drm: base prime/dma-buf support (v5)

This adds the basic drm dma-buf interface layer, called PRIME. This
commit doesn't add any driver support, it is simply and agreed upon starting
point so we can work towards merging driver support for the next merge window.

Current drivers with work done are nouveau, i915, udl, exynos and omap.

The main APIs exposed to userspace allow translating a 32-bit object handle
to a file descriptor, and a file descriptor to a 32-bit object handle.

The flags value is currently limited to O_CLOEXEC.

Acknowledgements:
Daniel Vetter: lots of review
Rob Clark: cleaned up lots of the internals and did lifetime review.

v2: rename some functions after Chris preferred a green shed
fix IS_ERR_OR_NULL -> IS_ERR
v3: Fix Ville pointed out using buffer + kmalloc
v4: add locking as per ickle review
v5: allow re-exporting the original dma-buf (Daniel)

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Rob Clark <rob.clark@linaro.org>
Reviewed-by: Sumit Semwal <sumit.semwal@linaro.org>
Reviewed-by: Inki Dae <inki.dae@samsung.com>
Acked-by: Ben Widawsky <benjamin.widawsky@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm.h b/include/drm/drm.h
index 34a7b89..64ff02d 100644
--- a/include/drm/drm.h
+++ b/include/drm/drm.h
@@ -617,6 +617,17 @@
 	__u64 value;
 };
 
+#define DRM_CLOEXEC O_CLOEXEC
+struct drm_prime_handle {
+	__u32 handle;
+
+	/** Flags.. only applicable for handle->fd */
+	__u32 flags;
+
+	/** Returned dmabuf file descriptor */
+	__s32 fd;
+};
+
 #include "drm_mode.h"
 
 #define DRM_IOCTL_BASE			'd'
@@ -673,7 +684,8 @@
 #define DRM_IOCTL_UNLOCK		DRM_IOW( 0x2b, struct drm_lock)
 #define DRM_IOCTL_FINISH		DRM_IOW( 0x2c, struct drm_lock)
 
-#define DRM_IOCTL_GEM_PRIME_OPEN        DRM_IOWR(0x2e, struct drm_gem_open)
+#define DRM_IOCTL_PRIME_HANDLE_TO_FD    DRM_IOWR(0x2d, struct drm_prime_handle)
+#define DRM_IOCTL_PRIME_FD_TO_HANDLE    DRM_IOWR(0x2e, struct drm_prime_handle)
 
 #define DRM_IOCTL_AGP_ACQUIRE		DRM_IO(  0x30)
 #define DRM_IOCTL_AGP_RELEASE		DRM_IO(  0x31)