https://bugs.freedesktop.org/show_bug.cgi?id=103575

Bug ID: 103575 Summary: eglQueryDevicesEXT returns 0 devices Product: Mesa Version: 17.2 Hardware: x86-64 (AMD64) OS: Linux (All) Status: NEW Severity: normal Priority: medium Component: Drivers/Gallium/r600 Assignee: dri-devel@lists.freedesktop.org Reporter: Hi-Angel@yandex.ru QA Contact: dri-devel@lists.freedesktop.org

I'm following this guide https://devblogs.nvidia.com/parallelforall/egl-eye-opengl-visualization-with... to choose a GPU through native means of EGL.

Using eglQueryDevicesEXT() in both modes, i.e. with "devices" array to get descriptions, as well as by passing 0 as "devices", results in 0 as a number of supported devices. Specification says that I should've get at least 1 (and I actually have two, r600g-managed, cards):

https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_device_enumerati...

EGL devices can be enumerated before EGL is initialized. Use:

    EGLBoolean eglQueryDevicesEXT(EGLint max_devices,
                                  EGLDeviceEXT *devices,
                                  EGLint *num_devices);

[SNIP]

If <devices> is NULL, then <max_devices> will be ignored, no devices will be returned in <devices>, and <num_devices> will be set to the number of supported devices in the system. All implementations must support at least one device.

On failure, EGL_FALSE is returned.

Below is the modified code I'm using:

#include <EGL/egl.h> #include <EGL/eglext.h> #include <stdio.h>

int main(int argc, char *argv[]) { EGLint numDevices;

PFNEGLQUERYDEVICESEXTPROC eglQueryDevicesEXT = (PFNEGLQUERYDEVICESEXTPROC) eglGetProcAddress("eglQueryDevicesEXT"); if (eglQueryDevicesEXT(2, 0, &numDevices) == EGL_FALSE) { puts("error in eglQueryDevicesEXT"); return 1; }

printf("Detected %d devices\n", numDevices); }