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From: "Ricardo B. Marliere" <ricardo@marliere.net>
Date: Tue, 05 Mar 2024 08:34:11 -0300
Subject: [PATCH RESEND drm-misc 2/4] drm/sysfs: make drm_class constant
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Message-Id: <20240305-class_cleanup-drm-v1-2-94f82740525a@marliere.net>
References: <20240305-class_cleanup-drm-v1-0-94f82740525a@marliere.net>
In-Reply-To: <20240305-class_cleanup-drm-v1-0-94f82740525a@marliere.net>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, 
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>, 
 David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>, 
 Hans de Goede <hdegoede@redhat.com>, Helge Deller <deller@gmx.de>, 
 Sumit Semwal <sumit.semwal@linaro.org>, 
 Benjamin Gaignard <benjamin.gaignard@collabora.com>, 
 Brian Starkey <Brian.Starkey@arm.com>, John Stultz <jstultz@google.com>, 
 "T.J. Mercier" <tjmercier@google.com>, 
 =?utf-8?q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 
 dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, 
 linux-fbdev@vger.kernel.org, linux-media@vger.kernel.org, 
 linaro-mm-sig@lists.linaro.org, 
 "Ricardo B. Marliere" <ricardo@marliere.net>

Since commit 43a7206b0963 ("driver core: class: make class_register() take
a const *"), the driver core allows for struct class to be in read-only
memory, so move the drm_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
---
 drivers/gpu/drm/drm_internal.h       |  2 +-
 drivers/gpu/drm/drm_privacy_screen.c |  2 +-
 drivers/gpu/drm/drm_sysfs.c          | 44 ++++++++++++++++--------------------
 3 files changed, 21 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index 8e4faf0a28e6..a881cd442a9b 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -142,7 +142,7 @@ bool drm_master_internal_acquire(struct drm_device *dev);
 void drm_master_internal_release(struct drm_device *dev);
 
 /* drm_sysfs.c */
-extern struct class *drm_class;
+extern const struct class drm_class;
 
 int drm_sysfs_init(void);
 void drm_sysfs_destroy(void);
diff --git a/drivers/gpu/drm/drm_privacy_screen.c b/drivers/gpu/drm/drm_privacy_screen.c
index 6cc39e30781f..2fbd24ba5818 100644
--- a/drivers/gpu/drm/drm_privacy_screen.c
+++ b/drivers/gpu/drm/drm_privacy_screen.c
@@ -401,7 +401,7 @@ struct drm_privacy_screen *drm_privacy_screen_register(
 	mutex_init(&priv->lock);
 	BLOCKING_INIT_NOTIFIER_HEAD(&priv->notifier_head);
 
-	priv->dev.class = drm_class;
+	priv->dev.class = &drm_class;
 	priv->dev.type = &drm_privacy_screen_type;
 	priv->dev.parent = parent;
 	priv->dev.release = drm_privacy_screen_device_release;
diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index a953f69a34b6..90145f9256a2 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -58,7 +58,15 @@ static struct device_type drm_sysfs_device_connector = {
 	.name = "drm_connector",
 };
 
-struct class *drm_class;
+static char *drm_devnode(const struct device *dev, umode_t *mode)
+{
+	return kasprintf(GFP_KERNEL, "dri/%s", dev_name(dev));
+}
+
+const struct class drm_class = {
+	.name = "drm",
+	.devnode = drm_devnode,
+};
 
 #ifdef CONFIG_ACPI
 static bool drm_connector_acpi_bus_match(struct device *dev)
@@ -93,11 +101,6 @@ static void drm_sysfs_acpi_register(void) { }
 static void drm_sysfs_acpi_unregister(void) { }
 #endif
 
-static char *drm_devnode(const struct device *dev, umode_t *mode)
-{
-	return kasprintf(GFP_KERNEL, "dri/%s", dev_name(dev));
-}
-
 static int typec_connector_bind(struct device *dev,
 				struct device *typec_connector, void *data)
 {
@@ -142,19 +145,16 @@ int drm_sysfs_init(void)
 {
 	int err;
 
-	drm_class = class_create("drm");
-	if (IS_ERR(drm_class))
-		return PTR_ERR(drm_class);
+	err = class_register(&drm_class);
+	if (err)
+		return err;
 
-	err = class_create_file(drm_class, &class_attr_version.attr);
+	err = class_create_file(&drm_class, &class_attr_version.attr);
 	if (err) {
-		class_destroy(drm_class);
-		drm_class = NULL;
+		class_unregister(&drm_class);
 		return err;
 	}
 
-	drm_class->devnode = drm_devnode;
-
 	drm_sysfs_acpi_register();
 	return 0;
 }
@@ -166,12 +166,9 @@ int drm_sysfs_init(void)
  */
 void drm_sysfs_destroy(void)
 {
-	if (IS_ERR_OR_NULL(drm_class))
-		return;
 	drm_sysfs_acpi_unregister();
-	class_remove_file(drm_class, &class_attr_version.attr);
-	class_destroy(drm_class);
-	drm_class = NULL;
+	class_remove_file(&drm_class, &class_attr_version.attr);
+	class_unregister(&drm_class);
 }
 
 static void drm_sysfs_release(struct device *dev)
@@ -372,7 +369,7 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
 		return -ENOMEM;
 
 	device_initialize(kdev);
-	kdev->class = drm_class;
+	kdev->class = &drm_class;
 	kdev->type = &drm_sysfs_device_connector;
 	kdev->parent = dev->primary->kdev;
 	kdev->groups = connector_dev_groups;
@@ -550,7 +547,7 @@ struct device *drm_sysfs_minor_alloc(struct drm_minor *minor)
 			minor_str = "card%d";
 
 		kdev->devt = MKDEV(DRM_MAJOR, minor->index);
-		kdev->class = drm_class;
+		kdev->class = &drm_class;
 		kdev->type = &drm_sysfs_device_minor;
 	}
 
@@ -579,10 +576,7 @@ struct device *drm_sysfs_minor_alloc(struct drm_minor *minor)
  */
 int drm_class_device_register(struct device *dev)
 {
-	if (!drm_class || IS_ERR(drm_class))
-		return -ENOENT;
-
-	dev->class = drm_class;
+	dev->class = &drm_class;
 	return device_register(dev);
 }
 EXPORT_SYMBOL_GPL(drm_class_device_register);

-- 
2.43.0