linux-kernel - Re: [PATCH v4 3/3] iio: light: Add support for ltrf216a sensor

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Message-ID: <88b33ada-e997-05e9-f555-b9c1ed369fb7@collabora.com>
Date:   Fri, 13 May 2022 19:10:05 +0530
From:   Shreeya Patel <shreeya.patel@...labora.com>
To:     Dmitry Osipenko <digetx@...il.com>, jic23@...nel.org,
        lars@...afoo.de, robh+dt@...nel.org, Zhigang.Shi@...eon.com,
        krisman@...labora.com
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...labora.com,
        alvaro.soliverez@...labora.com
Subject: Re: [PATCH v4 3/3] iio: light: Add support for ltrf216a sensor


On 13/05/22 05:24, Dmitry Osipenko wrote:

Hi Dmitry,

> 11.05.2022 12:40, Shreeya Patel пишет:
>> +static int ltrf216a_init(struct iio_dev *indio_dev)
>> +{
>> +	int ret;
>> +	struct ltrf216a_data *data = iio_priv(indio_dev);
>> +
>> +	ret = i2c_smbus_read_byte_data(data->client, LTRF216A_MAIN_CTRL);
>> +	if (ret < 0) {
>> +		dev_err(&data->client->dev, "Error reading LTRF216A_MAIN_CTRL\n");
>> +		return ret;
>> +	}
>> +
>> +	/* enable sensor */
>> +	ret |= FIELD_PREP(LTRF216A_ALS_ENABLE_MASK, 1);
>> +	ret = i2c_smbus_write_byte_data(data->client, LTRF216A_MAIN_CTRL, ret);
>> +	if (ret < 0) {
>> +		dev_err(&data->client->dev, "Error writing LTRF216A_MAIN_CTRL\n");
>> +		return ret;
>> +	}
> Couldn't you write "1" directly without reading?
>
> What about doing SW reset?

I think we are doing a read here just to make sure device registers are 
ready and accessible
without any issues.

Also, why would we want to do a SW reset here?

In the datasheet, I could see the following steps to enable the sensor
Supply VDD to Sensor (Sensor in Standby Mode) ---> Wait 100 ms (min) - 
initial startup time
---> I2C Command (Write) To enable sensor to Active Mode

Thanks,
Shreeya Patel

>