[PATCH v2 2/4] dma-buf: Document revoke semantics

[Leon Romanovsky <leon@kernel.org>]

From: Leon Romanovsky <leonro@nvidia.com>

Document a DMA-buf revoke mechanism that allows an exporter to explicitly
invalidate ("kill") a shared buffer after it has been handed out to
importers. Once revoked, all further CPU and device access is blocked, and
importers consistently observe failure.

This requires both importers and exporters to honor the revoke contract.

For importers, this means implementing .invalidate_mappings() and calling
dma_buf_pin() after the DMA‑buf is attached to verify the exporter’s support
for revocation.

For exporters, this means implementing the .pin() callback, which checks
the DMA‑buf attachment for a valid revoke implementation.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 include/linux/dma-buf.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 1b397635c793..e0bc0b7119f5 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -579,6 +579,25 @@ static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
 	return !!dmabuf->ops->pin;
 }
 
+/**
+ * dma_buf_attachment_is_revoke - check if a DMA-buf importer implements
+ * revoke semantics.
+ * @attach: the DMA-buf attachment to check
+ *
+ * Returns true if DMA-buf importer honors revoke semantics, which is
+ * negotiated with the exporter, by making sure that importer implements
+ * .invalidate_mappings() callback and calls to dma_buf_pin() after
+ * DMA-buf attach.
+ */
+static inline bool
+dma_buf_attachment_is_revoke(struct dma_buf_attachment *attach)
+{
+	return IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY) &&
+	       dma_buf_is_dynamic(attach->dmabuf) &&
+	       (attach->importer_ops &&
+		attach->importer_ops->invalidate_mappings);
+}
+
 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 					  struct device *dev);
 struct dma_buf_attachment *

-- 
2.52.0