[Intel-gfx] [RFC] drm/i915/dp: Remove i915.enable_dp_mst module parameter

[Nathan Schulte]

I wanted to add a note about why I initially proposed the modparam
enable_dp_mst: --

The problem I was facing is that an external DisplayPort adapter
(Sunix DPD2001: https://sunix.com/en/product_detail.php?pid=1720),
supporting both MST and SST, had no means of choosing SST
("splitting", single display) vs MST ("normal", additional display)
mode -- the MST mode is automatically selected if the graphics
advertised support, and SST otherwise.  This presented and issue when
using two of these devices with e.g. Intel HD 4600, which supports a
maximum of three displays.  At the time, disabling MST support was the
only mechanism [not yet] available to enable this setup.  A
per-port/channel disable is great, as likely are the debugfs
improvements since.

Finally, Sunix actually provided me with a customized firmware that
disabled MST support in the device, enabling the quad-monitor setup in
this situation, though the ability of the user to control the
driver/mode is preferred.  I'm happy to share this firmware if anyone
requests it.

I'm surprised and happy this modparam proved useful to others, and
glad it was accepted as a change.

Kudos,

--
Nathan