From: Leon Romanovsky <[email protected]> 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 <[email protected]> --- 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
