Commit | Line | Data |
---|---|---|
4debfe40 AR |
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 |