ACPI / hotplug: Use device offline/online for graceful hot-removal

Modify the generic ACPI hotplug code to be able to check if devices
scheduled for hot-removal may be gracefully removed from the system
using the device offline/online mechanism introduced previously.

Namely, make acpi_scan_hot_remove() handling device hot-removal call
device_offline() for all physical companions of the ACPI device nodes
involved in the operation and check the results.  If any of the
device_offline() calls fails, the function will not progress to the
removal phase (which cannot be aborted), unless its (new) force
argument is set (in case of a failing offline it will put the devices
offlined by it back online).

In support of 'forced' device hot-removal, add a new sysfs attribute
'force_remove' that will reside under /sys/firmware/acpi/hotplug/.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Toshi Kani <toshi.kani@hp.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index fcae5fa2e1b3..5c5d1624fa2c 100644
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -780,6 +780,33 @@ void acpi_sysfs_add_hotplug_profile(struct acpi_hotplug_profile *hotplug,
         pr_err(PREFIX "Unable to add hotplug profile '%s'\n", name);
 }
 
+static ssize_t force_remove_show(struct kobject *kobj,
+                                 struct kobj_attribute *attr, char *buf)
+{
+        return sprintf(buf, "%d\n", !!acpi_force_hot_remove);
+}
+
+static ssize_t force_remove_store(struct kobject *kobj,
+                                  struct kobj_attribute *attr,
+                                  const char *buf, size_t size)
+{
+        bool val;
+        int ret;
+
+        ret = strtobool(buf, &val);
+        if (ret < 0)
+                return ret;
+
+        lock_device_hotplug();
+        acpi_force_hot_remove = val;
+        unlock_device_hotplug();
+        return size;
+}
+
+static const struct kobj_attribute force_remove_attr =
+        __ATTR(force_remove, S_IRUGO | S_IWUSR, force_remove_show,
+               force_remove_store);
+
 int __init acpi_sysfs_init(void)
 {
         int result;
@@ -789,6 +816,10 @@ int __init acpi_sysfs_init(void)
                 return result;
 
         hotplug_kobj = kobject_create_and_add("hotplug", acpi_kobj);
+        result = sysfs_create_file(hotplug_kobj, &force_remove_attr.attr);
+        if (result)
+                return result;
+
         result = sysfs_create_file(acpi_kobj, &pm_profile_attr.attr);
         return result;
 }