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

[Alex David <alex.daerf@gmail.com>]

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Thanks for all your answers.

I understand that what I want to achieve seemed pretty confused. I will try
to clarify :

On real hardware, I have an I2C device used to get temperatures, pressure
etc... and it works on x86 and there were no QEMU virtualized hardware
corresponding.

I don't really need to simulate the I2C hardware in QEMU. Indeed, there are
few of them just sending regular i2c data. For some tests, I want to be
able to send/receive these ones from my daemon on the host. After some
researches, what I was thinking about was :

1) Use virtio-serial and write an I2C driver (guest kernel) that would
give/take data to/from i2c-1 and read/write to vportp0... Seemed a bit
ugly, so I wanted to try something else.

2) Write virtio-i2c (using i2c-driver and virtio kernel basics) that would
register, for example, i2c-1 and get/send data from my guest app, and use
virtio to send these data to host.

What I have done for now : I used virtio-serial / virtio-console in linux
kernel and inspired from virtio-pci to try to registers these "vport0pX" as
i2c-1, i2c-2 etc... and as i2c devices. I also wrote a virtio-i2c QEMU-side
to register as this hardware using virtio-i2c drivers. I think my
understanding of the architecture is probably not complete, as it seems
that this QEMU device doesn't automatically registers as a "virtio-i2c"
hardware that would launch my guest kernel driver.
My printk's in the "probe" are not printed. My driver is then never used.

My questions were then :
- My solution might be a bit complicated assuming I don't have that much
knowledge in the architecture (however I'm interested into learning...)
- Are there solutions that seems more adapted to my case ? Like using
USB-I2C bridge ?


2014-02-14 17:45 GMT+01:00 Paolo Bonzini <pbonzini@redhat.com>:

> Il 14/02/2014 17:31, Andreas Färber ha scritto:
>
>  While that is certainly possible in case host passthrough was desired,
>> maybe virtio was mixed up with VFIO?
>>
>
> I don't think so, VFIO is mostly about IOMMUs and protecting from DMA.
>
> Paolo
>

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