Re: [Qemu-devel] hw/arm: add Lego NXT board

[Alexander Graf]

On 07/15/2014 12:48 AM, Peter Maydell wrote:
> Right, but this is an optional part of Paolo's proposal as I understand
> it. You could just have your fake sensors be implemented by some
> userspace process on the other end of a filedescriptor, as you do now
> but with i2c rather than custom protocol. This would also let you run
> the same bit of firmware in the guest as would be on the real h/w.
>

Ah, thank you, I finally realised that you are talking about the
-chardev argument (I just discovered that option.) and not only about
linux character devices. It seems I reinvented the wheel while
implementing the pipes. What a waste of time :)

On 07/15/2014 09:06 AM, Paolo Bonzini wrote:
> As to the protocol, I found a datasheet of an I2C-to-UART bridge that
> could provide ideas:
> http://www.nxp.com/documents/data_sheet/SC18IM700.pdf chapter 7, it's
> very simple (just two commands, start and stop).
Thanks for the idea. I still don't get why it should be better to fake
an I2C device rather than a universal memory IO. I don't want to emulate
the controllers hardware, but only communicate the abstract
sensor/actuator values. In addition not all Sensors are I2C devices, so
there is no value in doing it via an I2C bus. Even the simple I2C
protocol mentioned in the data sheet is more complex than mine.

Could you point me to the code where the chardev devices are defined in
qemu?

Alexander