The loader ICD ordering could be random on Linux based on using readdir
to find ICD manifest files. This can result in random behaviors as
applications that select only the first device can switch which device is
used. To resolve this, we now sort based on device type and then
internally to the types based on PCI bus information.
This also introduces a VK_LOADER_DEFAULT_DEVICE environment variable
that can be used to force a specific PCI device. This environment variable
is actually a duplicate of the MESA_VK_DEVICE_SELECT variable, which is
also looked for if the loader environment variable is not found.
Note, that at least one ICD must support it for the extension to be used at all.
So we only do the sorting if one ICD supports it.
Fixes part of #657
Add a section warning about possible issues with bundling the
Khronos loader with an application/engine.
Also, rename "desktop loader" to "Khronos loader" since it is now
used for more than the original desktop targets.
Add a section in the application documentation on how to debug possible
layer issues.
Also add a small note on why a layer may need to intercept pre-instance
functions.
Feedback from Khronos was that "Implementation" was for the entire
set of Vulkan components underlying the application (including the
loader, layers, and drivers). Instead, what I had been calling
implementation should be called "Driver" including software
implementations of Vulkan at that level.
Also update the LOADER_DEBUG option "implem" to take "driver" as well.
All images also updated.
Update the loader documentation in the following ways:
1. Move documentation to new "docs" folder"
2. Split LoaderAndLayerInterface.md into multiple docs to focus
on target audience:
- Top-Level LoaderInterfaceArchitecture.md
- Applications LoaderApplicationInterface.md
- Layers LoaderLayerInterface.md
- ICDs LoaderImplementationInterface.md
3. Upload newer images and their corresponding original Inkscape files.
4. Cleanup and update sections on Linux directory search
5. Add new sections to detail items missing
- VkConfig
- Handling undef Fuchsia
6. Language cleanup
Thanks to @charles-lunarg and @smcv for feedback and various section language
corrections.
ZhangLiang