linux-kernel - [PATCH 1/4] usb: typec: Add port registration notifier

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Date:   Wed, 24 Nov 2021 15:10:08 -0800
From:   Prashant Malani <pmalani@...omium.org>
To:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     wonchung@...gle.com, bleung@...omium.org,
        heikki.krogerus@...ux.intel.com,
        Prashant Malani <pmalani@...omium.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christian König <christian.koenig@....com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Rajat Jain <rajatja@...gle.com>,
        Rikard Falkeborn <rikard.falkeborn@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: [PATCH 1/4] usb: typec: Add port registration notifier

Introduce a blocking notifier to be called when a new Type C port gets
registered with the connector class framework.

Signed-off-by: Prashant Malani <pmalani@...omium.org>
---
NOTE: typec_port_registration_register_notify() is a bit long,
so please let me know if you have any shorter suggestions for naming
this function.

 drivers/usb/typec/class.c | 30 ++++++++++++++++++++++++++++++
 include/linux/usb/typec.h | 13 +++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index aeef453aa658..14b82109b0f5 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -16,6 +16,8 @@
 #include "bus.h"
 #include "class.h"
 
+static BLOCKING_NOTIFIER_HEAD(typec_port_registration_notifier);
+
 static DEFINE_IDA(typec_index_ida);
 
 struct class typec_class = {
@@ -1979,6 +1981,32 @@ void typec_port_register_altmodes(struct typec_port *port,
 }
 EXPORT_SYMBOL_GPL(typec_port_register_altmodes);
 
+/**
+ *  typec_port_registration_register_notify - Register a notifier for Type C port registration.
+ *  @nb: notifier block to signal
+ *
+ *  This function allows callers to get a notification when a Type C port is registered with
+ *  the connector class.
+ */
+int typec_port_registration_register_notify(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&typec_port_registration_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(typec_port_registration_register_notify);
+
+/**
+ *  typec_port_registration_unregister_notify - Unregister a notifier for Type C port registration.
+ *  @nb: notifier block to unregister
+ *
+ *  This function allows callers to unregister notifiers which were previously registered using
+ *  typec_port_registration_register_notify().
+ */
+int typec_port_registration_unregister_notify(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&typec_port_registration_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(typec_port_registration_unregister_notify);
+
 /**
  * typec_register_port - Register a USB Type-C Port
  * @parent: Parent device
@@ -2086,6 +2114,8 @@ struct typec_port *typec_register_port(struct device *parent,
 	if (ret)
 		dev_warn(&port->dev, "failed to create symlinks (%d)\n", ret);
 
+	blocking_notifier_call_chain(&typec_port_registration_notifier, 0, port);
+
 	return port;
 }
 EXPORT_SYMBOL_GPL(typec_register_port);
diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
index e2e44bb1dad8..398317835f24 100644
--- a/include/linux/usb/typec.h
+++ b/include/linux/usb/typec.h
@@ -3,6 +3,7 @@
 #ifndef __LINUX_USB_TYPEC_H
 #define __LINUX_USB_TYPEC_H
 
+#include <linux/notifier.h>
 #include <linux/types.h>
 
 /* USB Type-C Specification releases */
@@ -308,6 +309,8 @@ int typec_get_negotiated_svdm_version(struct typec_port *port);
 #if IS_REACHABLE(CONFIG_TYPEC)
 int typec_link_port(struct device *port);
 void typec_unlink_port(struct device *port);
+int typec_port_registration_register_notify(struct notifier_block *nb);
+int typec_port_registration_unregister_notify(struct notifier_block *nb);
 #else
 static inline int typec_link_port(struct device *port)
 {
@@ -315,6 +318,16 @@ static inline int typec_link_port(struct device *port)
 }
 
 static inline void typec_unlink_port(struct device *port) { }
+
+int typec_port_registration_register_notify(struct notifier_block *nb)
+{
+	return 0;
+}
+
+int typec_port_registration_unregister_notify(struct notifier_block *nb)
+{
+	return 0;
+}
 #endif
 
 #endif /* __LINUX_USB_TYPEC_H */
-- 
2.34.0.rc2.393.gf8c9666880-goog