asyncio: Added Linux io_uring support.

CMakeLists.txt

@@ -290,6 +290,7 @@ set_option(SDL_SYSTEM_ICONV        "Use iconv() from system-installed libraries"
 set_option(SDL_LIBICONV            "Prefer iconv() from libiconv, if available, over libc version" OFF)
 set_option(SDL_GCC_ATOMICS         "Use gcc builtin atomics" ${SDL_GCC_ATOMICS_DEFAULT})
 dep_option(SDL_DBUS                "Enable D-Bus support" ON "${UNIX_SYS}" OFF)
+dep_option(SDL_LIBURING            "Enable liburing support" ON "${UNIX_SYS}" OFF)
 dep_option(SDL_DISKAUDIO           "Support the disk writer audio driver" ON "SDL_AUDIO" OFF)
 dep_option(SDL_DUMMYAUDIO          "Support the dummy audio driver" ON "SDL_AUDIO" OFF)
 dep_option(SDL_DUMMYVIDEO          "Use dummy video driver" ON "SDL_VIDEO" OFF)
@@ -1651,6 +1652,16 @@ elseif(UNIX AND NOT APPLE AND NOT RISCOS AND NOT HAIKU)
         set(SDL_USE_IME 1)
       endif()
 
+      if(SDL_LIBURING)
+        pkg_search_module(LIBURING liburing-ffi)
+        find_path(HAVE_LIBURING_H NAMES liburing.h)
+        if(LIBURING_FOUND AND HAVE_LIBURING_H)
+          set(HAVE_LIBURING_LIBURING_H TRUE)
+          sdl_include_directories(PRIVATE SYSTEM ${LIBURING_INCLUDE_DIRS})
+          set(HAVE_LIBURING TRUE)
+        endif()
+      endif()
+
       if((FREEBSD OR NETBSD) AND NOT HAVE_INOTIFY)
         set(LibInotify_PKG_CONFIG_SPEC libinotify)
         pkg_check_modules(PC_LIBINOTIFY IMPORTED_TARGET ${LibInotify_PKG_CONFIG_SPEC})
@@ -1714,6 +1725,10 @@ elseif(UNIX AND NOT APPLE AND NOT RISCOS AND NOT HAIKU)
       endif()
     endif()
 
+    if(HAVE_LIBURING_H)
+      sdl_sources("${SDL3_SOURCE_DIR}/src/file/io_uring/SDL_asyncio_liburing.c")
+    endif()
+
     # Always compiled for Linux, unconditionally:
     sdl_sources(
       "${SDL3_SOURCE_DIR}/src/core/linux/SDL_evdev_capabilities.c"

docs/README-linux.md

@@ -21,7 +21,7 @@ Ubuntu 18.04, all available features enabled:
     libxkbcommon-dev libdrm-dev libgbm-dev libgl1-mesa-dev libgles2-mesa-dev \
     libegl1-mesa-dev libdbus-1-dev libibus-1.0-dev libudev-dev fcitx-libs-dev
 
-Ubuntu 22.04+ can also add `libpipewire-0.3-dev libwayland-dev libdecor-0-dev` to that command line.
+Ubuntu 22.04+ can also add `libpipewire-0.3-dev libwayland-dev libdecor-0-dev liburing-dev` to that command line.
 
 Fedora 35, all available features enabled:
 
@@ -34,6 +34,8 @@ Fedora 35, all available features enabled:
     libdrm-devel mesa-libgbm-devel libusb-devel libdecor-devel \
     pipewire-jack-audio-connection-kit-devel \
 
+Fedora 39+ can also add `liburing-devel` to that command line.
+
 NOTES:
 - The sndio audio target is unavailable on Fedora (but probably not what you
   should want to use anyhow).

include/build_config/SDL_build_config.h.cmake

@@ -227,6 +227,7 @@
 #cmakedefine HAVE_LINUX_INPUT_H 1
 #cmakedefine HAVE_LIBUDEV_H 1
 #cmakedefine HAVE_LIBDECOR_H 1
+#cmakedefine HAVE_LIBURING_H 1
 
 #cmakedefine HAVE_D3D11_H @HAVE_D3D11_H@
 #cmakedefine HAVE_DDRAW_H @HAVE_DDRAW_H@

src/file/SDL_sysasyncio.h

@@ -28,7 +28,11 @@
 // is #defined to 0 instead and implement the SDL_SYS_* functions below in your
 // backend (having them maybe call into the SDL_SYS_*_Generic versions as a
 // fallback if the platform has functionality that isn't always available).
+#ifdef HAVE_LIBURING_H
+#define SDL_ASYNCIO_ONLY_HAVE_GENERIC 0
+#else
 #define SDL_ASYNCIO_ONLY_HAVE_GENERIC 1
+#endif
 
 // this entire thing is just juggling doubly-linked lists, so make some helper macros.
 #define LINKED_LIST_DECLARE_FIELDS(type, prefix) \