[PATCH 0/4] dev/io: Add packet processor

[Sebastian Huber]

The I/O packet processor provides a simple mechanism to exchange
reliable and in-order data through transmitting and receiving one
character at a time.

The I/O packet processor does not buffer data.  The processor uses a
stop-and-wait automatic repeat request method. There is at most one packet
in transmission.  The data transfer is done using a single character input
and output method.  The protocol uses 12-bit sequence numbers, so a host
could use a sliding window method to increase throughput.  All integers and
data are base64url encoded.  A 24-bit CRC is used to ensure the data
integrity.  The '{' character starts a packet.  The '}' character terminates
a packet.  The '#' character prefixes a 24-bit CRC value.  The ':' character
separates fields.  The '+' character prefixes data fields.  The following
packets are defined:

* hello: {<12-bit seq><12-bit ack>:H#<24-bit CRC>}

* acknowledge: {<12-bit seq><12-bit ack>:A#<24-bit CRC>}

* reject: {<12-bit seq><12-bit ack>
  :R:<12-bit seq of rejected packet>#<24-bit CRC>}

* jump: {<12-bit seq><12-bit ack>:J:<64-bit address>#<24-bit CRC>}

* load: {<12-bit seq><12-bit ack>:L:<64-bit load address>
  <64-bit load size in bytes>#<24-bit CRC>+<data to load>#<24-bit CRC>}

* signal: {<12-bit seq><12-bit ack>:S:<64-bit signal number>:
  <64-bit signal value>#<24-bit CRC>}

* channel: {<12-bit seq><12-bit ack>:C:<64-bit channel number>
  <64-bit data size in bytes>#<24-bit CRC>+<channel data>#<24-bit CRC>}

The intended use case are boot loaders and test runners.  For example, test
runners may interface with an external test server performing equipment
handling on request using the I/O packet processor.

Use _IO_Packet_initialize() to initialize the I/O packet processor.  Use
_IO_Packet_process() to drive the packet processing.  You can enqueue
packets for transmission with _IO_Packet_enqueue().  You can reliably send
signals with _IO_Packet_send().  You can reliably transmit and receive
channel data with _IO_Packet_channel_push() and
_IO_Packet_channel_exchange().

A simple boot loader could be implemented like this:

  #include <bsp.h>
  #include <rtems/bspIo.h>
  #include <rtems/counter.h>
  #include <rtems/dev/io.h>

  static void output_char( IO_Packet_control *self, uint8_t ch )
  {
    (void) self;
    rtems_putc( ch );
  }

  static IO_Packet_status event_handler(
    IO_Packet_control       *self,
    IO_Packet_event_control *ctrl,
    IO_Packet_event          evt
  )
  {
    (void) ctrl;

    switch ( evt ) {
      case IO_PACKET_EVENT_JUMP:
        _IO_Packet_send_acknowledge( self );
        bsp_restart( _IO_Packet_get_jump_address( self ) );
        break;
      case IO_PACKET_EVENT_LOAD_END:
        _IO_Packet_send_acknowledge( self );
        break;
      case IO_PACKET_EVENT_OUTPUT_END:
        rtems_putc( '\n' );
        break;
      default:
        break;
    }

    return IO_PACKET_SUCCESSFUL;
  }

  static uint32_t clock_monotonic( IO_Packet_control *self )
  {
    (void) self;
    return rtems_counter_read();
  }

  static void Init( rtems_task_argument arg )
  {
    IO_Packet_control self;
    IO_Packet_event_control event;

    (void) arg;
    _IO_Packet_initialize( &self, 0, NULL, output_char, clock_monotonic );
    _IO_Packet_prepend_event_handler( &self, &event, event_handler );

    while ( true ) {
      _IO_Packet_process( &self, getchark() );
    }
  }

Matthew Joyce (1):
  dev/io: Add base64 decoder

Sebastian Huber (3):
  dev/io: Make base64 encoding tables public
  dev/io: Add a CRC-24Q implementation
  dev/io: Add packet processor

 cpukit/dev/iobase64.c                         |  24 +-
 cpukit/dev/iobase64decode.c                   | 166 +++
 cpukit/dev/iocrc24q.c                         | 148 +++
 cpukit/dev/iopacket.c                         | 837 ++++++++++++++++
 cpukit/include/rtems/dev/io.h                 | 941 ++++++++++++++++++
 spec/build/cpukit/librtemscpu.yml             |   3 +
 .../build/testsuites/unit/unit-no-clock-0.yml |   3 +
 testsuites/unit/tc-io-base64-decode.c         | 180 ++++
 testsuites/unit/tc-io-packet.c                | 617 ++++++++++++
 9 files changed, 2912 insertions(+), 7 deletions(-)
 create mode 100644 cpukit/dev/iobase64decode.c
 create mode 100644 cpukit/dev/iocrc24q.c
 create mode 100644 cpukit/dev/iopacket.c
 create mode 100644 testsuites/unit/tc-io-base64-decode.c
 create mode 100644 testsuites/unit/tc-io-packet.c

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2.35.3