RFC: Remove pty(4)

Alfred Perlstein bright at mu.org
Wed Aug 20 18:04:18 UTC 2014

On 8/20/14 11:00 AM, Davide Italiano wrote:
> One of my personal goals for 11 is to get rid of cloning mechanism
> entirely, and pty(4) is one of the few in-kernel drivers still relying
> on such mechanism.
> It's not possible, at least to my understanding, converting pty(4) to
> cdevpriv(9) as happened with other drivers. This is mainly because we
> always need a pair of devices (/dev/ptyXX and /dev/ttyXX) and
> userspace loops over ptyXX and after it successfully opens it tries to
> open the other one with the same suffix. So, having a single device is
> not really enough.
> My option, instead, is that of removing pty(4), which is nothing more
> than a compatibility driver, and move pmtx(4) code somewhere else.
> The main drawback of the removal of this is that it makes impossible
> to run FreeBSD <= 7 jails and SSH into them. I personally don't
> consider this a huge issue, in light of the fact that FreeBSD-7 has
> been EOL for a long time, but I would like to hear other people
> comments.
> The code review for the proposed change can be found here:
> https://reviews.freebsd.org/D659
> If I won't get any objection I'll commit this in one week time, i.e.
> August 27th.
I don't think that we want to break userland apps pre-7.x.  Do you mean 
just jails are broken?  Or is all pre-7.x compat?  I believe either is 
dicey.  What is the reason for getting rid of cloning? What is the 
difficulty in maintaining the old interface?


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