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08 September 2024, 02:26:05 UTC
Revision 27667f4744fc5a0f3e50910e78740bac5670d18b authored by Linus Torvalds on 30 July 2015, 05:18:16 UTC, committed by Linus Torvalds on 02 August 2015, 18:02:16 UTC 
i915: temporary fix for DP MST docking station NULL pointer dereference
 
Ted Ts'o reports that his Lenovo T540p ThinkPad crashes at boot if
attached to the docking station.  This is a regression that he was able
to bisect to commit 8c7b5ccb7298: "drm/i915: Use atomic helpers for
computing changed flags:"

The reason seems to be the new call to drm_atomic_helper_check_modeset()
added to intel_modeset_compute_config(), which in turn calls
update_connector_routing(), and somehow ends up picking a NULL crtc for
the connector state, causing the subsequent drm_crtc_index() to OOPS.

Daniel Vetter says that the fundamental issue seems to be confusion in
the encoder selection, and this isn't the right fix, but while he chases
down the proper fix, this at least avoids the NULL pointer dereference
and makes Ted's docking station work again.

Reported-bisected-and-tested-by: Theodore Ts'o <tytso@mit.edu>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Mani Nikula <jani.nikula@linux.intel.com>
Cc: Dave Airlie <airlied@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent d4edea4
History
Tip revision: 27667f4744fc5a0f3e50910e78740bac5670d18b authored by Linus Torvalds on 30 July 2015, 05:18:16 UTC
i915: temporary fix for DP MST docking station NULL pointer dereference
Tip revision: 27667f4
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