[1/3] udmabuf: add documentation

Commit Message

Gerd Hoffmann Aug. 22, 2019, 9:36 a.m. UTC

Signed-off-by: Gerd Hoffmann <[e-mail]>
---
 include/uapi/linux/udmabuf.h         | 52 ++++++++++++++++++++++++++--
 Documentation/driver-api/dma-buf.rst |  8 +++++
 2 files changed, 57 insertions(+), 3 deletions(-)

Patch

diff --git a/include/uapi/linux/udmabuf.h b/include/uapi/linux/udmabuf.h
index 46b6532ed855..9fe440abf2f9 100644
--- a/include/uapi/linux/udmabuf.h
+++ b/include/uapi/linux/udmabuf.h
@@ -5,8 +5,39 @@ 
 #include <linux/types.h>
 #include <linux/ioctl.h>
 
+/**
+ * DOC: udmabuf
+ *
+ * udmabuf is a device driver which allows userspace to create
+ * dmabufs.  The memory used for these dmabufs must be backed by
+ * memfd.  The memfd must have F_SEAL_SHRINK and it must not have
+ * F_SEAL_WRITE.
+ *
+ * The driver has two ioctls, one to create a dmabuf from a single
+ * memory block and one to create a dmabuf from a list of memory
+ * blocks.
+ *
+ * UDMABUF_CREATE - _IOW('u', 0x42, udmabuf_create)
+ *
+ * UDMABUF_CREATE_LIST - _IOW('u', 0x43, udmabuf_create_list)
+ */
+
+#define UDMABUF_CREATE       _IOW('u', 0x42, struct udmabuf_create)
+#define UDMABUF_CREATE_LIST  _IOW('u', 0x43, struct udmabuf_create_list)
+
 #define UDMABUF_FLAGS_CLOEXEC	0x01
 
+/**
+ * struct udmabuf_create - create a dmabuf from a single memory block.
+ *
+ * @memfd: The file handle.
+ * @offset: Start of the buffer (from memfd start).
+ * Must be page aligned.
+ * @size: Size of the buffer.  Must be rounded to page size.
+ *
+ * @flags:
+ * UDMABUF_FLAGS_CLOEXEC: set CLOEXEC flag for the dmabuf.
+ */
 struct udmabuf_create {
 	__u32 memfd;
 	__u32 flags;
@@ -14,6 +45,15 @@  struct udmabuf_create {
 	__u64 size;
 };
 
+/**
+ * struct udmabuf_create_item - one memory block list item.
+ *
+ * @memfd: The file handle.
+ * @__pad: Padding field (unused).
+ * @offset: Start of the buffer (from memfd start).
+ * Must be page aligned.
+ * @size: Size of the buffer.  Must be rounded to page size.
+ */
 struct udmabuf_create_item {
 	__u32 memfd;
 	__u32 __pad;
@@ -21,13 +61,19 @@  struct udmabuf_create_item {
 	__u64 size;
 };
 
+/**
+ * struct udmabuf_create_list - create a dmabuf from a memory block list.
+ *
+ * @count: The number of list elements.
+ * @list: The memory block list
+ *
+ * @flags:
+ * UDMABUF_FLAGS_CLOEXEC: set CLOEXEC flag for the dmabuf.
+ */
 struct udmabuf_create_list {
 	__u32 flags;
 	__u32 count;
 	struct udmabuf_create_item list[];
 };
 
-#define UDMABUF_CREATE       _IOW('u', 0x42, struct udmabuf_create)
-#define UDMABUF_CREATE_LIST  _IOW('u', 0x43, struct udmabuf_create_list)
-
 #endif /* _UAPI_LINUX_UDMABUF_H */
diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst
index b541e97c7ab1..1f62c30a14b0 100644
--- a/Documentation/driver-api/dma-buf.rst
+++ b/Documentation/driver-api/dma-buf.rst
@@ -166,3 +166,11 @@  DMA Fence uABI/Sync File
 .. kernel-doc:: include/linux/sync_file.h
    :internal:
 
+Userspace DMA Buffer driver
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. kernel-doc:: include/uapi/linux/udmabuf.h
+   :doc: udmabuf
+
+.. kernel-doc:: include/uapi/linux/udmabuf.h
+   :internal: