X-Git-Url: https://sigrok.org/gitweb/?p=libsigrokdecode.git;a=blobdiff_plain;f=controller.c;h=8b9f793750bc7c9658c5e7e3fd51fcdd0ea3d105;hp=efeef2808e70c56fe074f9309a8f389acf160d20;hb=65e1c7d091956e42aa4d97d7b639e10076e6f8ff;hpb=e508088229e96423854ba6db63084c9bb18eeb34

diff --git a/controller.c b/controller.c
index efeef28..8b9f793 100644
--- a/controller.c
+++ b/controller.c
@@ -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
@@ -18,156 +18,27 @@
  * 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;
 
-/* TODO
-static GSList *pipelines = NULL;
-*/
+/* decoder.c */
+extern SRD_PRIV GSList *pd_list;
 
-/* lives in decoder.c */
-extern GSList *pd_list;
-extern GSList *di_list;
+/* module_sigrokdecode.c */
+extern SRD_PRIV PyMODINIT_FUNC PyInit_sigrokdecode(void);
 
-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;
-}
-
-struct srd_decoder_instance *get_di_by_decobject(void *decobject);
-
-static PyObject *Decoder_put(PyObject *self, PyObject *args)
-{
-	GSList *l;
-	PyObject *data;
-	struct srd_decoder_instance *di;
-	struct srd_pd_output *pdo;
-	int output_id;
-
-	if (!(di = get_di_by_decobject(self)))
-		return NULL;
-
-	printf("put: %s instance %x: ", di->decoder->name, (unsigned int) di);
-
-	if (!PyArg_ParseTuple(args, "iO", &output_id, &data))
-		return NULL;
-
-	if (!(l = g_slist_nth(di->pd_output, output_id)))
-		/* PD supplied invalid output id */
-		/* TODO: better error message */
-		return NULL;
-	pdo = l->data;
-
-	printf("output type %d: ", pdo->output_type);
-	PyObject_Print(data, stdout, Py_PRINT_RAW);
-	puts("");
-
-	Py_RETURN_NONE;
-}
-
-
-static PyObject *Decoder_output_new(PyObject *self, PyObject *py_output_type)
-{
-	PyObject *ret;
-	struct srd_decoder_instance *di;
-	char *protocol_id, *description;
-	int output_type, pdo_id;
-
-	if (!(di = get_di_by_decobject(self)))
-		return NULL;
-
-	printf("output_new di %s\n", di->decoder->name);
-
-//	if (!PyArg_ParseTuple(args, "i:output_type,s:protocol_id,s:description",
-//			&output_type, &protocol_id, &description))
-	if (!PyArg_ParseTuple(py_output_type, "i:output_type", &output_type))
-		return NULL;
-
-	protocol_id = "i2c";
-	description = "blah";
-	pdo_id = pd_output_new(di, output_type, protocol_id, description);
-	if (pdo_id < 0)
-		Py_RETURN_NONE;
-	else
-		ret = Py_BuildValue("i", pdo_id);
-
-	return ret;
-}
-
-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"},
-	{"output_new", Decoder_output_new, METH_VARARGS,
-	 "Create a new output stream"},
-	{NULL, NULL, 0, NULL}
-};
-
-
-typedef struct {
-	PyObject_HEAD
-} sigrok_Decoder_object;
-
-static PyTypeObject sigrok_Decoder_type = {
-	PyObject_HEAD_INIT(NULL)
-	.tp_name = "sigrok.Decoder",
-	.tp_basicsize = sizeof(sigrok_Decoder_object),
-	.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
-	.tp_doc = "Sigrok Decoder object",
-	.tp_methods = Decoder_methods,
-};
-
-PyMODINIT_FUNC init_sigrok_Decoder(void)
-{
-	PyObject *mod;
-
-	/* assign this here, for compiler portability */
-	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);
-
-}
-
-
-struct srd_decoder_instance *get_di_by_decobject(void *decobject)
-{
-	GSList *l;
-	struct srd_decoder_instance *di;
-
-	for (l = di_list; l; l = l->next) {
-		di = l->data;
-		if (decobject == di->py_instance)
-			return di;
-	}
-
-	return NULL;
-}
+/* type_logic.c */
+extern SRD_PRIV PyTypeObject srd_logic_type;
 
 /**
  * Initialize libsigrokdecode.
@@ -183,29 +54,52 @@ struct srd_decoder_instance *get_di_by_decobject(void *decobject)
  * 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.");
 
-	init_sigrok_Decoder();
+	/* Add our own module to the list of built-in modules. */
+	PyImport_AppendInittab("sigrokdecode", PyInit_sigrokdecode);
 
-	PyRun_SimpleString("import sys;");
-	if ((ret = set_modulepath()) != SRD_OK) {
+	/* Initialize the Python interpreter. */
+	Py_Initialize();
+
+	/* 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;
@@ -214,7 +108,6 @@ int srd_init(void)
 	return SRD_OK;
 }
 
-
 /**
  * Shutdown libsigrokdecode.
  *
@@ -223,14 +116,14 @@ 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(pd_list);
 
@@ -240,216 +133,666 @@ 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;
+		}
 
-	ret = PyRun_SimpleString("sys.path.append(r'" DECODERS_DIR "');");
+		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 = 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;
 	}
-	di_list = g_slist_append(di_list, 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)
+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;
+}
+
+/**
+ * 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_API struct srd_decoder_inst *srd_inst_find_by_obj(GSList *stack,
+							      PyObject *obj)
+{
+	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);
+	}
 
-int srd_session_start(const char *driver, int unitsize, uint64_t starttime,
-		uint64_t samplerate)
+	return di;
+}
+
+SRD_API int srd_inst_start(struct srd_decoder_inst *di, PyObject *args)
 {
-	PyObject *py_res;
-	GSList *d;
-	struct srd_decoder_instance *di;
+	PyObject *py_name, *py_res;
+	GSList *l;
+	struct srd_decoder_inst *next_di;
 
-	fprintf(stdout, "%s: %s\n", __func__, driver);
+	srd_dbg("Calling start() method on protocol decoder instance %s.",
+		di->inst_id);
 
-	for (d = di_list; d; d = d->next) {
-		di = d->data;
-		if (!(py_res = PyObject_CallMethod(di->py_instance, "start",
-					"{s:s,s:l,s:l,s:l}",
-					"driver", driver,
-					"unitsize", (long)unitsize,
-					"starttime", (long)starttime,
-					"samplerate", (long)samplerate))) {
-			if (PyErr_Occurred())
-				PyErr_Print(); /* Returns void. */
-
-			return SRD_ERR_PYTHON; /* TODO: More specific error? */
-		}
-		Py_XDECREF(py_res);
+	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 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_API 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_ARG; /* TODO: More specific error? */
-	if (inbuf == NULL)
-		return SRD_ERR_ARG; /* TODO: More specific error? */
-	if (inbuflen == 0) /* No point in working on empty buffers. */
-		return SRD_ERR_ARG; /* 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_API 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_API 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;
+	}
+}
+
+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;
+	}
+
+	Py_DecRef(args);
+
+	return ret;
+}
 
 /* Feed logic samples to decoder session. */
-int srd_session_feed(uint8_t *inbuf, uint64_t inbuflen)
+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 = di_list; d; d = d->next) {
-		if ((ret = srd_run_decoder(d->data, inbuf, inbuflen)) != SRD_OK)
+		if ((ret = srd_inst_decode(start_samplenum, d->data, inbuf,
+					       inbuflen)) != SRD_OK)
 			return ret;
 	}
 
 	return SRD_OK;
 }
 
-
-int pd_output_new(struct srd_decoder_instance *di, int output_type,
-		char *protocol_id, char *description)
+SRD_API int srd_register_callback(int output_type,
+				  srd_pd_output_callback_t cb, void *user_data)
 {
-	GSList *l;
-	struct srd_pd_output *pdo;
-	int pdo_id;
+	struct srd_pd_callback *pd_cb;
 
-	fprintf(stdout, "%s: output type %d, protocol_id %s, description %s\n",
-			__func__, output_type, protocol_id, description);
+	srd_dbg("Registering new callback for output type %d.", output_type);
 
-	pdo_id = -1;
-	for (l = di->pd_output; l; l = l->next) {
-		pdo = l->data;
-		if (pdo->pdo_id > pdo_id)
-			pdo_id = pdo->pdo_id;
+	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;
 	}
-	pdo_id++;
 
-	if (!(pdo = g_try_malloc(sizeof(struct srd_pd_output))))
-		return -1;
+	pd_cb->output_type = output_type;
+	pd_cb->callback = cb;
+	pd_cb->user_data = user_data;
+	callbacks = g_slist_append(callbacks, pd_cb);
 
-	pdo->pdo_id = pdo_id;
-	pdo->output_type = output_type;
-	pdo->protocol_id = g_strdup(protocol_id);
-	pdo->description = g_strdup(description);
-	di->pd_output = g_slist_append(di->pd_output, pdo);
-
-	return pdo_id;
+	return SRD_OK;
 }
 
+SRD_API 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;
+}
 
-//int srd_pipeline_new(int plid)
-//{
-//
-//
-//}
+/* 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;
+}