How to add a new device in QEMU source code?
What could be the step wise approach to emulate/add a new device in qemu using QOM approach?
What and where could be the changes with respect to DeviceState/BusState and other properties?
Answer
edu in-tree educational PCI device
- https://github.com/qemu/qemu/blob/v2.7.0/hw/misc/edu.c
- https://github.com/qemu/qemu/blob/v2.7.0/docs/specs/edu.txt
It is very easy to understand and well documented, so I recommend that you study it.
It exposes a minimal PCI device, with basic IO, interrupt generation, and DMA.
I've written a minimal Linux kernel module + userland tests to play with it at:
- https://github.com/cirosantilli/linux-kernel-module-cheat/blob/6788a577c394a2fc512d8f3df0806d84dc09f355/rootfs_overlay/pci.sh
- https://github.com/cirosantilli/linux-kernel-module-cheat/blob/6788a577c394a2fc512d8f3df0806d84dc09f355/kernel_module/pci.c
Out-of-tree devices
I asked if it is possible to make out-of-tree devices at: How to create out-of-tree QEMU devices? but it does not look like it.