diff options
| author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2020-12-11 16:58:43 +0100 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2020-12-16 11:28:34 +0100 |
| commit | c545781e1c55ab680dcc49c37212d5327b9d6812 (patch) | |
| tree | 14152db8d82354f45b4ff3e89270bc4b4010734e | |
| parent | 8ccf0a29af75326fb8e5ed6e51ff61e74b7ed2e4 (diff) | |
dma-buf: doc polish for pin/unpindrm-misc-next-2020-12-17
Motivated by a discussion with Christian and Thomas: Try to untangle a
bit what's relevant for importers and what's relevant for exporters.
Also add an assert that really only dynamic importers use the api
function, anything else doesn't make sense.
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20201211155843.3348718-4-daniel.vetter@ffwll.ch
| -rw-r--r-- | drivers/dma-buf/dma-buf.c | 19 | ||||
| -rw-r--r-- | include/linux/dma-buf.h | 8 |
2 files changed, 21 insertions, 6 deletions
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index a0a02ef888da..b8465243eca2 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -809,9 +809,15 @@ EXPORT_SYMBOL_GPL(dma_buf_detach); /** * dma_buf_pin - Lock down the DMA-buf - * * @attach: [in] attachment which should be pinned * + * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may + * call this, and only for limited use cases like scanout and not for temporary + * pin operations. It is not permitted to allow userspace to pin arbitrary + * amounts of buffers through this interface. + * + * Buffers must be unpinned by calling dma_buf_unpin(). + * * Returns: * 0 on success, negative error code on failure. */ @@ -820,6 +826,8 @@ int dma_buf_pin(struct dma_buf_attachment *attach) struct dma_buf *dmabuf = attach->dmabuf; int ret = 0; + WARN_ON(!dma_buf_attachment_is_dynamic(attach)); + dma_resv_assert_held(dmabuf->resv); if (dmabuf->ops->pin) @@ -830,14 +838,19 @@ int dma_buf_pin(struct dma_buf_attachment *attach) EXPORT_SYMBOL_GPL(dma_buf_pin); /** - * dma_buf_unpin - Remove lock from DMA-buf - * + * dma_buf_unpin - Unpin a DMA-buf * @attach: [in] attachment which should be unpinned + * + * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move + * any mapping of @attach again and inform the importer through + * &dma_buf_attach_ops.move_notify. */ void dma_buf_unpin(struct dma_buf_attachment *attach) { struct dma_buf *dmabuf = attach->dmabuf; + WARN_ON(!dma_buf_attachment_is_dynamic(attach)); + dma_resv_assert_held(dmabuf->resv); if (dmabuf->ops->unpin) diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 43802a31b25d..628681bf6c99 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -86,13 +86,15 @@ struct dma_buf_ops { * @pin: * * This is called by dma_buf_pin() and lets the exporter know that the - * DMA-buf can't be moved any more. + * DMA-buf can't be moved any more. The exporter should pin the buffer + * into system memory to make sure it is generally accessible by other + * devices. * * This is called with the &dmabuf.resv object locked and is mutual * exclusive with @cache_sgt_mapping. * - * This callback is optional and should only be used in limited use - * cases like scanout and not for temporary pin operations. + * This is called automatically for non-dynamic importers from + * dma_buf_attach(). * * Returns: * |