linux.git/drivers/char/n_tty.c, branch master

TTY: create drivers/tty and move the tty core files there

2010-11-05T15:10:33+00:00

The tty code should be in its own subdirectory and not in the char
driver with all of the cruft that is currently there.

Based on work done by Arnd Bergmann 

Acked-by: Arnd Bergmann 
Cc: Jiri Slaby 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

tty: Add EXTPROC support for LINEMODE

2010-08-10T20:47:39+00:00

This patch is against the 2.6.34 source.

Paraphrased from the 1989 BSD patch by David Borman @ cray.com:

     These are the changes needed for the kernel to support
     LINEMODE in the server.

     There is a new bit in the termios local flag word, EXTPROC.
     When this bit is set, several aspects of the terminal driver
     are disabled.  Input line editing, character echo, and mapping
     of signals are all disabled.  This allows the telnetd to turn
     off these functions when in linemode, but still keep track of
     what state the user wants the terminal to be in.

     New ioctl:
         TIOCSIG         Generate a signal to processes in the
                         current process group of the pty.

     There is a new mode for packet driver, the TIOCPKT_IOCTL bit.
     When packet mode is turned on in the pty, and the EXTPROC bit
     is set, then whenever the state of the pty is changed, the
     next read on the master side of the pty will have the TIOCPKT_IOCTL
     bit set.  This allows the process on the server side of the pty
     to know when the state of the terminal has changed; it can then
     issue the appropriate ioctl to retrieve the new state.

Since the original BSD patches accompanied the source code for telnet
I've left that reference here, but obviously the feature is useful for
any remote terminal protocol, including ssh.

The corresponding feature has existed in the BSD tty driver since 1989.
For historical reference, a good copy of the relevant files can be found
here:

http://anonsvn.mit.edu/viewvc/krb5/trunk/src/appl/telnet/?pathrev=17741

Signed-off-by: Howard Chu 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

ldisc n_tty: add new method n_tty_inherit_ops()

2010-03-12T23:52:43+00:00

This new method can be used to init a new struct tty_ldisc_ops as the
default tty_ldisc_N_TTY struct.

Signed-off-by: Rodolfo Giometti 
Cc: David Woodhouse 
Cc: Greg KH 
Cc: Alan Cox 
Cc: Alexander Gordeev 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

n_tty: move echoctl check and clean up logic

2009-09-19T20:13:34+00:00

Check L_ECHOCTL before insertting a character in the echo buffer
(rather than as the buffer is processed), to be more consistent with
when all other L_ flags are checked.  Also cleaned up the related logic.

Note that this and the previous patch ("n_tty: honor opost flag for echoes")
were verified together by the reporters of the bug that patch addresses
(http://bugs.linuxbase.org/show_bug.cgi?id=2692), and the test now passes.

Signed-off-by: Joe Peterson 
Cc: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

n_tty: honor opost flag for echoes

2009-09-19T20:13:34+00:00

Fixes the following bug:

      http://bugs.linuxbase.org/show_bug.cgi?id=2692

Causes processing of echoed characters (output from the echo buffer) to
honor the O_OPOST flag, which is consistent with the old behavior.

Note that this and the next patch ("n_tty: move echoctl check and
clean up logic") were verified together by the bug reporters, and
the test now passes.

Signed-off-by: Joe Peterson 
Cc: Linux Torvalds 
Signed-off-by: Greg Kroah-Hartman

n_tty: do O_ONLCR translation as a single write

2009-09-05T19:46:07+00:00

When translating CR to CRNL in the n_tty line discipline, we did it as
two tty_put_char() calls.  Which works, but is stupid, and has caused
problems before too with bad interactions with the write_room() logic.
The generic USB serial driver had that problem, for example.

Now the pty layer had similar issues after being moved to the generic
tty buffering code (in commit d945cb9cce20ac7143c2de8d88b187f62db99bdc:
"pty: Rework the pty layer to use the normal buffering logic").

So stop doing the silly separate two writes, and do it as a single write
instead.  That's what the n_tty layer already does for the space
expansion of tabs (XTABS), and it means that we'll now always have just
a single write for the CRNL to match the single 'tty_write_room()' test,
which hopefully means that the next time somebody screws up buffering,
it won't cause weeks of debugging.

Signed-off-by: Linus Torvalds

pty: avoid forcing 'low_latency' tty flag

2009-07-29T19:15:56+00:00

We really don't want to mark the pty as a low-latency device, because as
Alan points out, the ->write method can be called from an IRQ (ppp?),
and that means we can't use ->low_latency=1 as we take mutexes in the
low_latency case.

So rather than using low_latency to force the written data to be pushed
to the ldisc handling at 'write()' time, just make the reader side (or
the poll function) do the flush when it checks whether there is data to
be had.

This also fixes the problem with lost data in an emacs compile buffer
(bugzilla 13815), and we can thus revert the low_latency pty hack
(commit 3a54297478e6578f96fd54bf4daa1751130aca86: "pty: quickfix for the
pty ENXIO timing problems").

Signed-off-by: OGAWA Hirofumi 
Tested-by: Aneesh Kumar K.V 
[ Modified to do the tty_flush_to_ldisc() inside input_available_p() so
  that it triggers for both read and poll()  - Linus]
Signed-off-by: Linus Torvalds

n_tty: Fix echo race

2009-07-16T16:19:16+00:00

If a tty in N_TTY mode with echo enabled manages to get itself into a state
where
	- echo characters are pending
	- FASYNC is enabled
	- tty_write_wakeup is called from either
		- a device write path (pty)
		- an IRQ (serial)

then it either deadlocks or explodes taking a mutex in the IRQ path.

On the serial side it is almost impossible to reproduce because you have to
go from a full serial port to a near empty one with echo characters
pending. The pty case happens to have become possible to trigger using
emacs and ptys, the pty changes having created a scenario which shows up
this bug.

The code path is

	n_tty:process_echoes() (takes mutex)
	tty_io:tty_put_char()
	pty:pty_write  (or serial paths)
	tty_wakeup     (from pty_write or serial IRQ)
	n_tty_write_wakeup()
	process_echoes()
	*KABOOM*

Signed-off-by: Alan Cox 
Signed-off-by: Linus Torvalds

tty: simplify buffer allocator cleanups

2009-06-11T15:51:02+00:00

Having cleaned up the allocators we might as well remove the inline helpers
for some of it

Signed-off-by: Alan Cox

tty: remove buffer special casing

2009-06-11T15:51:02+00:00

Long long ago a 4K kmalloc allocated two pages so the tty layer used the
page allocator, except on some machines where the page size was huge. This was
removed from the core tty layer with the tty buffer re-implementation but not
from tty_audit or the n_tty ldisc.

Signed-off-by: Alan Cox 
Signed-off-by: Linus Torvalds