Re: [PATCH for-7.2 00/10] add hmp 'save-fdt' and 'info fdt' commands

[Daniel P . Berrangé]

On Fri, Jul 22, 2022 at 04:59:57PM -0300, Daniel Henrique Barboza wrote:
> Hi,
> 
> After dealing with a FDT element that isn't being shown in the userspace
> and having to shutdown the guest, dump the FDT using 'machine -dumpdtb' and
> then using 'dtc' to see what was inside the FDT, I thought it was a good
> idea to add extra support for FDT handling in QEMU.
> 
> This series introduces 2 commands. 'fdt-save' behaves similar to what
> 'machine -dumpdtb' does, with the advantage of saving the FDT of a running
> guest on demand. This command is implemented in patch 03.
> 
> The second command, 'info fdt <command>' is more sophisticated. This
> command can print specific nodes and properties of the FDT. A few
> examples:
> 
> - print the /cpus/cpu@0 from an ARM 'virt' machine:
> 
> (qemu) info fdt /cpus/cpu@0
> /cpus/cpu@0 {
>     phandle = <0x8001>
>     reg = <0x0>
>     compatible = 'arm,cortex-a57'
>     device_type = 'cpu'
> }
> (qemu) 
> 
> - print the device_type property of the interrupt-controller node of a
> pSeries machine:
> 
> (qemu) info fdt /interrupt-controller/device_type
> /interrupt-controller/device_type = 'PowerPC-External-Interrupt-Presentation'
> (qemu)

Please don't add new HMP-only commands. These should be provided
as QMP commands, where the HMP is a tiny shim to the QMP.

If you don't want to think about formally modelling the data
for 'info fdt' / 'query-fdt', then just put an 'x-' prefix on
the QMP command and return printed formatted data, as illustrated
in:

https://www.qemu.org/docs/master/devel/writing-monitor-commands.html#writing-a-debugging-aid-returning-unstructured-text

With regards,
Daniel
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