linux-kernel - [PATCH 5/7] drm/gem: Add a flag to control whether objects can be exported

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Message-Id: <20250318-drm-gem-shmem-v1-5-64b96511a84f@collabora.com>
Date: Tue, 18 Mar 2025 16:22:39 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
 Benno Lossin <benno.lossin@...ton.me>, 
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Sumit Semwal <sumit.semwal@...aro.org>, 
 Christian König <christian.koenig@....com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 rust-for-linux@...r.kernel.org, linux-media@...r.kernel.org, 
 linaro-mm-sig@...ts.linaro.org, Danilo Krummrich <dakr@...nel.org>, 
 Asahi Lina <lina@...hilina.net>, 
 Daniel Almeida <daniel.almeida@...labora.com>
Subject: [PATCH 5/7] drm/gem: Add a flag to control whether objects can be
 exported

From: Asahi Lina <lina@...hilina.net>

Drivers may want to support driver-private objects, which cannot be
shared. This allows them to share a single lock and enables other
optimizations.

Add an `exportable` field to drm_gem_object, which blocks PRIME export
if set to false. It is initialized to true in
drm_gem_private_object_init.

Signed-off-by: Asahi Lina <lina@...hilina.net>
Signed-off-by: Daniel Almeida <daniel.almeida@...labora.com>
---
 drivers/gpu/drm/drm_gem.c   | 1 +
 drivers/gpu/drm/drm_prime.c | 5 +++++
 include/drm/drm_gem.h       | 8 ++++++++
 3 files changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index ee811764c3df4b4e9c377a66afd4967512ba2001..8f998fe6beecd285ce3e2d5badfa95eb7d7bd548 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -195,6 +195,7 @@ void drm_gem_private_object_init(struct drm_device *dev,
 
 	drm_vma_node_reset(&obj->vma_node);
 	INIT_LIST_HEAD(&obj->lru_node);
+	obj->exportable = true;
 }
 EXPORT_SYMBOL(drm_gem_private_object_init);
 
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 32a8781cfd67b82ece7b7b94625715171bb41917..20aa350280abe9a6ed6742e131ff50c65bc9dfa9 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -387,6 +387,11 @@ static struct dma_buf *export_and_register_object(struct drm_device *dev,
 		return dmabuf;
 	}
 
+	if (!obj->exportable) {
+		dmabuf = ERR_PTR(-EINVAL);
+		return dmabuf;
+	}
+
 	if (obj->funcs && obj->funcs->export)
 		dmabuf = obj->funcs->export(obj, flags);
 	else
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index fdae947682cd0b7b06db5e35e120f049a0f30179..f700e4996eccb92597cca6b8c3df8e35b864c1e1 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -432,6 +432,14 @@ struct drm_gem_object {
 	 * The current LRU list that the GEM object is on.
 	 */
 	struct drm_gem_lru *lru;
+
+	/**
+	 * @exportable:
+	 *
+	 * Whether this GEM object can be exported via the drm_gem_object_funcs->export
+	 * callback. Defaults to true.
+	 */
+	bool exportable;
 };
 
 /**

-- 
2.48.1