Revert "vl: Fix to create migration object before block backends again"

[mirror_qemu.git] / docs / usb-storage.txt

diff --git a/docs/usb-storage.txt b/docs/usb-storage.txt
index fa93111cf68ae3f1254073996fdf1d105cd8ca1f..551af6f88bb16f8d9b567ca560280a002b5e0a44 100644 (file)
--- a/docs/usb-storage.txt
+++ b/docs/usb-storage.txt
@@ -5,7 +5,7 @@ qemu usb storage emulation
 QEMU has three devices for usb storage emulation.
 
 Number one emulates the classic bulk-only transport protocol which is
-used by 99% of the usb sticks on the marked today and is called
+used by 99% of the usb sticks on the market today and is called
 "usb-storage".  Usage (hooking up to xhci, other host controllers work
 too):
 
@@ -34,12 +34,24 @@ with tree logical units:
 Number three emulates the classic bulk-only transport protocol too.
 It's called "usb-bot".  It shares most code with "usb-storage", and
 the guest will not be able to see the difference.  The qemu command
-line interface is simliar to usb-uas though, i.e. no automatic scsi
+line interface is similar to usb-uas though, i.e. no automatic scsi
 disk creation.  It also features support for up to 16 LUNs.  The LUN
-numbers must be continous, i.e. for three devices you must use 0+1+2.
+numbers must be continuous, i.e. for three devices you must use 0+1+2.
 The 0+1+5 numbering from the "usb-uas" example isn't going to work
 with "usb-bot".
 
+Starting with qemu version 2.7 usb-bot and usb-uas devices can be
+hotplugged.  In the hotplug case they are added with "attached =
+false" so the guest will not see the device until the "attached"
+property is explicitly set to true.  That allows to attach one or more
+scsi devices before making the device visible to the guest, i.e. the
+workflow looks like this:
+
+   (1) device-add usb-bot,id=foo
+   (2) device-add scsi-{hd,cd},bus=foo.0,lun=0
+   (2b) optionally add more devices (luns 1 ... 15).
+   (3) scripts/qmp/qom-set foo.attached = true
+
 enjoy,
   Gerd