Re: [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?

[Alex David]

2014-02-17 11:38 GMT+01:00 Paolo Bonzini <address@hidden>:

Il 17/02/2014 11:01, Alex David ha scritto:

I indeed don't use paravirtualization.

Virtio _is_ paravirtualization. :)

Ok, now that seems much more understandable... I missed that point ha.

 

I'm emulating a bunch of sensors/actuators.

If I virtualize my sensors and attach them to the i2c-dev with -device,
how do I get those data on the host then ?

It depends on your use case.

It could be that you can make them return a constant value.

Otherwise, you may want to use a chardev for that purpose, or finally a QOM (QEMU Object Model) property.  For example, add

CONFIG_TMP105=y

to default-configs/x86_64-softmmu.mak before building QEMU, then do the following (indented = in the guest):

$ x86_64-softmmu/qemu-system-x86_64 --enable-kvm ~/test2.img  -m 256 \
   -device tmp105,id=sensor,address=0x50 \
   -qmp unix:$HOME/qmp.sock,server,nowait
$ qmp/qom-list -s ~/qmp.sock /machine/peripheral/sensor
temperature
@parent_bus/
address
hotpluggable
realized
type
$ scripts/qmp/qmp-shell ~/qmp.sock
(QEMU) qom-get path=/machine/peripheral/sensor property=temperature
{u'return': 0}
(QEMU) qom-get path=sensor property=address
{u'return': 80}

    # modprobe i2c-dev
    # i2cget -y 0 0x50 0 w
    0x0000

(QEMU) qom-set path=sensor property=temperature value=20000
{u'return': {}}

    # i2cget -y 0 0x50 0 w
    0x0014

For this particular sensor, you have to swap the two bytes and the result is 8.8 fixed-point.

Paolo

Thanks for your help. As you may see, I'm not that experienced in
QEMU/Linux kernel.

Ok, I'm gonna try these things. I might try to use a chardev also. Thanks for your help !