PM / sleep: Add support for read-only sysfs attributes

Some sysfs attributes in /sys/power/ should really be read-only,
so add support for that, convert those attributes to read-only
and drop the stub .show() routines from them.

Original-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit a1e9ca6967d68209c70e616a224efa89a6b86ca6)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

Author: rafaeljw

kernel/power/main.c

@@ -280,13 +280,7 @@ static ssize_t pm_wakeup_irq_show(struct kobject *kobj,
 	return pm_wakeup_irq ? sprintf(buf, "%u\n", pm_wakeup_irq) : -ENODATA;
 }
 
-static ssize_t pm_wakeup_irq_store(struct kobject *kobj,
-					struct kobj_attribute *attr,
-					const char *buf, size_t n)
-{
-	return -EINVAL;
-}
-power_attr(pm_wakeup_irq);
+power_attr_ro(pm_wakeup_irq);
 
 #else /* !CONFIG_PM_SLEEP_DEBUG */
 static inline void pm_print_times_init(void) {}
@@ -564,14 +558,7 @@ static ssize_t pm_trace_dev_match_show(struct kobject *kobj,
 	return show_trace_dev_match(buf, PAGE_SIZE);
 }
 
-static ssize_t
-pm_trace_dev_match_store(struct kobject *kobj, struct kobj_attribute *attr,
-			 const char *buf, size_t n)
-{
-	return -EINVAL;
-}
-
-power_attr(pm_trace_dev_match);
+power_attr_ro(pm_trace_dev_match);
 
 #endif /* CONFIG_PM_TRACE */
 

kernel/power/power.h

@@ -77,6 +77,15 @@ static struct kobj_attribute _name##_attr = {	\
 	.store	= _name##_store,		\
 }
 
+#define power_attr_ro(_name) \
+static struct kobj_attribute _name##_attr = {	\
+	.attr	= {				\
+		.name = __stringify(_name),	\
+		.mode = S_IRUGO,		\
+	},					\
+	.show	= _name##_show,			\
+}
+
 /* Preferred image size in bytes (default 500 MB) */
 extern unsigned long image_size;
 /* Size of memory reserved for drivers (default SPARE_PAGES x PAGE_SIZE) */