Hello,
On 9/9/26 12:35, Mark Cave-Ayland wrote:
On 04/09/2026 06:04, Cédric Le Goater wrote:
Add a DT-style alias container /machine/labels where board code registers
link<> properties pointing to well-known devices. Tests can then resolve
a device with a single QMP call (qom-get /machine/labels/<name>) instead
of walking the bus hierarchy.
Signed-off-by: Cédric Le Goater <[email protected]>
---
include/hw/arm/aspeed.h | 12 ++++++++++++
hw/arm/aspeed.c | 10 ++++++++++
2 files changed, 22 insertions(+)
diff --git a/include/hw/arm/aspeed.h b/include/hw/arm/aspeed.h
index 245d02e5f757..0b8b40262767 100644
--- a/include/hw/arm/aspeed.h
+++ b/include/hw/arm/aspeed.h
@@ -128,4 +128,16 @@ void aspeed_machine_ast2600_class_emmc_init(ObjectClass
*oc);
*/
void aspeed_connect_serial_hds_to_uarts(AspeedMachineState *bmc);
+/*
+ * aspeed_machine_add_label:
+ * @bmc: pointer to the #AspeedMachineState.
+ * @label: the label name for the device.
+ * @target: the device object to register.
+ *
+ * Register a well-known device under /machine/labels/<label> as a
+ * read-only link. Aborts on duplicate label names.
+ */
+void aspeed_machine_add_label(AspeedMachineState *bmc, const char *label,
+ Object *target);
+
#endif
diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
index 1f8d5d3e132d..79b8d55d66da 100644
--- a/hw/arm/aspeed.c
+++ b/hw/arm/aspeed.c
@@ -127,6 +127,14 @@ void aspeed_connect_serial_hds_to_uarts(AspeedMachineState
*bmc)
}
}
+void aspeed_machine_add_label(AspeedMachineState *bmc, const char *label,
+ Object *target)
+{
+ Object *labels = object_resolve_path_component(OBJECT(bmc), "labels");
+
+ object_property_add_const_link(labels, label, target);
+}
+
static void aspeed_machine_init(MachineState *machine)
{
AspeedMachineState *bmc = ASPEED_MACHINE(machine);
@@ -137,6 +145,8 @@ static void aspeed_machine_init(MachineState *machine)
DriveInfo *emmc0 = NULL;
bool boot_emmc;
+ object_property_add_new_container(OBJECT(machine), "labels");
+
bmc->soc = ASPEED_SOC(object_new(amc->soc_name));
object_property_add_child(OBJECT(machine), "soc", OBJECT(bmc->soc));
object_unref(OBJECT(bmc->soc));
Thanks for the proposal, Cédric! A few comments from me below:
1) Is there any reason it should be called labels as opposed to aliases?
none
The aliases name as used in Open Firmware feels more intuitive to me.
yes. It it just a name. aliases is fine for me unless it introduces
some confusion with object_property_add_alias().
2) If there is agreement in this approach, is there any reason why we shouldn't
create /machine/labels (or equivalent) for all QOM trees? I certainly think it
would be a useful addition going forward.
It is a trivial addition. We would need more maintainers to Ack
the concept though.
3) Is there any reason why we need to provide the machine object directly to
the aspeed_machine_add_label() function?
Only because it was selfishly introduced as a Aspeed machine helper !
If possible I think it makes sense to avoid the direct machine reference, in
case the underlying implementation changes i.e.
void machine_add_alias(const char *alias, Object *target)
{
Object *aliases = object_resolve_path("/machine/aliases", NULL);
object_property_add_const_link(aliases, alias, target);
}
ok.
Even better perhaps we should also generate an error if the alias already
exists to ensure they are always unique i.e.
bool machine_add_alias(const char *alias, Object *target,
Error **errp)
{
Object *aliases = object_resolve_path("/machine/aliases", NULL);
if (object_resolve_path_component(aliases, alias)) {
error_setg(errp, "machine alias '%s' already exists");
return false;
}
I don't think this is useful since object_property_add_const_link()
should abort in case of duplicate, which would be a modeling error
anyhow.
return (object_property_add_const_link(aliases, alias, target) !=
NULL);
}
4) Should we create a page in the documentation explaining which
devices/objects should be included in the alias list,
Any device in the QOM tree could have an alias. Why would you want
to limit the possible aliases? a part from dynamic ones.
which ones are added automatically,
That's dangerous. I would say none.
and what naming conventions should be used for devices e.g. serial0, net0 for a
network device etc.?
I would leave the choice to the person in charge of the SoC or the
machine.
5) What should happen to aliases for devices that are hot-plugged/hot-unplugged?
IMO, aliases are intended for devices "soldered" on the board,
created by the machine. Devices created via the command line or
QMP/HMP are excluded.
Thanks,
C.
