Message-ID: <74746223-a1aa-e9c6-622c-854526d0722d@kernel.org>
Date:   Sun, 23 Oct 2016 10:33:44 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Peter Rosin <peda@...ntia.se>, linux-kernel@...r.kernel.org
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/7] iio:core: add a callback to allow drivers to
 provide _available attributes

On 22/10/16 23:43, Peter Rosin wrote:
> From: Jonathan Cameron <jic23@...nel.org>
> 
> A large number of attributes can only take a limited range of values.
> Currently in IIO this is handled by directly registering additional
> *_available attributes thus providing this information to userspace.
> 
> It is desirable to provide this information via the core for much the same
> reason this was done for the actual channel information attributes in the
> first place.  If it isn't there, then it can only really be accessed from
> userspace.  Other in kernel IIO consumers have no access to what valid
> parameters are.
> 
> Two forms are currently supported:
> * list of values in one particular IIO_VAL_* format.
> 	e.g. 1.300000 1.500000 1.730000
> * range specification with a step size:
> 	e.g. [1.000000 0.500000 2.500000]
> 	equivalent to 1.000000 1.5000000 2.000000 2.500000
> 
> An addition set of masks are used to allow different sharing rules for the
> *_available attributes generated.
> 
> This allows for example:
> 
> in_accel_x_offset
> in_accel_y_offset
> in_accel_offset_available.
> 
> We could have gone with having a specification for each and every
> info_mask element but that would have meant changing the existing userspace
> ABI.  This approach does not.
I'm wondering what I meant by this... where does it cause use ABI issues?
Do you have any idea?

I'd forgotten I'd even done it like this rather than just insisting on 
available for everything (which is more logical to me as we should know
the range of everything).

It's pretty low cost though and gives a way of adding this to drivers
piecemeal which is probably a good idea!
> 
> Signed-off-by: Jonathan Cameron <jic23@...nel.org>
> [rather mindlessly forward ported from approx 3 years ago /peda]
More importantly shepherding it through review!

Naturally it's perfect code so not comments inline ;)

Thanks again for picking this up!

So... I want to see lots of comments on this. If people are happy with
it (unlikely ;) then please say so.  It's at least a bit controversial
and adds a 'lot' of new ABI.


Jonathan
> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
>  drivers/iio/industrialio-core.c | 232 +++++++++++++++++++++++++++++++++++-----
>  include/linux/iio/iio.h         |  11 ++
>  include/linux/iio/types.h       |   5 +
>  3 files changed, 223 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index fc340ed3dca1..93c69ebeda1e 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -575,51 +575,41 @@ int of_iio_read_mount_matrix(const struct device *dev,
>  #endif
>  EXPORT_SYMBOL(of_iio_read_mount_matrix);
>  
> -/**
> - * iio_format_value() - Formats a IIO value into its string representation
> - * @buf:	The buffer to which the formatted value gets written
> - * @type:	One of the IIO_VAL_... constants. This decides how the val
> - *		and val2 parameters are formatted.
> - * @size:	Number of IIO value entries contained in vals
> - * @vals:	Pointer to the values, exact meaning depends on the
> - *		type parameter.
> - *
> - * Return: 0 by default, a negative number on failure or the
> - *	   total number of characters written for a type that belongs
> - *	   to the IIO_VAL_... constant.
> - */
> -ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
> +static ssize_t __iio_format_value(char *buf, unsigned int type,
> +				  int size, const int *vals)
>  {
>  	unsigned long long tmp;
> +	int tmp0, tmp1;
>  	bool scale_db = false;
>  
>  	switch (type) {
>  	case IIO_VAL_INT:
> -		return sprintf(buf, "%d\n", vals[0]);
> +		return sprintf(buf, "%d", vals[0]);
>  	case IIO_VAL_INT_PLUS_MICRO_DB:
>  		scale_db = true;
>  	case IIO_VAL_INT_PLUS_MICRO:
>  		if (vals[1] < 0)
> -			return sprintf(buf, "-%d.%06u%s\n", abs(vals[0]),
> +			return sprintf(buf, "-%d.%06u%s", abs(vals[0]),
>  				       -vals[1], scale_db ? " dB" : "");
>  		else
> -			return sprintf(buf, "%d.%06u%s\n", vals[0], vals[1],
> +			return sprintf(buf, "%d.%06u%s", vals[0], vals[1],
>  				scale_db ? " dB" : "");
>  	case IIO_VAL_INT_PLUS_NANO:
>  		if (vals[1] < 0)
> -			return sprintf(buf, "-%d.%09u\n", abs(vals[0]),
> +			return sprintf(buf, "-%d.%09u", abs(vals[0]),
>  				       -vals[1]);
>  		else
> -			return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
> +			return sprintf(buf, "%d.%09u", vals[0], vals[1]);
>  	case IIO_VAL_FRACTIONAL:
>  		tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]);
> -		vals[0] = (int)div_s64_rem(tmp, 1000000000, &vals[1]);
> -		return sprintf(buf, "%d.%09u\n", vals[0], abs(vals[1]));
> +		tmp1 = vals[1];
> +		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
> +		return sprintf(buf, "%d.%09u", tmp0, abs(tmp1));
>  	case IIO_VAL_FRACTIONAL_LOG2:
>  		tmp = (s64)vals[0] * 1000000000LL >> vals[1];
> -		vals[1] = do_div(tmp, 1000000000LL);
> -		vals[0] = tmp;
> -		return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
> +		tmp1 = do_div(tmp, 1000000000LL);
> +		tmp0 = tmp;
> +		return sprintf(buf, "%d.%09u", tmp0, tmp1);
>  	case IIO_VAL_INT_MULTIPLE:
>  	{
>  		int i;
> @@ -628,13 +618,34 @@ ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
>  		for (i = 0; i < size; ++i)
>  			len += snprintf(&buf[len], PAGE_SIZE - len, "%d ",
>  								vals[i]);
> -		len += snprintf(&buf[len], PAGE_SIZE - len, "\n");
>  		return len;
>  	}
>  	default:
>  		return 0;
>  	}
>  }
> +
> +/**
> + * iio_format_value() - Formats a IIO value into its string representation
> + * @buf:	The buffer to which the formatted value gets written
> + * @type:	One of the IIO_VAL_... constants. This decides how the val
> + *		and val2 parameters are formatted.
> + * @size:	Number of IIO value entries contained in vals
> + * @vals:	Pointer to the values, exact meaning depends on the
> + *		type parameter.
> + *
> + * Return: 0 by default, a negative number on failure or the
> + *	   total number of characters written for a type that belongs
> + *	   to the IIO_VAL_... constant.
> + */
> +ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
> +{
> +	ssize_t len;
> +
> +	len = __iio_format_value(buf, type, size, vals);
> +
> +	return len + sprintf(buf + len, "\n");
> +}
>  EXPORT_SYMBOL_GPL(iio_format_value);
>  
>  static ssize_t iio_read_channel_info(struct device *dev,
> @@ -662,6 +673,113 @@ static ssize_t iio_read_channel_info(struct device *dev,
>  	return iio_format_value(buf, ret, val_len, vals);
>  }
>  
> +static ssize_t iio_format_avail_list(char *buf, const int *vals,
> +				     int type, int length)
> +{
> +	int i;
> +	ssize_t len = 0;
> +
> +	switch (type) {
> +	case IIO_VAL_INT:
> +		for (i = 0; i < length; i++) {
> +			len += __iio_format_value(buf + len, type, 1, &vals[i]);
> +			if (i < length - 1)
> +				len += snprintf(buf + len,
> +						PAGE_SIZE - len,
> +						" ");
> +			else
> +				len += snprintf(buf + len,
> +						PAGE_SIZE - len,
> +						"\n");
> +		}
> +		break;
> +	default:
> +		for (i = 0; i < length / 2; i++) {
> +			len += __iio_format_value(buf + len,
> +						  type,
> +						  2,
> +						  &vals[i * 2]);
> +			if (i < length / 2 - 1)
> +				len += snprintf(buf + len,
> +						PAGE_SIZE - len,
> +						" ");
> +			else
> +				len += snprintf(buf + len,
> +						PAGE_SIZE - len,
> +						"\n");
> +		}
> +	};
> +
> +	return len;
> +}
> +
> +static ssize_t iio_format_avail_range(char *buf, const int *vals, int type)
> +{
> +	int i;
> +	ssize_t len;
> +
> +	len = snprintf(buf, PAGE_SIZE, "[");
> +	switch (type) {
> +	case IIO_VAL_INT:
> +		for (i = 0; i < 3; i++) {
> +			len += __iio_format_value(buf + len, type, 1, &vals[i]);
> +			if (i < 2)
> +				len += snprintf(buf + len,
> +						PAGE_SIZE - len,
> +						" ");
> +			else
> +				len += snprintf(buf + len,
> +						PAGE_SIZE - len,
> +						"]\n");
> +		}
> +		break;
> +	default:
> +		for (i = 0; i < 3; i++) {
> +			len += __iio_format_value(buf + len,
> +						  type,
> +						  2,
> +						  &vals[i * 2]);
> +			if (i < 2)
> +				len += snprintf(buf + len,
> +						PAGE_SIZE - len,
> +						" ");
> +			else
> +				len += snprintf(buf + len,
> +						PAGE_SIZE - len,
> +						"]\n");
> +		}
> +	};
> +
> +	return len;
> +}
> +
> +static ssize_t iio_read_channel_info_avail(struct device *dev,
> +					   struct device_attribute *attr,
> +					   char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> +	const int *vals;
> +	int ret;
> +	int length;
> +	int type;
> +
> +	ret = indio_dev->info->read_avail(indio_dev, this_attr->c,
> +					  &vals, &type, &length,
> +					  this_attr->address);
> +
> +	if (ret < 0)
> +		return ret;
> +	switch (ret) {
> +	case IIO_AVAIL_LIST:
> +		return iio_format_avail_list(buf, vals, type, length);
> +	case IIO_AVAIL_RANGE:
> +		return iio_format_avail_range(buf, vals, type);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
>  /**
>   * iio_str_to_fixpoint() - Parse a fixed-point number from a string
>   * @str: The string to parse
> @@ -978,6 +1096,40 @@ static int iio_device_add_info_mask_type(struct iio_dev *indio_dev,
>  	return attrcount;
>  }
>  
> +static int iio_device_add_info_mask_type_avail(struct iio_dev *indio_dev,
> +					       struct iio_chan_spec const *chan,
> +					       enum iio_shared_by shared_by,
> +					       const long *infomask)
> +{
> +	int i, ret, attrcount = 0;
> +	char *avail_postfix;
> +
> +	for_each_set_bit(i, infomask, sizeof(infomask) * 8) {
> +		avail_postfix = kasprintf(GFP_KERNEL,
> +					  "%s_available",
> +					  iio_chan_info_postfix[i]);
> +		if (!avail_postfix)
> +			return -ENOMEM;
> +
> +		ret = __iio_add_chan_devattr(avail_postfix,
> +					     chan,
> +					     &iio_read_channel_info_avail,
> +					     NULL,
> +					     i,
> +					     shared_by,
> +					     &indio_dev->dev,
> +					     &indio_dev->channel_attr_list);
> +		kfree(avail_postfix);
> +		if ((ret == -EBUSY) && (shared_by != IIO_SEPARATE))
> +			continue;
> +		else if (ret < 0)
> +			return ret;
> +		attrcount++;
> +	}
> +
> +	return attrcount;
> +}
> +
>  static int iio_device_add_channel_sysfs(struct iio_dev *indio_dev,
>  					struct iio_chan_spec const *chan)
>  {
> @@ -993,6 +1145,14 @@ static int iio_device_add_channel_sysfs(struct iio_dev *indio_dev,
>  		return ret;
>  	attrcount += ret;
>  
> +	ret = iio_device_add_info_mask_type_avail(indio_dev, chan,
> +						  IIO_SEPARATE,
> +						  &chan->
> +						  info_mask_separate_available);
> +	if (ret < 0)
> +		return ret;
> +	attrcount += ret;
> +
>  	ret = iio_device_add_info_mask_type(indio_dev, chan,
>  					    IIO_SHARED_BY_TYPE,
>  					    &chan->info_mask_shared_by_type);
> @@ -1000,6 +1160,14 @@ static int iio_device_add_channel_sysfs(struct iio_dev *indio_dev,
>  		return ret;
>  	attrcount += ret;
>  
> +	ret = iio_device_add_info_mask_type_avail(indio_dev, chan,
> +						  IIO_SHARED_BY_TYPE,
> +						  &chan->
> +						  info_mask_shared_by_type_available);
> +	if (ret < 0)
> +		return ret;
> +	attrcount += ret;
> +
>  	ret = iio_device_add_info_mask_type(indio_dev, chan,
>  					    IIO_SHARED_BY_DIR,
>  					    &chan->info_mask_shared_by_dir);
> @@ -1007,6 +1175,13 @@ static int iio_device_add_channel_sysfs(struct iio_dev *indio_dev,
>  		return ret;
>  	attrcount += ret;
>  
> +	ret = iio_device_add_info_mask_type_avail(indio_dev, chan,
> +						  IIO_SHARED_BY_DIR,
> +						  &chan->info_mask_shared_by_dir_available);
> +	if (ret < 0)
> +		return ret;
> +	attrcount += ret;
> +
>  	ret = iio_device_add_info_mask_type(indio_dev, chan,
>  					    IIO_SHARED_BY_ALL,
>  					    &chan->info_mask_shared_by_all);
> @@ -1014,6 +1189,13 @@ static int iio_device_add_channel_sysfs(struct iio_dev *indio_dev,
>  		return ret;
>  	attrcount += ret;
>  
> +	ret = iio_device_add_info_mask_type_avail(indio_dev, chan,
> +						  IIO_SHARED_BY_ALL,
> +						  &chan->info_mask_shared_by_all_available);
> +	if (ret < 0)
> +		return ret;
> +	attrcount += ret;
> +
>  	if (chan->ext_info) {
>  		unsigned int i = 0;
>  		for (ext_info = chan->ext_info; ext_info->name; ext_info++) {
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index b4a0679e4a49..c0f897084620 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -269,9 +269,13 @@ struct iio_chan_spec {
>  		enum iio_endian endianness;
>  	} scan_type;
>  	long			info_mask_separate;
> +	long			info_mask_separate_available;
>  	long			info_mask_shared_by_type;
> +	long			info_mask_shared_by_type_available;
>  	long			info_mask_shared_by_dir;
> +	long			info_mask_shared_by_dir_available;
>  	long			info_mask_shared_by_all;
> +	long			info_mask_shared_by_all_available;
>  	const struct iio_event_spec *event_spec;
>  	unsigned int		num_event_specs;
>  	const struct iio_chan_spec_ext_info *ext_info;
> @@ -397,6 +401,13 @@ struct iio_info {
>  			int *val_len,
>  			long mask);
>  
> +	int (*read_avail)(struct iio_dev *indio_dev,
> +			  struct iio_chan_spec const *chan,
> +			  const int **vals,
> +			  int *type,
> +			  int *length,
> +			  long mask_el);
> +
>  	int (*write_raw)(struct iio_dev *indio_dev,
>  			 struct iio_chan_spec const *chan,
>  			 int val,
> diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h
> index 32b579525004..2aa7b6384d64 100644
> --- a/include/linux/iio/types.h
> +++ b/include/linux/iio/types.h
> @@ -29,4 +29,9 @@ enum iio_event_info {
>  #define IIO_VAL_FRACTIONAL 10
>  #define IIO_VAL_FRACTIONAL_LOG2 11
>  
> +enum iio_available_type {
> +	IIO_AVAIL_LIST,
> +	IIO_AVAIL_RANGE,
> +};
> +
>  #endif /* _IIO_TYPES_H_ */
> 

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