ACPI / property: Expose data-only subnodes via sysfs

Add infrastructure needed to expose data-only subnodes of ACPI
device objects introduced previously via sysfs.

Each data-only subnode is represented as a sysfs directory under
the directory corresponding to its parent object (a device or a
data-only subnode).  Each of them has a "path" attribute (containing
the full ACPI namespace path to the object the subnode data come from)
at this time.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>

3 files changed, 116 insertions, 15 deletions

diff --git a/drivers/acpi/device_sysfs.c b/drivers/acpi/device_sysfs.c
index 4ab4582e586b..707cf6213bc2 100644
--- a/drivers/acpi/device_sysfs.c
+++ b/drivers/acpi/device_sysfs.c
@@ -26,6 +26,106 @@
 
 #include "internal.h"
 
+static ssize_t acpi_object_path(acpi_handle handle, char *buf)
+{
+        struct acpi_buffer path = {ACPI_ALLOCATE_BUFFER, NULL};
+        int result;
+
+        result = acpi_get_name(handle, ACPI_FULL_PATHNAME, &path);
+        if (result)
+                return result;
+
+        result = sprintf(buf, "%s\n", (char*)path.pointer);
+        kfree(path.pointer);
+        return result;
+}
+
+struct acpi_data_node_attr {
+        struct attribute attr;
+        ssize_t (*show)(struct acpi_data_node *, char *);
+        ssize_t (*store)(struct acpi_data_node *, const char *, size_t count);
+};
+
+#define DATA_NODE_ATTR(_name)                   \
+        static struct acpi_data_node_attr data_node_##_name =   \
+                __ATTR(_name, 0444, data_node_show_##_name, NULL)
+
+static ssize_t data_node_show_path(struct acpi_data_node *dn, char *buf)
+{
+        return acpi_object_path(dn->handle, buf);
+}
+
+DATA_NODE_ATTR(path);
+
+static struct attribute *acpi_data_node_default_attrs[] = {
+        &data_node_path.attr,
+        NULL
+};
+
+#define to_data_node(k) container_of(k, struct acpi_data_node, kobj)
+#define to_attr(a) container_of(a, struct acpi_data_node_attr, attr)
+
+static ssize_t acpi_data_node_attr_show(struct kobject *kobj,
+                                        struct attribute *attr, char *buf)
+{
+        struct acpi_data_node *dn = to_data_node(kobj);
+        struct acpi_data_node_attr *dn_attr = to_attr(attr);
+
+        return dn_attr->show ? dn_attr->show(dn, buf) : -ENXIO;
+}
+
+static const struct sysfs_ops acpi_data_node_sysfs_ops = {
+        .show   = acpi_data_node_attr_show,
+};
+
+static void acpi_data_node_release(struct kobject *kobj)
+{
+        struct acpi_data_node *dn = to_data_node(kobj);
+        complete(&dn->kobj_done);
+}
+
+static struct kobj_type acpi_data_node_ktype = {
+        .sysfs_ops = &acpi_data_node_sysfs_ops,
+        .default_attrs = acpi_data_node_default_attrs,
+        .release = acpi_data_node_release,
+};
+
+static void acpi_expose_nondev_subnodes(struct kobject *kobj,
+                                        struct acpi_device_data *data)
+{
+        struct list_head *list = &data->subnodes;
+        struct acpi_data_node *dn;
+
+        if (list_empty(list))
+                return;
+
+        list_for_each_entry(dn, list, sibling) {
+                int ret;
+
+                init_completion(&dn->kobj_done);
+                ret = kobject_init_and_add(&dn->kobj, &acpi_data_node_ktype,
+                                           kobj, dn->name);
+                if (ret)
+                        acpi_handle_err(dn->handle, "Failed to expose (%d)\n", ret);
+                else
+                        acpi_expose_nondev_subnodes(&dn->kobj, &dn->data);
+        }
+}
+
+static void acpi_hide_nondev_subnodes(struct acpi_device_data *data)
+{
+        struct list_head *list = &data->subnodes;
+        struct acpi_data_node *dn;
+
+        if (list_empty(list))
+                return;
+
+        list_for_each_entry_reverse(dn, list, sibling) {
+                acpi_hide_nondev_subnodes(&dn->data);
+                kobject_put(&dn->kobj);
+        }
+}
+
 /**
  * create_pnp_modalias - Create hid/cid(s) string for modalias and uevent
  * @acpi_dev: ACPI device object.
@@ -323,20 +423,12 @@ static ssize_t acpi_device_adr_show(struct device *dev,
 }
 static DEVICE_ATTR(adr, 0444, acpi_device_adr_show, NULL);
 
-static ssize_t
-acpi_device_path_show(struct device *dev, struct device_attribute *attr, char *buf) {
+static ssize_t acpi_device_path_show(struct device *dev,
+                                     struct device_attribute *attr, char *buf)
+{
         struct acpi_device *acpi_dev = to_acpi_device(dev);
-        struct acpi_buffer path = {ACPI_ALLOCATE_BUFFER, NULL};
-        int result;
-
-        result = acpi_get_name(acpi_dev->handle, ACPI_FULL_PATHNAME, &path);
-        if (result)
-                goto end;
 
-        result = sprintf(buf, "%s\n", (char*)path.pointer);
-        kfree(path.pointer);
-end:
-        return result;
+        return acpi_object_path(acpi_dev->handle, buf);
 }
 static DEVICE_ATTR(path, 0444, acpi_device_path_show, NULL);
 
@@ -475,6 +567,8 @@ int acpi_device_setup_files(struct acpi_device *dev)
                                                     &dev_attr_real_power_state);
         }
 
+        acpi_expose_nondev_subnodes(&dev->dev.kobj, &dev->data);
+
 end:
         return result;
 }
@@ -485,6 +579,8 @@ end:
  */
 void acpi_device_remove_files(struct acpi_device *dev)
 {
+        acpi_hide_nondev_subnodes(&dev->data);
+
         if (dev->flags.power_manageable) {
                 device_remove_file(&dev->dev, &dev_attr_power_state);
                 if (dev->power.flags.power_resources)
diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
index 17c436de376b..333f9146d19e 100644
--- a/drivers/acpi/property.c
+++ b/drivers/acpi/property.c
@@ -64,12 +64,13 @@ static bool acpi_nondev_subnode_ok(acpi_handle scope,
                 goto fail;
 
         if (acpi_extract_properties(buf.pointer, &dn->data))
-                dn->data.pointer = buf.pointer;
+                dn->handle = handle;
 
         if (acpi_enumerate_nondev_subnodes(scope, buf.pointer, &dn->data))
-                dn->data.pointer = buf.pointer;
+                dn->handle = handle;
 
-        if (dn->data.pointer) {
+        if (dn->handle) {
+                dn->data.pointer = buf.pointer;
                 list_add_tail(&dn->sibling, list);
                 return true;
         }
@@ -302,6 +303,7 @@ static void acpi_destroy_nondev_subnodes(struct list_head *list)
 
         list_for_each_entry_safe_reverse(dn, next, list, sibling) {
                 acpi_destroy_nondev_subnodes(&dn->data.subnodes);
+                wait_for_completion(&dn->kobj_done);
                 list_del(&dn->sibling);
                 ACPI_FREE((void *)dn->data.pointer);
                 kfree(dn);
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 79cfee646d6b..e0d7c193d6e0 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -382,9 +382,12 @@ struct acpi_device {
 /* Non-device subnode */
 struct acpi_data_node {
         const char *name;
+        acpi_handle handle;
         struct fwnode_handle fwnode;
         struct acpi_device_data data;
         struct list_head sibling;
+        struct kobject kobj;
+        struct completion kobj_done;
 };
 
 static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent)