xrandr --listproviders does not detect nvidia

Question

I'm trying to configure 'Offloading Graphics Display with RandR 1.4' but xrandr detects only Intel video card:

$ xrandr --listproviders
Providers: number : 1
Provider 0: id: 0x45 cap: 0x2, Sink Output crtcs: 3 outputs: 3 associated providers: 0 name:modesetting

Video cards (laptop Acer Aspire V3-772G):

# lspci | grep -E 'VGA|3D'
00:02.0 VGA compatible controller: Intel Corporation Haswell Integrated Graphics Controller (rev 06)
01:00.0 3D controller: NVIDIA Corporation GK107M [GeForce GT 750M] (rev a1)

OS:

$ cat /etc/slackware-version 
Slackware 14.1
# uname -a
Linux darkstar 3.15.1-big_btz #3 SMP Mon Jul 14 15:56:31 EEST 2014 x86_64 Intel(R) Core(TM) i7-4702MQ CPU @ 2.20GHz GenuineIntel GNU/Linux

X:

$ ls -l /var/log/packages/xorg-server-*
-rw-r--r-- 1 root root 8245 Feb  8 07:52 /var/log/packages/xorg-server-1.14.3-x86_64-3_slack14.1
-rw-r--r-- 1 root root  712 Feb  8 07:52 /var/log/packages/xorg-server-xephyr-1.14.3-x86_64-3_slack14.1
-rw-r--r-- 1 root root  933 Feb  8 07:52 /var/log/packages/xorg-server-xnest-1.14.3-x86_64-3_slack14.1
-rw-r--r-- 1 root root 1027 Feb  8 07:52 /var/log/packages/xorg-server-xvfb-1.14.3-x86_64-3_slack14.1

Kernel config (full config):

# zcat /proc/config.gz | grep CONFIG_DRM
CONFIG_DRM=m
CONFIG_DRM_KMS_HELPER=m
CONFIG_DRM_KMS_FB_HELPER=y
CONFIG_DRM_LOAD_EDID_FIRMWARE=y
CONFIG_DRM_TTM=m
CONFIG_DRM_I2C_CH7006=m
CONFIG_DRM_I2C_SIL164=m
CONFIG_DRM_I2C_NXP_TDA998X=m
# CONFIG_DRM_TDFX is not set
# CONFIG_DRM_R128 is not set
# CONFIG_DRM_RADEON is not set
# CONFIG_DRM_NOUVEAU is not set
# CONFIG_DRM_I810 is not set
CONFIG_DRM_I915=m
CONFIG_DRM_I915_KMS=y
CONFIG_DRM_I915_FBDEV=y
CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT=y
# CONFIG_DRM_I915_UMS is not set
# CONFIG_DRM_MGA is not set
# CONFIG_DRM_SIS is not set
# CONFIG_DRM_VIA is not set
# CONFIG_DRM_SAVAGE is not set
CONFIG_DRM_VMWGFX=m
CONFIG_DRM_VMWGFX_FBCON=y
# CONFIG_DRM_GMA500 is not set
# CONFIG_DRM_UDL is not set
# CONFIG_DRM_AST is not set
# CONFIG_DRM_MGAG200 is not set
# CONFIG_DRM_CIRRUS_QEMU is not set
# CONFIG_DRM_QXL is not set
# CONFIG_DRM_BOCHS is not set
# CONFIG_DRM_PTN3460 is not set

Nvidia (install log):

$ nvidia-settings -v

nvidia-settings:  version 352.21  (buildmeister@swio-display-x64-rhel04-13)  Tue Jun  9 22:42:41 PDT 2015
  The NVIDIA X Server Settings tool.

  This program is used to configure the NVIDIA Linux graphics driver.
  For more detail, please see the nvidia-settings(1) man page.

Xrandr:

$ xrandr -v
xrandr program version       1.4.1
Server reports RandR version 1.4

P.S. I'm not sure how to check that appropriate driver interfaces are presented

o A Linux kernel with CONFIG_DRM enabled and the appropriate driver
     interfaces present:

        o drm_gem_prime_export

        o drm_gem_prime_import

        o gem_prime_pin

        o gem_prime_get_sg_table

        o gem_prime_import_sg_table

        o gem_prime_vmap

        o gem_prime_vunmap

Solution

I have a similar setup on Slackware:

# lspci | grep -E 'VGA|3D'
00:02.0 VGA compatible controller: Intel Corporation Haswell Integrated Graphics Controller (rev 06)
01:00.0 VGA compatible controller: NVIDIA Corporation GK106M [GeForce GTX 765M] (rev ff)}

And my xrandr only shows one card:

xrandr --listproviders
Providers: number : 1
Provider 0: id: 0x47 cap: 0xb, Source Output, Sink Output, Sink Offload crtcs: 4 outputs: 4 associated providers: 0 name:Intel

but my nVidia card still seems to be working (I use bumblebee / optirun)

$ optirun glxinfo | grep "OpenGL renderer"
OpenGL renderer string: GeForce GTX 765M/PCIe/SSE2

$ optirun glxgears -info
GL_RENDERER   = GeForce GTX 765M/PCIe/SSE2
GL_VERSION    = 4.5.0 NVIDIA 352.30
GL_VENDOR     = NVIDIA Corporation

and uses the Intel card if I don't run optirun:

$ glxinfo | grep "OpenGL renderer"
OpenGL renderer string: Mesa DRI Intel(R) Haswell Mobile

$ glxgears -info
Running synchronized to the vertical refresh.  The framerate should be
approximately the same as the monitor refresh rate.
GL_RENDERER   = Mesa DRI Intel(R) Haswell Mobile 
GL_VERSION    = 3.0 Mesa 10.5.4
GL_VENDOR     = Intel Open Source Technology Center

See http://docs.slackware.com/howtos:hardware:nvidia_optimus for setup instructions.