xen: pcpu: Use static attribute groups for sysfs entry

Instead of manual calls of device_create_file() and
device_remove_file(), assign the static attribute groups to the device
to register.  The conditional build of sysfs is done in is_visible
callback instead.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 28 insertions, 16 deletions

diff --git a/drivers/xen/pcpu.c b/drivers/xen/pcpu.c
index 0aac403d53fd..49e88f2ce7a1 100644
--- a/drivers/xen/pcpu.c
+++ b/drivers/xen/pcpu.c
@@ -132,6 +132,33 @@ static ssize_t __ref store_online(struct device *dev,
 }
 static DEVICE_ATTR(online, S_IRUGO | S_IWUSR, show_online, store_online);
 
+static struct attribute *pcpu_dev_attrs[] = {
+        &dev_attr_online.attr,
+        NULL
+};
+
+static umode_t pcpu_dev_is_visible(struct kobject *kobj,
+                                   struct attribute *attr, int idx)
+{
+        struct device *dev = kobj_to_dev(kobj);
+        /*
+         * Xen never offline cpu0 due to several restrictions
+         * and assumptions. This basically doesn't add a sys control
+         * to user, one cannot attempt to offline BSP.
+         */
+        return dev->id ? attr->mode : 0;
+}
+
+static const struct attribute_group pcpu_dev_group = {
+        .attrs = pcpu_dev_attrs,
+        .is_visible = pcpu_dev_is_visible,
+};
+
+static const struct attribute_group *pcpu_dev_groups[] = {
+        &pcpu_dev_group,
+        NULL
+};
+
 static bool xen_pcpu_online(uint32_t flags)
 {
         return !!(flags & XEN_PCPU_FLAGS_ONLINE);
@@ -181,9 +208,6 @@ static void unregister_and_remove_pcpu(struct pcpu *pcpu)
                 return;
 
         dev = &pcpu->dev;
-        if (dev->id)
-                device_remove_file(dev, &dev_attr_online);
-
         /* pcpu remove would be implicitly done */
         device_unregister(dev);
 }
@@ -200,6 +224,7 @@ static int register_pcpu(struct pcpu *pcpu)
         dev->bus = &xen_pcpu_subsys;
         dev->id = pcpu->cpu_id;
         dev->release = pcpu_release;
+        dev->groups = pcpu_dev_groups;
 
         err = device_register(dev);
         if (err) {
@@ -207,19 +232,6 @@ static int register_pcpu(struct pcpu *pcpu)
                 return err;
         }
 
-        /*
-         * Xen never offline cpu0 due to several restrictions
-         * and assumptions. This basically doesn't add a sys control
-         * to user, one cannot attempt to offline BSP.
-         */
-        if (dev->id) {
-                err = device_create_file(dev, &dev_attr_online);
-                if (err) {
-                        device_unregister(dev);
-                        return err;
-                }
-        }
-
         return 0;
 }