drm/vkms: Create a debugfs file to get vkms config data

Creating a vkms_config debugfs file in vkms_drv.c to get/track vkms config
data, for the long-term plan of making vkms configurable and have multiple
different instances.
Reviewed-by: Melissa Wen <melissa.srw@gmail.com>
Signed-off-by: Beatriz Martins de Carvalho <martinsdecarvalhobeatriz@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210708092002.11847-1-martinsdecarvalhobeatriz@gmail.com

drivers/gpu/drm/vkms/vkms_drv.c

@@ -28,6 +28,9 @@
 
 #include "vkms_drv.h"
 
+#include <drm/drm_print.h>
+#include <drm/drm_debugfs.h>
+
 #define DRIVER_NAME	"vkms"
 #define DRIVER_DESC	"Virtual Kernel Mode Setting"
 #define DRIVER_DATE	"20180514"
@@ -86,12 +89,37 @@ static void vkms_atomic_commit_tail(struct drm_atomic_state *old_state)
 	drm_atomic_helper_cleanup_planes(dev, old_state);
 }
 
+static int vkms_config_show(struct seq_file *m, void *data)
+{
+	struct drm_info_node *node = (struct drm_info_node *)m->private;
+	struct drm_device *dev = node->minor->dev;
+	struct vkms_device *vkmsdev = drm_device_to_vkms_device(dev);
+
+	seq_printf(m, "writeback=%d\n", vkmsdev->config->writeback);
+	seq_printf(m, "cursor=%d\n", vkmsdev->config->cursor);
+	seq_printf(m, "overlay=%d\n", vkmsdev->config->overlay);
+
+	return 0;
+}
+
+static const struct drm_info_list vkms_config_debugfs_list[] = {
+	{ "vkms_config", vkms_config_show, 0 },
+};
+
+static void vkms_config_debugfs_init(struct drm_minor *minor)
+{
+	drm_debugfs_create_files(vkms_config_debugfs_list, ARRAY_SIZE(vkms_config_debugfs_list),
+				 minor->debugfs_root, minor);
+}
+
 static const struct drm_driver vkms_driver = {
 	.driver_features	= DRIVER_MODESET | DRIVER_ATOMIC | DRIVER_GEM,
 	.release		= vkms_release,
 	.fops			= &vkms_driver_fops,
 	DRM_GEM_SHMEM_DRIVER_OPS,
 
+	.debugfs_init           = vkms_config_debugfs_init,
+
 	.name			= DRIVER_NAME,
 	.desc			= DRIVER_DESC,
 	.date			= DRIVER_DATE,