drm/i915: Insert i915_preliminary_hw_support variable.

On the worst scenario, users with new hardwares and old kernel from
enabling times can get black screens.  So, from now on, this
perliminary_hw_support module parameter shall be used by all upcoming
platforms that are still under enabling. The second option would be to
merge the pci ids after basic modeset works, but that makes testing
and development while bringing up hw a rather tedious afair.

Although it is uncomfortable for developers use this extra variable it
brings more stability for end users.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
[danvet: dropped the i915_ param prefix, i915.i915_ is just tedious.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -119,6 +119,13 @@ module_param_named(i915_enable_ppgtt, i915_enable_ppgtt, int, 0600);
 MODULE_PARM_DESC(i915_enable_ppgtt,
 		"Enable PPGTT (default: true)");
 
+unsigned int i915_preliminary_hw_support __read_mostly = 0;
+module_param_named(preliminary_hw_support, i915_preliminary_hw_support, int, 0600);
+MODULE_PARM_DESC(preliminary_hw_support,
+		"Enable preliminary hardware support. "
+		"Enable Haswell and ValleyView Support. "
+		"(default: false)");
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 
@@ -827,6 +834,12 @@ i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	struct intel_device_info *intel_info =
 		(struct intel_device_info *) ent->driver_data;
 
+	if (intel_info->is_haswell || intel_info->is_valleyview)
+		if(!i915_preliminary_hw_support) {
+			DRM_ERROR("Preliminary hardware support disabled\n");
+			return -ENODEV;
+		}
+
 	/* Only bind to function 0 of the device. Early generations
 	 * used function 1 as a placeholder for multi-head. This causes
 	 * us confusion instead, especially on the systems where both

drivers/gpu/drm/i915/i915_drv.h

@@ -1217,6 +1217,7 @@ extern int i915_enable_rc6 __read_mostly;
 extern int i915_enable_fbc __read_mostly;
 extern bool i915_enable_hangcheck __read_mostly;
 extern int i915_enable_ppgtt __read_mostly;
+extern unsigned int i915_preliminary_hw_support __read_mostly;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);