Wen Gong [off-list ref] writes:

When function return fail to __ath11k_mac_register after success called
ieee80211_register_hw, then it set wiphy->dev.parent to NULL by
SET_IEEE80211_DEV(ar->hw, NULL) in end of __ath11k_mac_register, then
cfg80211_get_drvinfo will be called by below call stack, but the
wiphy->dev.parent is NULL, so kernel crash.

[...]

+err_unregister_hw:
+		ieee80211_unregister_hw(ar->hw);
+
 err_free_if_combs:
 	kfree(ar->hw->wiphy->iface_combinations[0].limits);
 	kfree(ar->hw->wiphy->iface_combinations);

Incorrect indentation, I'm surprised checkpatch doesn't catch that. But
fixed this in the pending branch.

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