Edit File: dri3proto.txt
The DRI3 Extension Version 1.0 2013-6-4 Keith Packard keithp@keithp.com Intel Corporation 1. Introduction The DRI3 extension provides mechanisms to translate between direct rendered buffers and X pixmaps. When combined with the Present extension, a complete direct rendering solution for OpenGL is provided. The direct rendered buffers are passed across the protocol via standard POSIX file descriptor passing mechanisms. On Linux, these buffers are DMA-BUF objects. DRI3 also includes a mechanism to translate between Linux Futexes and X Sync extension Fences. This provides a synchronization mechanism which can be used to serialize access to shared render buffers. 1.1. Acknowledgments Eric Anholt <eric@anholt.net> Dave Airlie <airlied@redhat.com> Kristian Høgsberg <krh@bitplanet.net> James Jones <janomes@nvidia.com> Arthur Huillet <arthur.huillet@free.fr> ❄ ❄ ❄ ❄ ❄ ❄ ❄ 2. Data Types The DRI3 extension uses the RandR extension Provider data type to select among multiple GPUs on a single screen and the Sync extension fence object to provide graphics object synchronization. ❄ ❄ ❄ ❄ ❄ ❄ ❄ 4. Errors DRI3 defines no errors. ❄ ❄ ❄ ❄ ❄ ❄ ❄ 5. Events DRI3 defines no events. ❄ ❄ ❄ ❄ ❄ ❄ ❄ 6. Protocol Types DRI3 defines no new protocol types. ❄ ❄ ❄ ❄ ❄ ❄ ❄ 7. Extension Initialization The name of this extension is "DRI3" ┌─── DRI3QueryVersion client-major-version: CARD32 client-minor-version: CARD32 ▶ major-version: CARD32 minor-version: CARD32 └─── The client sends the highest supported version to the server and the server sends the highest version it supports, but no higher than the requested version. Major versions changes can introduce incompatibilities in existing functionality, minor version changes introduce only backward compatible changes. It is the clients responsibility to ensure that the server supports a version which is compatible with its expectations. Backwards compatible changes included addition of new requests. ❄ ❄ ❄ ❄ ❄ ❄ ❄ 8. Extension Requests ┌─── DRI3Open drawable: DRAWABLE provider: PROVIDER ▶ nfd: CARD8 device: FD └─── Errors: Drawable, Value, Match This requests that the X server open the direct rendering device associated with drawable and RandR provider. The provider must support SourceOutput or SourceOffload. The file descriptor for the device is returned in 'device'. 'nfd' will be set to one (this is strictly a convenience for XCB which otherwise would need request-specific information about how many file descriptors were associated with this reply). ┌─── DRI3PixmapFromBuffer pixmap: PIXMAP drawable: DRAWABLE size: CARD32 width, height, stride: CARD16 depth, bpp: CARD8 buffer: FD └─── Errors: Alloc, Drawable, IDChoice, Value, Match Creates a pixmap for the direct rendering object associated with 'buffer'. Changes to pixmap will be visible in that direct rendered object and changes to the direct rendered object will be visible in the pixmap. 'size' specifies the total size of the buffer bytes. 'width', 'height' describe the geometry (in pixels) of the underlying buffer. 'stride' specifies the number of bytes per scanline in the buffer. The pixels within the buffer are not required to be arranged in a simple linear fashion, but 'size' will be at least 'height' * 'stride'. Precisely how any additional information about the buffer is shared is outside the scope of this extension. If buffer cannot be used with the screen associated with drawable, a Match error is returned. If depth or bpp are not supported by the screen, a Value error is returned. ┌─── DRI3BufferFromPixmap pixmap: PIXMAP ▶ nfd: CARD8 size: CARD32 width, height, stride: CARD16 depth, bpp: CARD8 buffer: FD └─── Errors: Pixmap, Match Pass back a direct rendering object associated with pixmap. Changes to pixmap will be visible in that direct rendered object and changes to the direct rendered object will be visible in the pixmap. 'size' specifies the total size of the buffer bytes. 'width', 'height' describe the geometry (in pixels) of the underlying buffer. 'stride' specifies the number of bytes per scanline in the buffer. The pixels within the buffer are not required to be arranged in a simple linear fashion, but 'size' will be at least 'height' * 'stride'. Precisely how any additional information about the buffer is shared is outside the scope of this extension. If buffer cannot be used with the screen associated with drawable, a Match error is returned. ┌─── DRI3FenceFromFD drawable: DRAWABLE fence: FENCE initially-triggered: BOOL fd: FD └─── Errors: IDchoice, Drawable Creates a Sync extension Fence that provides the regular Sync extension semantics along with a file descriptor that provides a device-specific mechanism to manipulate the fence directly. Details about the mechanism used with this file descriptor are outside the scope of the DRI3 extension. ┌─── DRI3FDFromFence drawable: DRAWABLE fence: FENCE ▶ fd: FD └─── Errors: IDchoice, Drawable, Match Given a Sync extension Fence that provides the regular Sync extension semantics, returns a file descriptor that provides a device-specific mechanism to manipulate the fence directly. Details about the mechanism used with this file descriptor are outside the scope of the DRI3 extension. 'drawable' must be associated with a direct rendering device that 'fence' can work with, otherwise a Match error results. ❄ ❄ ❄ ❄ ❄ ❄ ❄ 9. Extension Events DRI3 defines no events. ❄ ❄ ❄ ❄ ❄ ❄ ❄ 10. Extension Versioning The DRI3 extension is adapted from the DRI2 extension. 1.0: First published version ❄ ❄ ❄ ❄ ❄ ❄ ❄ 11. Relationship with other extensions As an extension designed to support other extensions, there is naturally some interactions with other extensions. 11.1 GLX GLX is both an application interface and an X extension. OpenGL applications using the GLX API will use the GLX extension, DRI3 and Present when doing direct rendering. 11.2 Present The Present extension provides a way to synchronize the display of pixmap contents to the screen. When used in conjunction with DRI3, they provide a complete direct rendering solution for OpenGL or other APIs. 11.3 DRI2 DRI3 provides similar functionality to the DRI2Connect and DRI2GetBuffersWithFormat requests, however DRI3 uses file descriptors to refer to the direct rendering device and buffers. Present and DRI3 are designed in conjunction to replace DRI2 11.2 XvMC / Xv It might be nice to be able to reference YUV formatted direct rendered objects from the X server. ❄ ❄ ❄ ❄ ❄ ❄ ❄ Appendix A. Protocol Encoding Syntactic Conventions This document uses the same syntactic conventions as the core X protocol encoding document. A.1 Common Types None. A.2 Protocol Requests ┌─── DRI3QueryVersion 1 CARD8 major opcode 1 0 DRI3 opcode 2 3 length 4 CARD32 major version 4 CARD32 minor version ▶ 1 1 Reply 1 unused 2 CARD16 sequence number 4 0 reply length 4 CARD32 major version 4 CARD32 minor version 16 unused └─── ┌─── DRI3Open 1 CARD8 major opcode 1 1 DRI3 opcode 2 4 length 4 DRAWABLE drawable 4 CARD32 driver type 4 PROVIDER provider ▶ 1 1 Reply 1 1 nfd 2 CARD16 sequence number 4 (n + p) / 4 reply length 4 n driver name length (n) 20 unused n CARD8 driver name p unused, p=pad(n) 0 FD device └─── ┌─── DRI3PixmapFromBuffer 1 CARD8 major opcode 1 2 DRI3 opcode 2 6 length 4 Pixmap pixmap 4 Drawable drawable 4 CARD32 size 2 CARD16 width 2 CARD16 height 2 CARD16 stride 1 CARD8 depth 1 CARD8 bpp 0 FD buffer └─── ┌─── DRI3BufferFromPixmap 1 CARD8 major opcode 1 3 DRI3 opcode 2 2 length 4 Pixmap pixmap ▶ 1 1 Reply 1 1 nfd 2 CARD16 sequence number 4 0 reply length 4 CARD32 size 2 CARD16 width 2 CARD16 height 2 CARD16 stride 1 CARD8 depth 1 CARD8 bpp 12 unused 0 FD buffer └─── ┌─── DRI3FenceFromFD 1 CARD8 major opcode 1 4 DRI3 opcode 2 4 length 4 Drawable drawable 4 Fence fence 1 BOOL initially triggered 3 unused 0 FD fence fd └─── ┌─── DRI3FDFromFence 1 CARD8 major opcode 1 5 DRI3 opcode 2 3 length 4 Drawable drawable 4 Fence fence ▶ 1 1 Reply 1 1 nfd 2 CARD16 sequence number 4 0 reply length 24 unused 0 FD fence fd └─── A.3 Protocol Events The DRI3 extension defines no events. A.4 Protocol Errors The DRI3 extension defines no errors. ❄ ❄ ❄ ❄ ❄ ❄ ❄
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