SCSI: add asynchronous event notification API

Originally based on a patch by Kristen Carlson Accardi @ Intel.
Copious input from James Bottomley.
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/scsi/scsi_lib.c

@@ -2114,6 +2114,142 @@ scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
 }
 EXPORT_SYMBOL(scsi_device_set_state);
 
+/**
+ * 	sdev_evt_emit - emit a single SCSI device uevent
+ *	@sdev: associated SCSI device
+ *	@evt: event to emit
+ *
+ *	Send a single uevent (scsi_event) to the associated scsi_device.
+ */
+static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
+{
+	int idx = 0;
+	char *envp[3];
+
+	switch (evt->evt_type) {
+	case SDEV_EVT_MEDIA_CHANGE:
+		envp[idx++] = "SDEV_MEDIA_CHANGE=1";
+		break;
+
+	default:
+		/* do nothing */
+		break;
+	}
+
+	envp[idx++] = NULL;
+
+	kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
+}
+
+/**
+ * 	sdev_evt_thread - send a uevent for each scsi event
+ *	@work: work struct for scsi_device
+ *
+ *	Dispatch queued events to their associated scsi_device kobjects
+ *	as uevents.
+ */
+void scsi_evt_thread(struct work_struct *work)
+{
+	struct scsi_device *sdev;
+	LIST_HEAD(event_list);
+
+	sdev = container_of(work, struct scsi_device, event_work);
+
+	while (1) {
+		struct scsi_event *evt;
+		struct list_head *this, *tmp;
+		unsigned long flags;
+
+		spin_lock_irqsave(&sdev->list_lock, flags);
+		list_splice_init(&sdev->event_list, &event_list);
+		spin_unlock_irqrestore(&sdev->list_lock, flags);
+
+		if (list_empty(&event_list))
+			break;
+
+		list_for_each_safe(this, tmp, &event_list) {
+			evt = list_entry(this, struct scsi_event, node);
+			list_del(&evt->node);
+			scsi_evt_emit(sdev, evt);
+			kfree(evt);
+		}
+	}
+}
+
+/**
+ * 	sdev_evt_send - send asserted event to uevent thread
+ *	@sdev: scsi_device event occurred on
+ *	@evt: event to send
+ *
+ *	Assert scsi device event asynchronously.
+ */
+void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt)
+{
+	unsigned long flags;
+
+	if (!test_bit(evt->evt_type, sdev->supported_events)) {
+		kfree(evt);
+		return;
+	}
+
+	spin_lock_irqsave(&sdev->list_lock, flags);
+	list_add_tail(&evt->node, &sdev->event_list);
+	schedule_work(&sdev->event_work);
+	spin_unlock_irqrestore(&sdev->list_lock, flags);
+}
+EXPORT_SYMBOL_GPL(sdev_evt_send);
+
+/**
+ * 	sdev_evt_alloc - allocate a new scsi event
+ *	@evt_type: type of event to allocate
+ *	@gfpflags: GFP flags for allocation
+ *
+ *	Allocates and returns a new scsi_event.
+ */
+struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
+				  gfp_t gfpflags)
+{
+	struct scsi_event *evt = kzalloc(sizeof(struct scsi_event), gfpflags);
+	if (!evt)
+		return NULL;
+
+	evt->evt_type = evt_type;
+	INIT_LIST_HEAD(&evt->node);
+
+	/* evt_type-specific initialization, if any */
+	switch (evt_type) {
+	case SDEV_EVT_MEDIA_CHANGE:
+	default:
+		/* do nothing */
+		break;
+	}
+
+	return evt;
+}
+EXPORT_SYMBOL_GPL(sdev_evt_alloc);
+
+/**
+ * 	sdev_evt_send_simple - send asserted event to uevent thread
+ *	@sdev: scsi_device event occurred on
+ *	@evt_type: type of event to send
+ *	@gfpflags: GFP flags for allocation
+ *
+ *	Assert scsi device event asynchronously, given an event type.
+ */
+void sdev_evt_send_simple(struct scsi_device *sdev,
+			  enum scsi_device_event evt_type, gfp_t gfpflags)
+{
+	struct scsi_event *evt = sdev_evt_alloc(evt_type, gfpflags);
+	if (!evt) {
+		sdev_printk(KERN_ERR, sdev, "event %d eaten due to OOM\n",
+			    evt_type);
+		return;
+	}
+
+	sdev_evt_send(sdev, evt);
+}
+EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
+
 /**
  *	scsi_device_quiesce - Block user issued commands.
  *	@sdev:	scsi device to quiesce.

drivers/scsi/scsi_scan.c

@@ -236,6 +236,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
 	struct scsi_device *sdev;
 	int display_failure_msg = 1, ret;
 	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
+	extern void scsi_evt_thread(struct work_struct *work);
 
 	sdev = kzalloc(sizeof(*sdev) + shost->transportt->device_size,
 		       GFP_ATOMIC);
@@ -254,7 +255,9 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
 	INIT_LIST_HEAD(&sdev->same_target_siblings);
 	INIT_LIST_HEAD(&sdev->cmd_list);
 	INIT_LIST_HEAD(&sdev->starved_entry);
+	INIT_LIST_HEAD(&sdev->event_list);
 	spin_lock_init(&sdev->list_lock);
+	INIT_WORK(&sdev->event_work, scsi_evt_thread);
 
 	sdev->sdev_gendev.parent = get_device(&starget->dev);
 	sdev->sdev_target = starget;

drivers/scsi/scsi_sysfs.c

@@ -268,6 +268,7 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 	struct scsi_device *sdev;
 	struct device *parent;
 	struct scsi_target *starget;
+	struct list_head *this, *tmp;
 	unsigned long flags;
 
 	sdev = container_of(work, struct scsi_device, ew.work);
@@ -282,6 +283,16 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 	list_del(&sdev->starved_entry);
 	spin_unlock_irqrestore(sdev->host->host_lock, flags);
 
+	cancel_work_sync(&sdev->event_work);
+
+	list_for_each_safe(this, tmp, &sdev->event_list) {
+		struct scsi_event *evt;
+
+		evt = list_entry(this, struct scsi_event, node);
+		list_del(&evt->node);
+		kfree(evt);
+	}
+
 	if (sdev->request_queue) {
 		sdev->request_queue->queuedata = NULL;
 		/* user context needed to free queue */
@@ -614,6 +625,41 @@ sdev_show_modalias(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR(modalias, S_IRUGO, sdev_show_modalias, NULL);
 
+#define DECLARE_EVT_SHOW(name, Cap_name)				\
+static ssize_t								\
+sdev_show_evt_##name(struct device *dev, struct device_attribute *attr,	\
+				char *buf)				\
+{									\
+	struct scsi_device *sdev = to_scsi_device(dev);			\
+	int val = test_bit(SDEV_EVT_##Cap_name, sdev->supported_events);\
+	return snprintf(buf, 20, "%d\n", val);				\
+}
+
+#define DECLARE_EVT_STORE(name, Cap_name)				\
+static ssize_t								\
+sdev_store_evt_##name(struct device *dev, struct device_attribute *attr, \
+		      const char *buf, size_t count)			\
+{									\
+	struct scsi_device *sdev = to_scsi_device(dev);			\
+	int val = simple_strtoul(buf, NULL, 0);				\
+	if (val == 0)							\
+		clear_bit(SDEV_EVT_##Cap_name, sdev->supported_events);	\
+	else if (val == 1)						\
+		set_bit(SDEV_EVT_##Cap_name, sdev->supported_events);	\
+	else								\
+		return -EINVAL;						\
+	return count;							\
+}
+
+#define DECLARE_EVT(name, Cap_name)					\
+	DECLARE_EVT_SHOW(name, Cap_name)				\
+	DECLARE_EVT_STORE(name, Cap_name)				\
+	static DEVICE_ATTR(evt_##name, S_IRUGO, sdev_show_evt_##name,	\
+			   sdev_store_evt_##name);
+#define REF_EVT(name) &dev_attr_evt_##name.attr
+
+DECLARE_EVT(media_change, MEDIA_CHANGE)
+
 /* Default template for device attributes.  May NOT be modified */
 static struct attribute *scsi_sdev_attrs[] = {
 	&dev_attr_device_blocked.attr,
@@ -631,6 +677,7 @@ static struct attribute *scsi_sdev_attrs[] = {
 	&dev_attr_iodone_cnt.attr,
 	&dev_attr_ioerr_cnt.attr,
 	&dev_attr_modalias.attr,
+	REF_EVT(media_change),
 	NULL
 };
 

include/scsi/scsi_device.h

@@ -46,6 +46,22 @@ enum scsi_device_state {
 				 * to the scsi lld. */
 };
 
+enum scsi_device_event {
+	SDEV_EVT_MEDIA_CHANGE	= 1,	/* media has changed */
+
+	SDEV_EVT_LAST		= SDEV_EVT_MEDIA_CHANGE,
+	SDEV_EVT_MAXBITS	= SDEV_EVT_LAST + 1
+};
+
+struct scsi_event {
+	enum scsi_device_event	evt_type;
+	struct list_head	node;
+
+	/* put union of data structures, for non-simple event types,
+	 * here
+	 */
+};
+
 struct scsi_device {
 	struct Scsi_Host *host;
 	struct request_queue *request_queue;
@@ -127,6 +143,10 @@ struct scsi_device {
 	unsigned guess_capacity:1;	/* READ_CAPACITY might be too high by 1 */
 	unsigned retry_hwerror:1;	/* Retry HARDWARE_ERROR */
 
+	DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
+	struct list_head event_list;	/* asserted events */
+	struct work_struct event_work;
+
 	unsigned int device_blocked;	/* Device returned QUEUE_FULL. */
 
 	unsigned int max_device_blocked; /* what device_blocked counts down from  */
@@ -275,6 +295,11 @@ extern int scsi_test_unit_ready(struct scsi_device *sdev, int timeout,
 				int retries);
 extern int scsi_device_set_state(struct scsi_device *sdev,
 				 enum scsi_device_state state);
+extern struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
+					  gfp_t gfpflags);
+extern void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt);
+extern void sdev_evt_send_simple(struct scsi_device *sdev,
+			  enum scsi_device_event evt_type, gfp_t gfpflags);
 extern int scsi_device_quiesce(struct scsi_device *sdev);
 extern void scsi_device_resume(struct scsi_device *sdev);
 extern void scsi_target_quiesce(struct scsi_target *);