[Intel-gfx] [PATCH] drm/i915: Don't try to check max stride for disabled/non-existent display

[Chris Wilson]

Quoting Matt Roper (2020-08-10 19:08:51)
> Userspace may still create GEM dumb buffers even on platforms with
> disabled or non-existent display.  When creating dumb buffers we try to
> check the max fb stride for the platform by looking at the first pipe on
> the platform.  We previously fixed a crash related to accessing the
> non-existent PIPE_A in commit 8ac495f624a4 ("drm/i915: Don't oops in
> dumb_create ioctl if we have no crtcs") but the crash is back as of
> commit eae3da27ba84 ("drm/i915: Get first crtc instead of PIPE_A crtc")
> because we now try to iterate over the [uninitialized] crtc list.

drm_mode_config_init() is still being called
i915_driver_probe
  -> i915_driver_modeset_probe_noirq
    -> intel_modeset_init_noirq
      -> intel_mode_config_init
        -> drm_mode_config_init
regardless of the status for HAS_DISPLAY or INTEL_DISPLAY_ENABLED. So
drm_crtc_index(0) should be returning NULL?
-Chris