svn commit: r337750 - head/share/man/man4

[Warner Losh]

On Tue, Aug 14, 2018 at 7:58 AM, Ian Lepore <ian at freebsd.org> wrote:

> On Tue, 2018-08-14 at 13:52 +0000, Warner Losh wrote:
> > Author: imp
> > Date: Tue Aug 14 13:52:10 2018
> > New Revision: 337750
> > URL: https://svnweb.freebsd.org/changeset/base/337750
> >
> > Log:
> >   Add good description of init and lock devices from sio to uart.
> >
> > Modified:
> >   head/share/man/man4/uart.4
> >
> > Modified: head/share/man/man4/uart.4
> > =====================================================================
> > =========
> > --- head/share/man/man4/uart.4        Tue Aug 14 13:52:08 2018
> > (r337749)
> > +++ head/share/man/man4/uart.4        Tue Aug 14 13:52:10 2018
> > (r337750)
> > @@ -225,6 +225,52 @@ Generally speaking, a connection to a DB-9 style
> > conne
> >  level signal at up to 12 volts.
> >  A connection to header pins or an edge-connector on an embedded
> > board
> >  is typically a TTL signal at 3.3 or 5 volts.
> > +.Sh Special Devices
> > +The
> > +.Nm
> > +driver also supports an initial-state and a lock-state control
> > +device for each of the callin and the callout "data" devices.
> > +The termios settings of a data device are copied
> > +from those of the corresponding initial-state device
> > +on first opens and are not inherited from previous opens.
> > +Use
> > +.Xr stty 1
> > +in the normal way on the initial-state devices to program
> > +initial termios states suitable for your setup.
> > +.Pp
> > +The lock termios state acts as flags to disable changing
> > +the termios state.
> > +E.g., to lock a flag variable such as CRTSCTS, use
> > +.Em stty crtscts
> > +on the lock-state device.
> > +Speeds and special characters
> > +may be locked by setting the corresponding value in the lock-state
> > +device to any nonzero value.
> > +E.g., to lock a speed to 115200, use
> > +.Dq Li stty 115200
> > +on the initial-state device and
> > +.Dq Li stty 1
> > +on the lock-state device.
> > +.Pp
> > +Correct programs talking to correctly wired external devices
> > +work with almost arbitrary initial states and almost no locking,
> > +but other setups may benefit from changing some of the default
> > +initial state and locking the state.
> > +In particular, the initial states for non (POSIX) standard flags
> > +should be set to suit the devices attached and may need to be
> > +locked to prevent buggy programs from changing them.
> > +E.g., CRTSCTS should be locked on for devices that support
> > +RTS/CTS handshaking at all times and off for devices that do not
> > +support it at all.
> > +CLOCAL should be locked on for devices that do not support carrier.
> > +HUPCL may be locked off if you do not
> > +want to hang up for some reason.
> > +In general, very bad things happen
> > +if something is locked to the wrong state, and things should not
> > +be locked for devices that support more than one setting.
> > +The CLOCAL flag on callin ports should be locked off for logins
> > +to avoid certain security holes, but this needs to be done by
> > +getty if the callin port is used for anything else.
> >  .Sh FILES
> >  .Bl -tag -width "/dev/ttyu?.init" -compact
> >  .It Pa /dev/ttyu?
> >
>
> Now they're documented together with a different single driver of many
> that supports the feature. This is implemented in the tty layer and
> applies to all serial drivers, shouldn't it be documented in tty(4)?


Hmmm. You're right. I'd thought only uart supported it, but it looks like
you're right it's down a layer. I'll move again and put a xref.

Warner