Revert "sysfs, driver-core: remove unused {sysfs|device}_schedule_callback_owner()"

This reverts commit d1ba277e79889085a2faec3b68b91ce89c63f888.

As reported by Stephen, this patch breaks linux-next as a ppc patch
suddenly (after 2 years) started using this old api call.  So revert it
for now, it will go away in 3.15-rc2 when we can change the PPC call to
the new api.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 20da3ad1696b..0dd65281cc65 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -614,6 +614,39 @@ void device_remove_bin_file(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(device_remove_bin_file);
 
+/**
+ * device_schedule_callback_owner - helper to schedule a callback for a device
+ * @dev: device.
+ * @func: callback function to invoke later.
+ * @owner: module owning the callback routine
+ *
+ * Attribute methods must not unregister themselves or their parent device
+ * (which would amount to the same thing).  Attempts to do so will deadlock,
+ * since unregistration is mutually exclusive with driver callbacks.
+ *
+ * Instead methods can call this routine, which will attempt to allocate
+ * and schedule a workqueue request to call back @func with @dev as its
+ * argument in the workqueue's process context.  @dev will be pinned until
+ * @func returns.
+ *
+ * This routine is usually called via the inline device_schedule_callback(),
+ * which automatically sets @owner to THIS_MODULE.
+ *
+ * Returns 0 if the request was submitted, -ENOMEM if storage could not
+ * be allocated, -ENODEV if a reference to @owner isn't available.
+ *
+ * NOTE: This routine won't work if CONFIG_SYSFS isn't set!  It uses an
+ * underlying sysfs routine (since it is intended for use by attribute
+ * methods), and if sysfs isn't available you'll get nothing but -ENOSYS.
+ */
+int device_schedule_callback_owner(struct device *dev,
+		void (*func)(struct device *), struct module *owner)
+{
+	return sysfs_schedule_callback(&dev->kobj,
+			(void (*)(void *)) func, dev, owner);
+}
+EXPORT_SYMBOL_GPL(device_schedule_callback_owner);
+
 static void klist_children_get(struct klist_node *n)
 {
 	struct device_private *p = to_device_private_parent(n);