media: cec-notifier: add cec_notifier_parse_hdmi_phandle helper

Add helper function to parse the DT for the hdmi-phandle property
and return the corresponding struct device pointer.

It takes care to avoid increasing the device refcount since all
we need is the device pointer. This pointer is used in the
notifier list as a key, but it is never accessed by the CEC driver.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reported-by: Wen Yang <wen.yang99@zte.com.cn>
Acked-by: Wen Yang <wen.yang99@zte.com.cn>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/media/cec/cec-notifier.c b/drivers/media/cec/cec-notifier.c
index dd2078b27a41..9598c7778871 100644
--- a/drivers/media/cec/cec-notifier.c
+++ b/drivers/media/cec/cec-notifier.c
@@ -11,6 +11,7 @@
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <linux/kref.h>
+#include <linux/of_platform.h>
 
 #include <media/cec.h>
 #include <media/cec-notifier.h>
@@ -127,3 +128,32 @@ void cec_notifier_unregister(struct cec_notifier *n)
 	cec_notifier_put(n);
 }
 EXPORT_SYMBOL_GPL(cec_notifier_unregister);
+
+struct device *cec_notifier_parse_hdmi_phandle(struct device *dev)
+{
+	struct platform_device *hdmi_pdev;
+	struct device *hdmi_dev = NULL;
+	struct device_node *np;
+
+	np = of_parse_phandle(dev->of_node, "hdmi-phandle", 0);
+
+	if (!np) {
+		dev_err(dev, "Failed to find HDMI node in device tree\n");
+		return ERR_PTR(-ENODEV);
+	}
+	hdmi_pdev = of_find_device_by_node(np);
+	of_node_put(np);
+	if (hdmi_pdev) {
+		hdmi_dev = &hdmi_pdev->dev;
+		/*
+		 * Note that the device struct is only used as a key into the
+		 * cec_notifiers list, it is never actually accessed.
+		 * So we decrement the reference here so we don't leak
+		 * memory.
+		 */
+		put_device(hdmi_dev);
+		return hdmi_dev;
+	}
+	return ERR_PTR(-EPROBE_DEFER);
+}
+EXPORT_SYMBOL_GPL(cec_notifier_parse_hdmi_phandle);