From 3068a254d5519cd5116f61297462da6d1aa84c20 Mon Sep 17 00:00:00 2001
From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Date: Thu, 6 Jul 2017 11:42:00 +0200
Subject: [PATCH] rtc: introduce new registration method

Introduce rtc_register_device() to register an already allocated and
initialized struct rtc_device. It automatically sets up the owner and the
two steps allocation/registration will allow to remove race conditions in
the IRQ handling of some driver. It also allows to properly extend the core
without adding more arguments to rtc_device_register().

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
---
 drivers/rtc/class.c | 84 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/rtc.h |  7 ++++
 2 files changed, 91 insertions(+)

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 93ce88e1b1cb..58e2a05765bb 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -150,6 +150,7 @@ static SIMPLE_DEV_PM_OPS(rtc_class_dev_pm_ops, rtc_suspend, rtc_resume);
 #define RTC_CLASS_DEV_PM_OPS	NULL
 #endif
 
+/* Ensure the caller will set the id before releasing the device */
 static struct rtc_device *rtc_allocate_device(void)
 {
 	struct rtc_device *rtc;
@@ -372,6 +373,89 @@ void devm_rtc_device_unregister(struct device *dev, struct rtc_device *rtc)
 }
 EXPORT_SYMBOL_GPL(devm_rtc_device_unregister);
 
+static void devm_rtc_release_device(struct device *dev, void *res)
+{
+	struct rtc_device *rtc = *(struct rtc_device **)res;
+
+	if (rtc->registered)
+		rtc_device_unregister(rtc);
+	else
+		put_device(&rtc->dev);
+}
+
+struct rtc_device *devm_rtc_allocate_device(struct device *dev)
+{
+	struct rtc_device **ptr, *rtc;
+	int id, err;
+
+	id = rtc_device_get_id(dev);
+	if (id < 0)
+		return ERR_PTR(id);
+
+	ptr = devres_alloc(devm_rtc_release_device, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr) {
+		err = -ENOMEM;
+		goto exit_ida;
+	}
+
+	rtc = rtc_allocate_device();
+	if (!rtc) {
+		err = -ENOMEM;
+		goto exit_devres;
+	}
+
+	*ptr = rtc;
+	devres_add(dev, ptr);
+
+	rtc->id = id;
+	rtc->dev.parent = dev;
+	dev_set_name(&rtc->dev, "rtc%d", id);
+
+	return rtc;
+
+exit_devres:
+	devres_free(ptr);
+exit_ida:
+	ida_simple_remove(&rtc_ida, id);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
+
+int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
+{
+	struct rtc_wkalrm alrm;
+	int err;
+
+	if (!rtc->ops)
+		return -EINVAL;
+
+	rtc->owner = owner;
+
+	/* Check to see if there is an ALARM already set in hw */
+	err = __rtc_read_alarm(rtc, &alrm);
+	if (!err && !rtc_valid_tm(&alrm.time))
+		rtc_initialize_alarm(rtc, &alrm);
+
+	rtc_dev_prepare(rtc);
+
+	err = cdev_device_add(&rtc->char_dev, &rtc->dev);
+	if (err)
+		dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
+			 MAJOR(rtc->dev.devt), rtc->id);
+	else
+		dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
+			MAJOR(rtc->dev.devt), rtc->id);
+
+	rtc_proc_add_device(rtc);
+
+	rtc->registered = true;
+	dev_info(rtc->dev.parent, "registered as %s\n",
+		 dev_name(&rtc->dev));
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__rtc_register_device);
+
 static int __init rtc_init(void)
 {
 	rtc_class = class_create(THIS_MODULE, "rtc");
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index d354f56e0cf5..8e4a5f44f59e 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -142,6 +142,8 @@ struct rtc_device {
 	/* Some hardware can't support UIE mode */
 	int uie_unsupported;
 
+	bool registered;
+
 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
 	struct work_struct uie_task;
 	struct timer_list uie_timer;
@@ -163,6 +165,8 @@ extern struct rtc_device *devm_rtc_device_register(struct device *dev,
 					const char *name,
 					const struct rtc_class_ops *ops,
 					struct module *owner);
+struct rtc_device *devm_rtc_allocate_device(struct device *dev);
+int __rtc_register_device(struct module *owner, struct rtc_device *rtc);
 extern void rtc_device_unregister(struct rtc_device *rtc);
 extern void devm_rtc_device_unregister(struct device *dev,
 					struct rtc_device *rtc);
@@ -218,6 +222,9 @@ static inline bool is_leap_year(unsigned int year)
 	return (!(year % 4) && (year % 100)) || !(year % 400);
 }
 
+#define rtc_register_device(device) \
+	__rtc_register_device(THIS_MODULE, device)
+
 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 extern int rtc_hctosys_ret;
 #else
-- 
2.20.1