[Intel-gfx] [PATCH 3/4] drm/i915: Disable displays at the user's request

[Chris Wilson]

Quoting Chris Wilson (2018-09-13 14:16:28)
> +       /*
> +        * After completing our HW probe; tear it all down again (at the
> +        * user's request)!
> +        *
> +        * Along side the CRTCs and connectors, there is a medley of
> +        * auxiliary HW which control various powerwells and interact with
> +        * other state (such as the BIOS framebuffer occupying a portion
> +        * of reserved memory). If the user tells us to run without any
> +        * displays enabled, we still need to register all the display and
> +        * auxiliary HW in order to safely disable them.
> +        */
> +       if (i915_modparams.disable_display) {
> +               DRM_INFO("Display disabled (module parameter)\n");
> +               disable_display(dev_priv);
> +               mkwrite_device_info(dev_priv)->num_pipes = 0;
> +       }
> +
> +       if (INTEL_INFO(dev_priv)->num_pipes == 0) {
> +               dev_priv->psr.sink_support = false;
> +               drm_mode_config_cleanup(&dev_priv->drm);
> +               driver.driver_features &= ~(DRIVER_MODESET | DRIVER_ATOMIC);

Removing the feature seems like a good idea on surface (as we then don't
have to worry about hitting internals that expect crtcs and planes and
such), however more work required in declaring igt requirements than
simply having no pipes :)
-Chris