Subject: Re: [PATCH v3 2/8] iio: inkern: add helpers to query available values
 from channels
To: Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        Jonathan Cameron <jic23@kernel.org>
References: <1477262381-7800-1-git-send-email-peda@axentia.se>
 <1477262381-7800-3-git-send-email-peda@axentia.se>
 <c7848c84-960b-506f-f2e2-4aadfc5246f9@kernel.org>
 <alpine.DEB.2.02.1610301611070.32031@pmeerw.net>
CC: <linux-kernel@vger.kernel.org>, Hartmut Knaack <knaack.h@gmx.de>,
        Lars-Peter Clausen <lars@metafoo.de>, Rob Herring <robh+dt@kernel.org>,
        "Mark Rutland" <mark.rutland@arm.com>, <linux-iio@vger.kernel.org>,
        <devicetree@vger.kernel.org>
From: Peter Rosin <peda@axentia.se>
Organization: Axentia Technologies AB
Message-ID: <f4106f92-0011-a10d-653d-e315334d9472@axentia.se>
Date: Sun, 30 Oct 2016 22:12:32 +0100
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On 2016-10-30 16:23, Peter Meerwald-Stadler wrote:
> 
>> On 23/10/16 23:39, Peter Rosin wrote:
>>> Specifically a helper for reading the available maximum raw value of a
>>> channel and a helper for forwarding read_avail requests for raw values
>>> from one iio driver to an iio channel that is consumed.
>>>
>>> These rather specific helpers are in turn built with generic helpers
>>> making it easy to build more helpers for available values as needed.
>>>
>>> Signed-off-by: Peter Rosin <peda@axentia.se>
>> Looks good to me.  Just what I was after.
> 
> some comments below
>  
>> Jonathan
>>> ---
>>>  drivers/iio/inkern.c         | 97 ++++++++++++++++++++++++++++++++++++++++++++
>>>  include/linux/iio/consumer.h | 29 +++++++++++++
>>>  include/linux/iio/iio.h      | 17 ++++++++
>>>  3 files changed, 143 insertions(+)
>>>
>>> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
>>> index c4757e6367e7..74808f8a187a 100644
>>> --- a/drivers/iio/inkern.c
>>> +++ b/drivers/iio/inkern.c
>>> @@ -703,6 +703,103 @@ int iio_read_channel_scale(struct iio_channel *chan, int *val, int *val2)
>>>  }
>>>  EXPORT_SYMBOL_GPL(iio_read_channel_scale);
>>>  
>>> +static int iio_channel_read_avail(struct iio_channel *chan,
>>> +				  const int **vals, int *type, int *length,
>>> +				  enum iio_chan_info_enum info)
>>> +{
>>> +	if (!iio_channel_has_available(chan->channel, info))
>>> +		return -EINVAL;
>>> +
>>> +	return chan->indio_dev->info->read_avail(chan->indio_dev, chan->channel,
>>> +						 vals, type, length, info);
>>> +}
>>> +
>>> +int iio_read_avail_channel_raw(struct iio_channel *chan,
>>> +			       const int **vals, int *type, int *length)
>>> +{
>>> +	int ret;
>>> +
>>> +	mutex_lock(&chan->indio_dev->info_exist_lock);
>>> +	if (!chan->indio_dev->info) {
>>> +		ret = -ENODEV;
>>> +		goto err_unlock;
>>> +	}
>>> +
>>> +	ret = iio_channel_read_avail(chan,
>>> +				     vals, type, length, IIO_CHAN_INFO_RAW);
>>> +err_unlock:
>>> +	mutex_unlock(&chan->indio_dev->info_exist_lock);
>>> +
>>> +	return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(iio_read_avail_channel_raw);
>>> +
>>> +static int iio_channel_read_max(struct iio_channel *chan,
>>> +				int *val, int *val2, int *type,
>>> +				enum iio_chan_info_enum info)
>>> +{
>>> +	int unused;
>>> +	const int *vals;
>>> +	int length;
>>> +	int ret;
>>> +
>>> +	if (!val2)
>>> +		val2 = &unused;
>>> +
>>> +	ret = iio_channel_read_avail(chan, &vals, type, &length, info);
>>> +	switch (ret) {
>>> +	case IIO_AVAIL_RANGE:
>>> +		switch (*type) {
>>> +		case IIO_VAL_INT:
>>> +			*val = vals[2];
>>> +			break;
>>> +		default:
>>> +			*val = vals[4];
>>> +			*val2 = vals[5];
>>> +		}
>>> +		return 0;
>>> +
>>> +	case IIO_AVAIL_LIST:
>>> +		if (length <= 0)
>>> +			return -EINVAL;
>>> +		switch (*type) {
>>> +		case IIO_VAL_INT:
>>> +			*val = vals[--length];
>>> +			while (length) {
>>> +				if (vals[--length] > *val)
>>> +					*val = vals[length];
>>> +			}
>>> +			break;
>>> +		default:
>>> +			/* FIXME: learn about max for other iio values */
>>> +			return -EINVAL;
>>> +		}
>>> +		return 0;
>>> +
>>> +	default:
>>> +		return ret;
>>> +	}
>>> +}
>>> +
>>> +int iio_read_max_channel_raw(struct iio_channel *chan, int *val)
>>> +{
>>> +	int ret;
>>> +	int type;
>>> +
>>> +	mutex_lock(&chan->indio_dev->info_exist_lock);
>>> +	if (!chan->indio_dev->info) {
>>> +		ret = -ENODEV;
>>> +		goto err_unlock;
>>> +	}
>>> +
>>> +	ret = iio_channel_read_max(chan, val, NULL, &type, IIO_CHAN_INFO_RAW);
>>> +err_unlock:
>>> +	mutex_unlock(&chan->indio_dev->info_exist_lock);
>>> +
>>> +	return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(iio_read_max_channel_raw);
>>> +
>>>  int iio_get_channel_type(struct iio_channel *chan, enum iio_chan_type *type)
>>>  {
>>>  	int ret = 0;
>>> diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
>>> index 9edccfba1ffb..baab5e45734f 100644
>>> --- a/include/linux/iio/consumer.h
>>> +++ b/include/linux/iio/consumer.h
>>> @@ -226,6 +226,35 @@ int iio_read_channel_processed(struct iio_channel *chan, int *val);
>>>  int iio_write_channel_raw(struct iio_channel *chan, int val);
>>>  
>>>  /**
>>> + * iio_read_max_channel_raw() - read maximum available raw value from a given
>>> + *				channel
>>> + * @chan:		The channel being queried.
>>> + * @val:		Value read back.
>>> + *
>>> + * Note raw reads from iio channels are in adc counts and hence
> 
> "Note: raw reads..." would be easier...
> here and below

All other function comments lack the colon after that Note, so I was just
following that lead. I suggest that this can be fixed up later with one
patch for all comments, if needed?

> why is there no val2 here?

Everything else in inkern.c that handles the raw channel assumes it
is of type IIO_VAL_INT. Again, just following the lead.

> just reading the documentation ("maximum available raw value") I am not 
> sure what the function does: does it return the maximum value possible? or 
> the maximum value in some internal buffer? maximum value ever seen?

Maximum possible, that's what the available attribute is all
about; possible values. How about:

 * iio_read_max_channel_raw() - read maximum available raw value from a given
 *				channel, i.e. the maximum possible value.

>>> + * scale will need to be applied if standard units are required.
>>> + */
>>> +int iio_read_max_channel_raw(struct iio_channel *chan, int *val);
>>> +
>>> +/**
>>> + * iio_read_avail_channel_raw() - read available raw values from a given channel
>>> + * @chan:		The channel being queried.
>>> + * @vals:		Available values read back.
> 
> no vals2?

Same raw channel assumption about IIO_VAL_INT.

>>> + * @type:		Type of available values in vals.
> 
> it is not clear what type is

Same as in the iio_channel_has_info function right above which has
the same kind of explanation. Again, just following the lead.

>>> + * @length:		Number of entries in vals.
>>> + *
>>> + * Returns an error code, IIO_AVAIL_RANGE or IIO_AVAIL_LIST.
>>> + *
>>> + * For ranges, three vals are always returned; min, step and max.
>>> + * For lists, all the possible values are enumerated.
>>> + *
>>> + * Note raw available values from iio channels are in adc counts and
>>> + * hence scale will need to be applied if standard units are required.
>>> + */
>>> +int iio_read_avail_channel_raw(struct iio_channel *chan,
>>> +			       const int **vals, int *type, int *length);
>>> +
>>> +/**
>>>   * iio_get_channel_type() - get the type of a channel
>>>   * @channel:		The channel being queried.
>>>   * @type:		The type of the channel.
>>> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
>>> index 45b781084a4b..e565701d13ce 100644
>>> --- a/include/linux/iio/iio.h
>>> +++ b/include/linux/iio/iio.h
>>> @@ -315,6 +315,23 @@ static inline bool iio_channel_has_info(const struct iio_chan_spec *chan,
>>>  		(chan->info_mask_shared_by_all & BIT(type));
>>>  }
>>>  
>>> +/**
>>> + * iio_channel_has_available() - Checks if a channel has an available attribute
>>> + * @chan: The channel to be queried
>>> + * @type: Type of the available attribute to be checked
>>> + *
>>> + * Returns true if the channels supports reporting available values for the
> 
> channel

I'll fix that.

Sigh, I guess there's enough small changes that I'll need to do a v4.
I'll hold off on that for a couple of days though since there is
nothing badly wrong...

Cheers,
Peter

>>> + * given attribute type, false otherwise.
>>> + */
>>> +static inline bool iio_channel_has_available(const struct iio_chan_spec *chan,
>>> +					     enum iio_chan_info_enum type)
>>> +{
>>> +	return (chan->info_mask_separate_available & BIT(type)) |
>>> +		(chan->info_mask_shared_by_type_available & BIT(type)) |
>>> +		(chan->info_mask_shared_by_dir_available & BIT(type)) |
>>> +		(chan->info_mask_shared_by_all_available & BIT(type));
>>> +}
>>> +
>>>  #define IIO_CHAN_SOFT_TIMESTAMP(_si) {					\
>>>  	.type = IIO_TIMESTAMP,						\
>>>  	.channel = -1,							\
>>>
>>
>