[RFC][PATCH 7/8]: Auto-create ptmx node when mounting devpts

[H. Peter Anvin]

Eric W. Biederman wrote:
>> I had the new ptmx node only in 'multi-mount' mode initially. But if users
>> want the multi-mount semantics, /dev/ptmx must be a symlink. If its a symlink,
>> we break in the single-mount case (which does not have the ptmx node and
>> we don't support mknod in pts).
> 
> Then have user space make it a file bind mount instead of symlink.
> That should address all of the backwards compatibility concerns, and
> allow us to only create it when open.

The right thing is that, if you want to support back-and-forth flipping, 
to introduce a udev rule which looks for pts/ptmx, links to it if 
present, and otherwise creates the ptmx device node.

This is *only* required to support back-and-forth, and can be introduced 
at any time after this patch is in the kernel -- or even before.

	-hpa