On 16/12/16 15:00, Johan Hovold wrote: > But in a static setup, you control what firmware you load, so you don't > need it to be self-describing. That depends. Right now I don't see a good method for kernel and a firmware to agree on ownership of GPIOs (and other shared resources) for example. I know virtio/rproc (or some combination of the two) is supposed to be able to do this. Just transmitting a manifest over an RPC link seems much simpler than what I've seen of virtio/rproc so far - and I'm not convinced the two together can describe as much as a manifest file. On some platforms (taking Edison as an example) you load a firmware that basically just assumes it owns some pins. There's exactly zero synchronisation between the two AMP processors (no type of message passing to negotiate) between kernel and firmware (that I know of). So it's pretty easy to mess that type of setup up. Whereas if the firmware returned a descriptor (or made requests for certain shared resources) it would be a lot less brittle. Greybus (or another protocol) could be used to request allocation of a GPIO from Linux to firmware, same with UART, i2c or another piece of hardware that both sides of the message bus can own - but only one of them should own at any one time. That's at least part of the problem I was looking at greybus to solve. Perhaps though I have a hammer and so everything looks like a nail http://www.urbandictionary.com/define.php?term=Irish%20Screwdriver > The operations themselves could work as an RPC (e.g. using the raw > protocol), but using Greybus in a setup like this seems like a very > inefficient way to get things done. Maybe. Most of what's out there to talk to co-processors is pretty horrific as far as I can see - with almost no real synchronisation of resources. Maybe virtio and rproc will make more sense as I try use it more but right now my greybus hammer looks like a very handy tool... (hammer) _______________________________________________ greybus-dev mailing list greybus-dev@xxxxxxxxxxxxxxxx https://lists.linaro.org/mailman/listinfo/greybus-dev
|