]> sigrok.org Git - libsigrokdecode.git/blobdiff - controller.c
srd: last public/private fix, and docs for all publis functions.
[libsigrokdecode.git] / controller.c
index db2ed9b4e5091202dff16696962380a0929efc45..05dbf3eb8bbfea6609d24cc446fc87303c249ee1 100644 (file)
@@ -2,7 +2,7 @@
  * This file is part of the sigrok project.
  *
  * Copyright (C) 2010 Uwe Hermann <uwe@hermann-uwe.de>
- * Copyright (C) 2011 Bert Vermeulen <bert@biot.com>
+ * Copyright (C) 2012 Bert Vermeulen <bert@biot.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "sigrokdecode.h" /* First, so we avoid a _POSIX_C_SOURCE warning. */
+#include "sigrokdecode-internal.h"
 #include "config.h"
-#include <sigrokdecode.h> /* First, so we avoid a _POSIX_C_SOURCE warning. */
 #include <glib.h>
+#include <inttypes.h>
+#include <stdlib.h>
 
-/* TODO: this should probably be in sigrokdecode.h */
-/* Re-define some string functions for Python >= 3.0. */
-#if PY_VERSION_HEX >= 0x03000000
-#define PyString_AsString PyBytes_AsString
-#define PyString_FromString PyBytes_FromString
-#define PyString_Check PyBytes_Check
-#endif
+/* List of decoder instances. */
+static GSList *di_list = NULL;
 
+/* List of frontend callbacks to receive PD output. */
+static GSList *callbacks = NULL;
 
-static GSList *pipelines = NULL;
+/* decoder.c */
+extern SRD_PRIV GSList *pd_list;
 
-/* lives in decoder.c */
-extern GSList *list_pds;
-extern GSList *decoders;
-
-struct srd_pipeline {
-       int id;
-       GSList *decoders;
-};
-
-
-
-static PyObject *Decoder_init(PyObject *self, PyObject *args)
-{
-       (void)self;
-       (void)args;
-//     printf("init object %x\n", self);
-
-       Py_RETURN_NONE;
-}
-
-
-static PyObject *Decoder_put(PyObject *self, PyObject *args)
-{
-       PyObject *arg;
-
-//     printf("put object %x\n", self);
-
-       if (!PyArg_ParseTuple(args, "O:put", &arg))
-               return NULL;
-
-       // fprintf(stdout, "sigrok.put() called by decoder:\n");
-       PyObject_Print(arg, stdout, Py_PRINT_RAW);
-       puts("");
-
-       Py_RETURN_NONE;
-}
-
-static PyMethodDef no_methods[] = { {NULL, NULL, 0, NULL} };
-static PyMethodDef Decoder_methods[] = {
-       {"__init__", Decoder_init, METH_VARARGS, ""},
-       {"put", Decoder_put, METH_VARARGS,
-        "Accepts a dictionary with the following keys: time, duration, data"},
-       {NULL, NULL, 0, NULL}
-};
-
-
-// class Decoder(sigrok.Decoder):
-typedef struct {
-       PyObject_HEAD
-} sigrok_Decoder_object;
-
-static PyTypeObject sigrok_Decoder_type = {
-       PyObject_HEAD_INIT(NULL)
-       0,
-       "sigrok.Decoder",
-       sizeof(sigrok_Decoder_object),
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
-       "Sigrok Decoder object",
-       0,
-       0,
-       0,
-       0,
-       0,
-       0,
-       Decoder_methods,
-};
-
-PyMODINIT_FUNC init_sigrok_Decoder(void)
-{
-       PyObject *mod;
-
-       sigrok_Decoder_type.tp_new = PyType_GenericNew;
-       if (PyType_Ready(&sigrok_Decoder_type) < 0)
-               return;
-
-       mod = Py_InitModule3("sigrok", no_methods, "sigrok base classes");
-       Py_INCREF(&sigrok_Decoder_type);
-       PyModule_AddObject(mod, "Decoder", (PyObject *)&sigrok_Decoder_type);
-
-}
+/* module_sigrokdecode.c */
+extern SRD_PRIV PyMODINIT_FUNC PyInit_sigrokdecode(void);
 
+/* type_logic.c */
+extern SRD_PRIV PyTypeObject srd_logic_type;
 
 /**
  * Initialize libsigrokdecode.
@@ -145,29 +54,52 @@ PyMODINIT_FUNC init_sigrok_Decoder(void)
  * The caller is responsible for calling the clean-up function srd_exit(),
  * which will properly shut down libsigrokdecode and free its allocated memory.
  *
- * Multiple calls to srd_init(), without calling srd_exit() inbetween,
+ * Multiple calls to srd_init(), without calling srd_exit() in between,
  * are not allowed.
  *
+ * @param path Path to an extra directory containing protocol decoders
+ *             which will be added to the python sys.path, or NULL.
+ *
  * @return SRD_OK upon success, a (negative) error code otherwise.
  *         Upon Python errors, return SRD_ERR_PYTHON. If the sigrok decoders
  *         directory cannot be accessed, return SRD_ERR_DECODERS_DIR.
  *         If not enough memory could be allocated, return SRD_ERR_MALLOC.
  */
-int srd_init(void)
+SRD_API int srd_init(char *path)
 {
        int ret;
+       char *env_path;
 
-       /* Py_Initialize() returns void and usually cannot fail. */
-       Py_Initialize();
+       srd_dbg("Initializing libsigrokdecode.");
+
+       /* Add our own module to the list of built-in modules. */
+       PyImport_AppendInittab("sigrokdecode", PyInit_sigrokdecode);
 
-       init_sigrok_Decoder();
+       /* Initialize the Python interpreter. */
+       Py_Initialize();
 
-       PyRun_SimpleString("import sys;");
-       if ((ret = set_modulepath()) != SRD_OK) {
+       /* Installed decoders. */
+       if ((ret = add_modulepath(DECODERS_DIR)) != SRD_OK) {
                Py_Finalize();
                return ret;
        }
 
+       /* Path specified by the user. */
+       if (path) {
+               if ((ret = add_modulepath(path)) != SRD_OK) {
+                       Py_Finalize();
+                       return ret;
+               }
+       }
+
+       /* Environment variable overrides everything, for debugging. */
+       if ((env_path = getenv("SIGROKDECODE_DIR"))) {
+               if ((ret = add_modulepath(path)) != SRD_OK) {
+                       Py_Finalize();
+                       return ret;
+               }
+       }
+
        if ((ret = srd_load_all_decoders()) != SRD_OK) {
                Py_Finalize();
                return ret;
@@ -176,7 +108,6 @@ int srd_init(void)
        return SRD_OK;
 }
 
-
 /**
  * Shutdown libsigrokdecode.
  *
@@ -185,16 +116,16 @@ int srd_init(void)
  *
  * This function should only be called if there was a (successful!) invocation
  * of srd_init() before. Calling this function multiple times in a row, without
- * any successful srd_init() calls inbetween, is not allowed.
+ * any successful srd_init() calls in between, is not allowed.
  *
  * @return SRD_OK upon success, a (negative) error code otherwise.
  */
-int srd_exit(void)
+SRD_API int srd_exit(void)
 {
-       /* Unload/free all decoders, and then the list of decoders itself. */
-       /* TODO: Error handling. */
+       srd_dbg("Exiting libsigrokdecode.");
+
        srd_unload_all_decoders();
-       g_slist_free(list_pds);
+       g_slist_free(pd_list);
 
        /* Py_Finalize() returns void, any finalization errors are ignored. */
        Py_Finalize();
@@ -202,193 +133,707 @@ int srd_exit(void)
        return SRD_OK;
 }
 
+/**
+ * Add an additional search directory for the protocol decoders.
+ *
+ * The specified directory is prepended (not appended!) to Python's sys.path,
+ * in order to search for sigrok protocol decoders in the specified
+ * directories first, and in the generic Python module directories (and in
+ * the current working directory) last. This avoids conflicts if there are
+ * Python modules which have the same name as a sigrok protocol decoder in
+ * sys.path or in the current working directory.
+ *
+ * @param path Path to an extra directory containing protocol decoders
+ *             which will be added to the python sys.path, or NULL.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
+ */
+SRD_PRIV int add_modulepath(const char *path)
+{
+       PyObject *py_cur_path, *py_item;
+       GString *new_path;
+       int wc_len, i;
+       wchar_t *wc_new_path;
+       char *item;
+
+       srd_dbg("adding %s to module path", path);
+
+       new_path = g_string_sized_new(256);
+       g_string_assign(new_path, g_strdup(path));
+       py_cur_path = PySys_GetObject("path");
+       for (i = 0; i < PyList_Size(py_cur_path); i++) {
+               g_string_append(new_path, g_strdup(G_SEARCHPATH_SEPARATOR_S));
+               py_item = PyList_GetItem(py_cur_path, i);
+               if (!PyUnicode_Check(py_item))
+                       /* Shouldn't happen. */
+                       continue;
+               if (py_str_as_str(py_item, &item) != SRD_OK)
+                       continue;
+               g_string_append(new_path, item);
+       }
+
+       /* Convert to wide chars. */
+       wc_len = sizeof(wchar_t) * (new_path->len + 1);
+       if (!(wc_new_path = g_try_malloc(wc_len))) {
+               srd_dbg("malloc failed");
+               return SRD_ERR_MALLOC;
+       }
+       mbstowcs(wc_new_path, new_path->str, wc_len);
+       PySys_SetPath(wc_new_path);
+       g_string_free(new_path, TRUE);
+       g_free(wc_new_path);
+
+//#ifdef _WIN32
+//     gchar **splitted;
+//
+//     /*
+//      * On Windows/MinGW, Python's sys.path needs entries of the form
+//      * 'C:\\foo\\bar' instead of '/foo/bar'.
+//      */
+//
+//     splitted = g_strsplit(DECODERS_DIR, "/", 0);
+//     path = g_build_pathv("\\\\", splitted);
+//     g_strfreev(splitted);
+//#else
+//     path = g_strdup(DECODERS_DIR);
+//#endif
+
+       return SRD_OK;
+}
 
 /**
- * Add search directories for the protocol decoders.
+ * Set options in a decoder instance.
+ *
+ * @param di Decoder instance.
+ * @param options A GHashTable of options to set.
  *
- * TODO: add path from env var SIGROKDECODE_PATH, config etc
+ * Handled options are removed from the hash.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
  */
-int set_modulepath(void)
+SRD_API int srd_inst_set_options(struct srd_decoder_inst *di,
+                                    GHashTable *options)
 {
-       int ret;
+       PyObject *py_dec_options, *py_dec_optkeys, *py_di_options, *py_optval;
+       PyObject *py_optlist, *py_classval;
+       Py_UNICODE *py_ustr;
+       unsigned long long int val_ull;
+       int num_optkeys, ret, size, i;
+       char *key, *value;
+
+       if (!PyObject_HasAttrString(di->decoder->py_dec, "options")) {
+               /* Decoder has no options. */
+               if (g_hash_table_size(options) == 0) {
+                       /* No options provided. */
+                       return SRD_OK;
+               } else {
+                       srd_err("Protocol decoder has no options.");
+                       return SRD_ERR_ARG;
+               }
+               return SRD_OK;
+       }
+
+       ret = SRD_ERR_PYTHON;
+       key = NULL;
+       py_dec_options = py_dec_optkeys = py_di_options = py_optval = NULL;
+       py_optlist = py_classval = NULL;
+       py_dec_options = PyObject_GetAttrString(di->decoder->py_dec, "options");
+
+       /* All of these are synthesized objects, so they're good. */
+       py_dec_optkeys = PyDict_Keys(py_dec_options);
+       num_optkeys = PyList_Size(py_dec_optkeys);
+       if (!(py_di_options = PyObject_GetAttrString(di->py_inst, "options")))
+               goto err_out;
+       for (i = 0; i < num_optkeys; i++) {
+               /* Get the default class value for this option. */
+               py_str_as_str(PyList_GetItem(py_dec_optkeys, i), &key);
+               if (!(py_optlist = PyDict_GetItemString(py_dec_options, key)))
+                       goto err_out;
+               if (!(py_classval = PyList_GetItem(py_optlist, 1)))
+                       goto err_out;
+               if (!PyUnicode_Check(py_classval) && !PyLong_Check(py_classval)) {
+                       srd_err("Options of type %s are not yet supported.",
+                               Py_TYPE(py_classval)->tp_name);
+                       goto err_out;
+               }
+
+               if ((value = g_hash_table_lookup(options, key))) {
+                       /* An override for this option was provided. */
+                       if (PyUnicode_Check(py_classval)) {
+                               if (!(py_optval = PyUnicode_FromString(value))) {
+                                       /* Some UTF-8 encoding error. */
+                                       PyErr_Clear();
+                                       goto err_out;
+                               }
+                       } else if (PyLong_Check(py_classval)) {
+                               if (!(py_optval = PyLong_FromString(value, NULL, 0))) {
+                                       /* ValueError Exception */
+                                       PyErr_Clear();
+                                       srd_err("Option %s has invalid value "
+                                               "%s: expected integer.",
+                                               key, value);
+                                       goto err_out;
+                               }
+                       }
+                       g_hash_table_remove(options, key);
+               } else {
+                       /* Use the class default for this option. */
+                       if (PyUnicode_Check(py_classval)) {
+                               /* Make a brand new copy of the string. */
+                               py_ustr = PyUnicode_AS_UNICODE(py_classval);
+                               size = PyUnicode_GET_SIZE(py_classval);
+                               py_optval = PyUnicode_FromUnicode(py_ustr, size);
+                       } else if (PyLong_Check(py_classval)) {
+                               /* Make a brand new copy of the integer. */
+                               val_ull = PyLong_AsUnsignedLongLong(py_classval);
+                               if (val_ull == (unsigned long long)-1) {
+                                       /* OverFlowError exception */
+                                       PyErr_Clear();
+                                       srd_err("Invalid integer value for %s: "
+                                               "expected integer.", key);
+                                       goto err_out;
+                               }
+                               if (!(py_optval = PyLong_FromUnsignedLongLong(val_ull)))
+                                       goto err_out;
+                       }
+               }
+
+               /* If we got here, py_optval holds a known good new reference
+                * to the instance option to set.
+                */
+               if (PyDict_SetItemString(py_di_options, key, py_optval) == -1)
+                       goto err_out;
+       }
 
-       ret = PyRun_SimpleString("sys.path.append(r'" DECODERS_DIR "');");
+       ret = SRD_OK;
+
+err_out:
+       Py_XDECREF(py_optlist);
+       Py_XDECREF(py_di_options);
+       Py_XDECREF(py_dec_optkeys);
+       Py_XDECREF(py_dec_options);
+       g_free(key);
+       if (PyErr_Occurred())
+               catch_exception("Stray exception in srd_inst_set_options().");
 
        return ret;
 }
 
+/* Helper GComparefunc for g_slist_find_custom() in srd_inst_set_probes() */
+static gint compare_probe_id(struct srd_probe *a, char *probe_id)
+{
+       return strcmp(a->id, probe_id);
+}
 
-struct srd_decoder_instance *srd_instance_new(const char *id)
+/**
+ * Set probes in a decoder instance.
+ *
+ * @param di Decoder instance.
+ * @param probes A GHashTable of probes to set. Key is probe name, value is
+ *               the probe number. Samples passed to this instance will be
+ *               arranged in this order.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
+ */
+SRD_API int srd_inst_set_probes(struct srd_decoder_inst *di,
+                                   GHashTable *new_probes)
 {
+       GList *l;
+       GSList *sl;
+       struct srd_probe *p;
+       int *new_probemap, new_probenum;
+       char *probe_id, *probenum_str;
+
+       srd_dbg("set probes called for instance %s with list of %d probes",
+               di->inst_id, g_hash_table_size(new_probes));
+
+       if (g_hash_table_size(new_probes) == 0)
+               /* No probes provided. */
+               return SRD_OK;
+
+       if (di->dec_num_probes == 0) {
+               /* Decoder has no probes. */
+               srd_err("Protocol decoder %s has no probes to define.",
+                       di->decoder->name);
+               return SRD_ERR_ARG;
+       }
+
+       new_probemap = NULL;
+
+       if (!(new_probemap = g_try_malloc(sizeof(int) * di->dec_num_probes))) {
+               srd_err("Failed to g_malloc() new probe map.");
+               return SRD_ERR_MALLOC;
+       }
+
+       for (l = g_hash_table_get_keys(new_probes); l; l = l->next) {
+               probe_id = l->data;
+               probenum_str = g_hash_table_lookup(new_probes, probe_id);
+               if (!probenum_str) {
+                       /* Probe name was specified without a value. */
+                       srd_err("No probe number was specified for %s.",
+                               probe_id);
+                       g_free(new_probemap);
+                       return SRD_ERR_ARG;
+               }
+               new_probenum = strtol(probenum_str, NULL, 10);
+               if (!(sl = g_slist_find_custom(di->decoder->probes, probe_id,
+                               (GCompareFunc)compare_probe_id))) {
+                       /* Fall back on optional probes. */
+                       if (!(sl = g_slist_find_custom(di->decoder->opt_probes,
+                            probe_id, (GCompareFunc) compare_probe_id))) {
+                               srd_err("Protocol decoder %s has no probe "
+                                       "'%s'.", di->decoder->name, probe_id);
+                               g_free(new_probemap);
+                               return SRD_ERR_ARG;
+                       }
+               }
+               p = sl->data;
+               new_probemap[p->order] = new_probenum;
+               srd_dbg("setting probe mapping for %d = probe %d", p->order,
+                       new_probenum);
+       }
+       g_free(di->dec_probemap);
+       di->dec_probemap = new_probemap;
+
+       return SRD_OK;
+}
+
+/**
+ * Create a new protocol decoder instance.
+ *
+ * @param id Decoder 'id' field.
+ * @param options GHashtable of options which override the defaults set in
+ *                the decoder class.
+ *
+ * @return Pointer to a newly allocated struct srd_decoder_inst, or
+ *         NULL in case of failure.
+ */
+SRD_API struct srd_decoder_inst *srd_inst_new(const char *decoder_id,
+                                                     GHashTable *options)
+{
+       int i;
        struct srd_decoder *dec;
-       struct srd_decoder_instance *di;
-       PyObject *py_args;
+       struct srd_decoder_inst *di;
+       char *inst_id;
 
-       fprintf(stdout, "%s: %s\n", __func__, id);
+       srd_dbg("Creating new %s instance.", decoder_id);
 
-       if (!(dec = srd_get_decoder_by_id(id)))
+       if (!(dec = srd_get_decoder_by_id(decoder_id))) {
+               srd_err("Protocol decoder %s not found.", decoder_id);
                return NULL;
+       }
 
-       /* TODO: Error handling. Use g_try_malloc(). */
-       di = g_malloc(sizeof(*di));
+       if (!(di = g_try_malloc0(sizeof(struct srd_decoder_inst)))) {
+               srd_err("Failed to g_malloc() instance.");
+               return NULL;
+       }
+
+       inst_id = g_hash_table_lookup(options, "id");
        di->decoder = dec;
-       di->pd_output = NULL;
+       di->inst_id = g_strdup(inst_id ? inst_id : decoder_id);
+       g_hash_table_remove(options, "id");
+
+       /* Prepare a default probe map, where samples come in the
+        * order in which the decoder class defined them.
+        */
+       di->dec_num_probes = g_slist_length(di->decoder->probes) +
+                            g_slist_length(di->decoder->opt_probes);
+       if (di->dec_num_probes) {
+               if (!(di->dec_probemap =
+                    g_try_malloc(sizeof(int) * di->dec_num_probes))) {
+                       srd_err("Failed to g_malloc() probe map.");
+                       g_free(di);
+                       return NULL;
+               }
+               for (i = 0; i < di->dec_num_probes; i++)
+                       di->dec_probemap[i] = i;
+       }
 
-       /* Create an empty Python tuple. */
-       if (!(py_args = PyTuple_New(0))) { /* NEWREF */
+       /* Create a new instance of this decoder class. */
+       if (!(di->py_inst = PyObject_CallObject(dec->py_dec, NULL))) {
                if (PyErr_Occurred())
-                       PyErr_Print(); /* Returns void. */
-
-               return NULL; /* TODO: More specific error? */
+                       catch_exception("failed to create %s instance: ",
+                                       decoder_id);
+               g_free(di->dec_probemap);
+               g_free(di);
+               return NULL;
        }
 
-       /* Create an instance of the 'Decoder' class. */
-       di->py_instance = PyObject_Call(dec->py_decobj, py_args, NULL);
-       if (!di->py_instance) {
-               if (PyErr_Occurred())
-                       PyErr_Print(); /* Returns void. */
-               Py_XDECREF(py_args);
-               return NULL; /* TODO: More specific error? */
+       if (srd_inst_set_options(di, options) != SRD_OK) {
+               g_free(di->dec_probemap);
+               g_free(di);
+               return NULL;
        }
-       decoders = g_slist_append(decoders, di);
 
-       Py_XDECREF(py_args);
+       /* Instance takes input from a frontend by default. */
+       di_list = g_slist_append(di_list, di);
 
        return di;
 }
 
-
-int srd_instance_set_probe(struct srd_decoder_instance *di,
-                          const char *probename, int num)
+/**
+ * Stack a decoder instance on top of another.
+ *
+ * @param di_from The instance to move.
+ * @param di_to The instance on top of which di_from will be stacked.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
+ */
+SRD_API int srd_inst_stack(struct srd_decoder_inst *di_from,
+                              struct srd_decoder_inst *di_to)
 {
-       PyObject *probedict, *probenum;
-
-       probedict = PyObject_GetAttrString(di->py_instance, "probes"); /* NEWREF */
-       if (!probedict) {
-               if (PyErr_Occurred())
-                       PyErr_Print(); /* Returns void. */
-
-               return SRD_ERR_PYTHON; /* TODO: More specific error? */
+       if (!di_from || !di_to) {
+               srd_err("Invalid from/to instance pair.");
+               return SRD_ERR_ARG;
        }
 
-       probenum = PyInt_FromLong(num);
-       PyMapping_SetItemString(probedict, (char *)probename, probenum);
+       if (g_slist_find(di_list, di_to)) {
+               /* Remove from the unstacked list. */
+               di_list = g_slist_remove(di_list, di_to);
+       }
 
-       Py_XDECREF(probenum);
-       Py_XDECREF(probedict);
+       /* Stack on top of source di. */
+       di_from->next_di = g_slist_append(di_from->next_di, di_to);
 
        return SRD_OK;
 }
 
+/**
+ * Finds a decoder instance by its instance id, but only in the bottom
+ * level of instances -- instances already stacked on top of another one
+ * will not be found.
+ *
+ * @param inst_id The instance id to be found.
+ *
+ * @return Pointer to struct srd_decoder_inst, or NULL if not found.
+ */
+SRD_API struct srd_decoder_inst *srd_inst_find_by_id(char *inst_id)
+{
+       GSList *l;
+       struct srd_decoder_inst *tmp, *di;
+
+       di = NULL;
+       for (l = di_list; l; l = l->next) {
+               tmp = l->data;
+               if (!strcmp(tmp->inst_id, inst_id)) {
+                       di = tmp;
+                       break;
+               }
+       }
+
+       return di;
+}
 
-int srd_session_start(const char *driver, int unitsize, uint64_t starttime,
-               uint64_t samplerate)
+/**
+ * Finds a decoder instance by its Python object, i.e. that instance's
+ * instantiation of the sigrokdecode.Decoder class. This will recurse
+ * to find the instance anywhere in the stack tree.
+ *
+ * @param stack Pointer to a GSList of struct srd_decoder_inst,
+ *             indicating the stack to search. To start searching at the bottom
+ *             level of decoder instances, pass NULL.
+ * @param obj The Python class instantiation.
+ *
+ * @return Pointer to struct srd_decoder_inst, or NULL if not found.
+ */
+SRD_PRIV struct srd_decoder_inst *srd_inst_find_by_obj(GSList *stack,
+                                                             PyObject *obj)
 {
-       PyObject *py_res;
-       GSList *d;
-       struct srd_decoder_instance *di;
+       GSList *l;
+       struct srd_decoder_inst *tmp, *di;
+
+       di = NULL;
+       for (l = stack ? stack : di_list; di == NULL && l != NULL; l = l->next) {
+               tmp = l->data;
+               if (tmp->py_inst == obj)
+                       di = tmp;
+               else if (tmp->next_di)
+                       di = srd_inst_find_by_obj(tmp->next_di, obj);
+       }
 
-       fprintf(stdout, "%s: %s\n", __func__, driver);
+       return di;
+}
 
-       for (d = decoders; d; d = d->next) {
-               di = d->data;
-               if (!(py_res = PyObject_CallMethod(di->py_instance, "start",
-                                                "{s:s,s:i,s:d}",
-                                                "driver", driver,
-                                                "unitsize", unitsize,
-                                                "starttime", starttime))) {
-                       if (PyErr_Occurred())
-                               PyErr_Print(); /* Returns void. */
-
-                       return SRD_ERR_PYTHON; /* TODO: More specific error? */
-               }
-               Py_XDECREF(py_res);
+SRD_PRIV int srd_inst_start(struct srd_decoder_inst *di, PyObject *args)
+{
+       PyObject *py_name, *py_res;
+       GSList *l;
+       struct srd_decoder_inst *next_di;
+
+       srd_dbg("Calling start() method on protocol decoder instance %s.",
+               di->inst_id);
+
+       if (!(py_name = PyUnicode_FromString("start"))) {
+               srd_err("Unable to build Python object for 'start'.");
+               catch_exception("Protocol decoder instance %s: ",
+                               di->inst_id);
+               return SRD_ERR_PYTHON;
+       }
+
+       if (!(py_res = PyObject_CallMethodObjArgs(di->py_inst,
+                                                 py_name, args, NULL))) {
+               catch_exception("Protocol decoder instance %s: ",
+                               di->inst_id);
+               return SRD_ERR_PYTHON;
+       }
+
+       Py_DecRef(py_res);
+       Py_DecRef(py_name);
+
+       /* Start all the PDs stacked on top of this one. Pass along the
+        * metadata all the way from the bottom PD, even though it's only
+        * applicable to logic data for now.
+        */
+       for (l = di->next_di; l; l = l->next) {
+               next_di = l->data;
+               srd_inst_start(next_di, args);
        }
 
        return SRD_OK;
 }
 
-
 /**
  * Run the specified decoder function.
  *
- * @param dec TODO
- * @param inbuf TODO
- * @param inbuflen TODO
- * @param outbuf TODO
- * @param outbuflen TODO
+ * @param start_samplenum The starting sample number for the buffer's sample
+ *                       set, relative to the start of capture.
+ * @param di The decoder instance to call. Must not be NULL.
+ * @param inbuf The buffer to decode. Must not be NULL.
+ * @param inbuflen Length of the buffer. Must be > 0.
  *
  * @return SRD_OK upon success, a (negative) error code otherwise.
  */
-int srd_run_decoder(struct srd_decoder_instance *dec,
-                   uint8_t *inbuf, uint64_t inbuflen)
+SRD_PRIV int srd_inst_decode(uint64_t start_samplenum,
+                               struct srd_decoder_inst *di,
+                               uint8_t *inbuf, uint64_t inbuflen)
 {
-       PyObject *py_instance, *py_res;
-       /* FIXME: Don't have a timebase available here. Make one up. */
-       static int _timehack = 0;
-
-       _timehack += inbuflen;
+       PyObject *py_res;
+       srd_logic *logic;
+       uint64_t end_samplenum;
 
-//     fprintf(stdout, "%s: %s\n", __func__, dec->decoder->name);
+       srd_dbg("Calling decode() on instance %s with %d bytes starting "
+               "at sample %d.", di->inst_id, inbuflen, start_samplenum);
 
        /* Return an error upon unusable input. */
-       if (dec == NULL)
-               return SRD_ERR_ARGS; /* TODO: More specific error? */
-       if (inbuf == NULL)
-               return SRD_ERR_ARGS; /* TODO: More specific error? */
-       if (inbuflen == 0) /* No point in working on empty buffers. */
-               return SRD_ERR_ARGS; /* TODO: More specific error? */
-
-       /* TODO: Error handling. */
-       py_instance = dec->py_instance;
-       Py_XINCREF(py_instance);
-
-       if (!(py_res = PyObject_CallMethod(py_instance, "decode",
-                                          "{s:i,s:i,s:s#}",
-                                          "time", _timehack,
-                                          "duration", 10,
-                                          "data", inbuf, inbuflen))) { /* NEWREF */
-               if (PyErr_Occurred())
-                       PyErr_Print(); /* Returns void. */
+       if (!di) {
+               srd_dbg("empty decoder instance");
+               return SRD_ERR_ARG;
+       }
+       if (!inbuf) {
+               srd_dbg("NULL buffer pointer");
+               return SRD_ERR_ARG;
+       }
+       if (inbuflen == 0) {
+               srd_dbg("empty buffer");
+               return SRD_ERR_ARG;
+       }
 
+       /* Create new srd_logic object. Each iteration around the PD's loop
+        * will fill one sample into this object.
+        */
+       logic = PyObject_New(srd_logic, &srd_logic_type);
+       Py_INCREF(logic);
+       logic->di = di;
+       logic->start_samplenum = start_samplenum;
+       logic->itercnt = 0;
+       logic->inbuf = inbuf;
+       logic->inbuflen = inbuflen;
+       logic->sample = PyList_New(2);
+       Py_INCREF(logic->sample);
+
+       Py_IncRef(di->py_inst);
+       end_samplenum = start_samplenum + inbuflen / di->data_unitsize;
+       if (!(py_res = PyObject_CallMethod(di->py_inst, "decode",
+                                          "KKO", logic->start_samplenum,
+                                          end_samplenum, logic))) {
+               catch_exception("Protocol decoder instance %s: ",
+                               di->inst_id);
                return SRD_ERR_PYTHON; /* TODO: More specific error? */
        }
+       Py_DecRef(py_res);
 
-       Py_XDECREF(py_res);
        return SRD_OK;
 }
 
+SRD_PRIV void srd_inst_free(struct srd_decoder_inst *di)
+{
+       GSList *l;
+       struct srd_pd_output *pdo;
+
+       srd_dbg("Freeing instance %s", di->inst_id);
+
+       Py_DecRef(di->py_inst);
+       g_free(di->inst_id);
+       g_free(di->dec_probemap);
+       g_slist_free(di->next_di);
+       for (l = di->pd_output; l; l = l->next) {
+               pdo = l->data;
+               g_free(pdo->proto_id);
+               g_free(pdo);
+       }
+       g_slist_free(di->pd_output);
+}
+
+SRD_PRIV void srd_inst_free_all(GSList *stack)
+{
+       GSList *l;
+       struct srd_decoder_inst *di;
+
+       di = NULL;
+       for (l = stack ? stack : di_list; di == NULL && l != NULL; l = l->next) {
+               di = l->data;
+               if (di->next_di)
+                       srd_inst_free_all(di->next_di);
+               srd_inst_free(di);
+       }
+       if (!stack) {
+               g_slist_free(di_list);
+               di_list = NULL;
+       }
+}
+
+/**
+ * Start a decoding session.
+ *
+ * Decoders, instances and stack must have been prepared beforehand.
+ *
+ * @param num_probes The number of probes which the incoming feed will contain.
+ * @param unitsize The number of bytes per sample in the incoming feed.
+ * @param The samplerate of the incoming feed.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
+ */
+SRD_API int srd_session_start(int num_probes, int unitsize, uint64_t samplerate)
+{
+       PyObject *args;
+       GSList *d;
+       struct srd_decoder_inst *di;
+       int ret;
+
+       srd_dbg("Calling start() on all instances with %d probes, "
+               "unitsize %d samplerate %d.", num_probes, unitsize, samplerate);
+
+       /* Currently only one item of metadata is passed along to decoders,
+        * samplerate. This can be extended as needed.
+        */
+       if (!(args = Py_BuildValue("{s:l}", "samplerate", (long)samplerate))) {
+               srd_err("Unable to build Python object for metadata.");
+               return SRD_ERR_PYTHON;
+       }
+
+       /* Run the start() method on all decoders receiving frontend data. */
+       for (d = di_list; d; d = d->next) {
+               di = d->data;
+               di->data_num_probes = num_probes;
+               di->data_unitsize = unitsize;
+               di->data_samplerate = samplerate;
+               if ((ret = srd_inst_start(di, args) != SRD_OK))
+                       break;
+       }
 
-/* Feed logic samples to decoder session. */
-int srd_session_feed(uint8_t *inbuf, uint64_t inbuflen)
+       Py_DecRef(args);
+
+       return ret;
+}
+
+/**
+ * Feed a chunk of logic sample data to a running decoder session.
+ *
+ * @param start_samplenum The sample number of the first sample in this chunk.
+ * @param inbuf Pointer to sample data.
+ * @param inbuf Length in bytes of the buffer.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
+ */
+SRD_API int srd_session_feed(uint64_t start_samplenum, uint8_t *inbuf,
+                            uint64_t inbuflen)
 {
        GSList *d;
        int ret;
 
-//     fprintf(stdout, "%s: %d bytes\n", __func__, inbuflen);
+       srd_dbg("Calling decode() on all instances with starting sample "
+               "number %" PRIu64 ", %" PRIu64 " bytes at 0x%p",
+               start_samplenum, inbuflen, inbuf);
 
-       for (d = decoders; d; d = d->next) {
-               if ((ret = srd_run_decoder(d->data, inbuf, inbuflen)) != SRD_OK)
+       for (d = di_list; d; d = d->next) {
+               if ((ret = srd_inst_decode(start_samplenum, d->data, inbuf,
+                                              inbuflen)) != SRD_OK)
                        return ret;
        }
 
        return SRD_OK;
 }
 
+/**
+ * Register a decoder output callback function.
+ *
+ * The function will be called when a protocol decoder sends output back
+ * to the PD controller (except for Python objects, which only go up the
+ * stack).
+ *
+ * @param output_type The output type this callback will receive. Only one
+ * callback per output type can be registered.
+ * @param cb The function to call.
+ * @param user_data Unused.
+ */
+SRD_API int srd_register_callback(int output_type,
+                                 srd_pd_output_callback_t cb, void *user_data)
+{
+       struct srd_pd_callback *pd_cb;
 
-//int srd_pipeline_new(int plid)
-//{
-//
-//
-//}
-//
-//
-//int pd_output_new(int output_type, char *output_id, char *description)
-//{
-//
-//
-//}
+       srd_dbg("Registering new callback for output type %d.", output_type);
 
+       if (!(pd_cb = g_try_malloc(sizeof(struct srd_pd_callback)))) {
+               srd_err("Failed to g_malloc() struct srd_pd_callback.");
+               return SRD_ERR_MALLOC;
+       }
 
+       pd_cb->output_type = output_type;
+       pd_cb->callback = cb;
+       pd_cb->user_data = user_data;
+       callbacks = g_slist_append(callbacks, pd_cb);
 
+       return SRD_OK;
+}
 
+SRD_PRIV void *srd_find_callback(int output_type)
+{
+       GSList *l;
+       struct srd_pd_callback *pd_cb;
+       void *(cb);
+
+       cb = NULL;
+       for (l = callbacks; l; l = l->next) {
+               pd_cb = l->data;
+               if (pd_cb->output_type == output_type) {
+                       cb = pd_cb->callback;
+                       break;
+               }
+       }
+
+       return cb;
+}
+
+/* This is the backend function to Python sigrokdecode.add() call. */
+SRD_PRIV int pd_add(struct srd_decoder_inst *di, int output_type,
+                   char *proto_id)
+{
+       struct srd_pd_output *pdo;
+
+       srd_dbg("Instance %s creating new output type %d for %s.",
+               di->inst_id, output_type, proto_id);
+
+       if (!(pdo = g_try_malloc(sizeof(struct srd_pd_output)))) {
+               srd_err("Failed to g_malloc() struct srd_pd_output.");
+               return -1;
+       }
+
+       /* pdo_id is just a simple index, nothing is deleted from this list anyway. */
+       pdo->pdo_id = g_slist_length(di->pd_output);
+       pdo->output_type = output_type;
+       pdo->di = di;
+       pdo->proto_id = g_strdup(proto_id);
+       di->pd_output = g_slist_append(di->pd_output, pdo);
+
+       return pdo->pdo_id;
+}