This provides seperate
  tty_device_initialize_attr()
and
  tty_device_add_attr()

similar to device_initialize() and device_add().

Similiarly tty_port_initialize_device_attr() is added to match
tty_port_register_device_attr().

It will allow a client to separate initalization and adding of the
device.

Signed-off-by: NeilBrown <n...@brown.name>
---
 drivers/tty/tty_io.c   |  102 +++++++++++++++++++++++++++++++++---------------
 drivers/tty/tty_port.c |   24 +++++++++++
 include/linux/tty.h    |    9 ++++
 3 files changed, 104 insertions(+), 31 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index ccb99b772965..83ca25b9c2da 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3205,8 +3205,29 @@ static void tty_device_create_release(struct device *dev)
        kfree(dev);
 }
 
+int tty_device_add(struct tty_driver *driver, struct device *dev)
+{
+       int retval;
+       bool cdev = false;
+       int index = dev->devt - MKDEV(driver->major,
+                                     driver->minor_start);
+
+       if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
+               retval = tty_cdev_add(driver, dev->devt, index, 1);
+               if (retval)
+                       return retval;
+               cdev = true;
+       }
+       retval = device_add(dev);
+       if (retval == 0)
+               return 0;
+       if (cdev)
+               cdev_del(&driver->cdevs[index]);
+       return retval;
+}
+EXPORT_SYMBOL(tty_device_add);
 /**
- *     tty_register_device_attr - register a tty device
+ *     tty_device_initialize_attr - initialize a tty device, but don't 'add'
  *     @driver: the tty driver that describes the tty device
  *     @index: the index in the tty driver for this tty device
  *     @device: a struct device that is associated with this tty device.
@@ -3218,23 +3239,19 @@ static void tty_device_create_release(struct device 
*dev)
  *     Returns a pointer to the struct device for this tty device
  *     (or ERR_PTR(-EFOO) on error).
  *
- *     This call is required to be made to register an individual tty device
- *     if the tty driver's flags have the TTY_DRIVER_DYNAMIC_DEV bit set.  If
- *     that bit is not set, this function should not be called by a tty
- *     driver.
+ *     tty_device_add() must be called after this call returns successfully
+ *     before the device will be full registered and available.
  *
  *     Locking: ??
  */
-struct device *tty_register_device_attr(struct tty_driver *driver,
-                                  unsigned index, struct device *device,
-                                  void *drvdata,
-                                  const struct attribute_group **attr_grp)
+struct device *tty_device_initialize_attr(struct tty_driver *driver,
+                                         unsigned index, struct device *device,
+                                         void *drvdata,
+                                         const struct attribute_group 
**attr_grp)
 {
        char name[64];
        dev_t devt = MKDEV(driver->major, driver->minor_start) + index;
        struct device *dev = NULL;
-       int retval = -ENODEV;
-       bool cdev = false;
 
        if (index >= driver->num) {
                printk(KERN_ERR "Attempt to register invalid tty line number "
@@ -3247,19 +3264,11 @@ struct device *tty_register_device_attr(struct 
tty_driver *driver,
        else
                tty_line_name(driver, index, name);
 
-       if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
-               retval = tty_cdev_add(driver, devt, index, 1);
-               if (retval)
-                       goto error;
-               cdev = true;
-       }
-
        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
-       if (!dev) {
-               retval = -ENOMEM;
-               goto error;
-       }
+       if (!dev)
+               return ERR_PTR(-ENOMEM);
 
+       device_initialize(dev);
        dev->devt = devt;
        dev->class = tty_class;
        dev->parent = device;
@@ -3268,17 +3277,48 @@ struct device *tty_register_device_attr(struct 
tty_driver *driver,
        dev->groups = attr_grp;
        dev_set_drvdata(dev, drvdata);
 
-       retval = device_register(dev);
-       if (retval)
-               goto error;
-
        return dev;
+}
+EXPORT_SYMBOL_GPL(tty_device_initialize_attr);
 
-error:
-       put_device(dev);
-       if (cdev)
-               cdev_del(&driver->cdevs[index]);
-       return ERR_PTR(retval);
+/**
+ *     tty_register_device_attr - register a tty device
+ *     @driver: the tty driver that describes the tty device
+ *     @index: the index in the tty driver for this tty device
+ *     @device: a struct device that is associated with this tty device.
+ *             This field is optional, if there is no known struct device
+ *             for this tty device it can be set to NULL safely.
+ *     @drvdata: Driver data to be set to device.
+ *     @attr_grp: Attribute group to be set on device.
+ *
+ *     Returns a pointer to the struct device for this tty device
+ *     (or ERR_PTR(-EFOO) on error).
+ *
+ *     This call is required to be made to register an individual tty device
+ *     if the tty driver's flags have the TTY_DRIVER_DYNAMIC_DEV bit set.  If
+ *     that bit is not set, this function should not be called by a tty
+ *     driver.
+ *
+ *     Locking: ??
+ */
+struct device *tty_register_device_attr(struct tty_driver *driver,
+                                  unsigned index, struct device *device,
+                                  void *drvdata,
+                                  const struct attribute_group **attr_grp)
+{
+       struct device *dev;
+       int ret;
+
+       dev = tty_device_initialize_attr(driver, index, device,
+                                        drvdata, attr_grp);
+       if (IS_ERR(dev))
+               return dev;
+       ret = tty_device_add(driver, dev);
+       if (ret) {
+               put_device(dev);
+               return ERR_PTR(ret);
+       }
+       return dev;
 }
 EXPORT_SYMBOL_GPL(tty_register_device_attr);
 
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 40b31835f80b..f4145c0f1f45 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -97,6 +97,30 @@ struct device *tty_port_register_device_attr(struct tty_port 
*port,
 }
 EXPORT_SYMBOL_GPL(tty_port_register_device_attr);
 
+/**
+ * tty_port_initialize_device_attr - initialize tty device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ * @device: parent if exists, otherwise NULL
+ * @drvdata: Driver data to be set to device.
+ * @attr_grp: Attribute group to be set on device.
+ *
+ * It is the same as tty_initialize_device_attr except the provided @port is
+ * linked to a concrete tty specified by @index. Use this or tty_port_install
+ * (or both). Call tty_port_link_device as a last resort.
+ */
+struct device *tty_port_initialize_device_attr(struct tty_port *port,
+               struct tty_driver *driver, unsigned index,
+               struct device *device, void *drvdata,
+               const struct attribute_group **attr_grp)
+{
+       tty_port_link_device(port, driver, index);
+       return tty_device_initialize_attr(driver, index, device, drvdata,
+                                         attr_grp);
+}
+EXPORT_SYMBOL_GPL(tty_port_initialize_device_attr);
+
 int tty_port_alloc_xmit_buf(struct tty_port *port)
 {
        /* We may sleep in get_zeroed_page() */
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 04d5f1213700..1b371ba9ed09 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -436,6 +436,11 @@ extern struct device *tty_register_device_attr(struct 
tty_driver *driver,
                                unsigned index, struct device *device,
                                void *drvdata,
                                const struct attribute_group **attr_grp);
+extern struct device *tty_device_initialize_attr(struct tty_driver *driver,
+                               unsigned index, struct device *device,
+                               void *drvdata,
+                               const struct attribute_group **attr_grp);
+extern int tty_device_add(struct tty_driver *driver, struct device *dev);
 extern void tty_unregister_device(struct tty_driver *driver, unsigned index);
 extern int tty_read_raw_data(struct tty_struct *tty, unsigned char *bufp,
                             int buflen);
@@ -534,6 +539,10 @@ extern struct device *tty_port_register_device_attr(struct 
tty_port *port,
                struct tty_driver *driver, unsigned index,
                struct device *device, void *drvdata,
                const struct attribute_group **attr_grp);
+extern struct device *tty_port_initialize_device_attr(struct tty_port *port,
+               struct tty_driver *driver, unsigned index,
+               struct device *device, void *drvdata,
+               const struct attribute_group **attr_grp);
 extern int tty_port_alloc_xmit_buf(struct tty_port *port);
 extern void tty_port_free_xmit_buf(struct tty_port *port);
 extern void tty_port_destroy(struct tty_port *port);


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