Re: [ImageBuilder] uboot-script-gen: Add ability to configure static event channels

[Oleksandr Tyshchenko <Oleksandr_Tyshchenko@xxxxxxxx>]

On 29.09.25 22:52, Stefano Stabellini wrote:

Hello Stefano

> On Mon, 29 Sep 2025, Oleksandr Tyshchenko wrote:
>> Add DOMU_STATIC_EVTCHNS[number]="local_id local_port remote_id; ..."
>> configuration file string option specifying the static event channel
>> definitions for domain.
>>
>> The build script uses simple IDs to automatically and safely
>> generate the required unique phandle numbers for the device tree.
>> The user only needs to define simple numeric IDs and does not need
>> to manage complex phandle values.
>>
>> For the following example:
>> DOMU_STATIC_EVTCHNS[0]="1 10 2; 3 12 4"
>> DOMU_STATIC_EVTCHNS[1]="2 11 1; 4 13 3"
>>
>> it generates:
>> fdt mknod /chosen/domU0 evtchn@1
>> fdt set /chosen/domU0/evtchn@1 phandle <0xfffffffe>
>> fdt set /chosen/domU0/evtchn@1 compatible "xen,evtchn-v1"
>> fdt set /chosen/domU0/evtchn@1 xen,evtchn <10 0xfffffffd>
>> fdt mknod /chosen/domU0 evtchn@3
>> fdt set /chosen/domU0/evtchn@3 phandle <0xfffffffc>
>> fdt set /chosen/domU0/evtchn@3 compatible "xen,evtchn-v1"
>> fdt set /chosen/domU0/evtchn@3 xen,evtchn <12 0xfffffffb>
>> ...
>> fdt mknod /chosen/domU1 evtchn@2
>> fdt set /chosen/domU1/evtchn@2 phandle <0xfffffffd>
>> fdt set /chosen/domU1/evtchn@2 compatible "xen,evtchn-v1"
>> fdt set /chosen/domU1/evtchn@2 xen,evtchn <11 0xfffffffe>
>> fdt mknod /chosen/domU1 evtchn@4
>> fdt set /chosen/domU1/evtchn@4 phandle <0xfffffffb>
>> fdt set /chosen/domU1/evtchn@4 compatible "xen,evtchn-v1"
>> fdt set /chosen/domU1/evtchn@4 xen,evtchn <13 0xfffffffc>
> 
> I'd like to make an alternative suggestion. The user specifies triplets:
> DOMU_STATIC_EVTCHNS[0]="local-id remote-domid remote-id
> 
> To generate the example above:
> 
> DOMU_STATIC_EVTCHNS[0]="10 1 11; 12 1 13"
> DOMU_STATIC_EVTCHNS[1]="11 0 10; 13 0 12"

I guess by saying local-id and remote-id here you just meant local and 
remote event channels, right? If so, I would use local_port and remote_port.


> 
> I think this is better because it doesn't require to invent (useless)
> unique numbers as references. Instead, it focuses on the data that
> actually matters to the user: the event channel IDs at both ends and
> the domains involved. These are things the user must know anyway.
> 
> The only catch with this suggesion is the definition of "remote-domid":
> in reality the DOMU array index is not the domid in dom0less so we would
> have to clarify. Maybe we could define it as remote-domain-index or
> something like that.

I see, yes remote-domain-index sounds clear.


> 
> What do you think?

I think, it is a great approach. I will try to implement what you suggested.


> 
> 
> In ImageBuilder so far we have not used separators like ';' here but I
> think it does improve readability so I would keep it.

ok

[snip]