Determining the correct cylinder index from a known gas mix can be
complicated, but it is trivial to look up the gasmix from the cylinder_t
structure.
It makes sense to remember which cylinder is being used. This simplifies
handling changing a cylinder's gas mix, either directly by the user, or
indirectly in the planner. It also permits tracking of multiple cylinders of
the same mix, e.g. independent twins / sidemount.
Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
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