This tools displays content of registers in a human readable way. It was written with a focus on a simple description language

It was developed to display content of the iMX6 DDR controller registerss within a minimal bootloader but evolved to support other devices and setups.

Base ideas are:

reusability

processors have usually multiple instances of a processing unit; allow to use templates or already existing definitions (the @use keyword in combination with @disabled or @template)

simplicity

just simple text files; no XML, no binary files.

various datatypes

enumerations, integers, fixed point fractionals

large registers

registers can be up to 256 bits

various access modes

originally written for direct memory access but extended in the meantime for /dev/mem and /dev/i2c-X. Esepcially for the latter usecase, the description contains information about address width and device endianess.

complex bitmasks

sometimes, register fields are contained in non contiguous bits; this can be specified like @bits 10-8 16.

support of similar but still different processors

often, registers are similar across processor family but there can be still differences (different addresses, different number of unit instances). This can be specified by a [symbol] selector

Generated description stream consists of several (processor) units which have a set of registers with fields.

Sample:

@unit _UART
  @disabled      ## it is used a tamplate

  # addresses have a 32 bit width
  # registers have a 16 bit width
  # internal representation is little endian
  @regwidth 32 16 LE

  # look for register descriptions with a '*.reg' pattern in UART/
  @registers UART/

@unit UART0
  # use template
  @use _UART
  # physical address + unit size
  @reg 0x01230000 0x1000

@unit UART1
  @use _UART
  @reg 0x01240000 0x1000

## only available on a large cpu
@unit[large-cpu] UART2
  @use _UART
  @reg 0x01250000 0x1000

Sample:

@register CTRL0
  # relative to containig unit address
  @addr 0x0000
  @field ENABLE
    # a flag on bit position 0
    @boolean 0
  @field TYPE
    @bits 2-1
    @enum 0 "RS232"
    @enum 1 "RS485"
  @field DIVIDER
    # a 3.5 fixed point fractional
    @frac 10-8 7-3
  @field COUNTER
    @uint 15-11
    @ro

or

@register RX
  # on cpu-a at address 0x02 but 8 bit access
  @addr[cpu-a] 0x0002 8
  # on cpu-b at address 0x1000 with 32 bit access
  @addr[cpu-b] 0x0100 32

or

@register _IPU_CPMEM-W0
  @template
  # part of iMX6 CPMEM description which consists of two
  # 160 bit sized blocks
  @addr 0x00000000 160
  @field BM
    @bits 118-117
    @enum 0 "no block mode"
    @enum 1 "BW=8, BH=8"
    @enum 2 "BW=16, BH=16"

Base tool to compile the description files:

usage: decode-registers-gendesc [-h] [--define <symbol>] [--c-fill <file>]
                                [--c-defines <file>] [--datastream <file>]
                                [--datastream-c <file>] [--endian big|little]
                                [--unit-only <unit>] [--unit-exclude <unit>]
                                [--bga <bga>]
                                opt_directory

positional arguments:
  opt_directory

optional arguments:
  -h, --help            show this help message and exit
  --define <symbol>, -D <symbol>
                        define a symbol
  --c-fill <file>       output C code
  --c-defines <file>    output C symbols
  --datastream <file>   output raw datastream
  --datastream-c <file>
                        output raw datastream as C source
  --endian big|little   endianess of raw datastream
  --unit-only <unit>    include only listed unit files
  --unit-exclude <unit>
                        exclude listed unit files
  --bga <bga>           BGA to be used when generating pin definitions

Raw binary datastream; given to decode-device as the --definitions data stream

This mode is great for debugging the generated stream; this will produce C code fragments like

push_u16(5);                        /* number of units */
{ /* {{{ 8BIT unit */
  push_u32(0x00000000);             /* memory start address */
  push_u32(0x000000ff);             /* memory end address */
  push_data16( 4, "8BIT");          /* Unit id */
  push_data16( 4, "8BIT");          /* Unit name */
  push_u8(0);                       /* addr width */
  push_u8(UNIT_ENDIAN_BIG);
  push_u16(1);                      /* number of registers */
  { /* {{{ registers */
    { /* {{{ ID register */
      push_u32(0x00000000);         /* offset */
      push_u8(8);                   /* width */
      push_u8(3);                   /* flags */
      push_data16( 7, "8BIT_ID");   /* id */
      push_data16( 2, "ID");        /* name */
      push_u16(4);                  /* number of fields */
      { /* {{{ 4 fields */
        { /* {{{ VVBI field */
          push_u8(3);               /* flags */
          push_data16( 4, "VVBI");  /* id */
          push_data16( 4, "VVBI");  /* name */
          push_u8(TYPE_SINT);
          push_u8(0xf);             /* sint [3, 2, 1, 0]/8 */
        } /* }}} VVBI field */

Example:

0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x04, 0x00,
0x38, 0x42, 0x49, 0x54, 0x04, 0x00, 0x38, 0x42, 0x49, 0x54, 0x00, 0x02,
0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x03, 0x07, 0x00, 0x38, 0x42,

There are some magic values in certain fields (type, flags); C #define values are created in this mode:

#define UNIT_ENDIAN_BIG             2 /* big endian */
#define REGISTER_FLAG_ACCESS_READ   1 /* read access */
#define REGISTER_FLAG_ACCESS_WRITE  2 /* write access */
#define FIELD_FLAG_ACCESS_READ      1 /* read access */
#define FIELD_FLAG_ACCESS_WRITE     2 /* write access */

This tools takes a datastream file and dumps register content. It supports:

emulator mode

no real device access; interpretes data given by --value

i2c

acesses an i2c device (/dev/i2c-X)

memory

real devices memory (/dev/mem)

$ decode-device --type emu --definitions regstream-tw99x0.bin --value 0x23
======================== GENERIC ==============================
0x00000000 ID                           0x23
  revision                            : 3
  id                                  : 4

0x00000001 STATUS1                      0x23
  DET50                               : 50Hz
  MONO                                : true
  VLOCK                               : false
  FIELD                               : false
  SLOCK                               : true
  HLOCK                               : false
  VDLOSS                              : false

decode-device -T emu -d regstream-mx6q.bin @IPU1-CPMEM CH-I#0\* -v 42
======================== IPU1-CPMEM ==============================
0x02700000 CH-I#0_0                     0x00000000.00000000.00000000.00000000.0000002a
  XV                                  : 42
  YV                                  : 0
...
0x02700014 CH-I#0_1                     0x00000000.00000000.00000000.00000000.0000002a
  EBA0                                : 0x0000002a
  EBA1                                : 0x00000000
  ILO                                 : 0