[RFC] Discussion: VIDEO_NUM_DEVICES limit in v4l2-dev.c

Hi everyone,

I'm working on a project involving high density video processing on a
single server using a large number of v4l2 loopback devices to route
virtual video streams to tenants.

While doing so, I ran into the hard limit imposed by `VIDEO_NUM_DEVICES`
(currently 256) in `drivers/media/v4l2-core/v4l2-dev.c`. Looking through
the code and git history, this limit has been there for quite a long time.
However, after searching the mailing list archives, I couldn't find any
previous discussion regarding this limitation.

May I ask:

1. Is there any internal design constraint that requires limiting the
   number of V4L2 devices to 256 on modern kernels?

2. Has this limit been discussed previously, or is there any relevant
   discussion that I may have missed?

If the current limit is no longer intentional and there's no historical
context that I might've missed, I'd be happy to work on a patch series to
address it, and I would appreciate any guidance on the preferred direction.

Cheers,
-Ali