rfcomm_cleanup_ttys() is also called from rfcomm_init(), so it can't
have __exit.
Reported-by: NMat Martineau <mathewm@codeaurora.org>
Signed-off-by: NGustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

Those annotation save memory and space on the binary. __init code is
discarded just after execute and __exit code is discarded if the module
is built into the kernel image or unload of modules is not allowed.
Signed-off-by: NGustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

This patch removes from net/ (but not any netfilter files)
all the unnecessary return; statements that precede the
last closing brace of void functions.

It does not remove the returns that are immediately
preceded by a label as gcc doesn't like that.

Done via:
$ grep -rP --include=*.[ch] -l "return;\n}" net/ | \
  xargs perl -i -e 'local $/ ; while (<>) { s/\n[ \t\n]+return;\n}/\n}/g; print; }'
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

struct tty_operations::proc_fops took it's place and there is one less
create_proc_read_entry() user now!
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

dpm_list currently relies on the fact that child devices will
be registered after their parents to get a correct suspend
order. Using device_move() however destroys this assumption, as
an already registered device may be moved under a newly registered
one.

This patch adds a new argument to device_move(), allowing callers
to specify how dpm_list should be adapted.
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

It turns out that the following sequence of actions will reproduce the
oops:

  1. Create a new RFCOMM device (using RFCOMMCREATEDEV ioctl)
  2. (Try to) open the device
  3. Release the RFCOMM device (using RFCOMMRELEASEDEV ioctl)

At this point, the "/dev/rfcomm*" device is still in use, but it is gone
from the internal list, so the device id can be reused.

  4. Create a new RFCOMM device with the same device id as before

And now kobject will complain that the TTY already exists.

(See http://lkml.org/lkml/2008/7/13/89 for a reproducible test-case.)

This patch attempts to correct this by only removing the device from the
internal list of devices at the final unregister stage, so that the id
won't get reused until the device has been completely destructed.

This should be safe as the RFCOMM_TTY_RELEASED bit will be set for the
device and prevent the device from being reopened after it has been
released.

Based on a report from Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

With the introduction of CONFIG_DYNAMIC_PRINTK_DEBUG it is possible to
allow debugging without having to recompile the kernel. This patch turns
all BT_DBG() calls into pr_debug() to support dynamic debug messages.

As a side effect all CONFIG_BT_*_DEBUG statements are now removed and
some broken debug entries have been fixed.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

Move the line disciplines towards a conventional ->ops arrangement.  For
the moment the actual 'tty_ldisc' struct in the tty is kept as part of
the tty struct but this can then be changed if it turns out that when it
all settles down we want to refcount ldiscs separately to the tty.

Pull the ldisc code out of /proc and put it with our ldisc code.
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When an incoming RFCOMM socket connection gets converted into a TTY,
it can happen that packets are lost. This mainly happens with the
Handsfree profile where the remote side starts sending data right
away. The problem is that these packets are in the socket receive
queue. So when creating the TTY make sure to copy all pending packets
from the socket receive queue to a private queue inside the TTY.

To make this actually work, the flow control on the newly created TTY
will be disabled and only enabled again when the TTY is opened by an
application. And right before that, the pending packets will be put
into the TTY flip buffer.
Signed-off-by: NDenis Kenzior <denis.kenzior@trolltech.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

When switching a RFCOMM socket to a TTY, the remote modem status might
be needed later. Currently it is lost since the original configuration
is done via the socket interface. So store the modem status and reply
it when the socket has been converted to a TTY.
Signed-off-by: NDenis Kenzior <denis.kenzior@trolltech.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

While the RFCOMM TTY emulation can act like a real serial port, in
reality it is not used like this. So to not mess up stupid applications,
use the non-canonical mode by default.
Signed-off-by: NDenis Kenzior <denis.kenzior@trolltech.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

This patch removes CVS keywords that weren't updated for a long time
from comments.
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

There's logic in __rfcomm_dlc_close:
	rfcomm_dlc_lock(d);
	d->state = BT_CLOSED;
	d->state_changed(d, err);
	rfcomm_dlc_unlock(d);

In rfcomm_dev_state_change, it's possible that rfcomm_dev_put try to
take the dlc lock, then we will deadlock.

Here fixed it by unlock dlc before rfcomm_dev_get in
rfcomm_dev_state_change.

why not unlock just before rfcomm_dev_put? it's because there's
another problem.  rfcomm_dev_get/rfcomm_dev_del will take
rfcomm_dev_lock, but in rfcomm_dev_add the lock order is :
rfcomm_dev_lock --> dlc lock

so I unlock dlc before the taken of rfcomm_dev_lock.

Actually it's a regression caused by commit
1905f6c7 ("bluetooth :
__rfcomm_dlc_close lock fix"), the dlc state_change could be two
callbacks : rfcomm_sk_state_change and rfcomm_dev_state_change. I
missed the rfcomm_sk_state_change that time.

Thanks Arjan van de Ven <arjan@linux.intel.com> for the effort in
commit 4c8411f8 ("bluetooth: fix
locking bug in the rfcomm socket cleanup handling") but he missed the
rfcomm_dev_state_change lock issue.
Signed-off-by: NDave Young <hidave.darkstar@gmail.com>
Acked-by: NMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Lockdep warning will be trigged while rfcomm connection closing.

The locks taken in rfcomm_dev_add:
rfcomm_dev_lock --> d->lock

In __rfcomm_dlc_close:
d->lock --> rfcomm_dev_lock (in rfcomm_dev_state_change)

There's two way to fix it, one is in rfcomm_dev_add we first locking
d->lock then the rfcomm_dev_lock

The other (in this patch), remove the locking of d->lock for
rfcomm_dev_state_change because just locking "d->state = BT_CLOSED;"
is enough.

[  295.002046] =======================================================
[  295.002046] [ INFO: possible circular locking dependency detected ]
[  295.002046] 2.6.25-rc7 #1
[  295.002046] -------------------------------------------------------
[  295.002046] krfcommd/2705 is trying to acquire lock:
[  295.002046]  (rfcomm_dev_lock){-.--}, at: [<f89a090a>] rfcomm_dev_state_change+0x6a/0xd0 [rfcomm]
[  295.002046] 
[  295.002046] but task is already holding lock:
[  295.002046]  (&d->lock){--..}, at: [<f899c533>] __rfcomm_dlc_close+0x43/0xd0 [rfcomm]
[  295.002046] 
[  295.002046] which lock already depends on the new lock.
[  295.002046] 
[  295.002046] 
[  295.002046] the existing dependency chain (in reverse order) is:
[  295.002046] 
[  295.002046] -> #1 (&d->lock){--..}:
[  295.002046]        [<c0149b23>] check_prev_add+0xd3/0x200
[  295.002046]        [<c0149ce5>] check_prevs_add+0x95/0xe0
[  295.002046]        [<c0149f6f>] validate_chain+0x23f/0x320
[  295.002046]        [<c014b7b1>] __lock_acquire+0x1c1/0x760
[  295.002046]        [<c014c349>] lock_acquire+0x79/0xb0
[  295.002046]        [<c03d6b99>] _spin_lock+0x39/0x80
[  295.002046]        [<f89a01c0>] rfcomm_dev_add+0x240/0x360 [rfcomm]
[  295.002046]        [<f89a047e>] rfcomm_create_dev+0x6e/0xe0 [rfcomm]
[  295.002046]        [<f89a0823>] rfcomm_dev_ioctl+0x33/0x60 [rfcomm]
[  295.002046]        [<f899facc>] rfcomm_sock_ioctl+0x2c/0x50 [rfcomm]
[  295.002046]        [<c0363d38>] sock_ioctl+0x118/0x240
[  295.002046]        [<c0194196>] vfs_ioctl+0x76/0x90
[  295.002046]        [<c0194446>] do_vfs_ioctl+0x56/0x140
[  295.002046]        [<c0194569>] sys_ioctl+0x39/0x60
[  295.002046]        [<c0104faa>] syscall_call+0x7/0xb
[  295.002046]        [<ffffffff>] 0xffffffff
[  295.002046] 
[  295.002046] -> #0 (rfcomm_dev_lock){-.--}:
[  295.002046]        [<c0149a84>] check_prev_add+0x34/0x200
[  295.002046]        [<c0149ce5>] check_prevs_add+0x95/0xe0
[  295.002046]        [<c0149f6f>] validate_chain+0x23f/0x320
[  295.002046]        [<c014b7b1>] __lock_acquire+0x1c1/0x760
[  295.002046]        [<c014c349>] lock_acquire+0x79/0xb0
[  295.002046]        [<c03d6639>] _read_lock+0x39/0x80
[  295.002046]        [<f89a090a>] rfcomm_dev_state_change+0x6a/0xd0 [rfcomm]
[  295.002046]        [<f899c548>] __rfcomm_dlc_close+0x58/0xd0 [rfcomm]
[  295.002046]        [<f899d44f>] rfcomm_recv_ua+0x6f/0x120 [rfcomm]
[  295.002046]        [<f899e061>] rfcomm_recv_frame+0x171/0x1e0 [rfcomm]
[  295.002046]        [<f899e357>] rfcomm_run+0xe7/0x550 [rfcomm]
[  295.002046]        [<c013c18c>] kthread+0x5c/0xa0
[  295.002046]        [<c0105c07>] kernel_thread_helper+0x7/0x10
[  295.002046]        [<ffffffff>] 0xffffffff
[  295.002046] 
[  295.002046] other info that might help us debug this:
[  295.002046] 
[  295.002046] 2 locks held by krfcommd/2705:
[  295.002046]  #0:  (rfcomm_mutex){--..}, at: [<f899e2eb>] rfcomm_run+0x7b/0x550 [rfcomm]
[  295.002046]  #1:  (&d->lock){--..}, at: [<f899c533>] __rfcomm_dlc_close+0x43/0xd0 [rfcomm]
[  295.002046] 
[  295.002046] stack backtrace:
[  295.002046] Pid: 2705, comm: krfcommd Not tainted 2.6.25-rc7 #1
[  295.002046]  [<c0128a38>] ? printk+0x18/0x20
[  295.002046]  [<c014927f>] print_circular_bug_tail+0x6f/0x80
[  295.002046]  [<c0149a84>] check_prev_add+0x34/0x200
[  295.002046]  [<c0149ce5>] check_prevs_add+0x95/0xe0
[  295.002046]  [<c0149f6f>] validate_chain+0x23f/0x320
[  295.002046]  [<c014b7b1>] __lock_acquire+0x1c1/0x760
[  295.002046]  [<c014c349>] lock_acquire+0x79/0xb0
[  295.002046]  [<f89a090a>] ? rfcomm_dev_state_change+0x6a/0xd0 [rfcomm]
[  295.002046]  [<c03d6639>] _read_lock+0x39/0x80
[  295.002046]  [<f89a090a>] ? rfcomm_dev_state_change+0x6a/0xd0 [rfcomm]
[  295.002046]  [<f89a090a>] rfcomm_dev_state_change+0x6a/0xd0 [rfcomm]
[  295.002046]  [<f899c548>] __rfcomm_dlc_close+0x58/0xd0 [rfcomm]
[  295.002046]  [<f899d44f>] rfcomm_recv_ua+0x6f/0x120 [rfcomm]
[  295.002046]  [<f899e061>] rfcomm_recv_frame+0x171/0x1e0 [rfcomm]
[  295.002046]  [<c014abd9>] ? trace_hardirqs_on+0xb9/0x130
[  295.002046]  [<c03d6e89>] ? _spin_unlock_irqrestore+0x39/0x70
[  295.002046]  [<f899e357>] rfcomm_run+0xe7/0x550 [rfcomm]
[  295.002046]  [<c03d4559>] ? __sched_text_start+0x229/0x4c0
[  295.002046]  [<c0120000>] ? cpu_avg_load_per_task+0x20/0x30
[  295.002046]  [<f899e270>] ? rfcomm_run+0x0/0x550 [rfcomm]
[  295.002046]  [<c013c18c>] kthread+0x5c/0xa0
[  295.002046]  [<c013c130>] ? kthread+0x0/0xa0
[  295.002046]  [<c0105c07>] kernel_thread_helper+0x7/0x10
[  295.002046]  =======================
Signed-off-by: NDave Young <hidave.darkstar@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

rfcomm dev could be deleted in tty_hangup, so we must not call
rfcomm_dev_del again to prevent from destroying rfcomm dev before tty
close.
Signed-off-by: NDave Young <hidave.darkstar@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The rfcomm tty device will possibly retain even when conn is down, and
sysfs doesn't support zombie device moving, so this patch move the tty
device before conn device is destroyed.

For the bug refered please see :
http://lkml.org/lkml/2007/12/28/87Signed-off-by: NDave Young <hidave.darkstar@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

1) In tty.c the BUG_ON at line 115 will never be called, because the the
   before list_del_init in this same function.
	115          BUG_ON(!list_empty(&dev->list));
   So move the list_del_init to rfcomm_dev_del 

2) The rfcomm_dev_del could be called from diffrent path
   (rfcomm_tty_hangup/rfcomm_dev_state_change/rfcomm_release_dev),

   So add another BUG_ON when the rfcomm_dev_del is called more than
   one time.
Signed-off-by: NDave Young <hidave.darkstar@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Export the remote device address and channel of RFCOMM TTY device
via sysfs attributes. This allows udev to create better naming rules
for configured RFCOMM devices.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

Adrian Bunk wrote:
> Commit 8de0a154 added the following
> use-after-free in net/bluetooth/rfcomm/tty.c:
>
> <--  snip  -->
>
> ...
> static int rfcomm_dev_add(struct rfcomm_dev_req *req, struct rfcomm_dlc *dlc)
> {
> ...
>         if (IS_ERR(dev->tty_dev)) {
>                 list_del(&dev->list);
>                 kfree(dev);
>                 return PTR_ERR(dev->tty_dev);
>         }
> ...
>
> <--  snip  -->
>
> Spotted by the Coverity checker.

really good catch. I fully overlooked that one. The attached patch
should fix it.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch changes the RFCOMM TTY release process so that the TTY is kept
on the list until it is really freed. A new device flag is used to keep
track of released TTYs.
Signed-off-by: NVille Tervo <ville.tervo@nokia.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

The core problem is that RFCOMM socket layer ioctl can release
rfcomm_dev struct while RFCOMM TTY layer is still actively using
it. Calling tty_vhangup() is needed for a synchronous hangup before
rfcomm_dev is freed.

Addresses the oops at http://bugzilla.kernel.org/show_bug.cgi?id=7509Acked-by: NAlan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

If RFCOMM_RELEASE_ONHUP flag is on and rfcomm_release_dev is called
before connection is closed, rfcomm_dev is deleted twice from the
rfcomm_dev_list and refcount is messed up. This patch adds a check
before deleting device that the device actually is listed.
Signed-off-by: NVille Tervo <ville.tervo@nokia.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

In the case of bound RFCOMM TTY devices the parent is not available
before its usage. So when opening a RFCOMM TTY device, move it to
the corresponding ACL device as a child. When closing the device,
move it back to the virtual device tree.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

Signed-off-by: NYOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

If the DLC device is no longer attached to the TTY device, then return
errors or default values for various callbacks of the TTY layer.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

This is the grungy swap all the occurrences in the right places patch that
goes with the updates.  At this point we have the same functionality as
before (except that sgttyb() returns speeds not zero) and are ready to
begin turning new stuff on providing nobody reports lots of bugs

If you are a tty driver author converting an out of tree driver the only
impact should be termios->ktermios name changes for the speed/property
setting functions from your upper layers.

If you are implementing your own TCGETS function before then your driver
was broken already and its about to get a whole lot more painful for you so
please fix it 8)

Also fill in c_ispeed/ospeed on init for most devices, although the current
code will do this for you anyway but I'd like eventually to lose that extra
paranoia

[akpm@osdl.org: bluetooth fix]
[mp3@de.ibm.com: sclp fix]
[mp3@de.ibm.com: warning fix for tty3270]
[hugh@veritas.com: fix tty_ioctl powerpc build]
[jdike@addtoit.com: uml: fix ->set_termios declaration]
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NMartin Peschke <mp3@de.ibm.com>
Acked-by: NPeter Oberparleiter <oberpar@de.ibm.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NJeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

If the RFCOMM session is no longer attached to the TTY device, then it
makes no sense to go through with changing the termios settings.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

If the DLC device is no longer attached to the TTY device, then it
makes no sense to go through with changing the termios settings.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

When the connection lookup for the device structure fails, the reference
count for the HCI device needs to be decremented.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

As part of an SMP cleanliness pass over UML, I consted a bunch of
structures in order to not have to document their locking.  One of these
structures was a struct tty_operations.  In order to const it in UML
without introducing compiler complaints, the declaration of
tty_set_operations needs to be changed, and then all of its callers need to
be fixed.

This patch declares all struct tty_operations in the tree as const.  In all
cases, they are static and used only as input to tty_set_operations.  As an
extra check, I ran an i386 allyesconfig build which produced no extra
warnings.

53 drivers are affected.  I checked the history of a bunch of them, and in
most cases, there have been only a handful of maintenance changes in the
last six months.  serial_core.c was the busiest one that I looked at.
Signed-off-by: NJeff Dike <jdike@addtoit.com>
Acked-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch integrates the services of the Bluetooth protocols RFCOMM,
BNEP and HIDP into the driver model. This makes it possible to assign
the virtual TTY, network and input devices to a specific Bluetooth
connection.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

This patch makes the remaining transitions to use kzalloc().
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

Signed-off-by: NJörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

Remove TTY_DONT_FLIP tty flag.  This flag was introduced in 2.1.X kernels
to prevent the N_TTY line discipline functions read_chan() and
n_tty_receive_buf() from running at the same time.  2.2.15 introduced
tty->read_lock to protect access to the N_TTY read buffer, which is the
only state requiring protection between these two functions.

The current TTY_DONT_FLIP implementation is broken for SMP, and is not
universally honored by drivers that send data directly to the line
discipline receive_buf function.

Because TTY_DONT_FLIP is not necessary, is broken in implementation, and is
not universally honored, it is removed.
Signed-off-by: NPaul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I've always found this flag confusing.  Now that devfs is no longer around, it
has been renamed, and the documentation for when this flag should be used has
been updated.

Also fixes all drivers that use this flag.
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Also fixes all drivers that set this field.
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

net: Use <linux/capability.h> where capable() is used.
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The API and code have been through various bits of initial review by
serial driver people but they definitely need to live somewhere for a
while so the unconverted drivers can get knocked into shape, existing
drivers that have been updated can be better tuned and bugs whacked out.

This replaces the tty flip buffers with kmalloc objects in rings. In the
normal situation for an IRQ driven serial port at typical speeds the
behaviour is pretty much the same, two buffers end up allocated and the
kernel cycles between them as before.

When there are delays or at high speed we now behave far better as the
buffer pool can grow a bit rather than lose characters. This also means
that we can operate at higher speeds reliably.

For drivers that receive characters in blocks (DMA based, USB and
especially virtualisation) the layer allows a lot of driver specific
code that works around the tty layer with private secondary queues to be
removed. The IBM folks need this sort of layer, the smart serial port
people do, the virtualisers do (because a virtualised tty typically
operates at infinite speed rather than emulating 9600 baud).

Finally many drivers had invalid and unsafe attempts to avoid buffer
overflows by directly invoking tty methods extracted out of the innards
of work queue structs. These are no longer needed and all go away. That
fixes various random hangs with serial ports on overflow.

The other change in here is to optimise the receive_room path that is
used by some callers. It turns out that only one ldisc uses receive room
except asa constant and it updates it far far less than the value is
read. We thus make it a variable not a function call.

I expect the code to contain bugs due to the size alone but I'll be
watching and squashing them and feeding out new patches as it goes.

Because the buffers now dynamically expand you should only run out of
buffering when the kernel runs out of memory for real.  That means a lot of
the horrible hacks high performance drivers used to do just aren't needed any
more.

Description:

tty_insert_flip_char is an old API and continues to work as before, as does
tty_flip_buffer_push() [this is why many drivers dont need modification].  It
does now also return the number of chars inserted

There are also

tty_buffer_request_room(tty, len)

which asks for a buffer block of the length requested and returns the space
found.  This improves efficiency with hardware that knows how much to
transfer.

and tty_insert_flip_string_flags(tty, str, flags, len)

to insert a string of characters and flags

For a smart interface the usual code is

    len = tty_request_buffer_room(tty, amount_hardware_says);
    tty_insert_flip_string(tty, buffer_from_card, len);

More description!

At the moment tty buffers are attached directly to the tty.  This is causing a
lot of the problems related to tty layer locking, also problems at high speed
and also with bursty data (such as occurs in virtualised environments)

I'm working on ripping out the flip buffers and replacing them with a pool of
dynamically allocated buffers.  This allows both for old style "byte I/O"
devices and also helps virtualisation and smart devices where large blocks of
data suddenely materialise and need storing.

So far so good.  Lots of drivers reference tty->flip.*.  Several of them also
call directly and unsafely into function pointers it provides.  This will all
break.  Most drivers can use tty_insert_flip_char which can be kept as an API
but others need more.

At the moment I've added the following interfaces, if people think more will
be needed now is a good time to say

 int tty_buffer_request_room(tty, size)

Try and ensure at least size bytes are available, returns actual room (may be
zero).  At the moment it just uses the flipbuf space but that will change.
Repeated calls without characters being added are not cumulative.  (ie if you
call it with 1, 1, 1, and then 4 you'll have four characters of space.  The
other functions will also try and grow buffers in future but this will be a
more efficient way when you know block sizes.

 int tty_insert_flip_char(tty, ch, flag)

As before insert a character if there is room.  Now returns 1 for success, 0
for failure.

 int tty_insert_flip_string(tty, str, len)

Insert a block of non error characters.  Returns the number inserted.

 int tty_prepare_flip_string(tty, strptr, len)

Adjust the buffer to allow len characters to be added.  Returns a buffer
pointer in strptr and the length available.  This allows for hardware that
needs to use functions like insl or mencpy_fromio.
Signed-off-by: NAlan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: NHirokazu Takata <takata@linux-m32r.org>
Signed-off-by: NSerge Hallyn <serue@us.ibm.com>
Signed-off-by: NJeff Dike <jdike@addtoit.com>
Signed-off-by: NJohn Hawkes <hawkes@sgi.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

 - added typedef unsigned int __nocast gfp_t;

 - replaced __nocast uses for gfp flags with gfp_t - it gives exactly
   the same warnings as far as sparse is concerned, doesn't change
   generated code (from gcc point of view we replaced unsigned int with
   typedef) and documents what's going on far better.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>