Re: [PATCH v3 1/8] iio:core: add a callback to allow drivers to provide _available attributes

[Jonathan Cameron]

On 23/10/16 23:39, Peter Rosin wrote:
> From: Jonathan Cameron <jic23@xxxxxxxxxx>
> 
> 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.
> 
> Signed-off-by: Jonathan Cameron <jic23@xxxxxxxxxx>
> [forward ported, added some docs and fixed buffer overflows /peda]
> Signed-off-by: Peter Rosin <peda@xxxxxxxxxx>
Looks nicely cleaned up to me, but I'm really not going to be the best
person to review this.  So would appreciate anyone else who has the time
taking a look at this.

Thanks,

Jonathan
> ---
>  drivers/iio/industrialio-core.c | 259 +++++++++++++++++++++++++++++++++++-----
>  include/linux/iio/iio.h         |  29 +++++
>  include/linux/iio/types.h       |   5 +
>  3 files changed, 260 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index fc340ed3dca1..b35c61a31fa6 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -575,66 +575,82 @@ 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, size_t len, 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 snprintf(buf, len, "%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]),
> -				       -vals[1], scale_db ? " dB" : "");
> +			return snprintf(buf, len, "-%d.%06u%s", abs(vals[0]),
> +					-vals[1], scale_db ? " dB" : "");
>  		else
> -			return sprintf(buf, "%d.%06u%s\n", vals[0], vals[1],
> -				scale_db ? " dB" : "");
> +			return snprintf(buf, len, "%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]),
> -				       -vals[1]);
> +			return snprintf(buf, len, "-%d.%09u", abs(vals[0]),
> +					-vals[1]);
>  		else
> -			return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
> +			return snprintf(buf, len, "%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 snprintf(buf, len, "%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 snprintf(buf, len, "%d.%09u", tmp0, tmp1);
>  	case IIO_VAL_INT_MULTIPLE:
>  	{
>  		int i;
> -		int len = 0;
> +		int l = 0;
>  
> -		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;
> +		for (i = 0; i < size; ++i) {
> +			l += snprintf(&buf[l], len - l, "%d ", vals[i]);
> +			if (l >= len)
> +				break;
> +		}
> +		return l;
>  	}
>  	default:
>  		return 0;
>  	}
>  }
> +
> +/**
> + * iio_format_value() - Formats a IIO value into its string representation
> + * @buf:	The buffer to which the formatted value gets written
> + *		which is assumed to be big enough (i.e. PAGE_SIZE).
> + * @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, PAGE_SIZE, type, size, vals);
> +	if (len >= PAGE_SIZE - 1)
> +		return -EFBIG;
> +
> +	return len + sprintf(buf + len, "\n");
> +}
>  EXPORT_SYMBOL_GPL(iio_format_value);
>  
>  static ssize_t iio_read_channel_info(struct device *dev,
> @@ -662,6 +678,119 @@ 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, PAGE_SIZE - len,
> +						  type, 1, &vals[i]);
> +			if (len >= PAGE_SIZE)
> +				return -EFBIG;
> +			if (i < length - 1)
> +				len += snprintf(buf + len, PAGE_SIZE - len,
> +						" ");
> +			else
> +				len += snprintf(buf + len, PAGE_SIZE - len,
> +						"\n");
> +			if (len >= PAGE_SIZE)
> +				return -EFBIG;
> +		}
> +		break;
> +	default:
> +		for (i = 0; i < length / 2; i++) {
> +			len += __iio_format_value(buf + len, PAGE_SIZE - len,
> +						  type, 2, &vals[i * 2]);
> +			if (len >= PAGE_SIZE)
> +				return -EFBIG;
> +			if (i < length / 2 - 1)
> +				len += snprintf(buf + len, PAGE_SIZE - len,
> +						" ");
> +			else
> +				len += snprintf(buf + len, PAGE_SIZE - len,
> +						"\n");
> +			if (len >= PAGE_SIZE)
> +				return -EFBIG;
> +		}
> +	};
> +
> +	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, PAGE_SIZE - len,
> +						  type, 1, &vals[i]);
> +			if (len >= PAGE_SIZE)
> +				return -EFBIG;
> +			if (i < 2)
> +				len += snprintf(buf + len, PAGE_SIZE - len,
> +						" ");
> +			else
> +				len += snprintf(buf + len, PAGE_SIZE - len,
> +						"]\n");
> +			if (len >= PAGE_SIZE)
> +				return -EFBIG;
> +		}
> +		break;
> +	default:
> +		for (i = 0; i < 3; i++) {
> +			len += __iio_format_value(buf + len, PAGE_SIZE - len,
> +						  type, 2, &vals[i * 2]);
> +			if (len >= PAGE_SIZE)
> +				return -EFBIG;
> +			if (i < 2)
> +				len += snprintf(buf + len, PAGE_SIZE - len,
> +						" ");
> +			else
> +				len += snprintf(buf + len, PAGE_SIZE - len,
> +						"]\n");
> +			if (len >= PAGE_SIZE)
> +				return -EFBIG;
> +		}
> +	};
> +
> +	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 +1107,40 @@ 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 +1156,14 @@ 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 +1171,14 @@ 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 +1186,13 @@ 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 +1200,13 @@ 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..45b781084a4b 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -225,12 +225,22 @@ struct iio_event_spec {
>   *			endianness:	little or big endian
>   * @info_mask_separate: What information is to be exported that is specific to
>   *			this channel.
> + * @info_mask_separate_available: What availability information is to be
> + *			exported that is specific to this channel.
>   * @info_mask_shared_by_type: What information is to be exported that is shared
>   *			by all channels of the same type.
> + * @info_mask_shared_by_type_available: What availability information is to be
> + *			exported that is shared by all channels of the same
> + *			type.
>   * @info_mask_shared_by_dir: What information is to be exported that is shared
>   *			by all channels of the same direction.
> + * @info_mask_shared_by_dir_available: What availability information is to be
> + *			exported that is shared by all channels of the same
> + *			direction.
>   * @info_mask_shared_by_all: What information is to be exported that is shared
>   *			by all channels.
> + * @info_mask_shared_by_all_available: What availability information is to be
> + *			exported that is shared by all channels.
>   * @event_spec:		Array of events which should be registered for this
>   *			channel.
>   * @num_event_specs:	Size of the event_spec array.
> @@ -269,9 +279,13 @@ 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;
> @@ -349,6 +363,14 @@ struct iio_dev;
>   *			max_len specifies maximum number of elements
>   *			vals pointer can contain. val_len is used to return
>   *			length of valid elements in vals.
> + * @read_avail:		function to return the available values from the device.
> + *			mask specifies which value. Note 0 means the available
> + *			values for the channel in question.  Return value
> + *			specifies if a IIO_AVAIL_LIST or a IIO_AVAIL_RANGE is
> + *			returned in vals. The type of the vals are returned in
> + *			type and the number of vals is returned in length. For
> + *			ranges, there are always three vals returned; min, step
> + *			and max. For lists, all possible values are enumerated.
>   * @write_raw:		function to write a value to the device.
>   *			Parameters are the same as for read_raw.
>   * @write_raw_get_fmt:	callback function to query the expected
> @@ -397,6 +419,13 @@ 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);
> +
>  	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_ */
>