linux-kernel - [PATCH v2 08/15] drm/vkms: Add a validation function for VKMS configuration

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Message-ID: <20250211110912.15409-9-jose.exposito89@gmail.com>
Date: Tue, 11 Feb 2025 12:09:05 +0100
From: José Expósito <jose.exposito89@...il.com>
To: louis.chauvet@...tlin.com
Cc: hamohammed.sa@...il.com,
	simona@...ll.ch,
	melissa.srw@...il.com,
	maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	tzimmermann@...e.de,
	airlied@...il.com,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	José Expósito <jose.exposito89@...il.com>
Subject: [PATCH v2 08/15] drm/vkms: Add a validation function for VKMS configuration

From: Louis Chauvet <louis.chauvet@...tlin.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.

Reviewed-by: Louis Chauvet <louis.chauvet@...tlin.com>
Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>
Co-developed-by: José Expósito <jose.exposito89@...il.com>
Signed-off-by: José Expósito <jose.exposito89@...il.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 ++++++++++
 drivers/gpu/drm/vkms/vkms_drv.h               |  2 +-
 drivers/gpu/drm/vkms/vkms_output.c            |  3 +++
 5 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vkms/tests/vkms_config_test.c b/drivers/gpu/drm/vkms/tests/vkms_config_test.c
index 92798590051b..6e07139d261c 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 fcaa909fb2e0..0376dceaf6be 100644
--- a/drivers/gpu/drm/vkms/vkms_config.h
+++ b/drivers/gpu/drm/vkms/vkms_config.h
@@ -67,6 +67,16 @@ 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
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index a74a7fc3a056..95afc39ce985 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -204,7 +204,7 @@ struct vkms_config;
 struct vkms_device {
 	struct drm_device drm;
 	struct platform_device *platform;
-	const struct vkms_config *config;
+	struct vkms_config *config;
 };
 
 /*
diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
index 068a7f87ecec..414cc933af41 100644
--- a/drivers/gpu/drm/vkms/vkms_output.c
+++ b/drivers/gpu/drm/vkms/vkms_output.c
@@ -16,6 +16,9 @@ int vkms_output_init(struct vkms_device *vkmsdev)
 	int writeback;
 	unsigned int n;
 
+	if (!vkms_config_is_valid(vkmsdev->config))
+		return -EINVAL;
+
 	/*
 	 * Initialize used plane. One primary plane is required to perform the composition.
 	 *
-- 
2.48.1