On 2/24/23 4:48 PM, Elliot Berman wrote:

I'd be open to making GH_CREATE_VM take a struct argument today, but I 
really don't know what size or what needs to be in that struct. My hope 
is that we can get away with just an integer for future needs. If 
integer doesn't suit, then new ioctl would need to be created. I think 
there's same problem if I pick some struct today (the struct may not 
suit tomorrow and we need to create new ioctl for the new struct).

I'd like someone to back me up (or tell me I'm wrong), but...

I think you can still pass a void in/out pointer, which can
be interpreted in an IOCTL-specific way, as long as it can
be unambiguously processed.

So if you passed a non-null pointer, what it referred to
could contain a key that defines the way to interpret it.

You can't take away a behavior you've once supported, but I
*think* you can add a new behavior (with a new structure
that identifies itself).

So if that is correct, you can extend a single IOCTL.  But
sadly I can't tell you I'm sure this is correct.

					-Alex

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