linux-kernel - Re: [PATCH v8 5/5] iio: light: Add support for APDS9306 Light Sensor

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Date: Thu, 29 Feb 2024 23:04:04 +1030
From: Subhajit Ghosh <subhajit.ghosh@...aklogic.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Matti Vaittinen <mazziesaccount@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen
 <lars@...afoo.de>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Marek Vasut <marex@...x.de>,
 Anshul Dalal <anshulusr@...il.com>,
 Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Matt Ranostay <matt@...ostay.sg>,
 Stefan Windfeldt-Prytz <stefan.windfeldt-prytz@...s.com>,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 5/5] iio: light: Add support for APDS9306 Light Sensor

On 29/2/24 03:57, Andy Shevchenko wrote:
> On Wed, Feb 28, 2024 at 03:08:56PM +0200, Matti Vaittinen wrote:
>> On 2/28/24 14:24, Subhajit Ghosh wrote:
> 
> ...
> 
>>> +	ret = iio_gts_find_new_gain_by_old_gain_time(&data->gts, gain_old,
>>> +						     intg_old, val2, &gain_new);
>>
>> You don't use the 'ret' here, so maybe for the clarity, not assign it.
>> Or, maybe you wan't to try to squeeze out few cycles for succesful case and
>> check the ret for '0' - in which case you should be able to omit the check
>> right below as well as the call to iio_find_closest_gain_low(). OTOH, this
>> is likely not a "hot path" so I don't care too much about the extra call if
>> you think code is clearer this way.
>>
>>> +	if (gain_new < 0) {
>>> +		dev_err_ratelimited(dev, "Unsupported gain with time\n");
>>> +		return gain_new;
>>> +	}
> 
> What is the difference between negative response from the function itself and
> similar in gain_new?
> 
-ve response form the function is an error condition.
-ve value in gain_new means - no valid gains could be computed.
In case of error conditions from the function, the gain_new is also set to -1.
My use case is valid hardware gain so I went for checking only gain_new.
Matti will be the best person to answer on this.

Regards,
Subhajit Ghosh