[PATCH v25 01/10] drivers/base: refactor cpu.c to use .is_visible()

[Eric DeVolder <eric.devolder@oracle.com>]

Greg Kroah-Hartman requested that this file use the .is_visible()
method instead of #ifdefs for the attributes in cpu.c.

 static struct attribute *cpu_root_attrs[] = {
 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
    &dev_attr_probe.attr,
    &dev_attr_release.attr,
 #endif
    &cpu_attrs[0].attr.attr,
    &cpu_attrs[1].attr.attr,
    &cpu_attrs[2].attr.attr,
    &dev_attr_kernel_max.attr,
    &dev_attr_offline.attr,
    &dev_attr_isolated.attr,
 #ifdef CONFIG_NO_HZ_FULL
    &dev_attr_nohz_full.attr,
 #endif
 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
    &dev_attr_modalias.attr,
 #endif
    NULL
 };

To that end:
 - the .is_visible() method is implemented, and IS_ENABLED(), rather
   than #ifdef, is used to determine the visibility of the attribute.
 - the DEVICE_ATTR() attributes are moved outside of #ifdefs, so that
   those structs are always present for the cpu_root_attrs[].
 - the function body of the callback functions are now wrapped with
   IS_ENABLED(); as the callback function must exist now that the
   attribute is always compiled-in (though not necessarily visible).

No functionality change intended.

Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
 drivers/base/cpu.c   | 125 +++++++++++++++++++++++++++----------------
 include/linux/tick.h |   2 +-
 2 files changed, 81 insertions(+), 46 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index c1815b9dae68..2455cbcebc87 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -82,24 +82,27 @@ void unregister_cpu(struct cpu *cpu)
 	per_cpu(cpu_sys_devices, logical_cpu) = NULL;
 	return;
 }
+#endif /* CONFIG_HOTPLUG_CPU */
 
-#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 static ssize_t cpu_probe_store(struct device *dev,
 			       struct device_attribute *attr,
 			       const char *buf,
 			       size_t count)
 {
-	ssize_t cnt;
-	int ret;
+	if (IS_ENABLED(CONFIG_ARCH_CPU_PROBE_RELEASE)) {
+		ssize_t cnt;
+		int ret;
 
-	ret = lock_device_hotplug_sysfs();
-	if (ret)
-		return ret;
+		ret = lock_device_hotplug_sysfs();
+		if (ret)
+			return ret;
 
-	cnt = arch_cpu_probe(buf, count);
+		cnt = arch_cpu_probe(buf, count);
 
-	unlock_device_hotplug();
-	return cnt;
+		unlock_device_hotplug();
+		return cnt;
+	}
+	return 0;
 }
 
 static ssize_t cpu_release_store(struct device *dev,
@@ -107,23 +110,24 @@ static ssize_t cpu_release_store(struct device *dev,
 				 const char *buf,
 				 size_t count)
 {
-	ssize_t cnt;
-	int ret;
+	if (IS_ENABLED(CONFIG_ARCH_CPU_PROBE_RELEASE)) {
+		ssize_t cnt;
+		int ret;
 
-	ret = lock_device_hotplug_sysfs();
-	if (ret)
-		return ret;
+		ret = lock_device_hotplug_sysfs();
+		if (ret)
+			return ret;
 
-	cnt = arch_cpu_release(buf, count);
+		cnt = arch_cpu_release(buf, count);
 
-	unlock_device_hotplug();
-	return cnt;
+		unlock_device_hotplug();
+		return cnt;
+	}
+	return 0;
 }
 
 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
-#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
-#endif /* CONFIG_HOTPLUG_CPU */
 
 #ifdef CONFIG_KEXEC
 #include <linux/kexec.h>
@@ -273,14 +277,14 @@ static ssize_t print_cpus_isolated(struct device *dev,
 }
 static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);
 
-#ifdef CONFIG_NO_HZ_FULL
 static ssize_t print_cpus_nohz_full(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
-	return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(tick_nohz_full_mask));
+	if (IS_ENABLED(CONFIG_NO_HZ_FULL))
+		return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(tick_nohz_full_mask));
+	return 0;
 }
 static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
-#endif
 
 static void cpu_device_release(struct device *dev)
 {
@@ -301,30 +305,32 @@ static void cpu_device_release(struct device *dev)
 	 */
 }
 
-#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 static ssize_t print_cpu_modalias(struct device *dev,
 				  struct device_attribute *attr,
 				  char *buf)
 {
 	int len = 0;
-	u32 i;
-
-	len += sysfs_emit_at(buf, len,
-			     "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
-			     CPU_FEATURE_TYPEVAL);
-
-	for (i = 0; i < MAX_CPU_FEATURES; i++)
-		if (cpu_have_feature(i)) {
-			if (len + sizeof(",XXXX\n") >= PAGE_SIZE) {
-				WARN(1, "CPU features overflow page\n");
-				break;
+	if (IS_ENABLED(CONFIG_GENERIC_CPU_AUTOPROBE)) {
+		u32 i;
+
+		len += sysfs_emit_at(buf, len,
+					"cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
+					CPU_FEATURE_TYPEVAL);
+
+		for (i = 0; i < MAX_CPU_FEATURES; i++)
+			if (cpu_have_feature(i)) {
+				if (len + sizeof(",XXXX\n") >= PAGE_SIZE) {
+					WARN(1, "CPU features overflow page\n");
+					break;
+				}
+				len += sysfs_emit_at(buf, len, ",%04X", i);
 			}
-			len += sysfs_emit_at(buf, len, ",%04X", i);
-		}
-	len += sysfs_emit_at(buf, len, "\n");
+		len += sysfs_emit_at(buf, len, "\n");
+	}
 	return len;
 }
 
+#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 static int cpu_uevent(const struct device *dev, struct kobj_uevent_env *env)
 {
 	char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
@@ -451,32 +457,61 @@ struct device *cpu_device_create(struct device *parent, void *drvdata,
 }
 EXPORT_SYMBOL_GPL(cpu_device_create);
 
-#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
-#endif
 
 static struct attribute *cpu_root_attrs[] = {
-#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 	&dev_attr_probe.attr,
 	&dev_attr_release.attr,
-#endif
 	&cpu_attrs[0].attr.attr,
 	&cpu_attrs[1].attr.attr,
 	&cpu_attrs[2].attr.attr,
 	&dev_attr_kernel_max.attr,
 	&dev_attr_offline.attr,
 	&dev_attr_isolated.attr,
-#ifdef CONFIG_NO_HZ_FULL
 	&dev_attr_nohz_full.attr,
-#endif
-#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 	&dev_attr_modalias.attr,
-#endif
 	NULL
 };
 
+static umode_t
+cpu_root_attr_is_visible(struct kobject *kobj,
+			       struct attribute *attr, int unused)
+{
+	umode_t mode = attr->mode;
+
+	if (IS_ENABLED(CONFIG_ARCH_CPU_PROBE_RELEASE)) {
+		if (attr == &dev_attr_probe.attr)
+			return mode;
+		if (attr == &dev_attr_release.attr)
+			return mode;
+	}
+	if (attr == &cpu_attrs[0].attr.attr)
+		return mode;
+	if (attr == &cpu_attrs[1].attr.attr)
+		return mode;
+	if (attr == &cpu_attrs[2].attr.attr)
+		return mode;
+	if (attr == &dev_attr_kernel_max.attr)
+		return mode;
+	if (attr == &dev_attr_offline.attr)
+		return mode;
+	if (attr == &dev_attr_isolated.attr)
+		return mode;
+	if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
+		if (attr == &dev_attr_nohz_full.attr)
+			return mode;
+	}
+	if (IS_ENABLED(CONFIG_GENERIC_CPU_AUTOPROBE)) {
+		if (attr == &dev_attr_modalias.attr)
+			return mode;
+	}
+
+	return 0;
+}
+
 static const struct attribute_group cpu_root_attr_group = {
 	.attrs = cpu_root_attrs,
+	.is_visible = cpu_root_attr_is_visible,
 };
 
 static const struct attribute_group *cpu_root_attr_groups[] = {
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 9459fef5b857..a05fdd4b21f4 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -174,9 +174,9 @@ static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
 static inline void tick_nohz_idle_stop_tick_protected(void) { }
 #endif /* !CONFIG_NO_HZ_COMMON */
 
+extern cpumask_var_t tick_nohz_full_mask;
 #ifdef CONFIG_NO_HZ_FULL
 extern bool tick_nohz_full_running;
-extern cpumask_var_t tick_nohz_full_mask;
 
 static inline bool tick_nohz_full_enabled(void)
 {
-- 
2.31.1