Pre-Allocate pty devices in mod_event handler rather than using dev_clone

[davide]

Summary

root@maxwell:/home/davide # kldload pty
root@maxwell/home/davide # sysctl -a |grep pty
kern.tty_pty_warningcnt: 1
kern.npty: 32
debug.softdep.emptyjblocks: 0

root@maxwell:/home/davide # ls /dev/pty*
/dev/ptyl0 /dev/ptyl2 /dev/ptyl4 /dev/ptyl6 /dev/ptyl8 /dev/ptyla /dev/ptylc /dev/ptyle /dev/ptylg /dev/ptyli /dev/ptylk /dev/ptylm /dev/ptylo /dev/ptylq /dev/ptyls /dev/ptylu
/dev/ptyl1 /dev/ptyl3 /dev/ptyl5 /dev/ptyl7 /dev/ptyl9 /dev/ptylb /dev/ptyld /dev/ptylf /dev/ptylh /dev/ptylj /dev/ptyll /dev/ptyln /dev/ptylp /dev/ptylr /dev/ptylt /dev/ptylv

[ed]

sys/dev/pty/pty.c

62

I don't entirely see why we'd need this sysctl variable. The point is, the devices are created when you load the module. After the module has loaded, we never use this one again, meaning that the user still has no way to influence this, right?

The upper limit is also far too high. The naming scheme doesn't really allow you to create more.

119

So the point is: we originally used the naming scheme pty[pqrs][0-9a-v] and only later on added support for pty[l-o][0-9a-v] when that became insufficient. Please make sure that if npty is low, the first device you hand out is ptyp0. Otherwise you will break compatibility. See:

https://svnweb.freebsd.org/base/head/etc/etc.i386/ttys?r1=199250&r2=203068

139

Instead of coming up with complicated logic to compute the next device name, it's actually easier to recompute it entirely.

namedev[3] = "pqrsPQRS"[i / 32];
n = i % 32;
namedev[4] = n < 10 ? n + '0' : n - 10 + 'a';

[davide]

Drop this revision after discussion on the mailing list.