path: root/docs/qdev-device-use.txt

= How to convert to -device & friends =

=== Specifying Bus and Address on Bus ===

In qdev, each device has a parent bus.  Some devices provide one or
more buses for children.  You can specify a device's parent bus with
-device parameter bus.

A device typically has a device address on its parent bus.  For buses
where this address can be configured, devices provide a bus-specific
property.  These are

    bus     property name       value format
    PCI     addr                %x.%x (dev.fn, .fn optional)
    I2C     address             %u
    SCSI    scsi-id             %u

Example: device i440FX-pcihost is on the root bus, and provides a PCI
bus named pci.0.  To put a FOO device into its slot 4, use -device
FOO,bus=/i440FX-pcihost/pci.0,addr=4.  The abbreviated form bus=pci.0
also works as long as the bus name is unique.

Note: the USB device address can't be controlled at this time.

=== Block Devices ===

A QEMU block device (drive) has a host and a guest part.

In the general case, the guest device is connected to a controller
device.  For instance, the IDE controller provides two IDE buses, each
of which can have up to two ide-drive devices, and each ide-drive
device is a guest part, and is connected to a host part.

Except we sometimes lump controller, bus(es) and drive device(s) all
together into a single device.  For instance, the ISA floppy
controller is connected to up to two host drives.

The old ways to define block devices define host and guest part
together.  Sometimes, they can even define a controller device in
addition to the block device.

The new way keeps the parts separate: you create the host part with
-drive, and guest device(s) with -device.

The various old ways to define drives all boil down to the common form

    -drive if=TYPE,index=IDX,bus=BUS,unit=UNIT,HOST-OPTS...

TYPE, BUS and UNIT identify the controller device, which of its buses
to use, and the drive's address on that bus.  Details depend on TYPE.
IDX is an alternative way to specify BUS and UNIT.

In the new way, this becomes something like

   -drive if=none,id=DRIVE-ID,HOST-OPTS...
   -device DEVNAME,drive=DRIVE-ID,DEV-OPTS...

The -device argument differs in detail for each kind of drive:

* if=ide

  -device ide-drive,drive=DRIVE-ID,bus=IDE-BUS,unit=UNIT

  where IDE-BUS identifies an IDE bus, normally either ide.0 or ide.1,
  and UNIT is either 0 or 1.

  Bug: new way does not work for ide.1 unit 0 (in old terms: index=2)
  unless you disable the default CD-ROM with -nodefaults.

* if=scsi

  The old way implicitly creates SCSI controllers as needed.  The new
  way makes that explicit:

  -device lsi53c895a,id=ID

  As for all PCI devices, you can add bus=PCI-BUS,addr=DEVFN to
  control the PCI device address.

  This SCSI controller a single SCSI bus, named ID.0.  Put a disk on
  it:

  -device scsi-disk,drive=DRIVE-ID,bus=ID.0,scsi-id=SCSI-ID

* if=floppy

  -global isa-fdc,driveA=DRIVE-ID,driveB=DRIVE-ID

  This is -global instead of -device, because the floppy controller is
  created automatically, and we want to configure that one, not create
  a second one (which isn't possible anyway).

  Omitting a drive parameter makes that drive empty.

  Bug: driveA works only if you disable the default floppy drive with
  -nodefaults.

* if=virtio

  -device virtio-blk-pci,drive=DRIVE-ID,class=C,vectors=V,ioeventfd=IOEVENTFD

  This lets you control PCI device class and MSI-X vectors.

  IOEVENTFD controls whether or not ioeventfd is used for virtqueue notify.  It
  can be set to on (default) or off.

  As for all PCI devices, you can add bus=PCI-BUS,addr=DEVFN to
  control the PCI device address.

* if=pflash, if=mtd, if=sd, if=xen are not yet available with -device

For USB devices, the old way is actually different:

    -usbdevice disk:format=FMT:FILENAME

Provides much less control than -drive's HOST-OPTS...  The new way
fixes that:

    -device usb-storage,drive=DRIVE-ID

=== Character Devices ===

A QEMU character device has a host and a guest part.

The old ways to define character devices define host and guest part
together.

The new way keeps the parts separate: you create the host part with
-chardev, and the guest device with -device.

The various old ways to define a character device are all of the
general form

    -FOO FOO-OPTS...,LEGACY-CHARDEV

where FOO-OPTS... is specific to -FOO, and the host part
LEGACY-CHARDEV is the same everywhere.

In the new way, this becomes

    -chardev HOST-OPTS...,id=CHR-ID
    -device DEVNAME,chardev=CHR-ID,DEV-OPTS...

The appropriate DEVNAME depends on the machine type.  For type "pc":

* -serial becomes -device isa-serial,iobase=IOADDR,irq=IRQ,index=IDX

  This lets you control I/O ports and IRQs.

* -parallel becomes -device isa-parallel,iobase=IOADDR,irq=IRQ,index=IDX

  This lets you control I/O ports and IRQs.

* -usbdevice serial:vendorid=VID,productid=PRID becomes
  -device usb-serial,vendorid=VID,productid=PRID

* -usbdevice braille doesn't support LEGACY-CHARDEV syntax.  It always
  uses "braille".  With -device, this useful default is gone, so you
  have to use something like

  -device usb-braille,chardev=braille,vendorid=VID,productid=PRID
  -chardev braille,id=braille

* -virtioconsole is still being worked on

LEGACY-CHARDEV translates to -chardev HOST-OPTS... as follows:

* null becomes -chardev null

* pty, msmouse, braille, stdio likewise

* vc:WIDTHxHEIGHT becomes -chardev vc,width=WIDTH,height=HEIGHT

* vc:<COLS>Cx<ROWS>C becomes -chardev vc,cols=<COLS>,rows=<ROWS>

* con: becomes -chardev console

* COM<NUM> becomes -chardev serial,path=<NUM>

* file:FNAME becomes -chardev file,path=FNAME

* pipe:FNAME becomes -chardev pipe,path=FNAME

* tcp:HOST:PORT,OPTS... becomes -chardev socket,host=HOST,port=PORT,OPTS...

* telnet:HOST:PORT,OPTS... becomes
  -chardev socket,host=HOST,port=PORT,OPTS...,telnet=on

* udp:HOST:PORT@LOCALADDR:LOCALPORT becomes
  -chardev udp,host=HOST,port=PORT,localaddr=LOCALADDR,localport=LOCALPORT

* unix:FNAME becomes -chardev socket,path=FNAME

* /dev/parportN becomes -chardev parport,file=/dev/parportN

* /dev/ppiN likewise

* Any other /dev/FNAME becomes -chardev tty,path=/dev/FNAME

* mon:LEGACY-CHARDEV is special: it multiplexes the monitor onto the
  character device defined by LEGACY-CHARDEV.  -chardev provides more
  general multiplexing instead: you can connect up to four users to a
  single host part.  You need to pass mux=on to -chardev to enable
  switching the input focus.

QEMU uses LEGACY-CHARDEV syntax not just to set up guest devices, but
also in various other places such as -monitor or -net
user,guestfwd=...  You can use chardev:CHR-ID in place of
LEGACY-CHARDEV to refer to a host part defined with -chardev.

=== Network Devices ===

A QEMU network device (NIC) has a host and a guest part.

The old ways to define NICs define host and guest part together.  It
looks like this:

    -net nic,vlan=VLAN,macaddr=MACADDR,model=MODEL,name=ID,addr=STR,vectors=V

Except for USB it looks like this:

    -usbdevice net:vlan=VLAN,macaddr=MACADDR,name=ID,addr=STR,vectors=V

The new way keeps the parts separate: you create the host part with
-netdev, and the guest device with -device, like this:

    -netdev type=TYPE,id=NET-ID
    -device DEVNAME,netdev=NET-ID,mac=MACADDR,DEV-OPTS...

Unlike the old way, this creates just a network device, not a VLAN.
If you really want a VLAN, create it the usual way, then create the
guest device like this:

    -device DEVNAME,vlan=VLAN,mac=MACADDR,DEV-OPTS...

DEVNAME equals MODEL, except for virtio you have to name the virtio
device appropriate for the bus (virtio-net-pci for PCI), and for USB
NIC you have to use usb-net.

The old name=ID parameter becomes the usual id=ID with -device.

For PCI devices, you can add bus=PCI-BUS,addr=DEVFN to control the PCI
device address, as usual.  The old -net nic provides parameter addr
for that, it is silently ignored when the NIC is not a PCI device.

For virtio-net-pci, you can control whether or not ioeventfd is used for
virtqueue notify by setting ioeventfd= to on or off (default).

-net nic accepts vectors=V for all models, but it's silently ignored
except for virtio-net-pci (model=virtio).  With -device, only devices
that support it accept it.

Not all devices are available with -device at this time.  All PCI
devices and ne2k_isa are.

Some PCI devices aren't available with -net nic, e.g. i82558a.

Bug: usb-net does not work, yet.  Patch posted.

=== Graphics Devices ===

Host and guest part of graphics devices have always been separate.

The old way to define the guest graphics device is -vga VGA.

The new way is -device.  Map from -vga argument to -device:

    std         -device VGA
    cirrus      -device cirrus-vga
    vmware      -device vmware-svga
    xenfb       not yet available with -device

As for all PCI devices, you can add bus=PCI-BUS,addr=DEVFN to control
the PCI device address.

-device VGA supports properties bios-offset and bios-size, but they
aren't used with machine type "pc".

Bug: -device cirrus-vga and -device vmware-svga require -nodefaults.

Bug: the new way requires PCI; ISA VGA is not yet available with
-device.

Bug: the new way doesn't work for machine type "pc", because it
violates obscure device initialization ordering constraints.

=== Audio Devices ===

Host and guest part of audio devices have always been separate.

The old way to define guest audio devices is -soundhw C1,...

The new way is to define each guest audio device separately with
-device.

Map from -soundhw sound card name to -device:

    ac97        -device AC97
    cs4231a     -device cs4231a,iobase=IOADDR,irq=IRQ,dma=DMA
    es1370      -device ES1370
    gus         -device gus,iobase=IOADDR,irq=IRQ,dma=DMA,freq=F
    sb16        -device sb16,iobase=IOADDR,irq=IRQ,dma=DMA,dma16=DMA16,version=V
    adlib       not yet available with -device
    pcspk       not yet available with -device

For PCI devices, you can add bus=PCI-BUS,addr=DEVFN to control the PCI
device address, as usual.

=== USB Devices ===

The old way to define a virtual USB device is -usbdevice DRIVER:OPTS...

The new way is -device DEVNAME,DEV-OPTS...  Details depend on DRIVER:

* mouse           -device usb-mouse
* tablet          -device usb-tablet
* keyboard        -device usb-kdb
* wacom-tablet    -device usb-wacom-tablet
* host:...        See "Host Device Assignment"
* disk:...        See "Block Devices"
* serial:...      See "Character Devices"
* braille         See "Character Devices"
* net:...         See "Network Devices"
* bt:...          not yet available with -device

=== Watchdog Devices ===

Host and guest part of watchdog devices have always been separate.

The old way to define a guest watchdog device is -watchdog DEVNAME.
The new way is -device DEVNAME.  For PCI devices, you can add
bus=PCI-BUS,addr=DEVFN to control the PCI device address, as usual.

=== Host Device Assignment ===

QEMU supports assigning host PCI devices (qemu-kvm only at this time)
and host USB devices.

The old way to assign a host PCI device is

    -pcidevice host=ADDR,dma=none,id=ID

The new way is

    -device pci-assign,host=ADDR,iommu=IOMMU,id=ID

The old dma=none becomes iommu=0 with -device.

The old way to assign a host USB device is

    -usbdevice host:auto:BUS.ADDR:VID:PRID

where any of BUS, ADDR, VID, PRID can be the wildcard *.

The new way is

    -device usb-host,hostbus=BUS,hostaddr=ADDR,vendorid=VID,productid=PRID

where left out or zero BUS, ADDR, VID, PRID serve as wildcard.