[PATCH 1/4] video: add HDMI state notifier support

[hverkuil@xs4all.nl (Hans Verkuil)]

From: Hans Verkuil <hans.verkuil@cisco.com>

Add support for HDMI hotplug and EDID notifiers, which is used to convey
information from HDMI drivers to their CEC and audio counterparts.

Based on an earlier version from Russell King:

https://patchwork.kernel.org/patch/9277043/

The hdmi_notifier is a reference counted object containing the HDMI state
of an HDMI device.

When a new notifier is registered the current state will be reported to
that notifier at registration time.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
---
 drivers/video/Kconfig         |   3 +
 drivers/video/Makefile        |   1 +
 drivers/video/hdmi-notifier.c | 134 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/hdmi-notifier.h | 109 ++++++++++++++++++++++++++++++++++
 4 files changed, 247 insertions(+)
 create mode 100644 drivers/video/hdmi-notifier.c
 create mode 100644 include/linux/hdmi-notifier.h

diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 3c20af9..1ee7b9f 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -36,6 +36,9 @@ config VIDEOMODE_HELPERS
 config HDMI
 	bool
 
+config HDMI_NOTIFIERS
+	bool
+
 if VT
 	source "drivers/video/console/Kconfig"
 endif
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 9ad3c17..65f5649 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -1,5 +1,6 @@
 obj-$(CONFIG_VGASTATE)            += vgastate.o
 obj-$(CONFIG_HDMI)                += hdmi.o
+obj-$(CONFIG_HDMI_NOTIFIERS)      += hdmi-notifier.o
 
 obj-$(CONFIG_VT)		  += console/
 obj-$(CONFIG_LOGO)		  += logo/
diff --git a/drivers/video/hdmi-notifier.c b/drivers/video/hdmi-notifier.c
new file mode 100644
index 0000000..29e4225
--- /dev/null
+++ b/drivers/video/hdmi-notifier.c
@@ -0,0 +1,134 @@
+#include <linux/export.h>
+#include <linux/hdmi-notifier.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+
+static LIST_HEAD(hdmi_notifiers);
+static DEFINE_MUTEX(hdmi_notifiers_lock);
+
+struct hdmi_notifier *hdmi_notifier_get(struct device *dev)
+{
+	struct hdmi_notifier *n;
+
+	mutex_lock(&hdmi_notifiers_lock);
+	list_for_each_entry(n, &hdmi_notifiers, head) {
+		if (n->dev == dev) {
+			mutex_unlock(&hdmi_notifiers_lock);
+			kref_get(&n->kref);
+			return n;
+		}
+	}
+	n = kzalloc(sizeof(*n), GFP_KERNEL);
+	if (!n)
+		goto unlock;
+	n->dev = dev;
+	mutex_init(&n->lock);
+	BLOCKING_INIT_NOTIFIER_HEAD(&n->notifiers);
+	kref_init(&n->kref);
+	list_add_tail(&n->head, &hdmi_notifiers);
+unlock:
+	mutex_unlock(&hdmi_notifiers_lock);
+	return n;
+}
+EXPORT_SYMBOL_GPL(hdmi_notifier_get);
+
+static void hdmi_notifier_release(struct kref *kref)
+{
+	struct hdmi_notifier *n =
+		container_of(kref, struct hdmi_notifier, kref);
+
+	mutex_lock(&hdmi_notifiers_lock);
+	list_del(&n->head);
+	mutex_unlock(&hdmi_notifiers_lock);
+	kfree(n->edid);
+	kfree(n);
+}
+
+void hdmi_notifier_put(struct hdmi_notifier *n)
+{
+	kref_put(&n->kref, hdmi_notifier_release);
+}
+EXPORT_SYMBOL_GPL(hdmi_notifier_put);
+
+int hdmi_notifier_register(struct hdmi_notifier *n, struct notifier_block *nb)
+{
+	int ret = blocking_notifier_chain_register(&n->notifiers, nb);
+
+	if (ret)
+		return ret;
+	kref_get(&n->kref);
+	mutex_lock(&n->lock);
+	if (n->connected) {
+		blocking_notifier_call_chain(&n->notifiers, HDMI_CONNECTED, n);
+		if (n->edid_size)
+			blocking_notifier_call_chain(&n->notifiers, HDMI_NEW_EDID, n);
+		if (n->has_eld)
+			blocking_notifier_call_chain(&n->notifiers, HDMI_NEW_ELD, n);
+	}
+	mutex_unlock(&n->lock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hdmi_notifier_register);
+
+int hdmi_notifier_unregister(struct hdmi_notifier *n, struct notifier_block *nb)
+{
+	int ret = blocking_notifier_chain_unregister(&n->notifiers, nb);
+
+	if (ret == 0)
+		hdmi_notifier_put(n);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(hdmi_notifier_unregister);
+
+void hdmi_event_connect(struct hdmi_notifier *n)
+{
+	mutex_lock(&n->lock);
+	n->connected = true;
+	blocking_notifier_call_chain(&n->notifiers, HDMI_CONNECTED, n);
+	mutex_unlock(&n->lock);
+}
+EXPORT_SYMBOL_GPL(hdmi_event_connect);
+
+void hdmi_event_disconnect(struct hdmi_notifier *n)
+{
+	mutex_lock(&n->lock);
+	n->connected = false;
+	n->has_eld = false;
+	n->edid_size = 0;
+	blocking_notifier_call_chain(&n->notifiers, HDMI_DISCONNECTED, n);
+	mutex_unlock(&n->lock);
+}
+EXPORT_SYMBOL_GPL(hdmi_event_disconnect);
+
+int hdmi_event_new_edid(struct hdmi_notifier *n, const void *edid, size_t size)
+{
+	mutex_lock(&n->lock);
+	if (n->edid_allocated_size < size) {
+		void *p = kmalloc(size, GFP_KERNEL);
+
+		if (p == NULL) {
+			mutex_unlock(&n->lock);
+			return -ENOMEM;
+		}
+		kfree(n->edid);
+		n->edid = p;
+		n->edid_allocated_size = size;
+	}
+	memcpy(n->edid, edid, size);
+	n->edid_size = size;
+	blocking_notifier_call_chain(&n->notifiers, HDMI_NEW_EDID, n);
+	mutex_unlock(&n->lock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hdmi_event_new_edid);
+
+void hdmi_event_new_eld(struct hdmi_notifier *n, const u8 eld[128])
+{
+	mutex_lock(&n->lock);
+	memcpy(n->eld, eld, sizeof(n->eld));
+	n->has_eld = true;
+	blocking_notifier_call_chain(&n->notifiers, HDMI_NEW_ELD, n);
+	mutex_unlock(&n->lock);
+}
+EXPORT_SYMBOL_GPL(hdmi_event_new_eld);
diff --git a/include/linux/hdmi-notifier.h b/include/linux/hdmi-notifier.h
new file mode 100644
index 0000000..1d88db0
--- /dev/null
+++ b/include/linux/hdmi-notifier.h
@@ -0,0 +1,109 @@
+/*
+ * hdmi-notifier.h - notify interested parties of (dis)connect and EDID
+ * events
+ *
+ * Copyright 2016 Russell King <rmk+kernel@arm.linux.org.uk>
+ * Copyright 2016 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
+ */
+
+#ifndef LINUX_HDMI_NOTIFIER_H
+#define LINUX_HDMI_NOTIFIER_H
+
+#include <linux/types.h>
+#include <linux/notifier.h>
+#include <linux/kref.h>
+
+enum {
+	HDMI_CONNECTED,
+	HDMI_DISCONNECTED,
+	HDMI_NEW_EDID,
+	HDMI_NEW_ELD,
+};
+
+struct device;
+
+struct hdmi_notifier {
+	struct mutex lock;
+	struct list_head head;
+	struct kref kref;
+	struct blocking_notifier_head notifiers;
+	struct device *dev;
+
+	/* Current state */
+	bool connected;
+	bool has_eld;
+	unsigned char eld[128];
+	void *edid;
+	size_t edid_size;
+	size_t edid_allocated_size;
+};
+
+/**
+ * hdmi_notifier_get - find or create a new hdmi_notifier for the given device.
+ * @dev: device that sends the events.
+ *
+ * If a notifier for device @dev already exists, then increase the refcount
+ * and return that notifier.
+ *
+ * If it doesn't exist, then allocate a new notifier struct and return a
+ * pointer to that new struct.
+ *
+ * Return NULL if the memory could not be allocated.
+ */
+struct hdmi_notifier *hdmi_notifier_get(struct device *dev);
+
+/**
+ * hdmi_notifier_put - decrease refcount and delete when the refcount reaches 0.
+ * @n: notifier
+ */
+void hdmi_notifier_put(struct hdmi_notifier *n);
+
+/**
+ * hdmi_notifier_register - register the notifier with the notifier_block.
+ * @n: the HDMI notifier
+ * @nb: the notifier_block
+ */
+int hdmi_notifier_register(struct hdmi_notifier *n, struct notifier_block *nb);
+
+/**
+ * hdmi_notifier_unregister - unregister the notifier with the notifier_block.
+ * @n: the HDMI notifier
+ * @nb: the notifier_block
+ */
+int hdmi_notifier_unregister(struct hdmi_notifier *n, struct notifier_block *nb);
+
+/**
+ * hdmi_event_connect - send a connect event.
+ * @n: the HDMI notifier
+ *
+ * Send an HDMI_CONNECTED event to any registered parties.
+ */
+void hdmi_event_connect(struct hdmi_notifier *n);
+
+/**
+ * hdmi_event_disconnect - send a disconnect event.
+ * @n: the HDMI notifier
+ *
+ * Send an HDMI_DISCONNECTED event to any registered parties.
+ */
+void hdmi_event_disconnect(struct hdmi_notifier *n);
+
+/**
+ * hdmi_event_new_edid - send a new EDID event.
+ * @n: the HDMI notifier
+ *
+ * Send an HDMI_NEW_EDID event to any registered parties.
+ * This function will make a copy the EDID so it can return -ENOMEM if
+ * no memory could be allocated.
+ */
+int hdmi_event_new_edid(struct hdmi_notifier *n, const void *edid, size_t size);
+
+/**
+ * hdmi_event_new_eld - send a new ELD event.
+ * @n: the HDMI notifier
+ *
+ * Send an HDMI_NEW_ELD event to any registered parties.
+ */
+void hdmi_event_new_eld(struct hdmi_notifier *n, const u8 eld[128]);
+
+#endif
-- 
2.10.2