linux-kernel - [PATCH] drm/connector: notify userspace on hotplug after register complete

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Date:   Tue,  2 Jun 2020 20:37:31 -0700
From:   Jeykumar Sankaran <jsanka@...eaurora.org>
To:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     Jeykumar Sankaran <jsanka@...eaurora.org>, seanpaul@...omium.org,
        robdclark@...il.com, Steve Cohen <cohens@...eaurora.org>
Subject: [PATCH] drm/connector: notify userspace on hotplug after register complete

drm connector notifies userspace on hotplug event prematurely before
late_register and mode_object register completes. This leads to a race
between userspace and kernel on updating the IDR list. So, move the
notification to end of connector register.

Signed-off-by: Jeykumar Sankaran <jsanka@...eaurora.org>
Signed-off-by: Steve Cohen <cohens@...eaurora.org>
---
 drivers/gpu/drm/drm_connector.c | 5 +++++
 drivers/gpu/drm/drm_sysfs.c     | 3 ---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index b1099e1..d877ddc 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -27,6 +27,7 @@
 #include <drm/drm_print.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
+#include <drm/drm_sysfs.h>
 
 #include <linux/uaccess.h>
 
@@ -523,6 +524,10 @@ int drm_connector_register(struct drm_connector *connector)
 	drm_mode_object_register(connector->dev, &connector->base);
 
 	connector->registration_state = DRM_CONNECTOR_REGISTERED;
+
+	/* Let userspace know we have a new connector */
+	drm_sysfs_hotplug_event(connector->dev);
+
 	goto unlock;
 
 err_debugfs:
diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 939f003..f0336c8 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -291,9 +291,6 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
 		return PTR_ERR(connector->kdev);
 	}
 
-	/* Let userspace know we have a new connector */
-	drm_sysfs_hotplug_event(dev);
-
 	if (connector->ddc)
 		return sysfs_create_link(&connector->kdev->kobj,
 				 &connector->ddc->dev.kobj, "ddc");
-- 
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