[media] media: add CEC notifier support

Add support for CEC notifiers, which is used to convey CEC physical address
information from video drivers to their CEC counterpart driver(s).

Based on an earlier version from Russell King:

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

The cec_notifier is a reference counted object containing the CEC physical address
state of a video 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>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

MAINTAINERS

@@ -3066,7 +3066,7 @@ F:	drivers/net/ieee802154/cc2520.c
 F:	include/linux/spi/cc2520.h
 F:	Documentation/devicetree/bindings/net/ieee802154/cc2520.txt
 
-CEC DRIVER
+CEC FRAMEWORK
 M:	Hans Verkuil <hans.verkuil@cisco.com>
 L:	linux-media@vger.kernel.org
 T:	git git://linuxtv.org/media_tree.git
@@ -3076,9 +3076,11 @@ F:	Documentation/media/kapi/cec-core.rst
 F:	Documentation/media/uapi/cec
 F:	drivers/media/cec/
 F:	drivers/media/cec-edid.c
+F:	drivers/media/cec-notifier.c
 F:	drivers/media/rc/keymaps/rc-cec.c
 F:	include/media/cec.h
 F:	include/media/cec-edid.h
+F:	include/media/cec-notifier.h
 F:	include/uapi/linux/cec.h
 F:	include/uapi/linux/cec-funcs.h
 

drivers/media/Kconfig

@@ -99,6 +99,10 @@ config MEDIA_CEC_DEBUG
 config MEDIA_CEC_EDID
 	bool
 
+config MEDIA_CEC_NOTIFIER
+	bool
+	select MEDIA_CEC_EDID
+
 #
 # Media controller
 #	Selectable only for webcam/grabbers, as other drivers don't use it

drivers/media/Makefile

@@ -6,6 +6,10 @@ ifeq ($(CONFIG_MEDIA_CEC_EDID),y)
   obj-$(CONFIG_MEDIA_SUPPORT) += cec-edid.o
 endif
 
+ifeq ($(CONFIG_MEDIA_CEC_NOTIFIER),y)
+  obj-$(CONFIG_MEDIA_SUPPORT) += cec-notifier.o
+endif
+
 ifeq ($(CONFIG_MEDIA_CEC_SUPPORT),y)
   obj-$(CONFIG_MEDIA_SUPPORT) += cec/
 endif

drivers/media/cec-notifier.c

+/*
+ * cec-notifier.c - notify CEC drivers of physical address changes
+ *
+ * Copyright 2016 Russell King <rmk+kernel@arm.linux.org.uk>
+ * Copyright 2016-2017 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
+ *
+ * This program is free software; you may redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/export.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/kref.h>
+
+#include <media/cec-notifier.h>
+#include <drm/drm_edid.h>
+
+struct cec_notifier {
+	struct mutex lock;
+	struct list_head head;
+	struct kref kref;
+	struct device *dev;
+	struct cec_adapter *cec_adap;
+	void (*callback)(struct cec_adapter *adap, u16 pa);
+
+	u16 phys_addr;
+};
+
+static LIST_HEAD(cec_notifiers);
+static DEFINE_MUTEX(cec_notifiers_lock);
+
+struct cec_notifier *cec_notifier_get(struct device *dev)
+{
+	struct cec_notifier *n;
+
+	mutex_lock(&cec_notifiers_lock);
+	list_for_each_entry(n, &cec_notifiers, head) {
+		if (n->dev == dev) {
+			kref_get(&n->kref);
+			mutex_unlock(&cec_notifiers_lock);
+			return n;
+		}
+	}
+	n = kzalloc(sizeof(*n), GFP_KERNEL);
+	if (!n)
+		goto unlock;
+	n->dev = dev;
+	n->phys_addr = CEC_PHYS_ADDR_INVALID;
+	mutex_init(&n->lock);
+	kref_init(&n->kref);
+	list_add_tail(&n->head, &cec_notifiers);
+unlock:
+	mutex_unlock(&cec_notifiers_lock);
+	return n;
+}
+EXPORT_SYMBOL_GPL(cec_notifier_get);
+
+static void cec_notifier_release(struct kref *kref)
+{
+	struct cec_notifier *n =
+		container_of(kref, struct cec_notifier, kref);
+
+	list_del(&n->head);
+	kfree(n);
+}
+
+void cec_notifier_put(struct cec_notifier *n)
+{
+	mutex_lock(&cec_notifiers_lock);
+	kref_put(&n->kref, cec_notifier_release);
+	mutex_unlock(&cec_notifiers_lock);
+}
+EXPORT_SYMBOL_GPL(cec_notifier_put);
+
+void cec_notifier_set_phys_addr(struct cec_notifier *n, u16 pa)
+{
+	mutex_lock(&n->lock);
+	n->phys_addr = pa;
+	if (n->callback)
+		n->callback(n->cec_adap, n->phys_addr);
+	mutex_unlock(&n->lock);
+}
+EXPORT_SYMBOL_GPL(cec_notifier_set_phys_addr);
+
+void cec_notifier_set_phys_addr_from_edid(struct cec_notifier *n,
+					  const struct edid *edid)
+{
+	u16 pa = CEC_PHYS_ADDR_INVALID;
+
+	if (edid && edid->extensions)
+		pa = cec_get_edid_phys_addr((const u8 *)edid,
+				EDID_LENGTH * (edid->extensions + 1), NULL);
+	cec_notifier_set_phys_addr(n, pa);
+}
+EXPORT_SYMBOL_GPL(cec_notifier_set_phys_addr_from_edid);
+
+void cec_notifier_register(struct cec_notifier *n,
+			   struct cec_adapter *adap,
+			   void (*callback)(struct cec_adapter *adap, u16 pa))
+{
+	kref_get(&n->kref);
+	mutex_lock(&n->lock);
+	n->cec_adap = adap;
+	n->callback = callback;
+	n->callback(adap, n->phys_addr);
+	mutex_unlock(&n->lock);
+}
+EXPORT_SYMBOL_GPL(cec_notifier_register);
+
+void cec_notifier_unregister(struct cec_notifier *n)
+{
+	mutex_lock(&n->lock);
+	n->callback = NULL;
+	mutex_unlock(&n->lock);
+	cec_notifier_put(n);
+}
+EXPORT_SYMBOL_GPL(cec_notifier_unregister);

include/media/cec-notifier.h

+/*
+ * cec-notifier.h - notify CEC drivers of physical address changes
+ *
+ * Copyright 2016 Russell King <rmk+kernel@arm.linux.org.uk>
+ * Copyright 2016-2017 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
+ *
+ * This program is free software; you may redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef LINUX_CEC_NOTIFIER_H
+#define LINUX_CEC_NOTIFIER_H
+
+#include <linux/types.h>
+#include <media/cec-edid.h>
+
+struct device;
+struct edid;
+struct cec_adapter;
+struct cec_notifier;
+
+#ifdef CONFIG_MEDIA_CEC_NOTIFIER
+
+/**
+ * cec_notifier_get - find or create a new cec_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 cec_notifier *cec_notifier_get(struct device *dev);
+
+/**
+ * cec_notifier_put - decrease refcount and delete when the refcount reaches 0.
+ * @n: notifier
+ */
+void cec_notifier_put(struct cec_notifier *n);
+
+/**
+ * cec_notifier_set_phys_addr - set a new physical address.
+ * @n: the CEC notifier
+ * @pa: the CEC physical address
+ *
+ * Set a new CEC physical address.
+ */
+void cec_notifier_set_phys_addr(struct cec_notifier *n, u16 pa);
+
+/**
+ * cec_notifier_set_phys_addr_from_edid - set parse the PA from the EDID.
+ * @n: the CEC notifier
+ * @edid: the struct edid pointer
+ *
+ * Parses the EDID to obtain the new CEC physical address and set it.
+ */
+void cec_notifier_set_phys_addr_from_edid(struct cec_notifier *n,
+					  const struct edid *edid);
+
+/**
+ * cec_notifier_register - register a callback with the notifier
+ * @n: the CEC notifier
+ * @adap: the CEC adapter, passed as argument to the callback function
+ * @callback: the callback function
+ */
+void cec_notifier_register(struct cec_notifier *n,
+			   struct cec_adapter *adap,
+			   void (*callback)(struct cec_adapter *adap, u16 pa));
+
+/**
+ * cec_notifier_unregister - unregister the callback from the notifier.
+ * @n: the CEC notifier
+ */
+void cec_notifier_unregister(struct cec_notifier *n);
+
+#else
+static inline struct cec_notifier *cec_notifier_get(struct device *dev)
+{
+	/* A non-NULL pointer is expected on success */
+	return (struct cec_notifier *)0xdeadfeed;
+}
+
+static inline void cec_notifier_put(struct cec_notifier *n)
+{
+}
+
+static inline void cec_notifier_set_phys_addr(struct cec_notifier *n, u16 pa)
+{
+}
+
+static inline void cec_notifier_set_phys_addr_from_edid(struct cec_notifier *n,
+							const struct edid *edid)
+{
+}
+
+#endif
+
+#endif