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I'm very much a Xen newbie - ok, maybe not even that far along - so I hope this question isn't completely uninformed...

Do you have to have Linux running in dom0? Could it be a much simpler OSÂ that basically just allows access to GPIO without a lot of other overhead? Maybe I should back up a step: Is there always a Linux OS running in dom0 when you're running Mirage on a Cubieboard (as in your OSCON demo for example)?

Also, a bit of googling reveals http://wiki.xen.org/wiki/Driver_Domain
"A driver domain is unprivileged Xen domain that has been given responsibility for a particular piece of hardware. It runs a minimal kernel with only that hardware driver and the backend driver for that device class. Thus, if the hardware driver fails, the other domains (including Dom0) will survive and, when the driver domain is restarted, will be able to use the hardware again"

When they say "minimal kernel" there does that imply a Linux kernel?

Phil

On Sun, Aug 17, 2014 at 10:18 AM, Anil Madhavapeddy <anil@xxxxxxxxxx> wrote:

On 17 Aug 2014, at 12:14, Phil Tomson <philtomson@xxxxxxxxx> wrote:

I'm interested in Mirage for some embedded applications that interact with the Internet of Things either by http or other protocols (like MQTT or COAP).

So for example, let's say I've got a Cubieboard2 and I connect up an A/D board to collect data (temperature, weather data, etc.) and I want to setup an http server using Mirage that would serve up this data. The http part is straightforward. However, how does one interact with the GPIO pins on the Cubieboard? - that seems to be on the "other side of" Xen. So would one need to write some kind of device driver for Xen that interfaces to the Cubieboard's GPIO in order to do this? And if so, how would it be accessed by Mirage?

1. Is it possible?
2. If so, can you point me in the right direction?

The GPIO pins would, in the simplest instance, just be accessible from the Linux running in dom0. ÂAfter that, you can interface it to a Mirage VM via 'vchan':Âhttp://openmirage.org/blog/update-on-vchan

If you're feeling extra-paranoid, it's possible to move the GPIO handling code into an unprivileged VM, but the first step to do is to figure out the GPIO/Linux runes in dom0 first.

I'd be very interested in seeing how this goes...

-anil

Re: [MirageOS-devel] Mirage and sensor data