[Qemu-devel] [PATCH 0/5] Platform device support

[Alexander Graf <agraf@suse.de>]

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 or via really complicated command line arguments under
discussion upstream right now.

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.

So the idea for platform devices arose. A platform device is really just a
device that exposes its qemu_irq slots and memory regions to the world.

That allows us to write machine specific code that maps a platform device
wherever the machine thinks fits nicely. It also allows that same machine
to generate a device tree entry for platform devices easily, as it is fully
aware of the interrupt lines and places it was mapped to.

A device (read: user) 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 can get mapped at convenient places by the machine.

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...

Alexander Graf (5):
  Platform: Add platform device class
  Platform: Add serial device
  PPC: e500: Only create dt entries for existing serial ports
  PPC: e500: Support platform devices
  PPC: e500: Add support for platform serial devices

 default-configs/ppc-softmmu.mak   |   2 +
 default-configs/ppc64-softmmu.mak |   2 +
 hw/Makefile.objs                  |   1 +
 hw/char/Makefile.objs             |   1 +
 hw/char/serial-platform.c         | 103 +++++++++++++++
 hw/platform/Makefile.objs         |   1 +
 hw/platform/device.c              | 108 ++++++++++++++++
 hw/ppc/e500.c                     | 262 +++++++++++++++++++++++++++++++++++++-
 hw/ppc/e500.h                     |   1 +
 hw/ppc/e500plat.c                 |   1 +
 include/hw/char/serial-platform.h |  56 ++++++++
 include/hw/platform/device.h      |  45 +++++++
 12 files changed, 577 insertions(+), 6 deletions(-)
 create mode 100644 hw/char/serial-platform.c
 create mode 100644 hw/platform/Makefile.objs
 create mode 100644 hw/platform/device.c
 create mode 100644 include/hw/char/serial-platform.h
 create mode 100644 include/hw/platform/device.h

-- 
1.8.1.4