Re: [Bug 1906463] [NEW] "-device help" does not report all devices

[Markus Armbruster]

Doug Evans <1906463@bugs.launchpad.net> writes:

> Public bug reported:
>
> -device help doesn't report all devices.
> E.g., devices that are instantiated by a board don't get printed in part 
> because they don't exist when "-device help" is processed. As an experiment I 
> deferred processing of "-device help" as long as possible and some devices 
> were still not printed, so there's more going on here.
>
> QEMU commit hash: 944fdc5e27a5b5adbb765891e8e70e88ba9a00ec
>
> Repro:
> $ configure --target-list=arm-softmmu
> $ make
> $ ./qemu-system-arm -device help | grep npcm7xx
> <empty>
>
> I'd expect to see things like npcm7xx-rng in the output.

Works as intended.

"-device help" shows the devices that are available with -device.
npcm7xx-rng isn't:

    $ qemu-system-arm -M virt -device npcm7xx-rng
    qemu-system-arm: -device npcm7xx-rng: Parameter 'driver' expects pluggable 
device type

Monitor command "info qdm" shows all devices, including npcm7xx-rng:

    $ qemu-system-arm -M virt -monitor stdio
    QEMU 5.1.92 monitor - type 'help' for more information
    (qemu) info qdm
    [...]
    name "npcm7xx-rng", bus System, desc "NPCM7xx Random Number Generator", 
no-user
    [...]

Note "no-user": it's not available with -device.

> I can imagine enumerating board-provided devices is a challenge.
> Still, it'd be really nice if "-device help" printed them, and having
> "-device $driver,help" work as well.

It works:

    $ qemu-system-arm -M virt -device npcm7xx-rng,help
    npcm7xx-rng options:
      regs[0]=<child<qemu:memory-region>>

Hope this helps!