* [PATCH] RFC: qdev: add legacy properties only for those print()-able
@ 2025-10-15 10:54 marcandre.lureau
2025-10-21 7:51 ` Marc-André Lureau
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: marcandre.lureau @ 2025-10-15 10:54 UTC (permalink / raw)
To: qemu-devel
Cc: pbonzini, Marc-André Lureau, Daniel P. Berrangé,
Eduardo Habkost
From: Marc-André Lureau <marcandre.lureau@redhat.com>
The link properties are not printed in "info qtree", I don't know if
this was intentional. We currently register legacy properties for
link/ptr properties, but they don't have PropertyInfo getters (only
ObjectPropertyAccessor, when using non-legacy properties)
By not registering a (unusable?) legacy property, "info qtree" can now
print the link.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
hw/core/qdev-properties.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
index b7e8a89ba5..fe260a9670 100644
--- a/hw/core/qdev-properties.c
+++ b/hw/core/qdev-properties.c
@@ -1143,14 +1143,13 @@ static void qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop
{
g_autofree char *name = NULL;
- /* Register pointer properties as legacy properties */
- if (!prop->info->print && prop->info->get) {
+ if (!prop->info->print) {
return;
}
name = g_strdup_printf("legacy-%s", prop->name);
object_class_property_add(OBJECT_CLASS(dc), name, "str",
- prop->info->print ? qdev_get_legacy_property : prop->info->get,
+ qdev_get_legacy_property,
NULL, NULL, (Property *)prop);
}
--
2.51.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] RFC: qdev: add legacy properties only for those print()-able
2025-10-15 10:54 [PATCH] RFC: qdev: add legacy properties only for those print()-able marcandre.lureau
@ 2025-10-21 7:51 ` Marc-André Lureau
2025-10-21 8:18 ` Philippe Mathieu-Daudé
2025-10-21 12:53 ` Markus Armbruster
2 siblings, 0 replies; 6+ messages in thread
From: Marc-André Lureau @ 2025-10-21 7:51 UTC (permalink / raw)
To: qemu-devel; +Cc: pbonzini, Daniel P. Berrangé, Eduardo Habkost
[-- Attachment #1: Type: text/plain, Size: 1539 bytes --]
Hi!
On Wed, Oct 15, 2025 at 2:54 PM <marcandre.lureau@redhat.com> wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> The link properties are not printed in "info qtree", I don't know if
> this was intentional. We currently register legacy properties for
> link/ptr properties, but they don't have PropertyInfo getters (only
> ObjectPropertyAccessor, when using non-legacy properties)
>
> By not registering a (unusable?) legacy property, "info qtree" can now
> print the link.
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>
Any objections?
> ---
> hw/core/qdev-properties.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> index b7e8a89ba5..fe260a9670 100644
> --- a/hw/core/qdev-properties.c
> +++ b/hw/core/qdev-properties.c
> @@ -1143,14 +1143,13 @@ static void
> qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop
> {
> g_autofree char *name = NULL;
>
> - /* Register pointer properties as legacy properties */
> - if (!prop->info->print && prop->info->get) {
> + if (!prop->info->print) {
> return;
> }
>
> name = g_strdup_printf("legacy-%s", prop->name);
> object_class_property_add(OBJECT_CLASS(dc), name, "str",
> - prop->info->print ? qdev_get_legacy_property : prop->info->get,
> + qdev_get_legacy_property,
> NULL, NULL, (Property *)prop);
> }
>
> --
> 2.51.0
>
>
[-- Attachment #2: Type: text/html, Size: 2379 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] RFC: qdev: add legacy properties only for those print()-able
2025-10-15 10:54 [PATCH] RFC: qdev: add legacy properties only for those print()-able marcandre.lureau
2025-10-21 7:51 ` Marc-André Lureau
@ 2025-10-21 8:18 ` Philippe Mathieu-Daudé
2025-10-21 12:53 ` Markus Armbruster
2 siblings, 0 replies; 6+ messages in thread
From: Philippe Mathieu-Daudé @ 2025-10-21 8:18 UTC (permalink / raw)
To: marcandre.lureau, qemu-devel, Markus Armbruster
Cc: pbonzini, Daniel P. Berrangé, Eduardo Habkost
+Markus
On 15/10/25 12:54, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> The link properties are not printed in "info qtree", I don't know if
> this was intentional. We currently register legacy properties for
> link/ptr properties, but they don't have PropertyInfo getters (only
> ObjectPropertyAccessor, when using non-legacy properties)
>
> By not registering a (unusable?) legacy property, "info qtree" can now
> print the link.
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
> hw/core/qdev-properties.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> index b7e8a89ba5..fe260a9670 100644
> --- a/hw/core/qdev-properties.c
> +++ b/hw/core/qdev-properties.c
> @@ -1143,14 +1143,13 @@ static void qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop
> {
> g_autofree char *name = NULL;
>
> - /* Register pointer properties as legacy properties */
> - if (!prop->info->print && prop->info->get) {
> + if (!prop->info->print) {
> return;
> }
>
> name = g_strdup_printf("legacy-%s", prop->name);
> object_class_property_add(OBJECT_CLASS(dc), name, "str",
> - prop->info->print ? qdev_get_legacy_property : prop->info->get,
> + qdev_get_legacy_property,
> NULL, NULL, (Property *)prop);
> }
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] RFC: qdev: add legacy properties only for those print()-able
2025-10-15 10:54 [PATCH] RFC: qdev: add legacy properties only for those print()-able marcandre.lureau
2025-10-21 7:51 ` Marc-André Lureau
2025-10-21 8:18 ` Philippe Mathieu-Daudé
@ 2025-10-21 12:53 ` Markus Armbruster
2025-10-21 12:58 ` Marc-André Lureau
2 siblings, 1 reply; 6+ messages in thread
From: Markus Armbruster @ 2025-10-21 12:53 UTC (permalink / raw)
To: marcandre.lureau
Cc: qemu-devel, pbonzini, Daniel P. Berrangé, Eduardo Habkost
marcandre.lureau@redhat.com writes:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> The link properties are not printed in "info qtree", I don't know if
> this was intentional. We currently register legacy properties for
> link/ptr properties, but they don't have PropertyInfo getters (only
> ObjectPropertyAccessor, when using non-legacy properties)
>
> By not registering a (unusable?) legacy property, "info qtree" can now
> print the link.
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
> hw/core/qdev-properties.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> index b7e8a89ba5..fe260a9670 100644
> --- a/hw/core/qdev-properties.c
> +++ b/hw/core/qdev-properties.c
> @@ -1143,14 +1143,13 @@ static void qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop
> {
> g_autofree char *name = NULL;
>
> - /* Register pointer properties as legacy properties */
> - if (!prop->info->print && prop->info->get) {
> + if (!prop->info->print) {
> return;
> }
>
> name = g_strdup_printf("legacy-%s", prop->name);
> object_class_property_add(OBJECT_CLASS(dc), name, "str",
> - prop->info->print ? qdev_get_legacy_property : prop->info->get,
> + qdev_get_legacy_property,
> NULL, NULL, (Property *)prop);
> }
The old code confuses me. Let's go through it real slow.
/**
* qdev_class_add_legacy_property:
* @dev: Device to add the property to.
* @prop: The qdev property definition.
*
* Add a legacy QOM property to @dev for qdev property @prop.
*
* Legacy properties are string versions of QOM properties. The format of
* the string depends on the property type. Legacy properties are only
* needed for "info qtree".
*
* Do not use this in new code! QOM Properties added through this interface
* will be given names in the "legacy" namespace.
*/
static void qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop)
{
g_autofree char *name = NULL;
/* Register pointer properties as legacy properties */
The comment talks about "pointer properties". We used to call
properties defined with DEFINE_PROP_PTR() that way, but these were
deleted years ago. The comment is even older. I'm going to ignore it.
if (!prop->info->print && prop->info->get) {
return;
}
To get here, prop->info->print || !prop->info->get.
name = g_strdup_printf("legacy-%s", prop->name);
object_class_property_add(OBJECT_CLASS(dc), name, "str",
prop->info->print ? qdev_get_legacy_property : prop->info->get,
NULL, NULL, (Property *)prop);
If qdev property @prop has a .print() method, we create a QOM property
"legacy-FOO" of type "str" with qdev_get_legacy_property() as .get(),
and no .set() or .release().
qdev_get_legacy_property() is a QOM .get() wrapping around qdev
.print(): it calls .print() to format the property value as a string
(arbitrarily limited to 1023 characters), then visits it with
visit_type_str().
Aside: there seems to be just one property that implements .print():
DEFINE_PROP_PCI_DEVFN(), in qdev_prop_pci_devfn. Quite a lot of
infrastructure just for that.
Else, prop->info->get is null, because prop->info->print || !prop->info->get.
So we create a QOM property "legacy-FOO" with no .get(), .set(),
.release(). Why?
Your patch gets rid of these. How does this make "info qtree" show link
properties? Hmm... qdev_print_props() uses "legacy-FOO" instead of
"FOO" when it exists. But a "legacy-FOO" without a .get() will fail.
When it does, the property is skipped.
Is this what makes the patch work?
}
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] RFC: qdev: add legacy properties only for those print()-able
2025-10-21 12:53 ` Markus Armbruster
@ 2025-10-21 12:58 ` Marc-André Lureau
2025-10-22 8:18 ` Markus Armbruster
0 siblings, 1 reply; 6+ messages in thread
From: Marc-André Lureau @ 2025-10-21 12:58 UTC (permalink / raw)
To: Markus Armbruster
Cc: qemu-devel, pbonzini, Daniel P. Berrangé, Eduardo Habkost
Hi
On Tue, Oct 21, 2025 at 4:55 PM Markus Armbruster <armbru@redhat.com> wrote:
>
> marcandre.lureau@redhat.com writes:
>
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >
> > The link properties are not printed in "info qtree", I don't know if
> > this was intentional. We currently register legacy properties for
> > link/ptr properties, but they don't have PropertyInfo getters (only
> > ObjectPropertyAccessor, when using non-legacy properties)
> >
> > By not registering a (unusable?) legacy property, "info qtree" can now
> > print the link.
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> > hw/core/qdev-properties.c | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> > index b7e8a89ba5..fe260a9670 100644
> > --- a/hw/core/qdev-properties.c
> > +++ b/hw/core/qdev-properties.c
> > @@ -1143,14 +1143,13 @@ static void qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop
> > {
> > g_autofree char *name = NULL;
> >
> > - /* Register pointer properties as legacy properties */
> > - if (!prop->info->print && prop->info->get) {
> > + if (!prop->info->print) {
> > return;
> > }
> >
> > name = g_strdup_printf("legacy-%s", prop->name);
> > object_class_property_add(OBJECT_CLASS(dc), name, "str",
> > - prop->info->print ? qdev_get_legacy_property : prop->info->get,
> > + qdev_get_legacy_property,
> > NULL, NULL, (Property *)prop);
> > }
>
> The old code confuses me. Let's go through it real slow.
>
> /**
> * qdev_class_add_legacy_property:
> * @dev: Device to add the property to.
> * @prop: The qdev property definition.
> *
> * Add a legacy QOM property to @dev for qdev property @prop.
> *
> * Legacy properties are string versions of QOM properties. The format of
> * the string depends on the property type. Legacy properties are only
> * needed for "info qtree".
> *
> * Do not use this in new code! QOM Properties added through this interface
> * will be given names in the "legacy" namespace.
> */
> static void qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop)
> {
> g_autofree char *name = NULL;
>
> /* Register pointer properties as legacy properties */
>
> The comment talks about "pointer properties". We used to call
> properties defined with DEFINE_PROP_PTR() that way, but these were
> deleted years ago. The comment is even older. I'm going to ignore it.
>
> if (!prop->info->print && prop->info->get) {
> return;
> }
>
> To get here, prop->info->print || !prop->info->get.
>
> name = g_strdup_printf("legacy-%s", prop->name);
> object_class_property_add(OBJECT_CLASS(dc), name, "str",
> prop->info->print ? qdev_get_legacy_property : prop->info->get,
> NULL, NULL, (Property *)prop);
>
> If qdev property @prop has a .print() method, we create a QOM property
> "legacy-FOO" of type "str" with qdev_get_legacy_property() as .get(),
> and no .set() or .release().
>
> qdev_get_legacy_property() is a QOM .get() wrapping around qdev
> .print(): it calls .print() to format the property value as a string
> (arbitrarily limited to 1023 characters), then visits it with
> visit_type_str().
>
> Aside: there seems to be just one property that implements .print():
> DEFINE_PROP_PCI_DEVFN(), in qdev_prop_pci_devfn. Quite a lot of
> infrastructure just for that.
>
> Else, prop->info->get is null, because prop->info->print || !prop->info->get.
> So we create a QOM property "legacy-FOO" with no .get(), .set(),
> .release(). Why?
>
> Your patch gets rid of these. How does this make "info qtree" show link
> properties? Hmm... qdev_print_props() uses "legacy-FOO" instead of
> "FOO" when it exists. But a "legacy-FOO" without a .get() will fail.
> When it does, the property is skipped.
>
> Is this what makes the patch work?
>
Yes, that matches my understanding and I agree about your feeling
about the infrastructure just for DEVFN. But at the same time, it's
nice to have and I don't have a proposal to change that :)
--
Marc-André Lureau
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] RFC: qdev: add legacy properties only for those print()-able
2025-10-21 12:58 ` Marc-André Lureau
@ 2025-10-22 8:18 ` Markus Armbruster
0 siblings, 0 replies; 6+ messages in thread
From: Markus Armbruster @ 2025-10-22 8:18 UTC (permalink / raw)
To: Marc-André Lureau
Cc: qemu-devel, pbonzini, Daniel P. Berrangé, Eduardo Habkost
Marc-André Lureau <marcandre.lureau@gmail.com> writes:
[...]
> Yes, that matches my understanding and I agree about your feeling
> about the infrastructure just for DEVFN. But at the same time, it's
> nice to have and I don't have a proposal to change that :)
I have an idea on how to simplify things. If it works, I'll send a
patch.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2025-10-22 8:19 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-10-15 10:54 [PATCH] RFC: qdev: add legacy properties only for those print()-able marcandre.lureau
2025-10-21 7:51 ` Marc-André Lureau
2025-10-21 8:18 ` Philippe Mathieu-Daudé
2025-10-21 12:53 ` Markus Armbruster
2025-10-21 12:58 ` Marc-André Lureau
2025-10-22 8:18 ` Markus Armbruster
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).