From 1054432d0647e30eac6b20aca33c7dae67fe0160 Mon Sep 17 00:00:00 2001
From: Cunyin Chang <cunyin.chang@intel.com>
Date: Fri, 10 Mar 2017 13:07:33 +0800
Subject: [PATCH] doc: Add initial documentation for iscsi hotplug.

Change-Id: I432b83c9bf4a39cd061579d0318b91903299e080
Signed-off-by: Cunyin Chang <cunyin.chang@intel.com>
---
 doc/Doxyfile         |  1 +
 doc/iscsi/hotplug.md | 21 +++++++++++++++++++++
 doc/iscsi/index.md   |  1 +
 3 files changed, 23 insertions(+)
 create mode 100644 doc/iscsi/hotplug.md

diff --git a/doc/Doxyfile b/doc/Doxyfile
index a09a856a2..dbf05753f 100644
--- a/doc/Doxyfile
+++ b/doc/Doxyfile
@@ -768,6 +768,7 @@ INPUT                  = ../include/spdk \
                          ioat/index.md \
                          iscsi/index.md \
                          iscsi/getting_started.md \
+                         iscsi/hotplug.md \
                          nvme/index.md \
                          nvme/async_completion.md \
                          nvme/fabrics.md \
diff --git a/doc/iscsi/hotplug.md b/doc/iscsi/hotplug.md
new file mode 100644
index 000000000..7ecd06651
--- /dev/null
+++ b/doc/iscsi/hotplug.md
@@ -0,0 +1,21 @@
+# iSCSI Hotplug {#iscsi_hotplug}
+
+At the iSCSI level, we provide the following support for Hotplug:
+
+1. bdev/nvme:
+At the bdev/nvme level, we start one hotplug monitor which will call
+spdk_nvme_probe() periodically to get the hotplug events. We provide the
+private attach_cb and remove_cb for spdk_nvme_probe(). For the attach_cb,
+we will create the block device base on the NVMe device attached, and for the
+remove_cb, we will unregister the block device, which will also notify the
+upper level stack (for iSCSI target, the upper level stack is scsi/lun) to
+handle the hot-remove event.
+
+2. scsi/lun:
+When the LUN receive the hot-remove notification from block device layer,
+the LUN will be marked as removed, and all the IOs after this point will
+return with check condition status. Then the LUN starts one poller which will
+wait for all the commands which have already been submitted to block device to
+return back; after all the commands return back, the LUN will be deleted.
+
+@sa spdk_nvme_probe
diff --git a/doc/iscsi/index.md b/doc/iscsi/index.md
index a5951cac6..66a4477cc 100644
--- a/doc/iscsi/index.md
+++ b/doc/iscsi/index.md
@@ -1,3 +1,4 @@
 # iSCSI Target {#iscsi}
 
 - @ref iscsi_getting_started
+- @ref iscsi_hotplug