I'm trying to run Linux on a cheap ValleyView-based tablet "Krüger&Matz EDGE 1081" (aka KM1081):

Intel(R) Atom(TM) CPU  Z3735D @ 1.33GHz (4-core)
Linux 3.18.0+ SMP i686 (32-bit, basically vanilla 3.18)
gcc version 4.8.3
EFI v2.31 by American Megatrends (I'm using EFI STUB kernel feature)

00:00.0 Host bridge: Intel Corp ValleyView SSA-CUnit (rev 0d)
00:02.0 VGA compatible controller: Intel Corp ValleyView Gen7 (rev 0d)
00:14.0 USB controller: Intel Corp ValleyView USB xHCI Host Controller (rev 0d)
00:1a.0 Encryption controller: Intel Corp ValleyView SEC (rev 0d)
00:1f.0 ISA bridge: Intel Corp ValleyView Power Control Unit (rev 0d)

CONFIG_DRM_I915=m
CONFIG_DRM_I915_KMS=y
# CONFIG_DRM_I915_FBDEV is not set
# CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT is not set

rmmod i915 produces:

------------[ cut here ]------------
WARNING: CPU: 2 PID: 238 at /usr/src/linux/stable/lib/idr.c:506 idr_remove+0x233/0x240()
idr_remove called for id=0 which is not allocated.
Modules linked in: asix usbnet mii libphy mmc_block i915(-) intel_gtt drm_kms_helper iosf_mbi ac battery sdhci_acpi sdhci mmc_core
CPU: 2 PID: 238 Comm: rmmod Not tainted 3.18.0+ #171
Hardware name: To be filled by O.E.M., BIOS 5.6.5 09/24/2014
 00000000 00000000 c0a49d70 c1433489 c0a49db0 c0a49da0 c10372a5 c1528a7c
 c0a49dcc 000000ee c1528a5c 000001fa c11a0e63 c11a0e63 c0a49ddc c0a78184
 c0985308 c0a49db8 c10372ef 00000009 c0a49db0 c1528a7c c0a49dcc c0a49df8
Call Trace:
 [<c1433489>] dump_stack+0x41/0x52
 [<c10372a5>] warn_slowpath_common+0x75/0x90
 [<c11a0e63>] ? idr_remove+0x233/0x240
 [<c11a0e63>] ? idr_remove+0x233/0x240
 [<c10372ef>] warn_slowpath_fmt+0x2f/0x40
 [<c11a0e63>] idr_remove+0x233/0x240
 [<c1250696>] drm_mode_object_put+0x26/0x40
 [<c1254622>] drm_mode_destroy+0x12/0x20
 [<f8be9347>] intel_panel_fini+0x17/0x30 [i915]
 [<f8bdf87f>] intel_dsi_destroy+0x1f/0x50 [i915]
 [<f8bd7c7b>] ? intel_dp_connector_destroy+0x3b/0x50 [i915]
 [<c125188d>] drm_mode_config_cleanup+0xad/0x250
 [<f8bc8f49>] intel_modeset_cleanup+0x99/0xd0 [i915]
 [<f8bf23d7>] i915_driver_unload+0x1e7/0x250 [i915]
 [<c12455ee>] ? drm_lastclose+0x6e/0x110
 [<c124a2ab>] drm_dev_unregister+0x1b/0x90
 [<c124a49e>] drm_put_dev+0x1e/0x70
 [<c126778e>] ? __pm_runtime_resume+0x3e/0x50
 [<f8b6e29e>] i915_pci_remove+0xe/0x10 [i915]
 [<c11c395a>] pci_device_remove+0x2a/0xa0
 [<c12609cc>] __device_release_driver+0x5c/0xb0
 [<c1261057>] driver_detach+0x87/0x90
 [<c126077b>] bus_remove_driver+0x3b/0x80
 [<c12613c4>] driver_unregister+0x24/0x60
 [<c108998d>] ? stop_cpus+0x2d/0x40
 [<c1084ba0>] ? module_refcount+0x90/0x90
 [<c11c3693>] pci_unregister_driver+0x13/0x60
 [<c124ba07>] drm_pci_exit+0x77/0xa0
 [<f8bf40aa>] i915_exit+0x1b/0x4e [i915]
 [<c108631a>] SyS_delete_module+0xfa/0x160
...

then:
WARNING: CPU: 2 PID: 238 at /usr/src/linux/stable/drivers/gpu/drm/drm_crtc.c:5173 drm_mode_config_cleanup+0x225/0x250()
...

WARNING: CPU: 2 PID: 238 at /usr/src/linux/stable/drivers/gpu/drm/i915/i915_gem.c:4505 i915_gem_free_object+0x370/0x390 
...
[drm] Module unloaded

The i915 module can be subsequently insmod-ed.
Additional logs, testing etc. available of course.