[PATCH] add sysfs attr to re-emit device hotplug event

A "coldplug + udevstart" can be simple like this:
  for i in /sys/block/*/*/uevent; do echo 1 > $i; done
  for i in /sys/class/*/*/uevent; do echo 1 > $i; done
  for i in /sys/bus/*/devices/*/uevent; do echo 1 > $i; done

Signed-off-by: Kay Sievers <kay.sievers@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 55 insertions, 2 deletions

diff --git a/drivers/base/class.c b/drivers/base/class.c
index 73d44cf53db0..3cf6eb36f3d8 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -442,6 +442,13 @@ static ssize_t show_dev(struct class_device *class_dev, char *buf)
         return print_dev_t(buf, class_dev->devt);
 }
 
+static ssize_t store_uevent(struct class_device *class_dev,
+                            const char *buf, size_t count)
+{
+        kobject_hotplug(&class_dev->kobj, KOBJ_ADD);
+        return count;
+}
+
 void class_device_initialize(struct class_device *class_dev)
 {
         kobj_set_kset_s(class_dev, class_obj_subsys);
@@ -497,6 +504,12 @@ int class_device_add(struct class_device *class_dev)
                 goto register_done;
 
         /* add the needed attributes to this device */
+        class_dev->uevent_attr.attr.name = "uevent";
+        class_dev->uevent_attr.attr.mode = S_IWUSR;
+        class_dev->uevent_attr.attr.owner = parent->owner;
+        class_dev->uevent_attr.store = store_uevent;
+        class_device_create_file(class_dev, &class_dev->uevent_attr);
+
         if (MAJOR(class_dev->devt)) {
                 struct class_device_attribute *attr;
                 attr = kzalloc(sizeof(*attr), GFP_KERNEL);
@@ -505,12 +518,10 @@ int class_device_add(struct class_device *class_dev)
                         kobject_del(&class_dev->kobj);
                         goto register_done;
                 }
-
                 attr->attr.name = "dev";
                 attr->attr.mode = S_IRUGO;
                 attr->attr.owner = parent->owner;
                 attr->show = show_dev;
-                attr->store = NULL;
                 class_device_create_file(class_dev, attr);
                 class_dev->devt_attr = attr;
         }
@@ -621,6 +632,7 @@ void class_device_del(struct class_device *class_dev)
                 sysfs_remove_link(&class_dev->kobj, "device");
                 sysfs_remove_link(&class_dev->dev->kobj, class_name);
         }
+        class_device_remove_file(class_dev, &class_dev->uevent_attr);
         if (class_dev->devt_attr)
                 class_device_remove_file(class_dev, class_dev->devt_attr);
         class_device_remove_attrs(class_dev);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 31109193e2c4..ac4b5fdd95f5 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -154,6 +154,13 @@ static struct kset_hotplug_ops device_hotplug_ops = {
         .hotplug =      dev_hotplug,
 };
 
+static ssize_t store_uevent(struct device *dev, struct device_attribute *attr,
+                            const char *buf, size_t count)
+{
+        kobject_hotplug(&dev->kobj, KOBJ_ADD);
+        return count;
+}
+
 /**
  *      device_subsys - structure to be registered with kobject core.
  */
@@ -259,6 +266,14 @@ int device_add(struct device *dev)
 
         if ((error = kobject_add(&dev->kobj)))
                 goto Error;
+
+        dev->uevent_attr.attr.name = "uevent";
+        dev->uevent_attr.attr.mode = S_IWUSR;
+        if (dev->driver)
+                dev->uevent_attr.attr.owner = dev->driver->owner;
+        dev->uevent_attr.store = store_uevent;
+        device_create_file(dev, &dev->uevent_attr);
+
         kobject_hotplug(&dev->kobj, KOBJ_ADD);
         if ((error = device_pm_add(dev)))
                 goto PMError;
@@ -350,6 +365,7 @@ void device_del(struct device * dev)
 
         if (parent)
                 klist_del(&dev->knode_parent);
+        device_remove_file(dev, &dev->uevent_attr);
 
         /* Notify the platform of the removal, in case they
          * need to do anything...
diff --git a/drivers/block/genhd.c b/drivers/block/genhd.c
index d42840cc0d1d..486ce1fdeb8c 100644
--- a/drivers/block/genhd.c
+++ b/drivers/block/genhd.c
@@ -337,10 +337,30 @@ static ssize_t disk_attr_show(struct kobject *kobj, struct attribute *attr,
         return ret;
 }
 
+static ssize_t disk_attr_store(struct kobject * kobj, struct attribute * attr,
+                               const char *page, size_t count)
+{
+        struct gendisk *disk = to_disk(kobj);
+        struct disk_attribute *disk_attr =
+                container_of(attr,struct disk_attribute,attr);
+        ssize_t ret = 0;
+
+        if (disk_attr->store)
+                ret = disk_attr->store(disk, page, count);
+        return ret;
+}
+
 static struct sysfs_ops disk_sysfs_ops = {
         .show   = &disk_attr_show,
+        .store  = &disk_attr_store,
 };
 
+static ssize_t disk_uevent_store(struct gendisk * disk,
+                                 const char *buf, size_t count)
+{
+        kobject_hotplug(&disk->kobj, KOBJ_ADD);
+        return count;
+}
 static ssize_t disk_dev_read(struct gendisk * disk, char *page)
 {
         dev_t base = MKDEV(disk->major, disk->first_minor); 
@@ -382,6 +402,10 @@ static ssize_t disk_stats_read(struct gendisk * disk, char *page)
                 jiffies_to_msecs(disk_stat_read(disk, io_ticks)),
                 jiffies_to_msecs(disk_stat_read(disk, time_in_queue)));
 }
+static struct disk_attribute disk_attr_uevent = {
+        .attr = {.name = "uevent", .mode = S_IWUSR },
+        .store  = disk_uevent_store
+};
 static struct disk_attribute disk_attr_dev = {
         .attr = {.name = "dev", .mode = S_IRUGO },
         .show   = disk_dev_read
@@ -404,6 +428,7 @@ static struct disk_attribute disk_attr_stat = {
 };
 
 static struct attribute * default_attrs[] = {
+        &disk_attr_uevent.attr,
         &disk_attr_dev.attr,
         &disk_attr_range.attr,
         &disk_attr_removable.attr,