iio: Add helper functions for enum style channel attributes

We often have the case were we do have a enum style channel attribute. These
attributes have in common that they are a list of string values which usually
map in a 1-to-1 fashion to integer values.

This patch implements some common helper code for implementing enum style
channel attributes using extended channel attributes. The helper functions take
care of converting between the string and integer values, as well providing a
function for "_available" attributes which list all available enum items.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 63 insertions, 0 deletions

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 1ddd8861c71..56a3c0bc996 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -289,6 +289,69 @@ static ssize_t iio_write_channel_ext_info(struct device *dev,
 			       this_attr->c, buf, len);
 }
 
+ssize_t iio_enum_available_read(struct iio_dev *indio_dev,
+	uintptr_t priv, const struct iio_chan_spec *chan, char *buf)
+{
+	const struct iio_enum *e = (const struct iio_enum *)priv;
+	unsigned int i;
+	size_t len = 0;
+
+	if (!e->num_items)
+		return 0;
+
+	for (i = 0; i < e->num_items; ++i)
+		len += snprintf(buf + len, PAGE_SIZE - len, "%s ", e->items[i]);
+
+	/* replace last space with a newline */
+	buf[len - 1] = '\n';
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(iio_enum_available_read);
+
+ssize_t iio_enum_read(struct iio_dev *indio_dev,
+	uintptr_t priv, const struct iio_chan_spec *chan, char *buf)
+{
+	const struct iio_enum *e = (const struct iio_enum *)priv;
+	int i;
+
+	if (!e->get)
+		return -EINVAL;
+
+	i = e->get(indio_dev, chan);
+	if (i < 0)
+		return i;
+	else if (i >= e->num_items)
+		return -EINVAL;
+
+	return sprintf(buf, "%s\n", e->items[i]);
+}
+EXPORT_SYMBOL_GPL(iio_enum_read);
+
+ssize_t iio_enum_write(struct iio_dev *indio_dev,
+	uintptr_t priv, const struct iio_chan_spec *chan, const char *buf,
+	size_t len)
+{
+	const struct iio_enum *e = (const struct iio_enum *)priv;
+	unsigned int i;
+	int ret;
+
+	if (!e->set)
+		return -EINVAL;
+
+	for (i = 0; i < e->num_items; i++) {
+		if (sysfs_streq(buf, e->items[i]))
+			break;
+	}
+
+	if (i == e->num_items)
+		return -EINVAL;
+
+	ret = e->set(indio_dev, chan, i);
+	return ret ? ret : len;
+}
+EXPORT_SYMBOL_GPL(iio_enum_write);
+
 static ssize_t iio_read_channel_info(struct device *dev,
 				     struct device_attribute *attr,
 				     char *buf)