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Re: [Qemu-devel] Trying to write a new device / virtio-i2c ?
From: |
Andreas Färber |
Subject: |
Re: [Qemu-devel] Trying to write a new device / virtio-i2c ? |
Date: |
Fri, 14 Feb 2014 17:31:23 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 |
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
- [Qemu-devel] Trying to write a new device / virtio-i2c ?, Alex David, 2014/02/13
- Re: [Qemu-devel] Trying to write a new device / virtio-i2c ?, Stefan Hajnoczi, 2014/02/14
- Re: [Qemu-devel] Trying to write a new device / virtio-i2c ?, Paolo Bonzini, 2014/02/14
- Re: [Qemu-devel] Trying to write a new device / virtio-i2c ?,
Andreas Färber <=
- Re: [Qemu-devel] Trying to write a new device / virtio-i2c ?, Paolo Bonzini, 2014/02/14
- Re: [Qemu-devel] Trying to write a new device / virtio-i2c ?, Alex David, 2014/02/17
- Re: [Qemu-devel] Trying to write a new device / virtio-i2c ?, Paolo Bonzini, 2014/02/17
- Message not available
- [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?, Alex David, 2014/02/17
- Re: [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?, Paolo Bonzini, 2014/02/17
- Message not available
- Re: [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?, Paolo Bonzini, 2014/02/17
- Re: [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?, Alex David, 2014/02/17
- Re: [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?, Alex David, 2014/02/17
- Re: [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?, Paolo Bonzini, 2014/02/17
- Re: [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?, Alex David, 2014/02/17