X-Git-Url: https://repo.jachan.dev/qemu.git/blobdiff_plain/83199ca43c81e6931e62e133d9e53024108831ed..5fba0a72ec1968debca8bb80732cc75aa7cd8a21:/docs/usb-storage.txt

diff --git a/docs/usb-storage.txt b/docs/usb-storage.txt
index ff9755920d..fbc1f2edd8 100644
--- a/docs/usb-storage.txt
+++ b/docs/usb-storage.txt
@@ -2,10 +2,10 @@
 qemu usb storage emulation
 --------------------------
 
-Qemu has two emulations for usb storage devices.
+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):
 
@@ -31,6 +31,27 @@ with tree logical units:
        -device scsi-cd,bus=uas.0,scsi-id=0,lun=5,drive=uas-cdrom
 
 
+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
+disk creation.  It also features support for up to 16 LUNs.  The LUN
+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