Re: [Qemu-devel] QEMU configuration files

[Paul Brook]

> - Machine definitions contain machine parameters and device definitions.
> Device definitions are used to create new devices not instanciated in
> the hardcoded machine definition such as PCI and USB devices.
>...
> - Is it worth specifying board specific network controllers as separate
> devices (I tried to do that for smc91c111 devices) ? A simpler solution
> would be to add new machine parameters to do that.

IMHO the goal should be for most (maybe all) devices to be explicitly 
instantiated, not just the easy USB/PCI ones.  That may require additional 
work to specify things like IRQ routing and memory ranges.

For example there's no real reason why qemu needs to know about most of the 
the ARM boards I've added (e.g. integrator, versatile, realview and stellaris 
boards). They all use approximately the same set of modular components, just 
in connected in different combinations.  I suspect the same is true of many 
of the pxa boards, and proably many ColdFire devices.

This is maybe slightly different between emulating embedded boards and 
workstation/server class machines. For workstation/server emulation it's 
entirely reasonable to arbitrarily add/remove serial and network devices from 
a "PC" machine based on the user config. For embedded SoC devices you tend to 
want to emulate a fixed number of devices (matching those present on real 
hardware) and leave them present but disconnected if the user does not 
specify appropriate net/serial options.

On case where we currently do this is CDROMs.  Omitting -cdrom does not remove 
the cdrom from the machine, it just means an "empty" cdrom drive is created.

Paul