1 Name 2 3 MESA_image_dma_buf_export 4 5 Name Strings 6 7 EGL_MESA_image_dma_buf_export 8 9 Contributors 10 11 Dave Airlie 12 13 Contact 14 15 Dave Airlie (airlied 'at' redhat 'dot' com) 16 17 Status 18 19 Complete, shipping. 20 21 Version 22 23 Version 3, May 5, 2015 24 25 Number 26 27 EGL Extension #87 28 29 Dependencies 30 31 Requires EGL 1.4 or later. This extension is written against the 32 wording of the EGL 1.4 specification. 33 34 EGL_KHR_base_image is required. 35 36 The EGL implementation must be running on a Linux kernel supporting the 37 dma_buf buffer sharing mechanism. 38 39 Overview 40 41 This extension provides entry points for integrating EGLImage with the 42 dma-buf infrastructure. The extension allows creating a Linux dma_buf 43 file descriptor or multiple file descriptors, in the case of multi-plane 44 YUV image, from an EGLImage. 45 46 It is designed to provide the complementary functionality to 47 EGL_EXT_image_dma_buf_import. 48 49 IP Status 50 51 Open-source; freely implementable. 52 53 New Types 54 55 This extension uses the 64-bit unsigned integer type EGLuint64KHR 56 first introduced by the EGL_KHR_stream extension, but does not 57 depend on that extension. The typedef may be reproduced separately 58 for this extension, if not already present in eglext.h. 59 60 typedef khronos_uint64_t EGLuint64KHR; 61 62 New Procedures and Functions 63 64 EGLBoolean eglExportDMABUFImageQueryMESA(EGLDisplay dpy, 65 EGLImageKHR image, 66 int *fourcc, 67 int *num_planes, 68 EGLuint64KHR *modifiers); 69 70 EGLBoolean eglExportDMABUFImageMESA(EGLDisplay dpy, 71 EGLImageKHR image, 72 int *fds, 73 EGLint *strides, 74 EGLint *offsets); 75 76 New Tokens 77 78 None 79 80 81 Additions to the EGL 1.4 Specification: 82 83 To mirror the import extension, this extension attempts to return 84 enough information to enable an exported dma-buf to be imported 85 via eglCreateImageKHR and EGL_LINUX_DMA_BUF_EXT token. 86 87 Retrieving the information is a two step process, so two APIs 88 are required. 89 90 The first entrypoint 91 EGLBoolean eglExportDMABUFImageQueryMESA(EGLDisplay dpy, 92 EGLImageKHR image, 93 int *fourcc, 94 int *num_planes, 95 EGLuint64KHR *modifiers); 96 97 is used to retrieve the pixel format of the buffer, as specified by 98 drm_fourcc.h, the number of planes in the image and the Linux 99 drm modifiers. <fourcc>, <num_planes> and <modifiers> may be NULL, 100 in which case no value is retrieved. 101 102 The second entrypoint retrieves the dma_buf file descriptors, 103 strides and offsets for the image. The caller should pass 104 arrays sized according to the num_planes values retrieved previously. 105 Passing arrays of the wrong size will have undefined results. 106 If the number of fds is less than the number of planes, then 107 subsequent fd slots should contain -1. 108 109 EGLBoolean eglExportDMABUFImageMESA(EGLDisplay dpy, 110 EGLImageKHR image, 111 int *fds, 112 EGLint *strides, 113 EGLint *offsets); 114 115 <fds>, <strides>, <offsets> can be NULL if the infomatation isn't 116 required by the caller. 117 118 Issues 119 120 1. Should the API look more like an attribute getting API? 121 122 ANSWER: No, from a user interface pov, having to iterate across calling 123 the API up to 12 times using attribs seems like the wrong solution. 124 125 2. Should the API take a plane and just get the fd/stride/offset for that 126 plane? 127 128 ANSWER: UNKNOWN,this might be just as valid an API. 129 130 3. Does ownership of the file descriptor remain with the app? 131 132 ANSWER: Yes, the app is responsible for closing any fds retrieved. 133 134 4. If number of planes and number of fds differ what should we do? 135 136 ANSWER: Return -1 for the secondary slots, as this avoids having 137 to dup the fd extra times to make the interface sane. 138 139 Revision History 140 141 Version 3, May, 2015 142 Just use the KHR 64-bit type. 143 Version 2, March, 2015 144 Add a query interface (Dave Airlie) 145 Version 1, June 3, 2014 146 Initial draft (Dave Airlie) 147 148
