linux-kernel - Re: [RFC PATCH v2 3/7] iio: inkern: api for manipulating ext

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Date:   Mon, 21 Nov 2016 17:07:56 +0100
From:   Peter Rosin <peda@...ntia.se>
To:     Lars-Peter Clausen <lars@...afoo.de>,
        Jonathan Cameron <jic23@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Wolfram Sang <wsa@...-dreams.de>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-iio@...r.kernel.org>
Subject: Re: [RFC PATCH v2 3/7] iio: inkern: api for manipulating ext_info of
 iio channels

On 2016-11-21 16:45, Lars-Peter Clausen wrote:
> On 11/19/2016 04:38 PM, Jonathan Cameron wrote:
>> On 17/11/16 21:48, Peter Rosin wrote:
>>> Extend the inkern api with functions for reading and writing ext_info
>>> of iio channels.
>> I'd like Lars' feedback on this one.
>>
>> Superficially looks fine to me but I am not as familiar with this interface
>> as Lars is ;) (he wrote it IIRC:)
> 
> The implementation looks OK. I'm not necessarily convinced about the concept
> though, but the code is manageable so I guess it is OK.
> 
> The final version should add kernel API documentation for the new functions.

I added that in v3 that I sent earlier today.

>>> ---
>>>  drivers/iio/inkern.c         | 55 ++++++++++++++++++++++++++++++++++++++++++++
>>>  include/linux/iio/consumer.h |  6 +++++
>>>  2 files changed, 61 insertions(+)
>>>
>>> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
>>> index cfca17ba2535..a8099b164222 100644
>>> --- a/drivers/iio/inkern.c
>>> +++ b/drivers/iio/inkern.c
>>> @@ -850,3 +850,58 @@ int iio_write_channel_raw(struct iio_channel *chan, int val)
>>>  	return ret;
>>>  }
>>>  EXPORT_SYMBOL_GPL(iio_write_channel_raw);
>>> +
>>> +int iio_get_channel_ext_info_count(struct iio_channel *chan)
> 
> should be unsigned.

Correct, I had a plan to do that change, but it slipped my mind. Thanks
for catching it!

>>> +{
>>> +	const struct iio_chan_spec_ext_info *ext_info;
>>> +	unsigned int i = 0;
>>> +
>>> +	if (!chan->channel->ext_info)
>>> +		return i;
>>> +
>>> +	for (ext_info = chan->channel->ext_info; ext_info->name; ext_info++)
>>> +		++i;
>>> +
>>> +	return i;
>>> +}
>>> +EXPORT_SYMBOL_GPL(iio_get_channel_ext_info_count);
>>> +
>>> +ssize_t iio_read_channel_ext_info(struct iio_channel *chan,
>>> +				  const char *attr, char *buf)
>>> +{
>>> +	const struct iio_chan_spec_ext_info *ext_info;
>>> +
>>> +	if (!chan->channel->ext_info)
>>> +		return -EINVAL;
>>> +
>>> +	for (ext_info = chan->channel->ext_info; ext_info->name; ++ext_info) {
>>> +		if (strcmp(attr, ext_info->name))
>>> +			continue;
> 
> You could factor the lookup out into a helper function that is used for both
> read and write. And also stop searching once a match was found.

I'll do a lookup helper for v4. But the stop-searching-thing is already
done with the return statements at the end of the for-loops.

Thanks for looking!

Cheers,
Peter

>>> +
>>> +		return ext_info->read(chan->indio_dev, ext_info->private,
>>> +				      chan->channel, buf);
>>> +	}
>>> +
>>> +	return -EINVAL;
>>> +}
>>> +EXPORT_SYMBOL_GPL(iio_read_channel_ext_info);
>>> +
>>> +ssize_t iio_write_channel_ext_info(struct iio_channel *chan, const char *attr,
>>> +				   const char *buf, size_t len)
>>> +{
>>> +	const struct iio_chan_spec_ext_info *ext_info;
>>> +
>>> +	if (!chan->channel->ext_info)
>>> +		return -EINVAL;
>>> +
>>> +	for (ext_info = chan->channel->ext_info; ext_info->name; ++ext_info) {
>>> +		if (strcmp(attr, ext_info->name))
>>> +			continue;
>>> +
>>> +		return ext_info->write(chan->indio_dev, ext_info->private,
>>> +				       chan->channel, buf, len);
>>> +	}
>>> +
>>> +	return -EINVAL;
>>> +}
>>> +EXPORT_SYMBOL_GPL(iio_write_channel_ext_info);
>>> diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
>>> index 9a4f336d8b4a..471dece8729a 100644
>>> --- a/include/linux/iio/consumer.h
>>> +++ b/include/linux/iio/consumer.h
>>> @@ -299,4 +299,10 @@ int iio_read_channel_scale(struct iio_channel *chan, int *val,
>>>  int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
>>>  	int *processed, unsigned int scale);
>>>  
>>> +int iio_get_channel_ext_info_count(struct iio_channel *chan);
>>> +ssize_t iio_read_channel_ext_info(struct iio_channel *chan,
>>> +				  const char *attr, char *buf);
>>> +ssize_t iio_write_channel_ext_info(struct iio_channel *chan, const char *attr,
>>> +				   const char *buf, size_t len);
>>> +
>>>  #endif
>>>
>>
>