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

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Message-ID: <875ynexup1.fsf@collabora.com>
Date:   Tue, 12 Apr 2022 10:06:18 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Shreeya Patel <shreeya.patel@...labora.com>
Cc:     Jonathan Cameron <jic23@...nel.org>, krzk@...nel.org,
        lars@...afoo.de, robh+dt@...nel.org, Zhigang.Shi@...eon.com,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...labora.com,
        alvaro.soliverez@...labora.com
Subject: Re: [PATCH 3/3] iio: light: Add support for ltrf216a sensor

Shreeya Patel <shreeya.patel@...labora.com> writes:

>>> +	val_1 = i2c_smbus_read_byte_data(data->client, addr + 1);
>>> +	val_2 = i2c_smbus_read_byte_data(data->client, addr + 2);
>>> +	ret = (val_2 << 16) + (val_1 << 8) + val_0;
>> This is a le24_to_cpu() conversion.
>> Preferred choice would be to use something like
>> 	u8 buf[3];
>> 	int i;
>>
>> 	for (i = 0; i < 3; i++) {
>> 		ret = i2c_smbus_read_byte_data(data->client, addr);
>> 		if (ret < 0)
>> 			return ret;
>> 		buf[i] = ret;
>> 	}
>> 	return le24_to_cpu(buf);
>>
>
> We do not have any le24_to_cpu() function in current kernel source code.
> I was thinking to use le32_to_cpu() instead but it requires an argument of
> type __le32 and our case we storing the values in u8 buf[3] so I'm not
> really sure if it's possible to use le32_to_cpu() or any other function.

I guess you could make it a 32-bit buffer, keep the most
significant byte zeroed and return le32_to_cpu:

  u8 buf[4];

  memset(buf, 0x0, sizeof(buf));

  for (i = 0; i < 3; i++) {
 	ret = i2c_smbus_read_byte_data(data->client, addr);
 	if (ret < 0)
 		return ret;
	buf[i] = ret;
  }
  return le32_to_cpu(buf);

-- 
Gabriel Krisman Bertazi