Platforms without ISA and/or PCI have had a seriously hard time in the dynamic device creation world of QEMU. Devices on these were modeled as SysBus devices which can only be instantiated in machine files, not through -device.
Why is that so? Well, SysBus is trying to be incredibly generic. It allows you to plug any interrupt sender into any other interrupt receiver. It allows you to map a device's memory regions into any other random memory region. All of that only works from C code. But do we need that level of complexity for normal devices usually? In a normal platform world (SoCs, PV machines) we have a flat memory layout we can plug our device memory into. We also have a flat IRQ model where we can plug our device IRQs into. This platform bus creates a simple bus that models the easy world. It allows for dynamic device creation through -device. A device may or may not explictly request to be mapped at a specific IRQ and/or memory address. If no explicit mapping is requested, platform devices just get mapped at convenient places. This goes hand in hand with automatic device tree generation. When QEMU places devices somewhere and also generates a device tree to tell the guest where exactly those devices are, we close the cycle and everyone knows everything and lives happily ever after. The actual pressing issue this solves is that today it's impossible to spawn serial ports from the command line. With this patch set, it's possible to do so. But it lays the groundwork for much more... Alex Alexander Graf (9): PlatBus: Add Platform Bus PlatBus: Add abstract Platform Device PlatBus: Add Sysbus/Platform bridge device PlatBus: Hook up into Makefile system PPC: Add platform bus to the default compile set PlatBus: Add serial-platbus device PPC: Add PlatBus Serial to default configs PPC: E500: Spawn PlatBus bridge for ppce500 machine PPC: E500: Add PlatBus device tree walker default-configs/ppc-softmmu.mak | 2 + default-configs/ppc64-softmmu.mak | 2 + default-configs/ppcemb-softmmu.mak | 2 + hw/Makefile.objs | 1 + hw/char/Makefile.objs | 1 + hw/char/serial-platbus.c | 100 +++++++++++++++++++++++ hw/platbus/Makefile.objs | 1 + hw/platbus/bridge.c | 64 +++++++++++++++ hw/platbus/device.c | 162 +++++++++++++++++++++++++++++++++++++ hw/platbus/platbus.c | 107 ++++++++++++++++++++++++ hw/ppc/e500.c | 75 ++++++++++++++++- hw/ppc/e500.h | 1 + hw/ppc/e500plat.c | 1 + include/hw/char/serial-platbus.h | 56 +++++++++++++ include/hw/platbus/bridge.h | 32 ++++++++ include/hw/platbus/device.h | 102 +++++++++++++++++++++++ include/hw/platbus/platbus.h | 86 ++++++++++++++++++++ 17 files changed, 791 insertions(+), 4 deletions(-) create mode 100644 hw/char/serial-platbus.c create mode 100644 hw/platbus/Makefile.objs create mode 100644 hw/platbus/bridge.c create mode 100644 hw/platbus/device.c create mode 100644 hw/platbus/platbus.c create mode 100644 include/hw/char/serial-platbus.h create mode 100644 include/hw/platbus/bridge.h create mode 100644 include/hw/platbus/device.h create mode 100644 include/hw/platbus/platbus.h -- 1.8.1.4
