ACPI / hotplug: Introduce user space interface for hotplug profiles

Introduce user space interface for manipulating hotplug profiles
associated with ACPI scan handlers.

The interface consists of sysfs directories under
/sys/firmware/acpi/hotplug/, one for each hotplug profile, containing
an attribute allowing user space to manipulate the enabled field of
the corresponding profile.  Namely, switching the enabled attribute
from '0' to '1' will cause the common hotplug notify handler to be
installed for all ACPI namespace objects representing devices matching
the scan handler associated with the given hotplug profile (and
analogously for the converse switch).

Drivers willing to use the new user space interface should add their
ACPI scan handlers with the help of new funtion
acpi_scan_add_handler_with_hotplug().

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

3 files changed, 131 insertions, 0 deletions

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 3c94a732b4b3..c708e4bad967 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -42,6 +42,12 @@ void acpi_container_init(void);
 static inline void acpi_container_init(void) {}
 #endif
 
+void acpi_sysfs_add_hotplug_profile(struct acpi_hotplug_profile *hotplug,
+                                    const char *name);
+int acpi_scan_add_handler_with_hotplug(struct acpi_scan_handler *handler,
+                                       const char *hotplug_profile_name);
+void acpi_scan_hotplug_enabled(struct acpi_hotplug_profile *hotplug, bool val);
+
 #ifdef CONFIG_DEBUG_FS
 extern struct dentry *acpi_debugfs_dir;
 int acpi_debugfs_init(void);
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 45fbe95ba1f3..5458403c8249 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -63,6 +63,19 @@ int acpi_scan_add_handler(struct acpi_scan_handler *handler)
         return 0;
 }
 
+int acpi_scan_add_handler_with_hotplug(struct acpi_scan_handler *handler,
+                                       const char *hotplug_profile_name)
+{
+        int error;
+
+        error = acpi_scan_add_handler(handler);
+        if (error)
+                return error;
+
+        acpi_sysfs_add_hotplug_profile(&handler->hotplug, hotplug_profile_name);
+        return 0;
+}
+
 /*
  * Creates hid/cid(s) string needed for modalias and uevent
  * e.g. on a device with hid:IBM0001 and cid:ACPI0001 you get:
@@ -1690,6 +1703,52 @@ static bool acpi_scan_handler_matching(struct acpi_scan_handler *handler,
         return false;
 }
 
+static acpi_status acpi_scan_hotplug_modify(acpi_handle handle,
+                                            u32 lvl_not_used, void *data,
+                                            void **ret_not_used)
+{
+        struct acpi_scan_handler *handler = data;
+        struct acpi_device_info *info;
+        bool match = false;
+
+        if (ACPI_FAILURE(acpi_get_object_info(handle, &info)))
+                return AE_OK;
+
+        if (info->valid & ACPI_VALID_HID) {
+                char *idstr = info->hardware_id.string;
+                match = acpi_scan_handler_matching(handler, idstr, NULL);
+        }
+        kfree(info);
+        if (!match)
+                return AE_OK;
+
+        if (handler->hotplug.enabled)
+                acpi_install_notify_handler(handle, ACPI_SYSTEM_NOTIFY,
+                                            acpi_hotplug_notify_cb, NULL);
+        else
+                acpi_remove_notify_handler(handle, ACPI_SYSTEM_NOTIFY,
+                                           acpi_hotplug_notify_cb);
+
+        return AE_OK;
+}
+
+void acpi_scan_hotplug_enabled(struct acpi_hotplug_profile *hotplug, bool val)
+{
+        struct acpi_scan_handler *handler;
+
+        if (!!hotplug->enabled == !!val)
+                return;
+
+        mutex_lock(&acpi_scan_lock);
+
+        hotplug->enabled = val;
+        handler = container_of(hotplug, struct acpi_scan_handler, hotplug);
+        acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT, ACPI_UINT32_MAX,
+                            acpi_scan_hotplug_modify, NULL, handler, NULL);
+
+        mutex_unlock(&acpi_scan_lock);
+}
+
 static struct acpi_scan_handler *acpi_scan_match_handler(char *idstr,
                                         const struct acpi_device_id **matchid)
 {
diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index 41c0504470db..83db3a68a7ee 100644
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -7,6 +7,8 @@
 #include <linux/moduleparam.h>
 #include <acpi/acpi_drivers.h>
 
+#include "internal.h"
+
 #define _COMPONENT              ACPI_SYSTEM_COMPONENT
 ACPI_MODULE_NAME("sysfs");
 
@@ -249,6 +251,7 @@ module_param_call(acpica_version, NULL, param_get_acpica_version, NULL, 0444);
 static LIST_HEAD(acpi_table_attr_list);
 static struct kobject *tables_kobj;
 static struct kobject *dynamic_tables_kobj;
+static struct kobject *hotplug_kobj;
 
 struct acpi_table_attr {
         struct bin_attribute attr;
@@ -716,6 +719,67 @@ acpi_show_profile(struct device *dev, struct device_attribute *attr,
 static const struct device_attribute pm_profile_attr =
         __ATTR(pm_profile, S_IRUGO, acpi_show_profile, NULL);
 
+static ssize_t hotplug_enabled_show(struct kobject *kobj,
+                                    struct kobj_attribute *attr, char *buf)
+{
+        struct acpi_hotplug_profile *hotplug = to_acpi_hotplug_profile(kobj);
+
+        return sprintf(buf, "%d\n", hotplug->enabled);
+}
+
+static ssize_t hotplug_enabled_store(struct kobject *kobj,
+                                     struct kobj_attribute *attr,
+                                     const char *buf, size_t size)
+{
+        struct acpi_hotplug_profile *hotplug = to_acpi_hotplug_profile(kobj);
+        unsigned int val;
+
+        if (kstrtouint(buf, 10, &val) || val > 1)
+                return -EINVAL;
+
+        acpi_scan_hotplug_enabled(hotplug, val);
+        return size;
+}
+
+static struct kobj_attribute hotplug_enabled_attr =
+        __ATTR(enabled, S_IRUGO | S_IWUSR, hotplug_enabled_show,
+                hotplug_enabled_store);
+
+static struct attribute *hotplug_profile_attrs[] = {
+        &hotplug_enabled_attr.attr,
+        NULL
+};
+
+struct kobj_type acpi_hotplug_profile_ktype = {
+        .sysfs_ops = &kobj_sysfs_ops,
+        .default_attrs = hotplug_profile_attrs,
+};
+
+void acpi_sysfs_add_hotplug_profile(struct acpi_hotplug_profile *hotplug,
+                                    const char *name)
+{
+        int error;
+
+        if (!hotplug_kobj)
+                goto err_out;
+
+        kobject_init(&hotplug->kobj, &acpi_hotplug_profile_ktype);
+        error = kobject_set_name(&hotplug->kobj, "%s", name);
+        if (error)
+                goto err_out;
+
+        hotplug->kobj.parent = hotplug_kobj;
+        error = kobject_add(&hotplug->kobj, hotplug_kobj, NULL);
+        if (error)
+                goto err_out;
+
+        kobject_uevent(&hotplug->kobj, KOBJ_ADD);
+        return;
+
+ err_out:
+        pr_err(PREFIX "Unable to add hotplug profile '%s'\n", name);
+}
+
 int __init acpi_sysfs_init(void)
 {
         int result;
@@ -723,6 +787,8 @@ int __init acpi_sysfs_init(void)
         result = acpi_tables_sysfs_init();
         if (result)
                 return result;
+
+        hotplug_kobj = kobject_create_and_add("hotplug", acpi_kobj);
         result = sysfs_create_file(acpi_kobj, &pm_profile_attr.attr);
         return result;
 }