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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:03 EST.

1	fmc-chardev
2	===========
3	
4	This is a simple generic driver, that allows user access by means of a
5	character device (actually, one for each mezzanine it takes hold of).
6	
7	The char device is created as a misc device. Its name in /dev (as
8	created by udev) is the same name as the underlying FMC device. Thus,
9	the name can be a silly fmc-0000 look-alike if the device has no
10	identifiers nor bus_id, a more specific fmc-0400 if the device has a
11	bus-specific address but no associated name, or something like
12	fdelay-0400 if the FMC core can rely on both a mezzanine name and a bus
13	address.
14	
15	Currently the driver only supports read and write: you can lseek to the
16	desired address and read or write a register.
17	
18	The driver assumes all registers are 32-bit in size, and only accepts a
19	single read or write per system call. However, as a result of Unix read
20	and write semantics, users can simply fread or fwrite bigger areas in
21	order to dump or store bigger memory areas.
22	
23	There is currently no support for mmap, user-space interrupt management
24	and DMA buffers. They may be added in later versions, if the need
25	arises.
26	
27	The example below shows raw access to a SPEC card programmed with its
28	golden FPGA file, that features an SDB structure at offset 256 - i.e.
29	64 words.  The mezzanine's EEPROM in this case is not programmed, so the
30	default name is fmc-<bus><devfn>, and there are two cards in the system:
31	
32	  spusa.root# insmod fmc-chardev.ko
33	  [ 1073.339332] spec 0000:02:00.0: Driver has no ID: matches all
34	  [ 1073.345051] spec 0000:02:00.0: Created misc device "fmc-0200"
35	  [ 1073.350821] spec 0000:04:00.0: Driver has no ID: matches all
36	  [ 1073.356525] spec 0000:04:00.0: Created misc device "fmc-0400"
37	  spusa.root# ls -l /dev/fmc*
38	  crw------- 1 root root 10, 58 Nov 20 19:23 /dev/fmc-0200
39	  crw------- 1 root root 10, 57 Nov 20 19:23 /dev/fmc-0400
40	  spusa.root# dd bs=4 skip=64 count=1 if=/dev/fmc-0200 2> /dev/null | od -t x1z
41	  0000000 2d 42 44 53                                      >-BDS<
42	  0000004
43	
44	The simple program tools/fmc-mem in this package can access an FMC char
45	device and read or write a word or a whole area.  Actually, the program
46	is not specific to FMC at all, it just uses lseek, read and write.
47	
48	Its first argument is the device name, the second the offset, the third
49	(if any) the value to write and the optional last argument that must
50	begin with "+" is the number of bytes to read or write.  In case of
51	repeated reading data is written to stdout; repeated writes read from
52	stdin and the value argument is ignored.
53	
54	The following examples show reading the SDB magic number and the first
55	SDB record from a SPEC device programmed with its golden image:
56	
57	     spusa.root# ./fmc-mem /dev/fmc-0200 100
58	     5344422d
59	     spusa.root# ./fmc-mem /dev/fmc-0200 100 +40 | od -Ax -t x1z
60	     000000 2d 42 44 53 00 01 02 00 00 00 00 00 00 00 00 00  >-BDS............<
61	     000010 00 00 00 00 ff 01 00 00 00 00 00 00 51 06 00 00  >............Q...<
62	     000020 c9 42 a5 e6 02 00 00 00 11 05 12 20 2d 34 42 57  >.B......... -4BW<
63	     000030 73 6f 72 43 72 61 62 73 49 53 47 2d 00 20 20 20  >sorCrabsISG-.   <
64	     000040
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