vpi: add 'quickstart'

Author: umarcor

.github/workflows/test.yml

@@ -31,6 +31,7 @@ jobs:
             vhpidirect/arrays/intvector,
             vhpidirect/arrays/logicvector,
             vhpidirect/arrays/matrices,
+            vpi/quickstart,
           ]
     runs-on: ubuntu-latest
     env:
@@ -73,11 +74,12 @@ jobs:
             vhpidirect/quickstart/package,
             vhpidirect/quickstart/sharedvar,
             vhpidirect/shared/shlib,
-            #vhpidirect/shared/dlopen, ! dlfcn.h is not available on win
-            #vhpidirect/shared/shghdl, ! dlfcn.h is not available on win
+            #vhpidirect/shared/dlopen,  ! dlfcn.h is not available on win
+            #vhpidirect/shared/shghdl,  ! dlfcn.h is not available on win
             vhpidirect/arrays/intvector,
             vhpidirect/arrays/logicvector,
             vhpidirect/arrays/matrices,
+            vpi/quickstart,
           ]
     runs-on: windows-latest
     env:

doc/vpi/examples/index.rst

@@ -1,4 +1,20 @@
+.. program:: ghdl
+.. _COSIM:VPI:Examples:
+
 Examples
 ########
 
-TBC
+A very brief description of how to use VPI is that ``vpi_user.h`` provides dozens of functions to scan/navigate the hierarchy
+of the elaborated hardware design, and it allows to set callbacks for specific events/signals.
+
+.. NOTE::
+  Since VHDL sources are agnostic to the usage of VPI modules, most of the examples in this section reuse the same VHDL
+  sources. Readers should focus on the differences between the provided C files.
+
+.. ATTENTION::
+  On Windows, the directory containing ``libghdlvpi.dll`` needs to be added to the ``PATH``. This can be achieved with
+  :option:`--vpi-library-dir`, :option:`--vpi-library-dir-unix` or ``$(cd $(dirname $(which ghdl))/../lib; pwd)``.
+
+.. toctree::
+
+   quickstart

doc/vpi/examples/quickstart.rst

@@ -0,0 +1,17 @@
+.. program:: ghdl
+.. _COSIM:VPI:Examples:quickstart:
+
+Quick Start
+###########
+
+.. _COSIM:VPI:Examples:quickstart:hello:
+
+:cosimtree:`hello <vpi/quickstart/vpi_hello.c>`
+***********************************************
+
+This is the most minimal example, where a single callback is registered at the beginning of the simulation. The callback just
+prints ``Hello!``. Then, the simulation is executed as usual.
+
+VPI allows to register callbacks at multiple events and to optionally delay their execution after the event is triggered.
+The list of available callback reasons is defined in :ghdlsrc:`vpi_user.h <grt/vpi_user.h>`. The structure type that is used
+and required to register a callback, ``s_cb_data``, is also defined in the same header file.

vpi/ent.vhd

@@ -0,0 +1,26 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity ent is
+  generic (
+      G_WIDTH : natural := 4
+  );
+  port (
+    A : in std_logic_vector(G_WIDTH-1 downto 0);
+    B : in std_logic_vector(G_WIDTH-1 downto 0);
+    C : in std_logic;
+    Q : out std_logic_vector(G_WIDTH downto 0)
+  );
+end entity;
+
+architecture arch of ent is
+
+  signal c_in : unsigned(0 downto 0);
+
+begin
+
+  c_in <= to_unsigned(1,1) when C='1' else to_unsigned(0,1);
+  Q <= std_logic_vector(unsigned('0' & A) + unsigned(B) + c_in);
+
+end architecture;

vpi/quickstart/run.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env sh
+
+set -e
+
+cd $(dirname "$0")
+
+echo "> Analyze ent.vhd and tb.vhd"
+ghdl -a ../ent.vhd ../tb.vhd
+
+echo "> Elaborate tb"
+ghdl -e -o tb tb
+
+echo "> Compile vpi_hello.c"
+ghdl --vpi-compile gcc -c vpi_hello.c -o vpi.o
+
+echo "> Link vpi.o"
+ghdl --vpi-link gcc vpi.o -o vpi.vpi
+
+if [ "$OS" = "Windows_NT" ]; then
+  # Need to put the directory containing libghdlvpi.dll in the path.
+  PATH=$PATH:`ghdl --vpi-library-dir-unix`
+fi
+
+echo "> Execute tb"
+./tb --vpi=./vpi.vpi

vpi/quickstart/vpi_hello.c

@@ -0,0 +1,22 @@
+#include <vpi_user.h>
+#include <stdio.h>
+
+PLI_INT32 cb_hello(){
+  printf("Hello!\n");
+  return 0;
+}
+
+void entry_point_cb() {
+  s_cb_data cb;
+
+  cb.reason = cbStartOfSimulation;
+  cb.cb_rtn = &cb_hello;
+  cb.user_data = NULL;
+
+  if (vpi_register_cb(&cb) == NULL) {
+    vpi_printf ("cannot register cbStartOfSimulation call back\n");
+  }
+}
+
+// List of entry points called when the plugin is loaded
+void (*vlog_startup_routines[]) () = {entry_point_cb, 0};

vpi/tb.vhd

@@ -0,0 +1,41 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity tb is
+  generic (
+    G_WIDTH : natural := 4;
+    G_INST  : natural := 4
+  );
+end tb;
+
+architecture arch of tb is
+
+  signal a, b : std_logic_vector(G_INST*G_WIDTH-1 downto 0);
+  signal c : std_logic_vector(G_INST downto 0);
+
+begin
+
+  i_ent: for x in 0 to G_INST-1 generate
+    signal q: std_logic_vector(G_WIDTH downto 0);
+  begin
+    w_ent: entity work.ent
+      port map (
+        A => a((x+1)*G_WIDTH-1 downto x*G_WIDTH),
+        B => b((x+1)*G_WIDTH-1 downto x*G_WIDTH),
+        C => c(x),
+        Q => q
+      );
+    c(x+1) <= q(q'left);
+  end generate;
+
+  process
+  begin
+    a <= std_logic_vector(to_unsigned(2, a'length));
+    b <= std_logic_vector(to_unsigned(13, b'length));
+    c(0) <= '0';
+    wait for 10 ns;
+    wait;
+  end process;
+
+end architecture;