linux-toradex.git/include/linux/tty_driver.h, branch v4.6-rc6

devpts: more pty driver interface cleanups

2016-04-26T22:47:32+00:00

This is more prep-work for the upcoming pty changes.  Still just code
cleanup with no actual semantic changes.

This removes a bunch pointless complexity by just having the slave pty
side remember the dentry associated with the devpts slave rather than
the inode.  That allows us to remove all the "look up the dentry" code
for when we want to remove it again.

Together with moving the tty pointer from "inode->i_private" to
"dentry->d_fsdata" and getting rid of pointless inode locking, this
removes about 30 lines of code.  Not only is the end result smaller,
it's simpler and easier to understand.

The old code, for example, depended on the d_find_alias() to not just
find the dentry, but also to check that it is still hashed, which in
turn validated the tty pointer in the inode.

That is a _very_ roundabout way to say "invalidate the cached tty
pointer when the dentry is removed".

The new code just does

	dentry->d_fsdata = NULL;

in devpts_pty_kill() instead, invalidating the tty pointer rather more
directly and obviously.  Don't do something complex and subtle when the
obvious straightforward approach will do.

The rest of the patch (ie apart from code deletion and the above tty
pointer clearing) is just switching the calling convention to pass the
dentry or file pointer around instead of the inode.

Cc: Eric Biederman 
Cc: Peter Anvin 
Cc: Andy Lutomirski 
Cc: Al Viro 
Cc: Peter Hurley 
Cc: Serge Hallyn 
Cc: Willy Tarreau 
Cc: Aurelien Jarno 
Cc: Alan Cox 
Cc: Jann Horn 
Cc: Greg KH 
Cc: Jiri Slaby 
Cc: Florian Weimer 
Signed-off-by: Linus Torvalds

Avoid usb reset crashes by making tty_io cdevs truly dynamic

2015-08-03T22:24:43+00:00

Avoid usb reset crashes by making tty_io cdevs truly dynamic

Signed-off-by: Richard Watts 
Reported-by: Duncan Mackintosh 
Signed-off-by: Greg Kroah-Hartman

tty: Serialize tty flow control changes with flow_lock

2014-09-24T04:19:35+00:00

Without serialization, the flow control state can become inverted
wrt. the actual hardware state. For example,

CPU 0                          | CPU 1
stop_tty()                     |
  lock ctrl_lock               |
  tty->stopped = 1             |
  unlock ctrl_lock             |
                               | start_tty()
                               |   lock ctrl_lock
                               |   tty->stopped = 0
                               |   unlock ctrl_lock
                               |   driver->start()
  driver->stop()               |

In this case, the flow control state now indicates the tty has
been started, but the actual hardware state has actually been stopped.

Introduce tty->flow_lock spinlock to serialize tty flow control changes.
Split out unlocked __start_tty()/__stop_tty() flavors for use by
ioctl(TCXONC) in follow-on patch.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Document locking for tty driver methods

2014-07-10T23:05:19+00:00

The tty core calls the tty driver's open, close and hangup
methods holding the tty lock.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Document required behavior of tty driver close()

2013-02-04T23:40:28+00:00

If the tty driver open() fails, the tty driver close() is still
called during the resultant tty release.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

TTY: move cdev_add to tty_register_device

2012-08-13T23:45:39+00:00

We need the /dev/ node not to be available before we call
tty_register_device. Otherwise we might race with open and
tty_struct->port might not be available at that time.

This is not an issue now, but would be a problem after "TTY: use
tty_port_register_device" is applied.

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

TTY: add support for unnumbered device nodes

2012-08-13T23:45:38+00:00

This allows drivers like ttyprintk to avoid hacks to create an
unnumbered node in /dev. It used to set TTY_DRIVER_DYNAMIC_DEV in
flags and call device_create on its own. That is incorrect, because
TTY_DRIVER_DYNAMIC_DEV may be set only if tty_register_device is
called explicitly.

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

TTY: pty, switch to tty_alloc_driver

2012-08-13T23:45:38+00:00

Switch to the new driver allocation interface, as this is one of the
special call-sites. Here, we need TTY_DRIVER_DYNAMIC_ALLOC to not
allocate tty_driver->ports, cdevs and potentially other structures
because we reserve too many lines in pty. Instead, it provides the
tty_port<->tty_struct link in tty->ops->install already.

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

TTY: pass flags to alloc_tty_driver

2012-08-10T20:29:58+00:00

We need to allow drivers that use neither tty_port_install nor
tty_port_register_device to link a tty_port to a tty somehow.  To
avoid a race with open, this has to be performed before
tty_register_device. But currently tty_driver->ports is allocated even
in tty_register_device because we do not know whether this is the PTY
driver. The PTY driver is special here due to an excessive count of
lines it declares to handle. We cannot handle tty_ports there this
way.

To circumvent this, we start passing tty_driver flags to
alloc_tty_driver already and we create tty_alloc_driver for this
purpose. There we can allocate tty_driver->ports and do all the magic
between tty_alloc_driver and tty_register_device. Later we will
introduce tty_port_link_device function for that purpose.

All drivers should eventually switch to this new tty driver allocation
interface.

Signed-off-by: Jiri Slaby 
Signed-off-by: Greg Kroah-Hartman

tty: Move the handling of the tty release logic

2012-07-17T16:13:38+00:00

Now that we don't have tty->termios tied to drivers->tty we can untangle
the logic here. In addition we can push the removal logic out of the
destructor path.

At that point we can think about sorting out tty_port and console and all
the other ugly hangovers.

Signed-off-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman