Re: [PATCH v2 2/6] hwmon: (max6697) Drop platform data support

[Guenter Roeck <linux@roeck-us.net>]

On 7/24/24 17:54, Tzung-Bi Shih wrote:
> On Wed, Jul 24, 2024 at 10:40:20AM -0700, Guenter Roeck wrote:
>> On 7/24/24 08:41, Tzung-Bi Shih wrote:
>>> On Wed, Jul 24, 2024 at 07:25:31AM -0700, Guenter Roeck wrote:
>>>> On 7/24/24 06:03, Tzung-Bi Shih wrote:
>>>>> On Tue, Jul 23, 2024 at 08:44:43AM -0700, Guenter Roeck wrote:
>>>>>> +	if (data->type != max6581) {
>>>>>> +		if (of_property_read_bool(node, "resistance-cancellation") &&
>>>>>> +		    chip->valid_conf & MAX6697_CONF_RESISTANCE) {
>>>>>> +			confreg |= MAX6697_CONF_RESISTANCE;
>>>>>> +			factor = 1;
>>>>>> +		}
>>>>>> +	} else {
>>>>>> +		if (of_property_read_u32(node, "resistance-cancellation", &vals[0])) {
>>>>>> +			if (of_property_read_bool(node, "resistance-cancellation"))
>>>>>> +				vals[0] = 0xfe;
>>>>>> +			else
>>>>>> +				vals[0] = 0;
>>>>>> +		}
>>>>>> +
>>>>>> +		factor = hweight8(vals[0] & 0xfe);
>>>>>
>>>>> It doesn't AND with 0xfe originally.
>>>>>
>>>>
>>>> Yes, but the original code uses the value in
>>>> 	factor += hweight8(pdata->resistance_cancellation >> 1);
>>>> 	ret = i2c_smbus_write_byte_data(client, MAX6581_REG_RESISTANCE,
>>>>                                           pdata->resistance_cancellation >> 1);
>>>> which is effectively the same. I can't just use
>>>> 	factor = hweight8(vals[0] >> 1);
>>>> because, unlike resistance_cancellation, val[] is an u32 array which would
>>>> not auto-mask the upper bits.
>>>
>>> If you are worrying about:
>>> * MSB, it should be fine as it should only prepend 0s for right shift on
>>>     unsigned.
>>> * BIT(8), other `val[0] >> 1` should also share the same concern.
>>
>> BIT(8) is the concern. Yes, you are correct, I'll change the code to
>>
>> 	val[0] &= 0xfe;
>> 	factor = hweight8(vals[0]);
>> 	...
> 
> With that,
> Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
> 
> Note: there is another `vals[0] >> 1` for MAX6581_REG_IDEALITY_SELECT.

Good point. I masked that as well.

Thanks a lot for the reviews,
Guenter