ftdi_sio: Avoid losing bytes at tty-ldisc.

This patch was originally developed by Daniel Smertnig.  I
(Ian Abbott) made a few changes.  It has been tested by both
Daniel and I, at least for raw, non-canonical receive data
processing.

Here is Daniel's original description of the patch:

===
During a project in which I was using a FTDI 232BM to
transmit data at relative high speeds (625kBit/s), I
noticed a problem where data was lost even if flow
control was enabled: The FTDI-Driver receives 512 Bytes
of data over USB at a time, which consists of 8 64-Byte
packets. Subtracting the 2 bytes of status information
included in each packet this gives 496 "real" data
bytes per read.

This data is passed (indirectly, via the flip buffers)
to the tty line discipline which takes care of
throttling when there the free buffer space reaches
TTY_THRESHOLD_THROTTLE (128). Because the FTDI driver
processes up to 496 bytes at a time, throttling won't
happen in time and the line discipline will discard the
remaining bytes.

To avoid this the patch passes data in 62-byte blocks
to the tty layer and checks the available space in the
ldisc-buffers. If there isn't enough free space,
processing the rest of the data is delayed using a
workqueue.

Note: The original problem should be easily
reproducible with a userspace program which does slow &
small reads.
===
Signed-off-by: NIan Abbott <abbotti@mev.co.uk>
Signed-off-by: NDaniel Smertnig <daniel.smertnig@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

ftdi_sio: Add PID for "ELV USB Module UM100".
PID sent by Armin Laugher.
Signed-off-by: NIan Abbott <abbotti@mev.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Here are some spelling corrections for drivers/usb.

cancelation -> cancellation
succesful -> successful
cancelation -> cancellation
decriptor -> descriptor
Initalize -> Initialize
wierd -> weird
Protocoll -> Protocol
occured -> occurred
successfull -> successful
Procesing -> Processing
devide -> divide
Isochronuous -> Isochronous
noticable -> noticeable
Basicly -> Basically
transfering -> transferring
intialize -> initialize
Incomming -> Incoming
additionnal -> additional
asume -> assume
Unfortunatly -> Unfortunately
retreive -> retrieve
tranceiver -> transceiver
Compatiblity -> Compatibility
Incorprated -> Incorporated
existance -> existence
Ununsual -> Unusual
Signed-off-by: NSteven Cole <elenstev@mesatop.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

[ftdi_sio] Replaced redundant INTERFACE_A and INTERFACE_B macros with
the equivalent PIT_SIOA and PIT_SIOB macros.
Signed-off-by: NIan Abbott <abbotti@mev.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Some VID/PID updates for the ftdi_sio driver:

* The "Gude Analog- und Digitalsysteme GmbH" entries were missing from
  the "combined" table.
* Replaced FTDI_8U232AM_ALT_ALT_PID with 3 PIDs for devices from
  4n-galaxy.de.
* Removed redundant FTDI_RM_VID and renamed FTDI_RMCANVIEW_PID to
  FTDI_RM_CANVIEW_PID.
* Added VID/PID for serial converter in Mobility Electronics EasiDock
  USB 200 (mentioned by Gregory Schmitt).
* Added PID for Active Robots USB comms board (mentioned by John Koch).
Signed-off-by: NIan Abbott <abbotti@mev.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

diff -ur a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c

Get rid of a bunch of redundant NULL pointer checks in drivers/usb/*,
there's no need to check a pointer for NULL before calling kfree() on it.
Signed-off-by: NJesper Juhl <juhl-lkml@dif.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>


Index: gregkh-2.6/drivers/usb/class/audio.c
===================================================================

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!