iio: buffer: wrap all buffer attributes into iio_dev_attr

This change wraps all buffer attributes into iio_dev_attr objects, and
assigns a reference to the IIO buffer they belong to.

With the addition of multiple IIO buffers per one IIO device, we need a way
to know which IIO buffer is being enabled/disabled/controlled.

We know that all buffer attributes are device_attributes. So we can wrap
them with a iio_dev_attr types. In the iio_dev_attr type, we can also hold
a reference to an IIO buffer.
So, we end up being able to allocate wrapped attributes for all buffer
attributes (even the one from other drivers).

The neat part with this mechanism, is that we don't need to add any extra
cleanup, because these attributes are being added to a dynamic list that
will get cleaned up via iio_free_chan_devattr_list().

With this change, the 'buffer->scan_el_dev_attr_list' list is being renamed
to 'buffer->buffer_attr_list', effectively merging (or finalizing the
merge) of the buffer/ & scan_elements/ attributes internally.

Accessing these new buffer attributes can now be done via
'to_iio_dev_attr(attr)->buffer' inside the show/store handlers.

Signed-off-by: Alexandru Ardelean <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Cameron <[email protected]>

Author: commodo

drivers/iio/industrialio-buffer.c

@@ -253,8 +253,7 @@ static ssize_t iio_scan_el_show(struct device *dev,
 				char *buf)
 {
 	int ret;
-	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 
 	/* Ensure ret is 0 or 1. */
 	ret = !!test_bit(to_iio_dev_attr(attr)->address,
@@ -367,8 +366,8 @@ static ssize_t iio_scan_el_store(struct device *dev,
 	int ret;
 	bool state;
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
 	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+	struct iio_buffer *buffer = this_attr->buffer;
 
 	ret = strtobool(buf, &state);
 	if (ret < 0)
@@ -402,8 +401,7 @@ static ssize_t iio_scan_el_ts_show(struct device *dev,
 				   struct device_attribute *attr,
 				   char *buf)
 {
-	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 
 	return sprintf(buf, "%d\n", buffer->scan_timestamp);
 }
@@ -415,7 +413,7 @@ static ssize_t iio_scan_el_ts_store(struct device *dev,
 {
 	int ret;
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 	bool state;
 
 	ret = strtobool(buf, &state);
@@ -448,7 +446,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
 				     IIO_SEPARATE,
 				     &indio_dev->dev,
 				     buffer,
-				     &buffer->scan_el_dev_attr_list);
+				     &buffer->buffer_attr_list);
 	if (ret)
 		return ret;
 	attrcount++;
@@ -460,7 +458,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
 				     0,
 				     &indio_dev->dev,
 				     buffer,
-				     &buffer->scan_el_dev_attr_list);
+				     &buffer->buffer_attr_list);
 	if (ret)
 		return ret;
 	attrcount++;
@@ -473,7 +471,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
 					     0,
 					     &indio_dev->dev,
 					     buffer,
-					     &buffer->scan_el_dev_attr_list);
+					     &buffer->buffer_attr_list);
 	else
 		ret = __iio_add_chan_devattr("en",
 					     chan,
@@ -483,7 +481,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
 					     0,
 					     &indio_dev->dev,
 					     buffer,
-					     &buffer->scan_el_dev_attr_list);
+					     &buffer->buffer_attr_list);
 	if (ret)
 		return ret;
 	attrcount++;
@@ -495,8 +493,7 @@ static ssize_t iio_buffer_read_length(struct device *dev,
 				      struct device_attribute *attr,
 				      char *buf)
 {
-	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 
 	return sprintf(buf, "%d\n", buffer->length);
 }
@@ -506,7 +503,7 @@ static ssize_t iio_buffer_write_length(struct device *dev,
 				       const char *buf, size_t len)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 	unsigned int val;
 	int ret;
 
@@ -538,8 +535,7 @@ static ssize_t iio_buffer_show_enable(struct device *dev,
 				      struct device_attribute *attr,
 				      char *buf)
 {
-	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 
 	return sprintf(buf, "%d\n", iio_buffer_is_active(buffer));
 }
@@ -1154,7 +1150,7 @@ static ssize_t iio_buffer_store_enable(struct device *dev,
 	int ret;
 	bool requested_state;
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 	bool inlist;
 
 	ret = strtobool(buf, &requested_state);
@@ -1183,8 +1179,7 @@ static ssize_t iio_buffer_show_watermark(struct device *dev,
 					 struct device_attribute *attr,
 					 char *buf)
 {
-	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 
 	return sprintf(buf, "%u\n", buffer->watermark);
 }
@@ -1195,7 +1190,7 @@ static ssize_t iio_buffer_store_watermark(struct device *dev,
 					  size_t len)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 	unsigned int val;
 	int ret;
 
@@ -1228,8 +1223,7 @@ static ssize_t iio_dma_show_data_available(struct device *dev,
 						struct device_attribute *attr,
 						char *buf)
 {
-	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-	struct iio_buffer *buffer = indio_dev->buffer;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 
 	return sprintf(buf, "%zu\n", iio_buffer_data_available(buffer));
 }
@@ -1254,6 +1248,27 @@ static struct attribute *iio_buffer_attrs[] = {
 	&dev_attr_data_available.attr,
 };
 
+#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)
+
+static struct attribute *iio_buffer_wrap_attr(struct iio_buffer *buffer,
+					      struct attribute *attr)
+{
+	struct device_attribute *dattr = to_dev_attr(attr);
+	struct iio_dev_attr *iio_attr;
+
+	iio_attr = kzalloc(sizeof(*iio_attr), GFP_KERNEL);
+	if (!iio_attr)
+		return NULL;
+
+	iio_attr->buffer = buffer;
+	memcpy(&iio_attr->dev_attr, dattr, sizeof(iio_attr->dev_attr));
+	iio_attr->dev_attr.attr.name = kstrdup_const(attr->name, GFP_KERNEL);
+
+	list_add(&iio_attr->l, &buffer->buffer_attr_list);
+
+	return &iio_attr->dev_attr.attr;
+}
+
 static int iio_buffer_register_legacy_sysfs_groups(struct iio_dev *indio_dev,
 						   struct attribute **buffer_attrs,
 						   int buffer_attrcount,
@@ -1329,7 +1344,7 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
 	}
 
 	scan_el_attrcount = 0;
-	INIT_LIST_HEAD(&buffer->scan_el_dev_attr_list);
+	INIT_LIST_HEAD(&buffer->buffer_attr_list);
 	channels = indio_dev->channels;
 	if (channels) {
 		/* new magic */
@@ -1376,9 +1391,19 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
 
 	buffer_attrcount += ARRAY_SIZE(iio_buffer_attrs);
 
-	attrn = buffer_attrcount;
+	for (i = 0; i < buffer_attrcount; i++) {
+		struct attribute *wrapped;
+
+		wrapped = iio_buffer_wrap_attr(buffer, attr[i]);
+		if (!wrapped) {
+			ret = -ENOMEM;
+			goto error_free_scan_mask;
+		}
+		attr[i] = wrapped;
+	}
 
-	list_for_each_entry(p, &buffer->scan_el_dev_attr_list, l)
+	attrn = 0;
+	list_for_each_entry(p, &buffer->buffer_attr_list, l)
 		attr[attrn++] = &p->dev_attr.attr;
 
 	buffer->buffer_group.name = kasprintf(GFP_KERNEL, "buffer%d", index);
@@ -1412,7 +1437,7 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
 error_free_scan_mask:
 	bitmap_free(buffer->scan_mask);
 error_cleanup_dynamic:
-	iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
+	iio_free_chan_devattr_list(&buffer->buffer_attr_list);
 
 	return ret;
 }
@@ -1443,7 +1468,7 @@ static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer)
 	bitmap_free(buffer->scan_mask);
 	kfree(buffer->buffer_group.name);
 	kfree(buffer->buffer_group.attrs);
-	iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
+	iio_free_chan_devattr_list(&buffer->buffer_attr_list);
 }
 
 void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)

drivers/iio/industrialio-core.c

@@ -1357,7 +1357,7 @@ void iio_free_chan_devattr_list(struct list_head *attr_list)
 	struct iio_dev_attr *p, *n;
 
 	list_for_each_entry_safe(p, n, attr_list, l) {
-		kfree(p->dev_attr.attr.name);
+		kfree_const(p->dev_attr.attr.name);
 		list_del(&p->l);
 		kfree(p);
 	}

include/linux/iio/buffer_impl.h

@@ -97,8 +97,8 @@ struct iio_buffer {
 	/* @scan_timestamp: Does the scan mode include a timestamp. */
 	bool scan_timestamp;
 
-	/* @scan_el_dev_attr_list: List of scan element related attributes. */
-	struct list_head scan_el_dev_attr_list;
+	/* @buffer_attr_list: List of buffer attributes. */
+	struct list_head buffer_attr_list;
 
 	/*
 	 * @buffer_group: Attributes of the new buffer group.