regulator: event: Add regulator netlink event support

This commit introduces netlink event support to the regulator subsystem.

Changes:
- Introduce event.c and regnl.h for netlink event handling.
- Implement reg_generate_netlink_event to broadcast regulator events.
- Update Makefile to include the new event.c file.

Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
Link: https://lore.kernel.org/r/20231205105207.1262928-1-naresh.solanki@9elements.com
Signed-off-by: Mark Brown <broonie@kernel.org>

5 files changed, 133 insertions, 1 deletions

diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index f3ec24691378..550145f82726 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -56,6 +56,16 @@ config REGULATOR_USERSPACE_CONSUMER
 
 	  If unsure, say no.
 
+config REGULATOR_NETLINK_EVENTS
+	bool "Enable support for receiving regulator events via netlink"
+	depends on NET
+	help
+	  Enabling this option allows the kernel to broadcast regulator events using
+	  the netlink mechanism. User-space applications can subscribe to these events
+	  for real-time updates on various regulator events.
+
+	  If unsure, say no.
+
 config REGULATOR_88PG86X
 	tristate "Marvell 88PG86X voltage regulators"
 	depends on I2C
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index b2b059b5ee56..46fb569e6be8 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -5,6 +5,7 @@
 
 
 obj-$(CONFIG_REGULATOR) += core.o dummy.o fixed-helper.o helpers.o devres.o irq_helpers.o
+obj-$(CONFIG_REGULATOR_NETLINK_EVENTS) += event.o
 obj-$(CONFIG_OF) += of_regulator.o
 obj-$(CONFIG_REGULATOR_FIXED_VOLTAGE) += fixed.o
 obj-$(CONFIG_REGULATOR_VIRTUAL_CONSUMER) += virtual.o
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 4aa9ec8c22f3..a968dabb48f5 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -33,6 +33,7 @@
 
 #include "dummy.h"
 #include "internal.h"
+#include "regnl.h"
 
 static DEFINE_WW_CLASS(regulator_ww_class);
 static DEFINE_MUTEX(regulator_nesting_mutex);
@@ -4854,7 +4855,23 @@ static int _notifier_call_chain(struct regulator_dev *rdev,
 				  unsigned long event, void *data)
 {
 	/* call rdev chain first */
-	return blocking_notifier_call_chain(&rdev->notifier, event, data);
+	int ret =  blocking_notifier_call_chain(&rdev->notifier, event, data);
+
+	if (IS_REACHABLE(CONFIG_REGULATOR_NETLINK_EVENTS)) {
+		struct device *parent = rdev->dev.parent;
+		const char *rname = rdev_get_name(rdev);
+		char name[32];
+
+		/* Avoid duplicate debugfs directory names */
+		if (parent && rname == rdev->desc->name) {
+			snprintf(name, sizeof(name), "%s-%s", dev_name(parent),
+				 rname);
+			rname = name;
+		}
+		reg_generate_netlink_event(rname, event);
+	}
+
+	return ret;
 }
 
 int _regulator_bulk_get(struct device *dev, int num_consumers,
diff --git a/drivers/regulator/event.c b/drivers/regulator/event.c
new file mode 100644
index 000000000000..0ec58f306b38
--- /dev/null
+++ b/drivers/regulator/event.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Regulator event over netlink
+ *
+ * Author: Naresh Solanki <Naresh.Solanki@9elements.com>
+ */
+
+#include <regulator/regulator.h>
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "regnl.h"
+
+static unsigned int reg_event_seqnum;
+
+static const struct genl_multicast_group reg_event_mcgrps[] = {
+	{ .name = REG_GENL_MCAST_GROUP_NAME, },
+};
+
+static struct genl_family reg_event_genl_family __ro_after_init = {
+	.module = THIS_MODULE,
+	.name = REG_GENL_FAMILY_NAME,
+	.version = REG_GENL_VERSION,
+	.maxattr = REG_GENL_ATTR_MAX,
+	.mcgrps = reg_event_mcgrps,
+	.n_mcgrps = ARRAY_SIZE(reg_event_mcgrps),
+};
+
+int reg_generate_netlink_event(const char *reg_name, u64 event)
+{
+	struct sk_buff *skb;
+	struct nlattr *attr;
+	struct reg_genl_event *edata;
+	void *msg_header;
+	int size;
+
+	/* allocate memory */
+	size = nla_total_size(sizeof(struct reg_genl_event)) +
+	    nla_total_size(0);
+
+	skb = genlmsg_new(size, GFP_ATOMIC);
+	if (!skb)
+		return -ENOMEM;
+
+	/* add the genetlink message header */
+	msg_header = genlmsg_put(skb, 0, reg_event_seqnum++,
+				 &reg_event_genl_family, 0,
+				 REG_GENL_CMD_EVENT);
+	if (!msg_header) {
+		nlmsg_free(skb);
+		return -ENOMEM;
+	}
+
+	/* fill the data */
+	attr = nla_reserve(skb, REG_GENL_ATTR_EVENT, sizeof(struct reg_genl_event));
+	if (!attr) {
+		nlmsg_free(skb);
+		return -EINVAL;
+	}
+
+	edata = nla_data(attr);
+	memset(edata, 0, sizeof(struct reg_genl_event));
+
+	strscpy(edata->reg_name, reg_name, sizeof(edata->reg_name));
+	edata->event = event;
+
+	/* send multicast genetlink message */
+	genlmsg_end(skb, msg_header);
+	size = genlmsg_multicast(&reg_event_genl_family, skb, 0, 0, GFP_ATOMIC);
+
+	return size;
+}
+
+static int __init reg_event_genetlink_init(void)
+{
+	return genl_register_family(&reg_event_genl_family);
+}
+
+static int __init reg_event_init(void)
+{
+	int error;
+
+	/* create genetlink for acpi event */
+	error = reg_event_genetlink_init();
+	if (error)
+		pr_warn("Failed to create genetlink family for reg event\n");
+
+	return 0;
+}
+
+fs_initcall(reg_event_init);
diff --git a/drivers/regulator/regnl.h b/drivers/regulator/regnl.h
new file mode 100644
index 000000000000..bcba16cc05cc
--- /dev/null
+++ b/drivers/regulator/regnl.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Regulator event over netlink
+ *
+ * Author: Naresh Solanki <Naresh.Solanki@9elements.com>
+ */
+
+#ifndef __REGULATOR_EVENT_H
+#define __REGULATOR_EVENT_H
+
+int reg_generate_netlink_event(const char *reg_name, u64 event);
+
+#endif