Copyright 2013-2020 Tomi Valkeinen
WARNING: rwmem can break your hardware, use only if you know what you are doing.
rwmem is a small tool for reading and writing device registers. rwmem supports two modes: mmap mode and i2c mode.
In mmap mode rwmem accesses a file by memory mapping it. Using /dev/mem as the memory mapped file makes rwmem access memory and can thus be used to access devices which have memory mapped registers.
In i2c mode rwmem accesses an i2c peripheral by sending i2c messages to it.
rwmem features:
- addressing with 8/16/32/64 bit addresses
- accessing 8/16/32/64 bit memory locations
- little and big endian addressess and accesses
- bitfields
- address ranges
- register description database
You need meson, ninja and fmt for building. inih is an optional dependency.
git clone https://github.com/tomba/rwmem.git
cd rwmem
meson build
ninja -C build
Directions for cross compiling depend on your environment.
meson build --cross-file=<path-to-meson-cross-file>
ninja -C build
Here is my cross file for arm32 (where ${BROOT} is path to my buildroot output dir):
[binaries]
c = ['ccache', '${BROOT}/host/bin/arm-buildroot-linux-gnueabihf-gcc']
cpp = ['ccache', '${BROOT}/host/bin/arm-buildroot-linux-gnueabihf-g++']
ar = '${BROOT}/host/bin/arm-buildroot-linux-gnueabihf-ar'
strip = '${BROOT}/host/bin/arm-buildroot-linux-gnueabihf-strip'
pkgconfig = '${BROOT}/host/bin/pkg-config'
[host_machine]
system = 'linux'
cpu_family = 'arm'
cpu = 'arm'
endian = 'little'
You can use meson options to configure the build. E.g.
meson build -Dpyrwmem=disabled
Use meson configure build to see all the configuration options and their current values.
See meson_options.txt for rwmem specific options.
You can build a static rwmem executable e.g. with:
meson setup -Dfmt:cpp_std=c++20 -Dbuildtype=minsize -Db_lto=true -Dwrap_mode=forcefallback -Dpyrwmem=disabled -Ddefault_library=static -Dprefer_static=true -Dc_link_args="-s -static" -Dcpp_link_args="-s -static" build
ninja -C build
Show what's in memory location 0x58001000
$ rwmem 0x58001000
Show what's in memory locations between 0x58001000 to 0x58001040
$ rwmem 0x58001000-0x58001040
Show what's in memory locations between 0x58001000 to 0x58001040
$ rwmem 0x58001000+0x40
Show what's in memory location 0x58001000's bit 7 (i.e. 8th bit)
$ rwmem 0x58001000:7
Show what's in memory location 0x58001000's bits 7-4 (i.e. bits 4, 5, 6, 7)
$ rwmem 0x58001000:7:4
Write 0x12345678 to memory location 0x58001000
$ rwmem 0x58001000=0x12345678
Modify memory location 0x58001000's bits 7-4 to 0xf
$ rwmem 0x58001000:7:4=0xf
Show the byte at location 0x10 in file edid.bin
$ rwmem --mmap edid.bin -s 8 0x10
Set /dev/fb0 to red
$ rwmem -p q --mmap /dev/fb0 0x0..$((800*4*480))=0xff0000
Read a byte from i2c device 0x50 on bus 4, address 0x20
$ rwmem -s 8 --i2c=4:0x50 0x20
Read a 32 bit big endian value from 16 bit big endian address 0x800 from i2c device 0x50 on bus 4
$ rwmem -s 32be -S 16be --i2c=4:0x50 0x800
Show the whole DISPC address space
$ rwmem DISPC
Show the known registers in DISPC address space
$ rwmem DISPC.*
Show SYSCONFIG register in DISPC
$ rwmem DISPC.SYSCONFIG
Modify MIDLEMODE field in DISPC's SYSCONFIG register to 0x1
$ rwmem DISPC.SYSCONFIG:MIDLEMODE=0x1
List all registers in the register file
$ rwmem --list
List registers in DISPC
$ rwmem --list DISPC
List registers in DISPC
$ rwmem --list DISPC.*
List registers in DISPC starting with VID
$ rwmem --list DISPC.VID*
List fields in DISPC SYSCONFIG
$ rwmem --list DISPC.SYSCONFIG:*
Read binary dump of DISPC to dispc.bin file
$ rwmem --raw DISPC > dispc.bin
Show SYSCONFIG register, as defined in dispc.regs, in file dispc.bin
$ rwmem --mmap dispc.bin --regs dispc.regs --ignore-base DISPC.SYSCONFIG
The write mode parameter affects how rwmem handles writing.
Write mode 'w' means write-only. In this mode rwmem never reads from the address. This means that if you modify only certain bits with the bitfield operator, the rest of the bits will be set to 0.
Write mode 'rw' means read-write. In this mode rwmem reads from the address, modifies the value, and writes it back.
Write mode 'rwr' means read-write-read. This is the same as 'rw' except rwmem reads from the address again after writing for the purpose of showing the new value. This is the default mode.
The print mode parameter affects what rwmem will output.
'q' - quiet 'r' - print only register value, not individual fields 'rf' - print register and fields (when available).
In raw output mode rwmem will copy the values it reads to stdout without any formatting. This can be used to get binary dumps of memory areas.
You can set the size and endianness for data and for address with -s and -S options. The size and endianness for address is used only for i2c. The size is in number of bits, and endianness is "be", "le", "bes" or "les".
In addition to the normal big (be) and little endian (le), rwmem supports "swapped" modification for endianness (bes and les). In swapped endianness, 16 bit words of a 32 bit value are swapped, and similarly 32 bit words of a 64 bit value are swapped.
A register description file is a binary register database. See the code (regfiledata.h) and the included python scripts to see the details of the format.
It is easy to generate register description files using the rwmem.gen python module. Two additional python scripts can be used to parse IPXACT files (ipxact_parse.py) and csv files from rwmem v1 (csv_parse.py).
examples/bash_completion/rwmem is an example bash completion script for rwmem.
rwmem will look for configuration options from ~/.rwmem/rwmem.ini file.
examples/rwmem.ini has an example rwmem.ini file.
main.detect entry can be set to point to a script which should echo the name
of the platform rwmem is running on. The name of the platform is then used to
look for "platform" entries in the rwmem.ini, which can be used to define
platform specific rwmem configuration (mainline regfile for the time being).