linux-kernel - Re: [PATCH 5/5] iio: adc: ad7793: use read

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Message-ID: <4f00fe26-cb42-fc82-c97a-4c2191c0a243@metafoo.de>
Date:   Thu, 19 Mar 2020 09:38:50 +0100
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>,
        "ardeleanalex@...il.com" <ardeleanalex@...il.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "renatogeh@...il.com" <renatogeh@...il.com>,
        "Hennerich, Michael" <Michael.Hennerich@...log.com>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "Caprioru, Mircea" <Mircea.Caprioru@...log.com>
Subject: Re: [PATCH 5/5] iio: adc: ad7793: use read_avail iio hook for scale
 available

On 3/19/20 8:58 AM, Ardelean, Alexandru wrote:
> On Wed, 2020-03-18 at 16:10 +0100, Lars-Peter Clausen wrote:
>> On 3/18/20 2:40 PM, Alexandru Ardelean wrote:
>>> This change uses the read_avail and '.info_mask_shared_by_type_available'
>>> modifier to set the available scale.
>>> Essentially, nothing changes to the driver's ABI.
>>>
>>> The main idea for this patch is to remove the AD7793 driver from
>>> checkpatch's radar. There have been about ~3 attempts to fix/break the
>>> 'in_voltage-voltage_scale_available' attribute, because checkpatch assumed
>>> it to be an arithmetic operation and people were trying to change that.
>>
>> Yeah, probably a good idea!
>>
>>> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
>>> ---
>>>    drivers/iio/adc/ad7793.c | 53 +++++++++++++++++++++++++++-------------
>>>    1 file changed, 36 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/iio/adc/ad7793.c b/drivers/iio/adc/ad7793.c
>>> index 5592ae573e6b..fad98f1801db 100644
>>> --- a/drivers/iio/adc/ad7793.c
>>> +++ b/drivers/iio/adc/ad7793.c
>>> @@ -354,29 +354,28 @@ static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
>>>    static IIO_CONST_ATTR_NAMED(sampling_frequency_available_ad7797,
>>>    	sampling_frequency_available, "123 62 50 33 17 16 12 10 8 6 4");
>>>    
>>> -static ssize_t ad7793_show_scale_available(struct device *dev,
>>> -			struct device_attribute *attr, char *buf)
>>> +static int ad7793_read_avail(struct iio_dev *indio_dev,
>>> +			     struct iio_chan_spec const *chan,
>>> +			     const int **vals, int *type, int *length,
>>> +			     long mask)
>>>    {
>>> -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>>>    	struct ad7793_state *st = iio_priv(indio_dev);
>>> -	int i, len = 0;
>>>    
>>> -	for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
>>> -		len += sprintf(buf + len, "%d.%09u ", st->scale_avail[i][0],
>>> -			       st->scale_avail[i][1]);
>>> +	switch (mask) {
>>> +	case IIO_CHAN_INFO_SCALE:
>>> +		*vals = (int *)st->scale_avail;
>>
>> Can you change the type of scale_avail to int so we don't need the cast?
>>
> 
> So, I don't want to come-up as looking lazy.
> [I mean, I am lazy, but I don't want to look lazy.]
> 
> I took a look at what it means to change this to a simple array.
> The rework feels to me like a bit more noise than is probably worth it.
> I mean, if the purpose of the rework is to just get rid of this cast, then it
> feels noisy [to me].
> 
> That being said, if you insist, I can take a look and do a patch [before this
> one] to convert it to a simple array.

Hm, ok, looks like is more complicated to get rid of the cast than I 
though. So keep it.