Thomas Huth <th...@redhat.com> writes: > On 04/04/2019 15.29, Philippe Mathieu-Daudé wrote: >> On 4/4/19 12:07 PM, Paolo Bonzini wrote: >>> On 04/04/19 09:14, Thomas Huth wrote: >>>> The i8042 PS/2 controller is part of the chipset on the motherboard. >>>> It is instantiated by the machine init code, and it does not make sense >>>> to allow the user to plug an additional i8042 in any of the free ISA slots. >>>> Thus let's mark the device with user_creatable = false. >>>> >>>> Signed-off-by: Thomas Huth <th...@redhat.com> >>>> --- >>>> hw/input/pckbd.c | 2 ++ >>>> 1 file changed, 2 insertions(+) >>> >>> user_creatable is not for devices that are not pluggable in real life; >>> it is for devices that crash QEMU (!) or always fail if plugged by the user. > > ... hmm, but presenting devices to the user that are clearly not > intended for direct use is also not very nice, is it?
Maybe, but hiding them should be separate from marking devices that still defeat device_add. In the ideal world, we'd be able to start with an empty board, then build a machine with by wiring together devices. Say like use device_add to create and plug into parent bus, qom-set link properties to create additional wires. Plenty of devices fail at the device_add stage, or require additional wiring by code. These are marked not user_creatable. See also commit e90f2a8c3e0e677eeea46a9b401c3f98425ffa37. >>> So the question to ask is: would it make sense, and especially work, to >>> add an i8042 to machines that do have an ISA bridge (for example the Alpha?) Scratch the "would it make sense" part, keep the "would it work" part. > I don't think so. It is a device that is supposed to be part of the > chipset on the motherboard, so operating systems certainly don't know > how to use this device on other machines. > > And at least some part of the device have to be set up in source code > (see e.g. i8042_setup_a20_line() ...). If (and only if) the parts that need code are essential to the functioning the device, it should be marked not user_creatable. >> Correct me if I'm wrong but it seems no machine directly use a 8042 on a >> ISA bus, it is always part of a SuperIO chipset. It is not reflected in >> the code (in particular the X86 machines, but I'm working on cleaning this). Known issue: we model a bunch of x86 devices as ISA devices, even though they're actually part of a super i/o device connected via LPC bus. [...]
