LINUX_JoystickInit does a manual scan first so devices are sorted.
If SDL_UDEV_Init hasn't run by then, then the product info cannot
be looked up by SDL_UDEV_GetProductInfo and the initial-plugged-
in-device classification falls back to heuristic guessing.
I believe there was a O(n^2) device walking issues on startup
- MaybeAddDevice gets called for every device at startup
- MaybeAddDevice calls IsJoystick
- IsJoystick calls SDL_UDEV_GetProductInfo
- SDL_UDEV_GetProductInfo calls udev_enumerate_scan_devices
- udev_enumerate_scan_devices walks all the devices
Prior to commit 3b1e0e1 this was mostly masked as IsJoystick only
called SDL_UDEV_GetProductInfo when a JSIOCGNAME ioctl was
successful. This fixes the O(n^2) behaviour by directly getting
the device via udev_device_new_from_devnum (based on type, major,
and minor number) instead of enumerating everything via
udev_enumerate_scan_devices and matching on name.
The udev container issue is mostly to do with device notifications
and netlink. The device classification stuff just pokes file in /sys
and /run/udev. Doesn't hurt to try it first for classifying joysticks
and then fall to the guess heuristics if it fails.
Tyson Whitehead