drm/vkms: convert to use faux_device

The vkms driver does not need to create a platform device, as there is
no real platform resources associated it,  it only did so because it was
simple to do that in order to get a device to use for resource
management of drm resources.  Change the driver to use the faux device
instead as this is NOT a real platform device.

Tested-by: Louis Chauvet <louis.chauvet@bootlin.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/2025070147-antics-pleat-edd2@gregkh

Author: gregkh

drivers/gpu/drm/vkms/vkms_drv.c

@@ -10,7 +10,7 @@
  */
 
 #include <linux/module.h>
-#include <linux/platform_device.h>
+#include <linux/device/faux.h>
 #include <linux/dma-mapping.h>
 
 #include <drm/clients/drm_client_setup.h>
@@ -149,27 +149,27 @@ static int vkms_modeset_init(struct vkms_device *vkmsdev)
 static int vkms_create(struct vkms_config *config)
 {
 	int ret;
-	struct platform_device *pdev;
+	struct faux_device *fdev;
 	struct vkms_device *vkms_device;
 	const char *dev_name;
 
 	dev_name = vkms_config_get_device_name(config);
-	pdev = platform_device_register_simple(dev_name, -1, NULL, 0);
-	if (IS_ERR(pdev))
-		return PTR_ERR(pdev);
+	fdev = faux_device_create(dev_name, NULL, NULL);
+	if (!fdev)
+		return -ENODEV;
 
-	if (!devres_open_group(&pdev->dev, NULL, GFP_KERNEL)) {
+	if (!devres_open_group(&fdev->dev, NULL, GFP_KERNEL)) {
 		ret = -ENOMEM;
 		goto out_unregister;
 	}
 
-	vkms_device = devm_drm_dev_alloc(&pdev->dev, &vkms_driver,
+	vkms_device = devm_drm_dev_alloc(&fdev->dev, &vkms_driver,
 					 struct vkms_device, drm);
 	if (IS_ERR(vkms_device)) {
 		ret = PTR_ERR(vkms_device);
 		goto out_devres;
 	}
-	vkms_device->platform = pdev;
+	vkms_device->faux_dev = fdev;
 	vkms_device->config = config;
 	config->dev = vkms_device;
 
@@ -203,9 +203,9 @@ static int vkms_create(struct vkms_config *config)
 	return 0;
 
 out_devres:
-	devres_release_group(&pdev->dev, NULL);
+	devres_release_group(&fdev->dev, NULL);
 out_unregister:
-	platform_device_unregister(pdev);
+	faux_device_destroy(fdev);
 	return ret;
 }
 
@@ -231,19 +231,19 @@ static int __init vkms_init(void)
 
 static void vkms_destroy(struct vkms_config *config)
 {
-	struct platform_device *pdev;
+	struct faux_device *fdev;
 
 	if (!config->dev) {
 		DRM_INFO("vkms_device is NULL.\n");
 		return;
 	}
 
-	pdev = config->dev->platform;
+	fdev = config->dev->faux_dev;
 
 	drm_dev_unregister(&config->dev->drm);
 	drm_atomic_helper_shutdown(&config->dev->drm);
-	devres_release_group(&pdev->dev, NULL);
-	platform_device_unregister(pdev);
+	devres_release_group(&fdev->dev, NULL);
+	faux_device_destroy(fdev);
 
 	config->dev = NULL;
 }

drivers/gpu/drm/vkms/vkms_drv.h

@@ -232,13 +232,13 @@ struct vkms_config;
  * struct vkms_device - Description of a VKMS device
  *
  * @drm - Base device in DRM
- * @platform - Associated platform device
+ * @faux_dev - Associated faux device
  * @output - Configuration and sub-components of the VKMS device
  * @config: Configuration used in this VKMS device
  */
 struct vkms_device {
 	struct drm_device drm;
-	struct platform_device *platform;
+	struct faux_device *faux_dev;
 	const struct vkms_config *config;
 };