Le 04/11/2025 à 15:19, Marius Vlad a écrit :
On Tue, Nov 04, 2025 at 11:21:28AM +0100, Louis Chauvet wrote:
Le 03/11/2025 à 18:45, Marius Vlad a écrit :
vkms is missing any kind of HPD (polling/irq), so add polling to handle
hotplug events.
Hi,
Hi Louis, thanks for the quick reply!
I am a bit surprised by this addition, we currently have hotplug/unplug in
VKMS using configFS, and it seems to work. The current "irq" system is
writing in configFS the status and call drm_kms_helper_hotplug_event after
the status is updated [1].
The situation is that the VKMS connectors/card are also being exposed
through sysfs similar to real devices. That's where we trigger/simulate
a connector hot-plug without physically unplugging cables. Wasn't aware
that VKMS had something similar to that with ConfigFS, so that needs
adjusting.
Yes, that very recent, I am not surprised that you missed it.
I think the polling will not work, I read in the drm_kms_helper_poll_init
documentation that the connector is not polled if some connector flags are
not set [2]/[3].
In this case the loop will be no-op, but prior to the loop
`changed` is set to `changed = dev->mode_config.delayed_event` [1] so
the code at [2] will do run.
Ho, make sense, thanks for the explanation!
If the polling works, I don't think it will be enough for the current VKMS
implementation. Currently setting status using configFS will do everything
synchronously:
- Set the connector status (next call to connector->detect will have the new
value)
- Call drm_kms_helper_hotplug_event
With your implementation, I think you expect something to update
connector->status_changed in between, using polling if I understood
correctly, which will probably happen after the call to
drm_kms_helper_hotplug_event.
Right, that's another path for VKMS.
Let me know if you have any question about the current implementation, I
can help if needed.
[1]
https://elixir.bootlin.com/linux/v6.17.7/source/drivers/gpu/drm/drm_probe_helper.c#L769
[2]
https://elixir.bootlin.com/linux/v6.17.7/source/drivers/gpu/drm/drm_probe_helper.c#L846
[1]:https://gitlab.freedesktop.org/drm/misc/kernel/-/blob/drm-misc-next/drivers/gpu/drm/vkms/vkms_connector.c?ref_type=heads#L91-96
[2]:https://elixir.bootlin.com/linux/v6.17.7/source/drivers/gpu/drm/drm_probe_helper.c#L917-L918
[3]:https://elixir.bootlin.com/linux/v6.17.7/source/drivers/gpu/drm/drm_probe_helper.c#L793
Signed-off-by: Marius Vlad <[email protected]>
---
drivers/gpu/drm/vkms/vkms_drv.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index e8472d9b6e3b..ec815c42ef04 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -198,6 +198,9 @@ static int vkms_create(struct vkms_config *config)
if (ret)
goto out_devres;
+ /* init kms poll for handling hpd */
+ drm_kms_helper_poll_init(&vkms_device->drm);
+
drm_client_setup(&vkms_device->drm, NULL);
return 0;
@@ -240,6 +243,7 @@ static void vkms_destroy(struct vkms_config *config)
fdev = config->dev->faux_dev;
+ drm_kms_helper_poll_fini(&config->dev->drm);
drm_dev_unregister(&config->dev->drm);
drm_atomic_helper_shutdown(&config->dev->drm);
devres_release_group(&fdev->dev, NULL);
--
--
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
--
--
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
