Kernel driver i2c-floppy

Author: Herbert Poetzl <herbert@13thfloor.at>

This driver is for a simple do-it-yourself floppy controller to
I2C adapter which uses direct I/O access to control both Motor
Enable lines (A/B) and read back data via the Disk Changed line.

The following circuit is not suited to be used together with
a Floppy drive (which would need some logic to work properly)
but as replacement.

 +---+
 | F |  Motor Enable A [/MOTEA,10] -------------- SCL
 | L |
 | O |  Motor Enable B [/MOTEB,16] ------+------- SDA
 | P |                                   |
 | P |                                   |
 | Y |  Disk Change   [/DSKCHG,34] ------+    +-- GND
 +-+-+                                        |
   |                                          |
  GND	                                     GND

The Motor Enable output of floppy disk controllers is an open
drain output (48mA), usually pulled up to +5V via 1k or higher,
and the Disk Change is a Schmitt Trigger (0.8V/2.2V) input with
max 150uA input current (data taken from the WD/FDC 37C6xx
Floppy Disk Subsystem Controller datasheets, which basically
combine all the necessary parts of the PC floppy circuit).

So it should be fine to connect it to all 5V I2C devices, and
most 3.3V devices (which are usually capable of handling 5V
I2C bus voltages).

Power for those devices can be drawn from either the Floppy
power connector (+5V/+12V) or from the SATA 3.3V lines
(or if you prefer from some external source).
