FMC: add a software carrier driver

This fake carrier is designed to help FMC users understand how a
carrier driver works, and to experiment the behaviour with EEPROM
reprogramming (with a mezzanine driver commited later). This carrier
can register up to 4 (fake) mezzanines.

We have real carriers (both on PCI-E and VME), but they are bigger
things and are not part of this submission.
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
Acked-by: Juan David Gonzalez Cobas <dcobas@cern.ch>
Acked-by: Emilio G. Cota <cota@braap.org>
Acked-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/fmc/00-INDEX

@@ -24,3 +24,6 @@ mezzanine.txt
 
 identifiers.txt
 	- how identification and matching works
+
+fmc-fakedev.txt
+	- about drivers/fmc/fmc-fakedev.ko

Documentation/fmc/fmc-fakedev.txt

+fmc-fakedev
+===========
+
+This package includes a software-only device, called fmc-fakedev, which
+is able to register up to 4 mezzanines (by default it registers one).
+Unlike the SPEC driver, which creates an FMC device for each PCI cards
+it manages, this module creates a single instance of its set of
+mezzanines.
+
+It is meant as the simplest possible example of how a driver should be
+written, and it includes a fake EEPROM image (built using the tools
+described in *note FMC Identification::),, which by default is
+replicated for each fake mezzanine.
+
+You can also use this device to verify the match algorithms, by asking
+it to test your own EEPROM image. You can provide the image by means of
+the eeprom= module parameter: the new EEPROM image is loaded, as usual,
+by means of the firmware loader.  This example shows the defaults and a
+custom EEPROM image:
+
+     spusa.root# insmod fmc-fakedev.ko
+     [   99.971247]  fake-fmc-carrier: mezzanine 0
+     [   99.975393]       Manufacturer: fake-vendor
+     [   99.979624]       Product name: fake-design-for-testing
+     spusa.root# rmmod fmc-fakedev
+     spusa.root# insmod fmc-fakedev.ko eeprom=fdelay-eeprom.bin
+     [  121.447464]  fake-fmc-carrier: Mezzanine 0: eeprom "fdelay-eeprom.bin"
+     [  121.462725]  fake-fmc-carrier: mezzanine 0
+     [  121.466858]       Manufacturer: CERN
+     [  121.470477]       Product name: FmcDelay1ns4cha
+     spusa.root# rmmod fmc-fakedev
+
+After loading the device, you can use the write_ee method do modify its
+own internal fake EEPROM: whenever the image is overwritten starting at
+offset 0, the module will unregister and register again the FMC device.
+This is shown in fmc-write-eeprom.txt

drivers/fmc/Kconfig

@@ -15,3 +15,14 @@ menuconfig FMC
 	  The framework was born outside of the kernel and at this time
 	  the off-tree code base is more complete.  Code and documentation
 	  is at git://ohwr.org/fmc-projects/fmc-bus.git .
+
+if FMC
+
+config FMC_FAKEDEV
+	tristate "FMC fake device (software testing)"
+	help
+	  This is a fake carrier, bringing a default EEPROM content
+	  that can be rewritten at run time and usef for matching
+	  mezzanines.
+
+endif # FMC

drivers/fmc/Makefile

@@ -6,3 +6,5 @@ fmc-y += fmc-match.o
 fmc-y += fmc-sdb.o
 fmc-y += fru-parse.o
 fmc-y += fmc-dump.o
+
+obj-$(CONFIG_FMC_FAKEDEV) += fmc-fakedev.o