iio:core: add a callback to allow drivers to provide _available attri…

…butes

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 <[email protected]>
[forward ported, added some docs and fixed buffer overflows /peda]
Acked-by: Daniel Baluta <[email protected]>
Signed-off-by: Peter Rosin <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>

drivers/iio/industrialio-core.c

@@ -577,66 +577,82 @@ 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,
@@ -664,6 +680,119 @@ 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
@@ -980,6 +1109,40 @@ 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)
 {
@@ -995,27 +1158,57 @@ 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);
 	if (ret < 0)
 		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);
 	if (ret < 0)
 		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);
 	if (ret < 0)
 		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++) {