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