
>>   	.probe        = shtc1_probe,
>>
> Not sure how this works without setting of_match_table. I guess it just works
> accidentally because .id_table also provides a devicetree match. Still,
> of_match_table should be set.

Thanks, I will take care of this in the v2 version.

> 
> Guenter
>