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mesa/docs/_extra/specs/MESA_query_renderer.spec
Erik Faye-Lund 381fc0eca5 docs: include specs into the generated docs 
Unfortunately, it doesn't seem like there's a way to have sphinx copy
this without moving the files, becasue html_extra_path doesn't copy the
directory itself when given a directory, only files inside and
subdirectories.

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4630>
2020-06-13 10:42:01 +00:00

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Name
MESA_query_renderer
Name Strings
GLX_MESA_query_renderer
Contact
Ian Romanick <ian.d.romanick@intel.com>
IP Status
No known IP claims.
Status
Shipping as of Mesa 10.0
Version
Version 9, 09 November 2018
Number
OpenGL Extension #446
Dependencies
GLX 1.4 is required.
GLX_ARB_create_context and GLX_ARB_create_context_profile are required.
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 and
glXQueryCurrentRendererIntegerMESA:
GLX_RENDERER_VENDOR_ID_MESA 0x8183
GLX_RENDERER_DEVICE_ID_MESA 0x8184
GLX_RENDERER_VERSION_MESA 0x8185
GLX_RENDERER_ACCELERATED_MESA 0x8186
GLX_RENDERER_VIDEO_MEMORY_MESA 0x8187
GLX_RENDERER_UNIFIED_MEMORY_ARCHITECTURE_MESA 0x8188
GLX_RENDERER_PREFERRED_PROFILE_MESA 0x8189
GLX_RENDERER_OPENGL_CORE_PROFILE_VERSION_MESA 0x818A
GLX_RENDERER_OPENGL_COMPATIBILITY_PROFILE_VERSION_MESA 0x818B
GLX_RENDERER_OPENGL_ES_PROFILE_VERSION_MESA 0x818C
GLX_RENDERER_OPENGL_ES2_PROFILE_VERSION_MESA 0x818D
Accepted as an <attribute> in glXQueryRendererStringMESA and
glXQueryCurrentRendererStringMESA:
GLX_RENDERER_VENDOR_ID_MESA
GLX_RENDERER_DEVICE_ID_MESA
Additions to the OpenGL / WGL Specifications
None. This specification is written for GLX.
Additions to the GLX 1.4 Specification
[Add to Section 3.3.2 "GLX Versioning" of the GLX Specification]
To obtain information about the available renderers for a particular
display and screen,
Bool 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_COMPATIBILITY_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.
GLX_RENDERER_VENDOR_ID_MESA and GLX_RENDERER_DEVICE_ID_MESA may return
0xFFFFFFFF if the device does not have a PCI ID (because it is not a PCI
device) or if the PCI ID is not available. In this case the application
should rely on the string query instead.
If <attribute> is not a recognized value, False is returned, but no GLX
error is generated. Otherwise, True is returned.
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.
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 #13 GL functions (instead of GLX)?
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.
17) What about SoCs and other systems that don't have PCI?
RESOLVED. The GLX_RENDERER_VENDOR_ID_MESA and
GLX_RENDERER_DEVICE_ID_MESA integer queries may return 0xFFFFFFFF if a
PCI ID either does not exist or is not available. Implementations
should make every attempt to return as much information as is
possible. For example, if the implementation is running on a non-PCI
SoC with a Qualcomm GPU, GLX_RENDERER_VENDOR_ID_MESA should return
0x5143, but GLX_RENDERER_DEVICE_ID_MESA will return 0xFFFFFFFF.
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.
Version 6, 2013/10/25 - Fix a typo. Update the list of functions to
which the new enums can be passed. The "Current"
versions were previously missing.
Version 7, 2013/11/07 - Fix a couple more typos. Add issue #17 regarding
the PCI queries on systems that don't have PCI.
Version 8, 2014/02/14 - Fix a couple typos. GLX_RENDER_ID_MESA should
read GLX_RENDERER_ID_MESA. The VENDOR/DEVICE_ID
example given in issue #17 should be 0x5143 and
0xFFFFFFFF respectively.
Version 9, 2018/11/09 - Remove GLX_RENDERER_ID_MESA, which has never been
implemented. Remove the unnecessary interactions
with the GLX GLES profile extensions. Note the
official GL extension number. Specify the section
of the GLX spec to modify.
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