Am 14.02.2014 16:58, schrieb Paolo Bonzini: > Il 13/02/2014 14:26, Alex David ha scritto: >> After reading code, documentation and available things, I've been trying >> to write something like a "virtio-i2c" : I wrote a virtio-i2c module for >> my kernel (I used some examples from virtio-pci and virtio-console), it >> seems that it created a "i2c-1" device in /dev, >> >> My device that I launch with QEMU (-chardev >> socket,path=/tmp/test0,server,nowait,id=bob -device >> virtio-i2c,chardev=bob) doesn't seem to be recognized by the kernel >> driver : my probe function doesn't run. > > i2c is a bus, not directly a device. Do you want to pass an entire > adapter down to the guest? Or just a slave? > > QEMU has i2c emulation but it is bus-based, so you need one device per > slave + 1 for the adapter. x86 already has an I2C bus (actually it's > SMBus) that you may be able to use. So you probably want something like > > -object i2c-linux,file=/dev/i2c-1,id=i2c-backend > -device i2c-host,backend=i2c-backend,hostaddr=0x40,address=0x40 > -device i2c-host,backend=i2c-backend,hostaddr=0x50,address=0x50 > > and so on. i2c-linux would be the object issuing ioctls to /dev/i2c-1, > multiplexing access to the device for all the i2c-host devices.
While that is certainly possible in case host passthrough was desired, maybe virtio was mixed up with VFIO? For now I believe it is PCI-only and there was work on platform devices at KVM Forum 2013; for s390x a ccw backend may be needed, so maybe it's possible to extend vfio for I2C? If however it's just about QEMU reading data from a daemon on the host, a simple slave device might do and is then independent of host I2C devices. Regards, Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
