[S390] Support for disconnected devices reappearing on another subcha…

…nnel.

- create a 'pseudo_subchannel' per channel subsystem (the 'orphanage')
- use the orphanage as a shelter for ccw_devices that can't remain on the same
  subchannel

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/cio.c

@@ -415,6 +415,8 @@ cio_enable_subchannel (struct subchannel *sch, unsigned int isc)
 	CIO_TRACE_EVENT (2, "ensch");
 	CIO_TRACE_EVENT (2, sch->dev.bus_id);
 
+	if (sch_is_pseudo_sch(sch))
+		return -EINVAL;
 	ccode = stsch (sch->schid, &sch->schib);
 	if (ccode)
 		return -ENODEV;
@@ -462,6 +464,8 @@ cio_disable_subchannel (struct subchannel *sch)
 	CIO_TRACE_EVENT (2, "dissch");
 	CIO_TRACE_EVENT (2, sch->dev.bus_id);
 
+	if (sch_is_pseudo_sch(sch))
+		return 0;
 	ccode = stsch (sch->schid, &sch->schib);
 	if (ccode == 3)		/* Not operational. */
 		return -ENODEV;
@@ -496,7 +500,7 @@ cio_disable_subchannel (struct subchannel *sch)
 	return ret;
 }
 
-static int cio_create_sch_lock(struct subchannel *sch)
+int cio_create_sch_lock(struct subchannel *sch)
 {
 	sch->lock = kmalloc(sizeof(spinlock_t), GFP_KERNEL);
 	if (!sch->lock)

drivers/s390/cio/cio.h

@@ -131,6 +131,8 @@ extern int cio_set_options (struct subchannel *, int);
 extern int cio_get_options (struct subchannel *);
 extern int cio_modify (struct subchannel *);
 
+int cio_create_sch_lock(struct subchannel *);
+
 /* Use with care. */
 #ifdef CONFIG_CCW_CONSOLE
 extern struct subchannel *cio_probe_console(void);

drivers/s390/cio/css.c

@@ -580,19 +580,32 @@ css_cm_enable_store(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR(cm_enable, 0644, css_cm_enable_show, css_cm_enable_store);
 
-static inline void __init
-setup_css(int nr)
+static inline int __init setup_css(int nr)
 {
 	u32 tod_high;
+	int ret;
 
 	memset(css[nr], 0, sizeof(struct channel_subsystem));
+	css[nr]->pseudo_subchannel =
+		kzalloc(sizeof(*css[nr]->pseudo_subchannel), GFP_KERNEL);
+	if (!css[nr]->pseudo_subchannel)
+		return -ENOMEM;
+	css[nr]->pseudo_subchannel->dev.parent = &css[nr]->device;
+	css[nr]->pseudo_subchannel->dev.release = css_subchannel_release;
+	sprintf(css[nr]->pseudo_subchannel->dev.bus_id, "defunct");
+	ret = cio_create_sch_lock(css[nr]->pseudo_subchannel);
+	if (ret) {
+		kfree(css[nr]->pseudo_subchannel);
+		return ret;
+	}
 	mutex_init(&css[nr]->mutex);
 	css[nr]->valid = 1;
 	css[nr]->cssid = nr;
 	sprintf(css[nr]->device.bus_id, "css%x", nr);
 	css[nr]->device.release = channel_subsystem_release;
 	tod_high = (u32) (get_clock() >> 32);
 	css_generate_pgid(css[nr], tod_high);
+	return 0;
 }
 
 /*
@@ -629,31 +642,42 @@ init_channel_subsystem (void)
 			ret = -ENOMEM;
 			goto out_unregister;
 		}
-		setup_css(i);
-		ret = device_register(&css[i]->device);
+		ret = setup_css(i);
 		if (ret)
 			goto out_free;
+		ret = device_register(&css[i]->device);
+		if (ret)
+			goto out_free_all;
 		if (css_characteristics_avail &&
 		    css_chsc_characteristics.secm) {
 			ret = device_create_file(&css[i]->device,
 						 &dev_attr_cm_enable);
 			if (ret)
 				goto out_device;
 		}
+		ret = device_register(&css[i]->pseudo_subchannel->dev);
+		if (ret)
+			goto out_file;
 	}
 	css_init_done = 1;
 
 	ctl_set_bit(6, 28);
 
 	for_each_subchannel(__init_channel_subsystem, NULL);
 	return 0;
+out_file:
+	device_remove_file(&css[i]->device, &dev_attr_cm_enable);
 out_device:
 	device_unregister(&css[i]->device);
+out_free_all:
+	kfree(css[i]->pseudo_subchannel->lock);
+	kfree(css[i]->pseudo_subchannel);
 out_free:
 	kfree(css[i]);
 out_unregister:
 	while (i > 0) {
 		i--;
+		device_unregister(&css[i]->pseudo_subchannel->dev);
 		if (css_characteristics_avail && css_chsc_characteristics.secm)
 			device_remove_file(&css[i]->device,
 					   &dev_attr_cm_enable);
@@ -665,6 +689,11 @@ init_channel_subsystem (void)
 	return ret;
 }
 
+int sch_is_pseudo_sch(struct subchannel *sch)
+{
+	return sch == to_css(sch->dev.parent)->pseudo_subchannel;
+}
+
 /*
  * find a driver for a subchannel. They identify by the subchannel
  * type with the exception that the console subchannel driver has its own

drivers/s390/cio/css.h

@@ -160,6 +160,8 @@ struct channel_subsystem {
 	int cm_enabled;
 	void *cub_addr1;
 	void *cub_addr2;
+	/* for orphaned ccw devices */
+	struct subchannel *pseudo_subchannel;
 };
 #define to_css(dev) container_of(dev, struct channel_subsystem, device)
 
@@ -187,6 +189,8 @@ void css_clear_subchannel_slow_list(void);
 int css_slow_subchannels_exist(void);
 extern int need_rescan;
 
+int sch_is_pseudo_sch(struct subchannel *);
+
 extern struct workqueue_struct *slow_path_wq;
 extern struct work_struct slow_path_work;