backends/cxxrtl/cxxrtl_capi.h

   1 /*
   2  *  yosys -- Yosys Open SYnthesis Suite
   3  *
   4  *  Copyright (C) 2020  whitequark <whitequark@whitequark.org>
   5  *
   6  *  Permission to use, copy, modify, and/or distribute this software for any
   7  *  purpose with or without fee is hereby granted.
   8  *
   9  *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  *
  17  */
  18
  19 #ifndef CXXRTL_CAPI_H
  20 #define CXXRTL_CAPI_H
  21
  22 // This file is a part of the CXXRTL C API. It should be used together with `cxxrtl_capi.cc`.
  23 //
  24 // The CXXRTL C API makes it possible to drive CXXRTL designs using C or any other language that
  25 // supports the C ABI, for example, Python. It does not provide a way to implement black boxes.
  26
  27 #include <stddef.h>
  28 #include <stdint.h>
  29
  30 #ifdef __cplusplus
  31 extern "C" {
  32 #endif
  33
  34 // Opaque reference to a design toplevel.
  35 //
  36 // A design toplevel can only be used to create a design handle.
  37 typedef struct _cxxrtl_toplevel *cxxrtl_toplevel;
  38
  39 // The constructor for a design toplevel is provided as a part of generated code for that design.
  40 // Its prototype matches:
  41 //
  42 // cxxrtl_toplevel <design-name>_create();
  43
  44 // Opaque reference to a design handle.
  45 //
  46 // A design handle is required by all operations in the C API.
  47 typedef struct _cxxrtl_handle *cxxrtl_handle;
  48
  49 // Create a design handle from a design toplevel.
  50 //
  51 // The `design` is consumed by this operation and cannot be used afterwards.
  52 cxxrtl_handle cxxrtl_create(cxxrtl_toplevel design);
  53
  54 // Release all resources used by a design and its handle.
  55 void cxxrtl_destroy(cxxrtl_handle handle);
  56
  57 // Simulate the design to a fixed point.
  58 //
  59 // Returns the number of delta cycles.
  60 size_t cxxrtl_step(cxxrtl_handle handle);
  61
  62 // Type of a simulated object.
  63 enum cxxrtl_type {
  64         // Values correspond to singly buffered netlist nodes, i.e. nodes driven exclusively by
  65         // combinatorial cells, or toplevel input nodes.
  66         //
  67         // Values can be inspected via the `curr` pointer and modified via the `next` pointer (which are
  68         // equal for values); however, note that changes to the bits driven by combinatorial cells will
  69         // be ignored.
  70         //
  71         // Values always have depth 1.
  72         CXXRTL_VALUE = 0,
  73
  74         // Wires correspond to doubly buffered netlist nodes, i.e. nodes driven, at least in part, by
  75         // storage cells, or by combinatorial cells that are a part of a feedback path.
  76         //
  77         // Wires can be inspected via the `curr` pointer and modified via the `next` pointer (which are
  78         // distinct for wires); however, note that changes to the bits driven by combinatorial cells will
  79         // be ignored.
  80         //
  81         // Wires always have depth 1.
  82         CXXRTL_WIRE = 1,
  83
  84         // Memories correspond to memory cells.
  85         //
  86         // Memories can be inspected and modified via the `curr` pointer. Due to a limitation of this
  87         // API, memories cannot yet be modified in a guaranteed race-free way, and the `next` pointer is
  88         // always NULL.
  89         CXXRTL_MEMORY = 2,
  90
  91         // More object types will be added in the future, but the existing ones will never change.
  92 };
  93
  94 // Description of a simulated object.
  95 //
  96 // The `data` array can be accessed directly to inspect and, if applicable, modify the bits
  97 // stored in the object.
  98 struct cxxrtl_object {
  99         // Type of the object.
 100         //
 101         // All objects have the same memory layout determined by `width` and `depth`, but the type
 102         // determines all other properties of the object.
 103         uint32_t type; // actually `enum cxxrtl_type`
 104
 105         // Width of the object in bits.
 106         size_t width;
 107
 108         // Depth of the object. Only meaningful for memories; for other objects, always 1.
 109         size_t depth;
 110
 111         // Bits stored in the object, as 32-bit chunks, least significant bits first.
 112         //
 113         // The width is rounded up to a multiple of 32; the padding bits are always set to 0 by
 114         // the simulation code, and must be always written as 0 when modified by user code.
 115         // In memories, every element is stored contiguously. Therefore, the total number of chunks
 116         // in any object is `((width + 31) / 32) * depth`.
 117         //
 118         // To allow the simulation to be partitioned into multiple independent units communicating
 119         // through wires, the bits are double buffered. To avoid race conditions, user code should
 120         // always read from `curr` and write to `next`. The `curr` pointer is always valid; for objects
 121         // that cannot be modified, or cannot be modified in a race-free way, `next` is NULL.
 122         uint32_t *curr;
 123         uint32_t *next;
 124
 125         // More description fields will be added in the future, but the existing ones will never change.
 126 };
 127
 128 // Retrieve description of a simulated object.
 129 //
 130 // The `name` is the full hierarchical name of the object in the Yosys notation, where public names
 131 // have a `\` prefix and hierarchy levels are separated by single spaces. For example, if
 132 // the top-level module instantiates a module `foo`, which in turn contains a wire `bar`, the full
 133 // hierarchical name is `\foo \bar`.
 134 //
 135 // Returns the object if it was found, NULL otherwise. The returned value is valid until the design
 136 // is destroyed.
 137 struct cxxrtl_object *cxxrtl_get(cxxrtl_handle handle, const char *name);
 138
 139 // Enumerate simulated objects.
 140 //
 141 // For every object in the simulation, `callback` is called with the provided `data`, the full
 142 // hierarchical name of the object (see `cxxrtl_get` for details), and the object description.
 143 // The provided `name` and `object` values are valid until the design is destroyed.
 144 void cxxrtl_enum(cxxrtl_handle handle, void *data,
 145                  void (*callback)(void *data, const char *name, struct cxxrtl_object *object));
 146
 147 #ifdef __cplusplus
 148 }
 149 #endif
 150
 151 #endif