[PATCH 06/13] drm/vkms: Add a validation function for VKMS configuration

["José Expósito" <jose.exposito89@gmail.com>]

From: Louis Chauvet <louis.chauvet@bootlin.com>

As the configuration will be used by userspace, add a validator to avoid
creating a broken DRM device.

For the moment, the function always returns true, but rules will be
added in future patches.

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
 drivers/gpu/drm/vkms/tests/vkms_config_test.c |  2 ++
 drivers/gpu/drm/vkms/vkms_config.c            |  5 +++++
 drivers/gpu/drm/vkms/vkms_config.h            | 10 ++++++++++
 3 files changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/vkms/tests/vkms_config_test.c b/drivers/gpu/drm/vkms/tests/vkms_config_test.c
index 526800b1afb4..66c2c6cb4a0e 100644
--- a/drivers/gpu/drm/vkms/tests/vkms_config_test.c
+++ b/drivers/gpu/drm/vkms/tests/vkms_config_test.c
@@ -54,6 +54,8 @@ static void vkms_config_test_default_config(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, config->writeback, params->enable_writeback);
 	KUNIT_EXPECT_EQ(test, config->overlay, params->enable_overlay);
 
+	KUNIT_EXPECT_TRUE(test, vkms_config_is_valid(config));
+
 	vkms_config_destroy(config);
 }
 
diff --git a/drivers/gpu/drm/vkms/vkms_config.c b/drivers/gpu/drm/vkms/vkms_config.c
index 11b0e539920b..67f71d29596e 100644
--- a/drivers/gpu/drm/vkms/vkms_config.c
+++ b/drivers/gpu/drm/vkms/vkms_config.c
@@ -47,6 +47,11 @@ void vkms_config_destroy(struct vkms_config *config)
 	kfree(config);
 }
 
+bool vkms_config_is_valid(struct vkms_config *config)
+{
+	return true;
+}
+
 static int vkms_config_show(struct seq_file *m, void *data)
 {
 	struct drm_debugfs_entry *entry = m->private;
diff --git a/drivers/gpu/drm/vkms/vkms_config.h b/drivers/gpu/drm/vkms/vkms_config.h
index 3e4f39cbe2e2..963f22b9b4bd 100644
--- a/drivers/gpu/drm/vkms/vkms_config.h
+++ b/drivers/gpu/drm/vkms/vkms_config.h
@@ -64,6 +64,16 @@ vkms_config_get_device_name(struct vkms_config *config)
 	return config->dev_name;
 }
 
+/**
+ * vkms_config_is_valid() - Validate a configuration
+ * @config: Configuration to validate
+ *
+ * Returns:
+ * Whether the configuration is valid or not.
+ * For example, a configuration without primary planes is not valid.
+ */
+bool vkms_config_is_valid(struct vkms_config *config);
+
 /**
  * vkms_config_register_debugfs() - Register a debugfs file to show the device's
  * configuration
-- 
2.48.1