drm/gem: Inline drm_gem_pin() into PRIME helpers

Inline drm_gem_pin() into its only caller drm_gem_map_attach()
and update the documentation in the callback's purpose. Do the
equivalent for drm_gem_unpin(). Also add stricter error checking
on the involved locking.

The pin operation in the GEM object functions is a helper for
PRIME-exported buffer objects. Having drm_gem_pin() gives the
impression of a general-purpose interface, which is not the case.
Removing it makes the pin callback a bit harder to misuse.

v2:
- clarify comment on pin callback (Dmitry)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://lore.kernel.org/r/20250526132634.531789-5-tzimmermann@suse.de

1 files changed, 20 insertions, 2 deletions

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index d828502268b8..a1852c02f512 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -599,6 +599,7 @@ int drm_gem_map_attach(struct dma_buf *dma_buf,
 		       struct dma_buf_attachment *attach)
 {
 	struct drm_gem_object *obj = dma_buf->priv;
+	int ret;
 
 	/*
 	 * drm_gem_map_dma_buf() requires obj->get_sg_table(), but drivers
@@ -608,7 +609,16 @@ int drm_gem_map_attach(struct dma_buf *dma_buf,
 	    !obj->funcs->get_sg_table)
 		return -ENOSYS;
 
-	return drm_gem_pin(obj);
+	if (!obj->funcs->pin)
+		return 0;
+
+	ret = dma_resv_lock(obj->resv, NULL);
+	if (ret)
+		return ret;
+	ret = obj->funcs->pin(obj);
+	dma_resv_unlock(obj->resv);
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_gem_map_attach);
 
@@ -625,8 +635,16 @@ void drm_gem_map_detach(struct dma_buf *dma_buf,
 			struct dma_buf_attachment *attach)
 {
 	struct drm_gem_object *obj = dma_buf->priv;
+	int ret;
 
-	drm_gem_unpin(obj);
+	if (!obj->funcs->unpin)
+		return;
+
+	ret = dma_resv_lock(obj->resv, NULL);
+	if (drm_WARN_ON(obj->dev, ret))
+		return;
+	obj->funcs->unpin(obj);
+	dma_resv_unlock(obj->resv);
 }
 EXPORT_SYMBOL(drm_gem_map_detach);