linux-kernel - [PATCH v4 1/5] rtc: sysfs: facilitate attribute add to rtc device

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Date:   Tue, 10 Jul 2018 09:44:15 +0000
From:   Denis OSTERLAND <denis.osterland@...hl.com>
To:     "a.zummo@...ertech.it" <a.zummo@...ertech.it>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "m.grzeschik@...gutronix.de" <m.grzeschik@...gutronix.de>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        Denis OSTERLAND <denis.osterland@...hl.com>
Subject: [PATCH v4 1/5] rtc: sysfs: facilitate attribute add to rtc device

From: Denis Osterland <Denis.Osterland@...hl.com>

This patches addresses following problem:
rtc_allocate_device
devm_device_add_group  <-- kernel oops / null pointer, because
			sysfs entry does not yet exist
rtc_register_device
rc = devm_device_add_group
if (rc)
	return rc;     <-- forbidden to return error code
			after device register

In case groups were not yet registered (kobj.state_in_sysfs == 0)
rtc_add_group just addes given group to dev.groups,
otherwise it uses devm_device_add_group.

Signed-off-by: Denis Osterland <Denis.Osterland@...hl.com>
---
 drivers/rtc/rtc-core.h  |  6 ++++++
 drivers/rtc/rtc-sysfs.c | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/drivers/rtc/rtc-core.h b/drivers/rtc/rtc-core.h
index 0abf98983e13..81d1c3ce7a96 100644
--- a/drivers/rtc/rtc-core.h
+++ b/drivers/rtc/rtc-core.h
@@ -40,9 +40,15 @@ static inline void rtc_proc_del_device(struct rtc_device *rtc)
 
 #ifdef CONFIG_RTC_INTF_SYSFS
 const struct attribute_group **rtc_get_dev_attribute_groups(void);
+int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp);
 #else
 static inline const struct attribute_group **rtc_get_dev_attribute_groups(void)
 {
 	return NULL;
 }
+static inline
+int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
+{
+	return 0;
+}
 #endif
diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 454da38c6012..9a177b8f761b 100644
--- a/drivers/rtc/rtc-sysfs.c
+++ b/drivers/rtc/rtc-sysfs.c
@@ -317,3 +317,42 @@ const struct attribute_group **rtc_get_dev_attribute_groups(void)
 {
 	return rtc_attr_groups;
 }
+
+static size_t rtc_group_count(struct rtc_device *rtc)
+{
+	const struct attribute_group **groups = rtc->dev.groups;
+	size_t cnt = 0;
+
+	if (groups)
+		for (; *groups; groups++)
+			cnt++;
+
+	return cnt;
+}
+
+static inline int
+__rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
+{
+	size_t cnt = rtc_group_count(rtc);
+	const struct attribute_group **groups, **old;
+
+	groups = devm_kzalloc(&rtc->dev, (cnt+2)*sizeof(*groups), GFP_KERNEL);
+	if (IS_ERR_OR_NULL(groups))
+		return PTR_ERR(groups);
+	memcpy(groups, rtc->dev.groups, cnt*sizeof(*groups));
+	groups[cnt] = grp;
+
+	old = rtc->dev.groups;
+	rtc->dev.groups = groups;
+	if (old != rtc_attr_groups)
+		devm_kfree(&rtc->dev, old);
+
+	return 0;
+}
+
+int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
+{
+	return rtc->dev.kobj.state_in_sysfs ?
+		devm_device_add_group(&rtc->dev, grp) :
+		__rtc_add_group(rtc, grp);
+}
-- 
2.18.0



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