X-Git-Url: https://sigrok.org/gitweb/?p=libsigrokdecode.git;a=blobdiff_plain;f=controller.c;h=cabca3b5edbf5a6acb57243d684291013142d7aa;hp=1ed852bea9b539ca8c3cf8c5379191617e130e0c;hb=0ff2d191726ef2e5a30ce697c7c93e4b0b1605f3;hpb=f9a3947a7a8d884de6c55693b216f89b1d27d979

diff --git a/controller.c b/controller.c
index 1ed852b..cabca3b 100644
--- a/controller.c
+++ b/controller.c
@@ -18,78 +18,157 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "config.h"
 #include "sigrokdecode.h" /* First, so we avoid a _POSIX_C_SOURCE warning. */
+#include "sigrokdecode-internal.h"
+#include "config.h"
 #include <glib.h>
 #include <inttypes.h>
+#include <stdlib.h>
+
+/**
+ * @mainpage libsigrokdecode API
+ *
+ * @section sec_intro Introduction
+ *
+ * The <a href="http://sigrok.org">sigrok</a> project aims at creating a
+ * portable, cross-platform, Free/Libre/Open-Source signal analysis software
+ * suite that supports various device types (such as logic analyzers,
+ * oscilloscopes, multimeters, and more).
+ *
+ * <a href="http://sigrok.org/wiki/Libsigrokdecode">libsigrokdecode</a> is a
+ * shared library written in C which provides the basic API for (streaming)
+ * protocol decoding functionality.
+ *
+ * The <a href="http://sigrok.org/wiki/Protocol_decoders">protocol decoders</a>
+ * are written in Python (>= 3.0).
+ *
+ * @section sec_api API reference
+ *
+ * See the "Modules" page for an introduction to various libsigrokdecode
+ * related topics and the detailed API documentation of the respective
+ * functions.
+ *
+ * You can also browse the API documentation by file, or review all
+ * data structures.
+ *
+ * @section sec_mailinglists Mailing lists
+ *
+ * There are two mailing lists for sigrok/libsigrokdecode: <a href="https://lists.sourceforge.net/lists/listinfo/sigrok-devel">sigrok-devel</a> and <a href="https://lists.sourceforge.net/lists/listinfo/sigrok-commits">sigrok-commits</a>.
+ *
+ * @section sec_irc IRC
+ *
+ * You can find the sigrok developers in the
+ * <a href="irc://chat.freenode.net/sigrok">\#sigrok</a>
+ * IRC channel on Freenode.
+ *
+ * @section sec_website Website
+ *
+ * <a href="http://sigrok.org/wiki/Libsigrokdecode">sigrok.org/wiki/Libsigrokdecode</a>
+ */
+
+/**
+ * @file
+ *
+ * Initializing and shutting down libsigrokdecode.
+ */
+
+/**
+ * @defgroup grp_init Initialization
+ *
+ * Initializing and shutting down libsigrokdecode.
+ *
+ * Before using any of the libsigrokdecode functionality, srd_init() must
+ * be called to initialize the library.
+ *
+ * When libsigrokdecode functionality is no longer needed, srd_exit() should
+ * be called.
+ *
+ * @{
+ */
 
+/* List of decoder instances. */
+static GSList *di_list = NULL;
 
+/* List of frontend callbacks to receive decoder output. */
 static GSList *callbacks = NULL;
 
-/* TODO
-static GSList *pipelines = NULL;
-struct srd_pipeline {
-	int id;
-	GSList *decoders;
-};
-*/
+/** @cond PRIVATE */
 
-/* lives in decoder.c */
-extern GSList *pd_list;
-extern GSList *di_list;
+/* decoder.c */
+extern SRD_PRIV GSList *pd_list;
 
-/* lives in module_sigrokdecode.c */
+/* module_sigrokdecode.c */
+/* FIXME: SRD_PRIV causes issues on MinGW. Investigate. */
 extern PyMODINIT_FUNC PyInit_sigrokdecode(void);
 
-/* lives in type_logic.c */
-extern PyTypeObject srd_logic_type;
+/* type_logic.c */
+extern SRD_PRIV PyTypeObject srd_logic_type;
 
+/** @endcond */
 
 /**
  * Initialize libsigrokdecode.
  *
  * This initializes the Python interpreter, and creates and initializes
- * a "sigrok" Python module with a single put() method.
+ * a "sigrokdecode" Python module.
  *
  * Then, it searches for sigrok protocol decoder files (*.py) in the
  * "decoders" subdirectory of the the sigrok installation directory.
  * All decoders that are found are loaded into memory and added to an
- * internal list of decoders, which can be queried via srd_list_decoders().
+ * internal list of decoders, which can be queried via srd_decoders_list().
  *
  * 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(const char *path)
 {
 	int ret;
+	char *env_path;
 
+	srd_dbg("Initializing libsigrokdecode.");
+
+	/* Add our own module to the list of built-in modules. */
 	PyImport_AppendInittab("sigrokdecode", PyInit_sigrokdecode);
 
-	/* Py_Initialize() returns void and usually cannot fail. */
+	/* Initialize the Python interpreter. */
 	Py_Initialize();
 
-	if ((ret = set_modulepath()) != SRD_OK) {
+	/* Installed decoders. */
+	if ((ret = srd_decoder_searchpath_add(DECODERS_DIR)) != SRD_OK) {
 		Py_Finalize();
 		return ret;
 	}
 
-	if ((ret = srd_load_all_decoders()) != SRD_OK) {
-		Py_Finalize();
-		return ret;
+	/* Path specified by the user. */
+	if (path) {
+		if ((ret = srd_decoder_searchpath_add(path)) != SRD_OK) {
+			Py_Finalize();
+			return ret;
+		}
+	}
+
+	/* Environment variable overrides everything, for debugging. */
+	if ((env_path = getenv("SIGROKDECODE_DIR"))) {
+		if ((ret = srd_decoder_searchpath_add(env_path)) != SRD_OK) {
+			Py_Finalize();
+			return ret;
+		}
 	}
 
 	return SRD_OK;
 }
 
-
 /**
  * Shutdown libsigrokdecode.
  *
@@ -98,16 +177,17 @@ 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_unload_all_decoders();
+	srd_dbg("Exiting libsigrokdecode.");
+
+	srd_decoder_unload_all();
 	g_slist_free(pd_list);
+	pd_list = NULL;
 
 	/* Py_Finalize() returns void, any finalization errors are ignored. */
 	Py_Finalize();
@@ -115,235 +195,731 @@ 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 the directory containing protocol decoders which shall
+ *             be added to the Python sys.path, or NULL.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
+ *
+ * @private
+ */
+SRD_PRIV int srd_decoder_searchpath_add(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.
+ * @defgroup grp_instances Decoder instances
  *
- * TODO: add path from env var SIGROKDECODE_PATH, config etc
+ * Decoder instance handling.
+ *
+ * @{
  */
-int set_modulepath(void)
+
+/**
+ * Set one or more options in a decoder instance.
+ *
+ * Handled options are removed from the hash.
+ *
+ * @param di Decoder instance.
+ * @param options A GHashTable of options to set.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
+ */
+SRD_API int srd_inst_option_set(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 = SRD_OK;
 
-	PyRun_SimpleString("import sys");
-	ret = PyRun_SimpleString("sys.path.append(r'" DECODERS_DIR "');");
+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())
+		srd_exception_catch("Stray exception in srd_inst_option_set().");
 
 	return ret;
 }
 
+/* Helper GComparefunc for g_slist_find_custom() in srd_inst_probe_set_all() */
+static gint compare_probe_id(const struct srd_probe *a, const char *probe_id)
+{
+	return strcmp(a->id, probe_id);
+}
 
-struct srd_decoder_instance *srd_instance_new(const char *id)
+/**
+ * Set all probes in a decoder instance.
+ *
+ * This function sets _all_ probes for the specified decoder instance, i.e.,
+ * it overwrites any probes that were already defined (if any).
+ *
+ * @param di Decoder instance.
+ * @param new_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_probe_set_all(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;
+	int i, num_required_probes;
+
+	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 now, map all indexes to probe -1 (can be overridden later).
+	 * This -1 is interpreted as an unspecified probe later.
+	 */
+	for (i = 0; i < di->dec_num_probes; i++)
+		new_probemap[i] = -1;
+
+	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: %s (index %d) = probe %d.",
+			p->id, p->order, new_probenum);
+	}
+
+	srd_dbg("Final probe map:");
+	num_required_probes = g_slist_length(di->decoder->probes);
+	for (i = 0; i < di->dec_num_probes; i++) {
+		srd_dbg(" - index %d = probe %d (%s)", i, new_probemap[i],
+		        (i < num_required_probes) ? "required" : "optional");
+	}
+
+	g_free(di->dec_probemap);
+	di->dec_probemap = new_probemap;
+
+	return SRD_OK;
+}
+
+/**
+ * Create a new protocol decoder instance.
+ *
+ * @param decoder_id Decoder 'id' field.
+ * @param options GHashtable of options which override the defaults set in
+ *                the decoder class. May be NULL.
+ *
+ * @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;
+
+	srd_dbg("Creating new %s instance.", decoder_id);
 
-	fprintf(stdout, "%s: %s\n", __func__, id);
+	if (!(dec = srd_decoder_get_by_id(decoder_id))) {
+		srd_err("Protocol decoder %s not found.", decoder_id);
+		return NULL;
+	}
 
-	if (!(dec = srd_get_decoder_by_id(id)))
+	if (!(di = g_try_malloc0(sizeof(struct srd_decoder_inst)))) {
+		srd_err("Failed to g_malloc() instance.");
 		return NULL;
+	}
 
-	/* TODO: Error handling. Use g_try_malloc(). */
-	di = g_malloc(sizeof(*di));
 	di->decoder = dec;
-	di->pd_output = NULL;
-	di->unitsize = 0;
+	if (options) {
+		inst_id = g_hash_table_lookup(options, "id");
+		di->inst_id = g_strdup(inst_id ? inst_id : decoder_id);
+		g_hash_table_remove(options, "id");
+	} else
+		di->inst_id = g_strdup(decoder_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? */
+			srd_exception_catch("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 (options && srd_inst_option_set(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)
+/**
+ * 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 = PyLong_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;
 }
 
+/**
+ * Find a decoder instance by its instance ID.
+ *
+ * Only the bottom level of instances are searched -- 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(const 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(int num_probes, int unitsize, uint64_t samplerate)
+/**
+ * Find a decoder instance by its Python object.
+ *
+ * I.e. find 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.
+ *
+ * @private
+ */
+SRD_PRIV struct srd_decoder_inst *srd_inst_find_by_obj(const GSList *stack,
+		const PyObject *obj)
 {
-	PyObject *py_res;
-	GSList *d;
-	struct srd_decoder_instance *di;
+	const 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\n", __func__);
+	return di;
+}
 
-	for (d = di_list; d; d = d->next) {
-		di = d->data;
-		di->num_probes = num_probes;
-		di->unitsize = unitsize;
-		di->samplerate = samplerate;
-		if (!(py_res = PyObject_CallMethod(di->py_instance, "start",
-				    "{s:l}",
-					"samplerate", (long)samplerate))) {
-			if (PyErr_Occurred())
-				PyErr_Print(); /* Returns void. */
-
-			return SRD_ERR_PYTHON; /* TODO: More specific error? */
-		}
-		Py_XDECREF(py_res);
+/** @private */
+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'.");
+		srd_exception_catch("Protocol decoder instance %s: ",
+				    di->inst_id);
+		return SRD_ERR_PYTHON;
+	}
+
+	if (!(py_res = PyObject_CallMethodObjArgs(di->py_inst,
+						  py_name, args, NULL))) {
+		srd_exception_catch("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.
+ *
+ * @private
  */
-int srd_run_decoder(uint64_t timeoffset, uint64_t duration,
-		struct srd_decoder_instance *di, uint8_t *inbuf, uint64_t inbuflen)
+SRD_PRIV int srd_inst_decode(uint64_t start_samplenum,
+		const struct srd_decoder_inst *di, const uint8_t *inbuf,
+		uint64_t inbuflen)
 {
-	PyObject *py_instance, *py_res;
+	PyObject *py_res;
 	srd_logic *logic;
+	uint64_t end_samplenum;
 
-	/* Return an error upon unusable input. */
-	if (di == 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? */
+	srd_dbg("Calling decode() on instance %s with %d bytes starting "
+		"at sample %d.", di->inst_id, inbuflen, start_samplenum);
 
-	/* TODO: Error handling. */
-	py_instance = di->py_instance;
-	Py_XINCREF(py_instance);
+	/* Return an error upon unusable input. */
+	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->di = (struct srd_decoder_inst *)di;
+	logic->start_samplenum = start_samplenum;
 	logic->itercnt = 0;
-	logic->inbuf = inbuf;
+	logic->inbuf = (uint8_t *)inbuf;
 	logic->inbuflen = inbuflen;
 	logic->sample = PyList_New(2);
 	Py_INCREF(logic->sample);
 
-	if (!(py_res = PyObject_CallMethod(py_instance, "decode",
-			"KKO", timeoffset, duration, logic))) {
-		if (PyErr_Occurred())
-			PyErr_Print(); /* Returns void. */
-
-		return SRD_ERR_PYTHON; /* TODO: More specific error? */
+	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))) {
+		srd_exception_catch("Protocol decoder instance %s: ",
+				    di->inst_id);
+		return SRD_ERR_PYTHON;
 	}
-
-	Py_XDECREF(py_res);
+	Py_DecRef(py_res);
 
 	return SRD_OK;
 }
 
-
-/* Feed logic samples to decoder session. */
-int srd_session_feed(uint64_t timeoffset, uint64_t duration, uint8_t *inbuf,
-		uint64_t inbuflen)
+/** @private */
+SRD_PRIV void srd_inst_free(struct srd_decoder_inst *di)
 {
-	GSList *d;
-	int ret;
+	GSList *l;
+	struct srd_pd_output *pdo;
 
-//	fprintf(stdout, "%s: %d bytes\n", __func__, inbuflen);
+	srd_dbg("Freeing instance %s", di->inst_id);
 
-	for (d = di_list; d; d = d->next) {
-		if ((ret = srd_run_decoder(timeoffset, duration, d->data, inbuf,
-				inbuflen)) != SRD_OK)
-			return ret;
+	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);
+}
 
-	return SRD_OK;
+/** @private */
+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;
+	}
 }
 
+/** @} */
+
+/**
+ * @defgroup grp_session Session handling
+ *
+ * Starting and handling decoding sessions.
+ *
+ * @{
+ */
 
-int pd_add(struct srd_decoder_instance *di, int output_type,
-		char *protocol_id)
+/**
+ * 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 samplerate 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)
 {
-	struct srd_pd_output *pdo;
+	PyObject *args;
+	GSList *d;
+	struct srd_decoder_inst *di;
+	int ret;
 
-	if (!(pdo = g_try_malloc(sizeof(struct srd_pd_output))))
-		return -1;
+	ret = SRD_OK;
 
-	/* pdo_id is just a simple index, nothing is deleted from this list anway */
-	pdo->pdo_id = g_slist_length(di->pd_output);
-	pdo->output_type = output_type;
-	pdo->decoder = di->decoder;
-	pdo->protocol_id = g_strdup(protocol_id);
-	di->pd_output = g_slist_append(di->pd_output, pdo);
+	srd_dbg("Calling start() on all instances with %d probes, "
+		"unitsize %d samplerate %d.", num_probes, unitsize, samplerate);
 
-	fprintf(stdout, "%s: output type %d, protocol_id %s, id %d\n",
-			__func__, output_type, protocol_id, pdo->pdo_id);
+	/*
+	 * 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;
+	}
 
-	return pdo->pdo_id;
+	/* 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;
 }
 
-struct srd_decoder_instance *get_di_by_decobject(void *decobject)
+/**
+ * Send 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 inbuflen Length in bytes of the buffer.
+ *
+ * @return SRD_OK upon success, a (negative) error code otherwise.
+ */
+SRD_API int srd_session_send(uint64_t start_samplenum, const uint8_t *inbuf,
+		uint64_t inbuflen)
 {
-	GSList *l;
-	struct srd_decoder_instance *di;
+	GSList *d;
+	int ret;
 
-	for (l = di_list; l; l = l->next) {
-		di = l->data;
-		if (decobject == di->py_instance)
-			return di;
+	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_inst_decode(start_samplenum, d->data, inbuf,
+					   inbuflen)) != SRD_OK)
+			return ret;
 	}
 
-	return NULL;
+	return SRD_OK;
 }
 
-int srd_register_callback(int output_type, void *cb)
+/**
+ * Register/add 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. Must not be NULL.
+ * @param cb_data Private data for the callback function. Can be NULL.
+ */
+SRD_API int srd_pd_output_callback_add(int output_type,
+		srd_pd_output_callback_t cb, void *cb_data)
 {
 	struct srd_pd_callback *pd_cb;
 
-	if (!(pd_cb = g_try_malloc(sizeof(struct srd_pd_callback))))
+	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->cb = cb;
+	pd_cb->cb_data = cb_data;
 	callbacks = g_slist_append(callbacks, pd_cb);
 
-	printf("got cb for %d: %p\n", output_type, cb);
 	return SRD_OK;
 }
 
-void *srd_find_callback(int output_type)
+/** @private */
+SRD_PRIV void *srd_pd_output_callback_find(int output_type)
 {
 	GSList *l;
 	struct srd_pd_callback *pd_cb;
@@ -353,7 +929,7 @@ void *srd_find_callback(int output_type)
 	for (l = callbacks; l; l = l->next) {
 		pd_cb = l->data;
 		if (pd_cb->output_type == output_type) {
-			cb = pd_cb->callback;
+			cb = pd_cb->cb;
 			break;
 		}
 	}
@@ -361,12 +937,29 @@ void *srd_find_callback(int output_type)
 	return cb;
 }
 
-//int srd_pipeline_new(int plid)
-//{
-//
-//
-//}
+/* This is the backend function to Python sigrokdecode.add() call. */
+/** @private */
+SRD_PRIV int srd_inst_pd_output_add(struct srd_decoder_inst *di,
+				    int output_type, const 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;
+}
 
+/** @} */