This patch adds the ability to open a network data connection over a mux
virtual tty channel. This is for modems that support data connections
with raw IP frames instead of PPP. On high speed data connections this
eliminates a significant amount of PPP overhead. To use this interface,
the application must first tell the modem to open a network connection on
a virtual tty. Once that has been accomplished, the app will issue an
IOCTL on that virtual tty to create the network interface. The IOCTL will
return the index of the interface created.

The two IOCTL commands are:

    ioctl( fd, GSMIOC_ENABLE_NET );

    ioctl( fd, GSMIOC_DISABLE_NET );
Signed-off-by: NRuss Gorby <russ.gorby@intel.com>
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

The n_gsm driver being an ldisc, does not provide a convenient method
e.g. udev to create the tty device nodes automatically when the ldisc
is opened.

The TTY device nodes are now created via calls to tty_register_device
from the ldisc open.
Signed-off-by: NRuss Gorby <russ.gorby@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This reverts commit b1c43f82.

It was broken in so many ways, and results in random odd pty issues.

It re-introduced the buggy schedule_work() in flush_to_ldisc() that can
cause endless work-loops (see commit a5660b41: "tty: fix endless
work loop when the buffer fills up").

It also used an "unsigned int" return value fo the ->receive_buf()
function, but then made multiple functions return a negative error code,
and didn't actually check for the error in the caller.

And it didn't actually work at all.  BenH bisected down odd tty behavior
to it:
  "It looks like the patch is causing some major malfunctions of the X
   server for me, possibly related to PTYs.  For example, cat'ing a
   large file in a gnome terminal hangs the kernel for -minutes- in a
   loop of what looks like flush_to_ldisc/workqueue code, (some ftrace
   data in the quoted bits further down).

   ...

   Some more data: It -looks- like what happens is that the
   flush_to_ldisc work queue entry constantly re-queues itself (because
   the PTY is full ?) and the workqueue thread will basically loop
   forver calling it without ever scheduling, thus starving the consumer
   process that could have emptied the PTY."

which is pretty much exactly the problem we fixed in a5660b41.

Milton Miller pointed out the 'unsigned int' issue.
Reported-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Reported-by: NMilton Miller <miltonm@bga.com>
Cc: Stefan Bigler <stefan.bigler@keymile.com>
Cc: Toby Gray <toby.gray@realvnc.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

- kenrel -> kernel
- whetehr -> whether
- ttt -> tt
- sss -> ss
Signed-off-by: NJustin P. Mattock <justinmattock@gmail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Use the standard mechanism to print a hex buffer
to eliminate empty printf warning.

A couple % smaller text and data too.

$ size drivers/tty/n_gsm.o*
   text	   data	    bss	    dec	    hex	filename
  23543	    312	   6376	  30231	   7617	drivers/tty/n_gsm.o.new
  24051	    408	   6496	  30955	   78eb	drivers/tty/n_gsm.o.old
Signed-off-by: NJoe Perches <joe@perches.com>
Acked-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

it makes it simpler to keep track of the amount of
bytes received and simplifies how flush_to_ldisc counts
the remaining bytes. It also fixes a bug of lost bytes
on n_tty when flushing too many bytes via the USB
serial gadget driver.
Tested-by: NStefan Bigler <stefan.bigler@keymile.com>
Tested-by: NToby Gray <toby.gray@realvnc.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Problem description:
  gsm_queue() calculate a CRC for arrived frames. As a last step of
  CRC calculation it call

    gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs);

  This work perfectly for the case of GSM0 mode as gsm->received_fcs
  contain the last piece of data required to generate final CRC.

  gsm->received_fcs is not used for GSM1 mode. Thus we put an
  additional byte to CRC calculation. As result we get a wrong CRC
  and reject incoming frame.
Signed-off-by: NMikhail Kshevetskiy <mikhail.kshevetskiy@gmail.com>
Acked-by: NAlan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Fixes generated by 'codespell' and manually reviewed.
Signed-off-by: NLucas De Marchi <lucas.demarchi@profusion.mobi>

* the GSM 07.10 specification says in 5.4.3.1 that
'both stations shall set the P bit to 0'
  thanks to Alan Cox for finding this explanation in the spec

* without this fix, on Telit & Sim.com modems, opening a new DLC
randomly fails. Not setting PF bit of the control byte gives a
reliable behaviour on these modems.
Signed-off-by: NEric Bénard <eric@eukrea.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Only oddities here are a couple of drivers that bogusly called the ldisc
helpers instead of returning -ENOIOCTLCMD. Fix the bug and the rest goes
away.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Doing tiocmget was such fun we should do tiocmset as well for the same
reasons
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

We don't actually need this and it causes problems for internal use of
this functionality. Currently there is a single use of the FILE * pointer.
That is the serial core which uses it to check tty_hung_up_p. However if
that is true then IO_ERROR is also already set so the check may be removed.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This field is settable but did not get copied.
Signed-off-by: NKen Mills <ken.k.mills@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

gsm_data_alloc buffer allocation could fail and it is not being checked.

Add check for allocated buffer and return if the buffer allocation
fails.
Signed-off-by: NKen Mills <ken.k.mills@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Fix message length handling when building header

When the message length is greater than 127, the length field in the header
is built incorrectly. According to the spec, when the length is less than 128
the length field is a single byte formatted as: bbbbbbb1. When it is greater
than 127 then the field is two bytes of the format: bbbbbbb0 bbbbbbbb.
Signed-off-by: NKen Mills <ken.k.mills@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

[Original From Ken Mills but I redid it using pr_ helpers instead]

Also fix up coding style, there are two warnings left but that is where
the CodingStyle tools blow up because they cannot handle

	if (blah) {
		foo
	} else switch (x) {
		case 1:
		}
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

The mux supports several encoding schemes. Encoding 0 is a "not
recommended" mode still sometimes used. This has now been tested with
hardware that supports this mode, and found wanting.

Fix the FCS handling in this mode and correct the state machine.
Signed-off-by: NKen Mills <ken.k.mills@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

If the mux is configured with a large mru/mtu the existing code gets the
byte ordering wrong for the header.
Signed-off-by: NKen Mills <ken.k.mills@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

The n2 field is settable but didn't get propogated
Signed-off-by: NKen Mills <ken.k.mills@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

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 <arnd@arndb.de>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Add a spin_unlock_irqrestore missing on the error path.  Converting the
return to break leads to the spin_unlock_irqrestore at the end of the
function.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression E1;
@@

* spin_lock_irqsave(E1,...);
  <+... when != E1
  if (...) {
    ... when != E1
*   return ...;
  }
  ...+>
* spin_unlock_irqrestore(E1,...);
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/n_gsm.c: linux/timer.h is included more than once.
Signed-off-by: NAndrea Gelmini <andrea.gelmini@gelma.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

In gsm_dlci_data_kick() we call gsm_dlci_data_sweep() with the
"gsm->tx_lock" held so we can't lock it again inside
gsm_dlci_data_sweep().  I removed that lock from and added one to
gsmld_write_wakeup() instead.  The sweep function is only called from
those two places.
Signed-off-by: NDan Carpenter <error27@gmail.com>
Acked-by: NAlan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Add an implementation of GSM 0710 MUX. The implementation currently supports

- Basic and advanced framing (as either end of the link)
- UI or UIH data frames
- Adaption layer 1-4 (1 and 2 via tty, 3 and 4 as skbuff lists)
- Modem and control messages including the correct retry process
- Flow control

and exposes the MUX channels as a set of virtual tty devices including modem
signals. This is an experimental driver.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>