Add udmabuf misc device

A driver to let userspace turn memfd regions into dma-bufs.

Use case:  Allows qemu create dmabufs for the vga framebuffer or
virtio-gpu ressources.  Then they can be passed around to display
those guest things on the host.  To spice client for classic full
framebuffer display, and hopefully some day to wayland server for
seamless guest window display.

qemu test branch:
  https://git.kraxel.org/cgit/qemu/log/?h=sirius/udmabuf

Cc: David Airlie <airlied@linux.ie>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20180827093444.23623-1-kraxel@redhat.com

1 files changed, 33 insertions, 0 deletions

diff --git a/include/uapi/linux/udmabuf.h b/include/uapi/linux/udmabuf.h
new file mode 100644
index 000000000000..46b6532ed855
--- /dev/null
+++ b/include/uapi/linux/udmabuf.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_LINUX_UDMABUF_H
+#define _UAPI_LINUX_UDMABUF_H
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+#define UDMABUF_FLAGS_CLOEXEC	0x01
+
+struct udmabuf_create {
+	__u32 memfd;
+	__u32 flags;
+	__u64 offset;
+	__u64 size;
+};
+
+struct udmabuf_create_item {
+	__u32 memfd;
+	__u32 __pad;
+	__u64 offset;
+	__u64 size;
+};
+
+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 */