Cc: Greg KH <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Lezcano <redacted>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
---

V5:
  - Decrease log level from 'info' to 'debug'
  - Remove the refcount, it is pointless, lifetime cycle is already
    handled by the device refcounting. The dtpm node allocator is in
    charge of freeing it.
  - Rename the functions to 'dtpm_add, dtpm_del, dtpm_lookup'
  - Fix missing kfrees when deleting the node from the list
V4:
  - Fixed typo in the commit log
V2:
  - Fixed error code path by dropping lock
---
 drivers/powercap/dtpm.c     | 121 ++++++++++++++++++++++++++++++++++--
 drivers/powercap/dtpm_cpu.c |   8 +--
 include/linux/dtpm.h        |   6 ++
 3 files changed, 127 insertions(+), 8 deletions(-)

diff --git a/drivers/powercap/dtpm.c b/drivers/powercap/dtpm.c
index 58433b8ef9a1..8df7adeed0cf 100644
--- a/drivers/powercap/dtpm.c
+++ b/drivers/powercap/dtpm.c

@@ -34,6 +34,14 @@ static DEFINE_MUTEX(dtpm_lock);
 static struct powercap_control_type *pct;
 static struct dtpm *root;
 
+struct dtpm_node {
+	const char *name;
+	struct dtpm *dtpm;
+	struct list_head node;
+};
+
+static LIST_HEAD(dtpm_list);
+
 static int get_time_window_us(struct powercap_zone *pcz, int cid, u64 *window)
 {
 	return -ENOSYS;

@@ -152,6 +160,113 @@ static int __dtpm_update_power(struct dtpm *dtpm)
 	return ret;
 }
 
+static struct dtpm *__dtpm_lookup(const char *name)
+{
+	struct dtpm_node *node;
+
+	list_for_each_entry(node, &dtpm_list, node) {
+		if (!strcmp(name, node->name))
+			return node->dtpm;
+	}
+
+	return NULL;
+}
+
+/**
+ * dtpm_lookup - Lookup for a registered dtpm node given its name
+ * @name: the name of the dtpm device
+ *
+ * The function looks up in the list of the registered dtpm
+ * devices. This function must be called to create a dtpm node in the
+ * powercap hierarchy.
+ *
+ * Return: a pointer to a dtpm structure, NULL if not found.
+ */
+struct dtpm *dtpm_lookup(const char *name)
+{
+	struct dtpm *dtpm;
+
+	mutex_lock(&dtpm_lock);
+	dtpm = __dtpm_lookup(name);
+	mutex_unlock(&dtpm_lock);
+
+	return dtpm;
+}
+
+/**
+ * dtpm_add - Add the dtpm in the dtpm list
+ * @name: a name used as an identifier
+ * @dtpm: the dtpm node to be registered
+ *
+ * Stores the dtpm device in a list. The list contains all the devices
+ * which are power capable in terms of limitation and power
+ * consumption measurements. Even if conceptually, a power capable
+ * device won't register itself twice, the function will check if it
+ * was already registered in order to prevent a misuse of the API.
+ *
+ * Return: 0 on success, -EEXIST if the device name is already present
+ * in the list, -ENOMEM in case of memory allocation failure.
+ */
+int dtpm_add(const char *name, struct dtpm *dtpm)