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>

3 files changed, 186 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 88de771d3569..0e81e4cf8876 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2115,6 +2115,142 @@ 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.
  *
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index b53c5f67e372..40ea71cd2ca6 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/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;
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index d531ceeb0d8c..f374fdcb6815 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/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
 };