linux-kernel - Re: [PATCH v2 07/16] iio: adc: sun4i-gpadc-iio: rework: support nvmem calibration data

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Date:   Fri, 2 Feb 2018 16:24:49 +0100
From:   Philipp Rossak <embed3d@...il.com>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     lee.jones@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
        wens@...e.org, linux@...linux.org.uk, jic23@...nel.org,
        knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net,
        davem@...emloft.net, hans.verkuil@...co.com, mchehab@...nel.org,
        rask@...melder.dk, clabbe.montjoie@...il.com, sean@...s.org,
        krzk@...nel.org, quentin.schulz@...e-electrons.com,
        icenowy@...c.io, edu.molinas@...il.com, singhalsimran0@...il.com,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v2 07/16] iio: adc: sun4i-gpadc-iio: rework: support nvmem
 calibration data


>>
>>>>    	/* prevents concurrent reads of temperature and ADC */
>>>>    	struct mutex			mutex;
>>>>    	struct thermal_zone_device	*tzd;
>>>> @@ -561,6 +569,9 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
>>>>    	struct resource *mem;
>>>>    	void __iomem *base;
>>>>    	int ret;
>>>> +	struct nvmem_cell *cell;
>>>> +	ssize_t cell_size;
>>>> +	u64 *cell_data;
>>>>    	info->data = of_device_get_match_data(&pdev->dev);
>>>>    	if (!info->data)
>>>> @@ -575,6 +586,39 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
>>>>    	if (IS_ERR(base))
>>>>    		return PTR_ERR(base);
>>>> +	info->has_calibration_data[0] = false;
>>>> +	info->has_calibration_data[1] = false;
>>>> +
>>>> +	if (!info->data->supports_nvmem)
>>>> +		goto no_nvmem;
>>>> +
>>>> +	cell = nvmem_cell_get(&pdev->dev, "calibration");
>>>> +	if (IS_ERR(cell)) {
>>>> +		if (PTR_ERR(cell) == -EPROBE_DEFER)
>>>> +			return PTR_ERR(cell);
>>>> +		goto no_nvmem;
>>>
>>> goto considered evil ? :)
>>
>> this was a suggestion from Jonatan in version one, to make the code better
>> readable.
> 
> Isn't
> 
> if (info->data->supports_nvmem && IS_ERR(cell = nvmem_cell_get()))
> 
> pretty much the same thing?
> 
> Maxime
> 
I would say :

if (info->data->supports_nvmem && !IS_ERR(cell = nvmem_cell_get())) is

the same.
This would require an else if statement like this:

else if (info->data->supports_nvmem && PTR_ERR(cell) == -EPROBE_DEFER)
		return PTR_ERR(cell);

to avoid errors if the thermal sensor is probed before the sid driver.

Philipp