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

[Gedare Bloom]

On Sun, Jan 21, 2024 at 4:43 PM Chris Johns <chrisj at rtems.org> wrote:
>
> Hi,
>
> There are a few things I do not understand about this addition. I brief review
> of the code seems OK but I am struggling to understand the requirements driving
> this addition. Can a ticket please be created with the requirements and a real
> world use case of how it would be used and what problem(s) it solves?
>
> I also think dev/io.h and dev/iopacket.c are too generic for something thing
> that appears to be specific to a specific use case.
>
+1

I'm immediately thinking about the Regulator package that Joel added.
This I/O Packet Processor appears to fall in a similar category.

> Chris
>
> On 15/1/2024 8:45 pm, Sebastian Huber wrote:
> > 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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