[RFC PATCH 3/5] drivers: base: Introducing software nodes to the firmware node framework

[Heikki Krogerus]

Software node is a new struct fwnode_handle type that can be
used to describe devices in kernel (software). It is meant
to complement fwnodes representing real firmware nodes when
they are incomplete (for example missing device properties)
and to supply the primary fwnode when the firmware lacks
hardware description for a device completely.

The software node type is really meant to replace the
currently used "property_set" struct fwnode_handle type. The
handling of struct property_set is glued to the generic
device property handling code, and it is not possible to
create a struct property_set independently from a device
that it is bind to. struct property_set is only created when
device properties are added to already initialized struct
device, and control of it is only possible from the generic
property handling code.

Software nodes are instead designed to be created
independently from the device entries (struct device). It
makes them much more flexible, as then the device meant to
be bind to the node can be created at a later time, and from
another location. It is also possible to bind multiple
devices to a single software node if needed.

The software node implementation also includes support for
node hierarchy, which was the main motivation for this
commit. The node hierarchy was something that was requested
for the struct property_set, but it did not seem reasonable
to try to extend the property_set support for that purpose.
struct property_set was really meant only for device
property handling like the name suggests.

Support for struct property_set is not yet removed in this
commit, but it will be in the following one.

Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
---
 .../ABI/testing/sysfs-devices-software_node   |  27 +
 drivers/base/Makefile                         |   2 +-
 drivers/base/core.c                           |   4 +
 drivers/base/swnode.c                         | 628 ++++++++++++++++++
 include/linux/property.h                      |  12 +
 5 files changed, 672 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ABI/testing/sysfs-devices-software_node
 create mode 100644 drivers/base/swnode.c

diff --git a/Documentation/ABI/testing/sysfs-devices-software_node b/Documentation/ABI/testing/sysfs-devices-software_node
new file mode 100644
index 000000000000..3b0b24ae39e7
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-software_node
@@ -0,0 +1,27 @@
+What:		/sys/devices/.../software_node/
+Date:		January 2019
+Contact:	Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
+Description:
+		This directory contains the details about the device that are
+		assigned in kernel (i.e. software), as opposed to the
+		firmware_node directory which contains the details that are
+		assigned for the device in firmware. The main attributes in the
+		directory will show the properties the device has, and the
+		relationship it has to some of the other devices.
+
+What:		/sys/devices/.../software_node/properties/
+Date:		January 2019
+Contact:	Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
+Description:
+		The /sys/devices/.../software_node/properties directory contains
+		device properties that are assigned in kernel for the device.
+		These properties may be additional properties on top of the ones
+		that the firmware has assigned for the device. The device
+		properties that the firmware supplies for the device are not
+		visible in this directory.
+
+		Every property that has been assigned in kernel for the device
+		will have its own attribute file under this directory, and those
+		files will be named with the names of the properties. Reading
+		one of these files will return the value or values the property
+		has.
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 704f44295810..157452080f3d 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -6,7 +6,7 @@ obj-y			:= component.o core.o bus.o dd.o syscore.o \
 			   cpu.o firmware.o init.o map.o devres.o \
 			   attribute_container.o transport_class.o \
 			   topology.o container.o property.o cacheinfo.o \
-			   devcon.o
+			   devcon.o swnode.o
 obj-$(CONFIG_DEVTMPFS)	+= devtmpfs.o
 obj-y			+= power/
 obj-$(CONFIG_ISA_BUS_API)	+= isa.o
diff --git a/drivers/base/core.c b/drivers/base/core.c
index d0b5b9d6f19e..6a8a12d32562 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -738,6 +738,10 @@ device_platform_notify(struct device *dev, enum kobject_action action)
 	if (ret)
 		return ret;
 
+	ret = software_node_notify(dev, action);
+	if (ret)
+		return ret;
+
 	if (platform_notify && action == KOBJ_ADD)
 		platform_notify(dev);
 	else if (platform_notify_remove && action == KOBJ_REMOVE)
diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
new file mode 100644
index 000000000000..77d5645d2fcf
--- /dev/null
+++ b/drivers/base/swnode.c
@@ -0,0 +1,628 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Software nodes for the firmware node framework.
+ *
+ * Copyright (C) 2018, Intel Corporation
+ * Authors: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+struct software_node {
+	int id;
+	struct kobject kobj;
+	struct fwnode_handle fwnode;
+
+	/* hierarchy */
+	struct ida child_ids;
+	struct list_head entry;
+	struct list_head children;
+	struct software_node *parent;
+
+	/* properties */
+	struct kobj_attribute *property_attrs;
+	struct attribute_group property_group;
+	const struct property_entry *properties;
+};
+
+static DEFINE_IDA(swnode_root_ids);
+static struct kset *swnode_kset;
+
+#define kobj_to_swnode(_kobj_) container_of(_kobj_, struct software_node, kobj)
+
+static const struct fwnode_operations software_node_ops;
+
+bool is_software_node(const struct fwnode_handle *fwnode)
+{
+	return !IS_ERR_OR_NULL(fwnode) && fwnode->ops == &software_node_ops;
+}
+
+#define to_software_node(__fwnode)					\
+	({								\
+		typeof(__fwnode) __to_software_node_fwnode = __fwnode;	\
+									\
+		is_software_node(__to_software_node_fwnode) ?		\
+			container_of(__to_software_node_fwnode,		\
+				     struct software_node, fwnode) :	\
+			NULL;						\
+	})
+
+/* -------------------------------------------------------------------------- */
+/* property_entry processing */
+
+static const struct property_entry *
+property_entry_get(const struct property_entry *prop, const char *name)
+{
+	if (!prop)
+		return NULL;
+
+	for (; prop->name; prop++)
+		if (!strcmp(name, prop->name))
+			return prop;
+
+	return NULL;
+}
+
+static const void *property_get_pointer(const struct property_entry *prop)
+{
+	switch (prop->type) {
+	case DEV_PROP_U8:
+		if (prop->is_array)
+			return prop->pointer.u8_data;
+		return &prop->value.u8_data;
+	case DEV_PROP_U16:
+		if (prop->is_array)
+			return prop->pointer.u16_data;
+		return &prop->value.u16_data;
+	case DEV_PROP_U32:
+		if (prop->is_array)
+			return prop->pointer.u32_data;
+		return &prop->value.u32_data;
+	case DEV_PROP_U64:
+		if (prop->is_array)
+			return prop->pointer.u64_data;
+		return &prop->value.u64_data;
+	case DEV_PROP_STRING:
+		if (prop->is_array)
+			return prop->pointer.str;
+		return &prop->value.str;
+	default:
+		return NULL;
+	}
+}
+
+static const void *property_entry_find(const struct property_entry *props,
+				       const char *propname, size_t length)
+{
+	const struct property_entry *prop;
+	const void *pointer;
+
+	prop = property_entry_get(props, propname);
+	if (!prop)
+		return ERR_PTR(-EINVAL);
+	pointer = property_get_pointer(prop);
+	if (!pointer)
+		return ERR_PTR(-ENODATA);
+	if (length > prop->length)
+		return ERR_PTR(-EOVERFLOW);
+	return pointer;
+}
+
+static int property_entry_read_u8_array(const struct property_entry *props,
+					const char *propname,
+					u8 *values, size_t nval)
+{
+	const void *pointer;
+	size_t length = nval * sizeof(*values);
+
+	pointer = property_entry_find(props, propname, length);
+	if (IS_ERR(pointer))
+		return PTR_ERR(pointer);
+
+	memcpy(values, pointer, length);
+	return 0;
+}
+
+static int property_entry_read_u16_array(const struct property_entry *props,
+					 const char *propname,
+					 u16 *values, size_t nval)
+{
+	const void *pointer;
+	size_t length = nval * sizeof(*values);
+
+	pointer = property_entry_find(props, propname, length);
+	if (IS_ERR(pointer))
+		return PTR_ERR(pointer);
+
+	memcpy(values, pointer, length);
+	return 0;
+}
+
+static int property_entry_read_u32_array(const struct property_entry *props,
+					 const char *propname,
+					 u32 *values, size_t nval)
+{
+	const void *pointer;
+	size_t length = nval * sizeof(*values);
+
+	pointer = property_entry_find(props, propname, length);
+	if (IS_ERR(pointer))
+		return PTR_ERR(pointer);
+
+	memcpy(values, pointer, length);
+	return 0;
+}
+
+static int property_entry_read_u64_array(const struct property_entry *props,
+					 const char *propname,
+					 u64 *values, size_t nval)
+{
+	const void *pointer;
+	size_t length = nval * sizeof(*values);
+
+	pointer = property_entry_find(props, propname, length);
+	if (IS_ERR(pointer))
+		return PTR_ERR(pointer);
+
+	memcpy(values, pointer, length);
+	return 0;
+}
+
+static int
+property_entry_count_elems_of_size(const struct property_entry *props,
+				   const char *propname, size_t length)
+{
+	const struct property_entry *prop;
+
+	prop = property_entry_get(props, propname);
+	if (!prop)
+		return -EINVAL;
+
+	return prop->length / length;
+}
+
+static int property_entry_read_int_array(const struct property_entry *props,
+					 const char *name,
+					 unsigned int elem_size, void *val,
+					 size_t nval)
+{
+	if (!val)
+		return property_entry_count_elems_of_size(props, name,
+							  elem_size);
+	switch (elem_size) {
+	case sizeof(u8):
+		return property_entry_read_u8_array(props, name, val, nval);
+	case sizeof(u16):
+		return property_entry_read_u16_array(props, name, val, nval);
+	case sizeof(u32):
+		return property_entry_read_u32_array(props, name, val, nval);
+	case sizeof(u64):
+		return property_entry_read_u64_array(props, name, val, nval);
+	}
+
+	return -ENXIO;
+}
+
+static int property_entry_read_string_array(const struct property_entry *props,
+					    const char *propname,
+					    const char **strings, size_t nval)
+{
+	const struct property_entry *prop;
+	const void *pointer;
+	size_t array_len, length;
+
+	/* Find out the array length. */
+	prop = property_entry_get(props, propname);
+	if (!prop)
+		return -EINVAL;
+
+	if (!prop->is_array)
+		/* The array length for a non-array string property is 1. */
+		array_len = 1;
+	else
+		/* Find the length of an array. */
+		array_len = property_entry_count_elems_of_size(props, propname,
+							  sizeof(const char *));
+
+	/* Return how many there are if strings is NULL. */
+	if (!strings)
+		return array_len;
+
+	array_len = min(nval, array_len);
+	length = array_len * sizeof(*strings);
+
+	pointer = property_entry_find(props, propname, length);
+	if (IS_ERR(pointer))
+		return PTR_ERR(pointer);
+
+	memcpy(strings, pointer, length);
+
+	return array_len;
+}
+
+/* -------------------------------------------------------------------------- */
+/* fwnode operations */
+
+static struct fwnode_handle *software_node_get(struct fwnode_handle *fwnode)
+{
+	struct software_node *swnode = to_software_node(fwnode);
+
+	kobject_get(&swnode->kobj);
+
+	return &swnode->fwnode;
+}
+
+static void software_node_put(struct fwnode_handle *fwnode)
+{
+	struct software_node *swnode = to_software_node(fwnode);
+
+	kobject_put(&swnode->kobj);
+}
+
+static bool software_node_property_present(const struct fwnode_handle *fwnode,
+					   const char *propname)
+{
+	return !!property_entry_get(to_software_node(fwnode)->properties,
+				    propname);
+}
+
+static int software_node_read_int_array(const struct fwnode_handle *fwnode,
+					const char *propname,
+					unsigned int elem_size, void *val,
+					size_t nval)
+{
+	struct software_node *swnode = to_software_node(fwnode);
+
+	return property_entry_read_int_array(swnode->properties, propname,
+					     elem_size, val, nval);
+}
+
+static int software_node_read_string_array(const struct fwnode_handle *fwnode,
+					   const char *propname,
+					   const char **val, size_t nval)
+{
+	struct software_node *swnode = to_software_node(fwnode);
+
+	return property_entry_read_string_array(swnode->properties, propname,
+						val, nval);
+}
+
+struct fwnode_handle *
+software_node_get_parent(const struct fwnode_handle *fwnode)
+{
+	struct software_node *swnode = to_software_node(fwnode);
+
+	return swnode->parent ? &swnode->parent->fwnode : NULL;
+}
+
+struct fwnode_handle *
+software_node_get_next_child(const struct fwnode_handle *fwnode,
+			     struct fwnode_handle *child)
+{
+	struct software_node *p = to_software_node(fwnode);
+	struct software_node *c = to_software_node(child);
+
+	if (list_empty(&p->children) ||
+	    (c && list_is_last(&c->entry, &p->children)))
+		return NULL;
+
+	if (c)
+		c = list_next_entry(c, entry);
+	else
+		c = list_first_entry(&p->children, struct software_node, entry);
+	return &c->fwnode;
+}
+
+struct fwnode_handle *
+software_node_get_named_child(const struct fwnode_handle *fwnode,
+			      const char *name)
+{
+	struct software_node *swnode = to_software_node(fwnode);
+	const struct property_entry *prop;
+	struct software_node *child;
+
+	list_for_each_entry(child, &swnode->children, entry) {
+		prop = property_entry_get(child->properties, "name");
+		if (!prop)
+			continue;
+
+		if (!strcmp(name, prop->value.str))
+			return software_node_get(&child->fwnode);
+	}
+
+	return NULL;
+}
+
+static const struct fwnode_operations software_node_ops = {
+	.get = software_node_get,
+	.put = software_node_put,
+	.property_present = software_node_property_present,
+	.property_read_int_array = software_node_read_int_array,
+	.property_read_string_array = software_node_read_string_array,
+	.get_parent = software_node_get_parent,
+	.get_next_child_node = software_node_get_next_child,
+	.get_named_child_node = software_node_get_named_child,
+};
+
+/* -------------------------------------------------------------------------- */
+
+static ssize_t property_array_show(const struct property_entry *prop, char *buf)
+{
+	int ret = 0;
+	int i;
+
+	switch (prop->type) {
+	case DEV_PROP_U8:
+		for (i = 0; i < prop->length / sizeof(u8); i++)
+			ret += sprintf(buf + ret, "%u\n",
+				       prop->pointer.u8_data[i]);
+		break;
+	case DEV_PROP_U16:
+		for (i = 0; i < prop->length / sizeof(u16); i++)
+			ret += sprintf(buf + ret, "0x%x\n",
+				       prop->pointer.u16_data[i]);
+		break;
+	case DEV_PROP_U32:
+		for (i = 0; i < prop->length / sizeof(u32); i++)
+			ret += sprintf(buf + ret, "0x%x\n",
+				       prop->pointer.u8_data[i]);
+		break;
+	case DEV_PROP_U64:
+		for (i = 0; i < prop->length / sizeof(u64); i++)
+			ret += sprintf(buf + ret, "0x%llx\n",
+				       prop->pointer.u64_data[i]);
+		break;
+	case DEV_PROP_STRING:
+		for (i = 0; i < prop->length / sizeof(const char *); i++)
+			ret += sprintf(buf + ret, "%s\n", prop->pointer.str[i]);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static ssize_t software_node_property_show(struct kobject *kobj,
+					   struct kobj_attribute *attr,
+					   char *buf)
+{
+	struct software_node *swnode = kobj_to_swnode(kobj);
+	const struct property_entry *prop;
+
+	for (prop = swnode->properties; prop->name; prop++)
+		if (prop->name == attr->attr.name)
+			break;
+
+	if (prop->is_array)
+		return property_array_show(prop, buf);
+
+	/* boolean property */
+	if (!prop->length)
+		return sprintf(buf, "1\n");
+
+	switch (prop->type) {
+	case DEV_PROP_U8:
+		return sprintf(buf, "%u\n", prop->value.u8_data);
+	case DEV_PROP_U16:
+		return sprintf(buf, "0x%x\n", prop->value.u16_data);
+	case DEV_PROP_U32:
+		return sprintf(buf, "0x%x\n", prop->value.u32_data);
+	case DEV_PROP_U64:
+		return sprintf(buf, "0x%llx\n", prop->value.u64_data);
+	case DEV_PROP_STRING:
+		return sprintf(buf, "%s\n", prop->value.str);
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static int
+software_node_register_properties(struct software_node *swnode,
+				  const struct property_entry *properties)
+{
+	struct kobj_attribute *property_attrs;
+	struct attribute **group_attrs;
+	struct property_entry *props;
+	int i, n = 0;
+
+	if (!properties)
+		return 0;
+
+	while (properties[n].name)
+		n++;
+
+	property_attrs = kcalloc(n, sizeof(*property_attrs), GFP_KERNEL);
+	if (!property_attrs)
+		return -ENOMEM;
+
+	group_attrs = kcalloc(n + 1, sizeof(*group_attrs), GFP_KERNEL);
+	if (!group_attrs) {
+		kfree(property_attrs);
+		return -ENOMEM;
+	}
+
+	props = property_entries_dup(properties);
+	if (IS_ERR(props)) {
+		kfree(property_attrs);
+		kfree(group_attrs);
+		return PTR_ERR(props);
+	}
+
+	for (i = 0; i < n; i++) {
+		sysfs_attr_init(&property_attrs[i].attr);
+		property_attrs[i].attr.mode = 0444;
+		property_attrs[i].attr.name = props[i].name;
+		property_attrs[i].show = software_node_property_show;
+		group_attrs[i] = &property_attrs[i].attr;
+	}
+
+	swnode->property_group.name = "properties";
+	swnode->property_group.attrs = group_attrs;
+	swnode->property_attrs = property_attrs;
+	swnode->properties = props;
+
+	return sysfs_create_group(&swnode->kobj, &swnode->property_group);
+}
+
+static void software_node_release(struct kobject *kobj)
+{
+	struct software_node *swnode = kobj_to_swnode(kobj);
+
+	if (swnode->parent) {
+		ida_simple_remove(&swnode->parent->child_ids, swnode->id);
+		list_del(&swnode->entry);
+	} else {
+		ida_simple_remove(&swnode_root_ids, swnode->id);
+	}
+
+	ida_destroy(&swnode->child_ids);
+	property_entries_free(swnode->properties);
+	kfree(swnode->property_group.attrs);
+	kfree(swnode->property_attrs);
+	kfree(swnode);
+}
+
+static struct kobj_type software_node_type = {
+	.release = software_node_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+};
+
+#define NODE_NAME_MAXSIZE	11
+
+struct fwnode_handle *
+fwnode_create_software_node(const struct property_entry *properties,
+			    const struct fwnode_handle *parent)
+{
+	char node_name[NODE_NAME_MAXSIZE];
+	struct software_node *p = NULL;
+	struct software_node *swnode;
+	int ret;
+
+	if (parent) {
+		if (IS_ERR(parent))
+			return ERR_CAST(parent);
+		if (!is_software_node(parent))
+			return ERR_PTR(-EINVAL);
+		p = to_software_node(parent);
+	}
+
+	swnode = kzalloc(sizeof(*swnode), GFP_KERNEL);
+	if (!swnode)
+		return ERR_PTR(-ENOMEM);
+
+	swnode->id = ida_simple_get(p ? &p->child_ids : &swnode_root_ids, 0, 0,
+				    GFP_KERNEL);
+	if (swnode->id < 0) {
+		kfree(swnode);
+		return ERR_PTR(swnode->id);
+	}
+
+	sprintf(node_name, "node%d", swnode->id);
+
+	swnode->kobj.kset = swnode_kset;
+	swnode->fwnode.ops = &software_node_ops;
+
+	ida_init(&swnode->child_ids);
+	INIT_LIST_HEAD(&swnode->entry);
+	INIT_LIST_HEAD(&swnode->children);
+	swnode->parent = p;
+
+	if (p)
+		list_add_tail(&swnode->entry, &p->children);
+
+	ret = kobject_init_and_add(&swnode->kobj, &software_node_type,
+				   p ? &p->kobj : NULL, node_name);
+	if (ret) {
+		kobject_put(&swnode->kobj);
+		return ERR_PTR(ret);
+	}
+
+	ret = software_node_register_properties(swnode, properties);
+	if (ret) {
+		kobject_put(&swnode->kobj);
+		return ERR_PTR(ret);
+	}
+
+	kobject_uevent(&swnode->kobj, KOBJ_ADD);
+	return &swnode->fwnode;
+}
+EXPORT_SYMBOL_GPL(fwnode_create_software_node);
+
+void fwnode_remove_software_node(struct fwnode_handle *fwnode)
+{
+	struct software_node *swnode = to_software_node(fwnode);
+
+	if (!swnode)
+		return;
+
+	if (swnode->properties)
+		sysfs_remove_group(&swnode->kobj, &swnode->property_group);
+
+	kobject_put(&swnode->kobj);
+}
+EXPORT_SYMBOL_GPL(fwnode_remove_software_node);
+
+int software_node_notify(struct device *dev, unsigned long action)
+{
+	struct fwnode_handle *fwnode = dev_fwnode(dev);
+	struct software_node *swnode;
+	int ret;
+
+	if (!fwnode)
+		return 0;
+
+	if (!is_software_node(fwnode))
+		fwnode = fwnode->secondary;
+	if (!is_software_node(fwnode))
+		return 0;
+
+	swnode = to_software_node(fwnode);
+
+	switch (action) {
+	case KOBJ_ADD:
+		ret = sysfs_create_link(&dev->kobj, &swnode->kobj,
+					"software_node");
+		if (ret)
+			break;
+
+		ret = sysfs_create_link(&swnode->kobj, &dev->kobj,
+					dev_name(dev));
+		if (ret) {
+			sysfs_remove_link(&dev->kobj, "software_node");
+			break;
+		}
+		kobject_get(&swnode->kobj);
+		break;
+	case KOBJ_REMOVE:
+		sysfs_remove_link(&swnode->kobj, dev_name(dev));
+		sysfs_remove_link(&dev->kobj, "software_node");
+		kobject_put(&swnode->kobj);
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+static int __init software_node_init(void)
+{
+	swnode_kset = kset_create_and_add("software_nodes", NULL, kernel_kobj);
+	if (!swnode_kset)
+		return -ENOMEM;
+	return 0;
+}
+postcore_initcall(software_node_init);
+
+static void __exit software_node_exit(void)
+{
+	ida_destroy(&swnode_root_ids);
+	kset_unregister(swnode_kset);
+}
+__exitcall(software_node_exit);
diff --git a/include/linux/property.h b/include/linux/property.h
index ac8a1ebc4c1b..3789ec755fb6 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -311,4 +311,16 @@ fwnode_graph_get_remote_node(const struct fwnode_handle *fwnode, u32 port,
 int fwnode_graph_parse_endpoint(const struct fwnode_handle *fwnode,
 				struct fwnode_endpoint *endpoint);
 
+/* -------------------------------------------------------------------------- */
+/* Software fwnode support - when HW description is incomplete or missing */
+
+bool is_software_node(const struct fwnode_handle *fwnode);
+
+int software_node_notify(struct device *dev, unsigned long action);
+
+struct fwnode_handle *
+fwnode_create_software_node(const struct property_entry *properties,
+			    const struct fwnode_handle *parent);
+void fwnode_remove_software_node(struct fwnode_handle *fwnode);
+
 #endif /* _LINUX_PROPERTY_H_ */
-- 
2.19.1