[PATCH v24 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 #ifdefs guarding the attributes in the cpu_root_attrs[] are moved
   to the corresponding callback function; 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 | 67 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 53 insertions(+), 14 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index c1815b9dae68..75fa46a567a1 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -82,13 +82,14 @@ 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)
 {
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 	ssize_t cnt;
 	int ret;
 
@@ -100,6 +101,9 @@ static ssize_t cpu_probe_store(struct device *dev,
 
 	unlock_device_hotplug();
 	return cnt;
+#else
+	return 0;
+#endif
 }
 
 static ssize_t cpu_release_store(struct device *dev,
@@ -107,6 +111,7 @@ static ssize_t cpu_release_store(struct device *dev,
 				 const char *buf,
 				 size_t count)
 {
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 	ssize_t cnt;
 	int ret;
 
@@ -118,12 +123,13 @@ static ssize_t cpu_release_store(struct device *dev,
 
 	unlock_device_hotplug();
 	return cnt;
+#else
+	return 0;
+#endif
 }
 
 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 +279,16 @@ 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)
 {
+#ifdef CONFIG_NO_HZ_FULL
 	return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(tick_nohz_full_mask));
+#else
+	return 0;
+#endif
 }
 static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
-#endif
 
 static void cpu_device_release(struct device *dev)
 {
@@ -301,12 +309,12 @@ 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;
+#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 	u32 i;
 
 	len += sysfs_emit_at(buf, len,
@@ -322,9 +330,11 @@ static ssize_t print_cpu_modalias(struct device *dev,
 			len += sysfs_emit_at(buf, len, ",%04X", i);
 		}
 	len += sysfs_emit_at(buf, len, "\n");
+#endif
 	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 +461,61 @@ 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[] = {
-- 
2.31.1