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,
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].
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].
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.
[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
