<div dir="ltr">On 1 March 2013 15:14, Ian Romanick <<a href="mailto:idr@freedesktop.org" target="_blank">idr@freedesktop.org</a>> wrote: <div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Since last September I've been gradually working on an extension to let applications query information about the renderer before (and after) creating a context. I've talked it over with a few ISVs and with various other folks. I also gathered some input from folks at FOSDEM after my talk there. After going through several iterations of review and modification, I think it's finally ready for wider input. Some of the earliest feedback that I got was that many ISVs really like the interface that fills this niche on Mac OS. It's a pretty nice API, and this API is modeled after it. There are, however, some differences. I've pasted the spec below so that people can provide in-line comments. I've also pushed a branch with the spec and the initial implementation. There are a few things potentially provided by the spec that are not included in the initial implementation. I've implemented a couple unit tests, and I have some piglit tests in-progress. <a href="http://cgit.freedesktop.org/~idr/mesa/log/?h=query-renderer" target="_blank">http://cgit.freedesktop.org/~idr/mesa/log/?h=query-renderer</a> I'm mostly looking for input on the specification itself. Once this is good, I will also add EGL support. Name MESA_query_renderer Name Strings GLX_MESA_query_renderer Contact Ian Romanick <<a href="mailto:ian.d.romanick@intel.com" target="_blank">ian.d.romanick@intel.com</a>> IP Status No known IP claims. Status Incomplete. DO NOT SHIP. Version Version 5, 14-February-2013 Number TBD. Dependencies GLX 1.4 is required. GLX_ARB_create_context and GLX_ARB_create_context_profile are required. This extension interacts with GLX_EXT_create_context_es2_profile and GLX_EXT_create_context_es_profile. Overview In many situations, applications want to detect characteristics of a rendering device before creating a context for that device. Information gathered at this stage may guide choices the application makes about color depth, number of samples per-pixel, texture quality, and so on. In addition, versions of supported APIs and implementation API preference may also guide start-up decisions made by the application. For example, one implementation may prefer vertex data be supplied using methods only available in a compatibility profile, but another implementation may only support the desired version in a core profile. There are also cases where more than one renderer may be available per display. For example, there is typically a hardware implementation and a software based implementation. There are cases where an application may want to pick one over the other. One such situation is when the software implementation supports more features than the hardware implementation. Another situation is when a particular version of the hardware implementation is blacklisted due to known bugs. This extension provides a mechanism for the application to query all of the available renderers for a particular display and screen. In addition, this extension provides a mechanism for applications to create contexts with respect to a specific renderer. New Procedures and Functions Bool glXQueryRendererIntegerMESA(Display *dpy, int screen, int renderer, int attribute, unsigned int *value); Bool glXQueryCurrentRendererIntegerMESA(int attribute, unsigned int *value); const char *glXQueryRendererStringMESA(Display *dpy, int screen, int renderer, int attribute); const char *glXQueryCurrentRendererStringMESA(int attribute); New Tokens Accepted as an <attribute> in glXQueryRendererIntegerMESA: GLX_RENDERER_VENDOR_ID_MESA 0xXXXX GLX_RENDERER_DEVICE_ID_MESA 0xXXXX GLX_RENDERER_VERSION_MESA 0xXXXX GLX_RENDERER_ACCELERATED_MESA 0xXXXX GLX_RENDERER_VIDEO_MEMORY_MESA 0xXXXX GLX_RENDERER_UNIFIED_MEMORY_ARCHITECTURE_MESA 0xXXXX GLX_RENDERER_PREFERRED_PROFILE_MESA 0xXXXX GLX_RENDERER_OPENGL_CORE_PROFILE_VERSION_MESA 0xXXXX GLX_RENDERER_OPENGL_COMPATIBILITY_PROFILE_VERSION_MESA 0xXXXX GLX_RENDERER_OPENGL_ES_PROFILE_VERSION_MESA 0xXXXX GLX_RENDERER_OPENGL_ES2_PROFILE_VERSION_MESA 0xXXXX Accepted as an <attribute> in glXQueryRendererStringMESA: GLX_RENDERER_VENDOR_ID_MESA GLX_RENDERER_DEVICE_ID_MESA Accepted as an attribute name in <*attrib_list> in glXCreateContextAttribsARB: GLX_RENDERER_ID_MESA 0xXXXX Additions to the OpenGL / WGL Specifications None. This specification is written for GLX. Additions to the GLX 1.4 Specification [Add the following to Section X.Y.Z of the GLX Specification] To obtain information about the available renderers for a particular display and screen, void glXQueryRendererIntegerMESA(Display *dpy, int screen, int renderer, int attribute, unsigned int *value); can be used. The value for <attribute> will be returned in one or more integers specified by <value>. The values, data sizes, and descriptions of each renderer attribute are listed in the table below. GLX renderer attribute number description of values ---------------------- --------- ----------- GLX_RENDERER_VENDOR_ID_MESA 1 PCI ID of the device vendor GLX_RENDERER_DEVICE_ID_MESA 1 PCI ID of the device GLX_RENDERER_VERSION_MESA 3 Major, minor, and patch level of the renderer implementation GLX_RENDERER_ACCELERATED_MESA 1 Boolean indicating whether or not the renderer is hardware accelerated GLX_RENDERER_VIDEO_MEMORY_MESA 1 Number of megabytes of video memory available to the renderer GLX_RENDERER_UNIFIED_MEMORY_ARCHITECTURE_MESA 1 Boolean indicating whether or not the renderer uses a unified memory architecture or has separate "on-card" and GART memory. GLX_RENDERER_PREFERRED_PROFILE_MESA 1 Bitmask of the preferred context profile for this renderer. This value is suitable to be supplied with the GLX_CONTEXT_PROFILE_MASK_ARB attribute to glXCreateContextAttribsARB GLX_RENDERER_OPENGL_CORE_PROFILE_VERSION_MESA 2 Maximum core profile major and minor version supported by the renderer GLX_RENDERER_OPENGL_COMPATIBILITY_PROFILE_VERSION_MESA 2 Maximum compatibility profile major and minor version supported by the renderer GLX_RENDERER_OPENGL_ES_PROFILE_VERSION_MESA 2 Maximum OpenGL ES 1.x major and minor version supported by the renderer GLX_RENDERER_OPENGL_ES2_PROFILE_VERSION_MESA 2 Maximum OpenGL ES 2.x or 3.x major and minor version supported by the renderer In the table, boolean attributes will have either the value 0 or 1. GLX_RENDERER_OPENGL_CORE_PROFILE_VERSION_MESA, GLX_RENDERER_OPENGL_COMAPTIBILITY_PROFILE_VERSION_MESA, GLX_RENDERER_OPENGL_ES_PROFILE_VERSION_MESA, and GLX_RENDERER_OPENGL_ES2_PROFILE_VERSION_MESA each return <0, 0> in *value if no version of that profile is supported. If <attribute> is not a recognized value, False is returned, but no GLX error is generated. Otherwise, True is returned. </blockquote><div> </div><div>It would be nice to clarify (a) what happens to <value> if <attribute> is unrecognized, and (b) that no error is generated if <attribute> is recognized. Here's a possibility that clarifies these things and I suspect matches your intent: "If <attribute> is not a recognized value, False is returned and no data is written to <value>. Otherwise, True is returned. Regardless of whether <attribute> is a recognized value, no GLX error is generated. </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> String versions of some attributes may also be queried using const char *glXQueryRendererStringMESA(Display *dpy, int screen, int renderer, int attribute); The value for <attribute> will be returned in one or more integers specified by <value>. The values, data sizes, and descriptions of each renderer attribute are listed in the table below. GLX renderer attribute description ---------------------- ----------- GLX_RENDERER_VENDOR_ID_MESA Name of the renderer provider. This may differ from the vendor name of the underlying hardware. GLX_RENDERER_DEVICE_ID_MESA Name of the renderer. This may differ from the name of the underlying hardware (e.g., for a software renderer). If <attribute> is not a recognized value, NULL is returned, but no GLX error is generated. The string returned for GLX_RENDERER_VENDOR_ID_MESA will have the same format as the string that would be returned by glGetString of GL_VENDOR. It may, however, have a different value. The string returned for GLX_RENDERER_DEVICE_ID_MESA will have the same format as the string that would be returned by glGetString of GL_RENDERER. It may, however, have a different value. </blockquote><div> </div><div>It's not obvious to me why these two queries might return different values than the corresponding glGetString calls. It might be nice to have a "for example". </div><div>(Issue #15 looks like it's trying to address this question, but I'm afraid I don't understand.) </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> [Add to section section 3.3.7 "Rendering Contexts"] The attribute name GLX_RENDERER_ID_MESA specified the index of the render </blockquote><div> </div><div>I think you mean "specifies". </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> against which the context should be created. The default value of GLX_RENDER_ID_MESA is 0. [Add to list of errors for glXCreateContextAttribsARB in section section 3.3.7 "Rendering Contexts"] * If the value of GLX_RENDERER_ID_MESA specifies a non-existent renderer, BadMatch is generated. Dependencies on GLX_EXT_create_context_es_profile and GLX_EXT_create_context_es2_profile If neither extension is supported, remove all mention of GLX_RENDERER_OPENGL_ES2_PROFILE_VERSION_MESA from the spec. If GLX_EXT_create_context_es_profile is not supported, remove all mention of GLX_RENDERER_OPENGL_ES_PROFILE_VERSION_MESA from the spec. Issues 1) How should the difference between on-card and GART memory be exposed? UNRESOLVED. 2) How should memory limitations of unified memory architecture (UMA) systems be exposed? UNRESOLVED. Some hardware has different per-process and global limits for memory that can be accessed within a single draw call. 3) How should the renderer's API preference be advertised? UNRESOLVED. The common case for desktop renderers is to prefer either core or compatibility. However, some renderers may actually prefer an ES context. This leaves the application in a tough spot if it can only support core or compatibility and the renderer says it wants ES. 4) Should OpenGL ES 2.0 and OpenGL ES 3.0 be treated separately? RESOLVED. No. OpenGL ES 3.0 is backwards compatible with OpenGL ES 2.0. Applications can detect OpenGL ES 3.0 support by querying GLX_RENDERER_OPENGL_ES2_PROFILE_VERSION_MESA. 5) How can applications tell the difference between different hardware renderers for the same device? For example, whether the renderer is the open-source driver or the closed-source driver. RESOLVED. Assuming this extension is ever implemented outside Mesa, applications can query GLX_RENDERER_VENDOR_ID_MESA from glXQueryRendererStringMESA. This will almost certainly return different strings for open-source and closed-source drivers. 6) What is the value of GLX_RENDERER_UNIFIED_MEMORY_ARCHITECTURE_MESA for software renderers? UNRESOLVED. Video (display) memory and texture memory is not unified for software implementations, so it seems reasonable for this to be False. 7) How does an application determine the number of available renderers? UNRESOLVED. 8) What happens if a fbconfig is used to create context on a renderer that cannot support it? For example, if a multisampled config is used with a software renderer that does not support multisampling. RESOLVED. The language for glXCreateContextAttribsARB already covers this case. Context creation will fail, and BadMatch is generated. 9) In addition to being able to query the supported versions, should applications also be able to query the supported extensions? RESOLVED. No. Desktop OpenGL core profiles and OpenGL ES 3.0 have moved away from the monolithic string returned by glGetString of GL_EXTENSIONS. Providing the newer indexed query would require adding a lot of extra infrastructure, and it would probably provide little benefit to applications. 10) What combination of values for GLX_RENDERER_PREFERRED_PROFILE_MESA, GLX_RENDERER_OPENGL_COMPATIBILITY_PROFILE_VERSION_MESA, and GLX_RENDERER_OPENGL_CORE_PROFILE_VERSION_MESA should be returned for a renderer that only supports OpenGL 3.1 without the GL_ARB_compatibility extension? RESOLVED. The renderer will return GLX_CONTEXT_CORE_PROFILE_BIT_ARB for GLX_RENDERER_PREFERRED_PROFILE_MESA. Further, the renderer will return <3,0> for GLX_RENDERER_OPENGL_COMPATIBILITY_PROFILE_VERSION_MESA because OpenGL 3.1 without GL_ARB_compatibility is not backwards compatible with previous versions of OpenGL. The render will return <3,1> for GLX_RENDERER_OPENGL_CORE_PROFILE_VERSION_MESA indicating that support for OpenGL 3.1 is available. Even though there is no OpenGL 3.1 core profile, the values returned for GLX_RENDERER_PREFERRED_PROFILE_MESA and GLX_RENDERER_OPENGL_CORE_PROFILE_VERSION_MESA can be supplied with the GLX_CONTEXT_PROFILE_MASK_ARB and GLX_CONTEXT_{MAJOR,MINOR}_VERSION_ARB attributes of glXCreateContextAttribsARB without error. If the requested OpenGL version is less than 3.2, the GLX_CONTEXT_PROFILE_MASK_ARB attribute is ignored by glXCreateContextAttribsARB. 11) How can application learn about multi-GPU (e.g., SLI, CrossFireX, etc.) configurations? UNRESOLVED. Based on ISV feedback, this is important information to provide to the application. Given the variety of possible hardware configurations (e.g., Hybrid CrossFireX) and different rendering modes (e.g., split-frame rendering vs. alternate-frame rendering), it's not clear how this information can be communicated. It is likely that this will be left to a layered extension. 12) Should capability queries similar to those in GL_ARB_internalformat_query or GL_ARB_internalformat_query2 be added? RESOLVED. No. With the possible exception of the texture size queries, it seems unlikely that applications would ever use this information before creating a context. 13) Existing GL extensions (e.g., GL_ATI_meminfo and GL_NVX_gpu_memory_info) allow easy queries after context creation. With this extension it is a bit of a pain for a portable application to query the information after context creation. RESOLVED. Add versions of the queries that implicitly take the display, screen, and renderer from the currently bound context. 14) Why not make the queries from issue #14 GL functions (instead of GLX)? </blockquote><div> </div><div>I'm assuming this is a typo and issue #14 isn't trying to refer to itself :) </div><div> </div> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> RESOLVED. It is fairly compelling for the post-creation queries to just use glGetInteger and glGetString. However, the GL enums and the GLX enums would have different names and would almost certainly have different values. It seems like this would cause more problems than it would solve. 15) Should the string queries be required to return the same values as glGetString(GL_VENDOR) and glGetString(GL_RENDERER)? UNRESOLVED. This may be useful for applications that already do device detection based on these strings. 16) What type should the value parameter of glXQueryRendererIntegerMESA and glXQueryCurrentRendererIntegerMESA be? UNRESOLVED. Other similar GLX query functions just use int or unsigned int, so that's what this extension uses for now. However, an expeclitly sized value, such as uint32_t or uint64_t, seems preferable. Revision History Version 1, 2012/08/27 - Initial version Version 2, 2012/09/04 - Specify behavior of implementations that do not support certain profiles. Change wording of issue #8 to be more clear. Make some wording changes to issue #10 to clarify the resolution a bit. Version 3, 2012/09/23 - Add issue #11 regarding multi-GPU systems. Version 4, 2013/02/01 - Add issue #12 regarding texture / renderbuffer format queries. Version 5, 2013/02/14 - Add issues #13 and #14 regarding simpler queires after the context is created and made current. Add issue #15 regarding the string query. Add issue #16 regarding the value type returned by the Integer functions. _______________________________________________ mesa-dev mailing list <a href="mailto:mesa-dev@lists.freedesktop.org" target="_blank">mesa-dev@lists.freedesktop.org</a> <a href="http://lists.freedesktop.org/mailman/listinfo/mesa-dev" target="_blank">http://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> </blockquote></div> </div></div>