X-Git-Url: https://sigrok.org/gitweb/?p=libsigrok.git;a=blobdiff_plain;f=src%2Fscpi%2Fscpi.c;h=c01791ef5ecebc8ac43300db1248a36081951f92;hp=f87bf9eba239325107a1903eb6d682bd6f282028;hb=4c7296644461e39cd06f5f5fa0898a4c189f43e1;hpb=d5a61aaf2d634c4558bda225e64e720104a0203f

diff --git a/src/scpi/scpi.c b/src/scpi/scpi.c
index f87bf9eb..c01791ef 100644
--- a/src/scpi/scpi.c
+++ b/src/scpi/scpi.c
@@ -2,6 +2,7 @@
  * This file is part of the libsigrok project.
  *
  * Copyright (C) 2013 poljar (Damir Jelić) <poljarinho@gmail.com>
+ * Copyright (C) 2015 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
@@ -29,6 +30,16 @@
 #define SCPI_READ_RETRIES 100
 #define SCPI_READ_RETRY_TIMEOUT_US (10 * 1000)
 
+static const char *scpi_vendors[][2] = {
+	{ "Agilent Technologies", "Agilent" },
+	{ "CHROMA", "Chroma" },
+	{ "Chroma ATE", "Chroma" },
+	{ "HEWLETT-PACKARD", "HP" },
+	{ "Keysight Technologies", "Keysight" },
+	{ "PHILIPS", "Philips" },
+	{ "RIGOL TECHNOLOGIES", "Rigol" },
+};
+
 /**
  * Parse a string representation of a boolean-like value into a gboolean.
  * Similar to sr_parse_boolstring but rejects strings which do not represent
@@ -89,7 +100,7 @@ static const struct sr_scpi_dev_inst *scpi_devs[] = {
 #ifdef HAVE_LIBGPIB
 	&scpi_libgpib_dev,
 #endif
-#ifdef HAVE_LIBSERIALPORT
+#ifdef HAVE_SERIAL_COMM
 	&scpi_serial_dev, /* Must be last as it matches any resource. */
 #endif
 };
@@ -122,6 +133,183 @@ static struct sr_dev_inst *sr_scpi_scan_resource(struct drv_context *drvc,
 	return sdi;
 }
 
+/**
+ * Send a SCPI command with a variadic argument list without mutex.
+ *
+ * @param scpi Previously initialized SCPI device structure.
+ * @param format Format string.
+ * @param args Argument list.
+ *
+ * @return SR_OK on success, SR_ERR on failure.
+ */
+static int scpi_send_variadic(struct sr_scpi_dev_inst *scpi,
+			 const char *format, va_list args)
+{
+	va_list args_copy;
+	char *buf;
+	int len, ret;
+
+	/* Get length of buffer required. */
+	va_copy(args_copy, args);
+	len = sr_vsnprintf_ascii(NULL, 0, format, args_copy);
+	va_end(args_copy);
+
+	/* Allocate buffer and write out command. */
+	buf = g_malloc0(len + 2);
+	sr_vsprintf_ascii(buf, format, args);
+	if (buf[len - 1] != '\n')
+		buf[len] = '\n';
+
+	/* Send command. */
+	ret = scpi->send(scpi->priv, buf);
+
+	/* Free command buffer. */
+	g_free(buf);
+
+	return ret;
+}
+
+/**
+ * Send a SCPI command without mutex.
+ *
+ * @param scpi Previously initialized SCPI device structure.
+ * @param format Format string, to be followed by any necessary arguments.
+ *
+ * @return SR_OK on success, SR_ERR on failure.
+ */
+static int scpi_send(struct sr_scpi_dev_inst *scpi, const char *format, ...)
+{
+	va_list args;
+	int ret;
+
+	va_start(args, format);
+	ret = scpi_send_variadic(scpi, format, args);
+	va_end(args);
+
+	return ret;
+}
+
+/**
+ * Send data to SCPI device without mutex.
+ *
+ * TODO: This is only implemented in TcpRaw, but never used.
+ * TODO: Use Mutex at all?
+ *
+ * @param scpi Previously initialised SCPI device structure.
+ * @param buf Buffer with data to send.
+ * @param len Number of bytes to send.
+ *
+ * @return Number of bytes read, or SR_ERR upon failure.
+ */
+static int scpi_write_data(struct sr_scpi_dev_inst *scpi, char *buf, int maxlen)
+{
+	return scpi->write_data(scpi->priv, buf, maxlen);
+}
+
+/**
+ * Read part of a response from SCPI device without mutex.
+ *
+ * @param scpi Previously initialised SCPI device structure.
+ * @param buf Buffer to store result.
+ * @param maxlen Maximum number of bytes to read.
+ *
+ * @return Number of bytes read, or SR_ERR upon failure.
+ */
+static int scpi_read_data(struct sr_scpi_dev_inst *scpi, char *buf, int maxlen)
+{
+	return scpi->read_data(scpi->priv, buf, maxlen);
+}
+
+/**
+ * Do a non-blocking read of up to the allocated length, and
+ * check if a timeout has occured, without mutex.
+ *
+ * @param scpi Previously initialised SCPI device structure.
+ * @param response Buffer to which the response is appended.
+ * @param abs_timeout_us Absolute timeout in microseconds
+ *
+ * @return read length on success, SR_ERR* on failure.
+ */
+static int scpi_read_response(struct sr_scpi_dev_inst *scpi,
+				GString *response, gint64 abs_timeout_us)
+{
+	int len, space;
+
+	space = response->allocated_len - response->len;
+	len = scpi->read_data(scpi->priv, &response->str[response->len], space);
+
+	if (len < 0) {
+		sr_err("Incompletely read SCPI response.");
+		return SR_ERR;
+	}
+
+	if (len > 0) {
+		g_string_set_size(response, response->len + len);
+		return len;
+	}
+
+	if (g_get_monotonic_time() > abs_timeout_us) {
+		sr_err("Timed out waiting for SCPI response.");
+		return SR_ERR_TIMEOUT;
+	}
+
+	return 0;
+}
+
+/**
+ * Send a SCPI command, receive the reply and store the reply in
+ * scpi_response, without mutex.
+ *
+ * @param scpi Previously initialised SCPI device structure.
+ * @param command The SCPI command to send to the device.
+ * @param scpi_response Pointer where to store the SCPI response.
+ *
+ * @return SR_OK on success, SR_ERR on failure.
+ */
+static int scpi_get_data(struct sr_scpi_dev_inst *scpi,
+				const char *command, GString **scpi_response)
+{
+	int ret;
+	GString *response;
+	int space;
+	gint64 timeout;
+
+	/* Optionally send caller provided command. */
+	if (command) {
+		if (scpi_send(scpi, command) != SR_OK)
+			return SR_ERR;
+	}
+
+	/* Initiate SCPI read operation. */
+	if (sr_scpi_read_begin(scpi) != SR_OK)
+		return SR_ERR;
+
+	/* Keep reading until completion or until timeout. */
+	timeout = g_get_monotonic_time() + scpi->read_timeout_us;
+
+	response = *scpi_response;
+
+	while (!sr_scpi_read_complete(scpi)) {
+		/* Resize the buffer when free space drops below a threshold. */
+		space = response->allocated_len - response->len;
+		if (space < 128) {
+			int oldlen = response->len;
+			g_string_set_size(response, oldlen + 1024);
+			g_string_set_size(response, oldlen);
+		}
+
+		/* Read another chunk of the response. */
+		ret = scpi_read_response(scpi, response, timeout);
+
+		if (ret < 0)
+			return ret;
+		if (ret > 0)
+			timeout = g_get_monotonic_time() + scpi->read_timeout_us;
+	}
+
+	return SR_OK;
+}
+
 SR_PRIV GSList *sr_scpi_scan(struct drv_context *drvc, GSList *options,
 		struct sr_dev_inst *(*probe_device)(struct sr_scpi_dev_inst *scpi))
 {
@@ -190,7 +378,7 @@ SR_PRIV struct sr_scpi_dev_inst *scpi_dev_inst_new(struct drv_context *drvc,
 			scpi = g_malloc(sizeof(*scpi));
 			*scpi = *scpi_dev;
 			scpi->priv = g_malloc0(scpi->priv_size);
-			scpi->read_timeout_ms = 1000;
+			scpi->read_timeout_us = 1000 * 1000;
 			params = g_strsplit(resource, "/", 0);
 			if (scpi->dev_inst_new(scpi->priv, drvc, resource,
 			                       params, serialcomm) != SR_OK) {
@@ -214,9 +402,26 @@ SR_PRIV struct sr_scpi_dev_inst *scpi_dev_inst_new(struct drv_context *drvc,
  */
 SR_PRIV int sr_scpi_open(struct sr_scpi_dev_inst *scpi)
 {
+	g_mutex_init(&scpi->scpi_mutex);
+
 	return scpi->open(scpi);
 }
 
+/**
+ * Get the connection ID of the SCPI device.
+ *
+ * @param scpi Previously initialized SCPI device structure.
+ * @param connection_id Pointer where to store the connection ID. The caller
+ *        is responsible for g_free()ing the string when it is no longer needed.
+ *
+ * @return SR_OK on success, SR_ERR on failure.
+ */
+SR_PRIV int sr_scpi_connection_id(struct sr_scpi_dev_inst *scpi,
+		char **connection_id)
+{
+	return scpi->connection_id(scpi, connection_id);
+}
+
 /**
  * Add an event source for an SCPI device.
  *
@@ -268,7 +473,9 @@ SR_PRIV int sr_scpi_send(struct sr_scpi_dev_inst *scpi,
 	int ret;
 
 	va_start(args, format);
-	ret = sr_scpi_send_variadic(scpi, format, args);
+	g_mutex_lock(&scpi->scpi_mutex);
+	ret = scpi_send_variadic(scpi, format, args);
+	g_mutex_unlock(&scpi->scpi_mutex);
 	va_end(args);
 
 	return ret;
@@ -286,26 +493,11 @@ SR_PRIV int sr_scpi_send(struct sr_scpi_dev_inst *scpi,
 SR_PRIV int sr_scpi_send_variadic(struct sr_scpi_dev_inst *scpi,
 			 const char *format, va_list args)
 {
-	va_list args_copy;
-	char *buf;
-	int len, ret;
-
-	/* Get length of buffer required. */
-	va_copy(args_copy, args);
-	len = vsnprintf(NULL, 0, format, args_copy);
-	va_end(args_copy);
-
-	/* Allocate buffer and write out command. */
-	buf = g_malloc0(len + 2);
-	vsprintf(buf, format, args);
-	if (buf[len - 1] != '\n')
-		buf[len] = '\n';
+	int ret;
 
-	/* Send command. */
-	ret = scpi->send(scpi->priv, buf);
-
-	/* Free command buffer. */
-	g_free(buf);
+	g_mutex_lock(&scpi->scpi_mutex);
+	ret = scpi_send_variadic(scpi, format, args);
+	g_mutex_unlock(&scpi->scpi_mutex);
 
 	return ret;
 }
@@ -334,7 +526,37 @@ SR_PRIV int sr_scpi_read_begin(struct sr_scpi_dev_inst *scpi)
 SR_PRIV int sr_scpi_read_data(struct sr_scpi_dev_inst *scpi,
 			char *buf, int maxlen)
 {
-	return scpi->read_data(scpi->priv, buf, maxlen);
+	int ret;
+
+	g_mutex_lock(&scpi->scpi_mutex);
+	ret = scpi_read_data(scpi, buf, maxlen);
+	g_mutex_unlock(&scpi->scpi_mutex);
+
+	return ret;
+}
+
+/**
+ * Send data to SCPI device.
+ *
+ * TODO: This is only implemented in TcpRaw, but never used.
+ * TODO: Use Mutex at all?
+ *
+ * @param scpi Previously initialised SCPI device structure.
+ * @param buf Buffer with data to send.
+ * @param len Number of bytes to send.
+ *
+ * @return Number of bytes read, or SR_ERR upon failure.
+ */
+SR_PRIV int sr_scpi_write_data(struct sr_scpi_dev_inst *scpi,
+			char *buf, int maxlen)
+{
+	int ret;
+
+	g_mutex_lock(&scpi->scpi_mutex);
+	ret = scpi_write_data(scpi, buf, maxlen);
+	g_mutex_unlock(&scpi->scpi_mutex);
+
+	return ret;
 }
 
 /**
@@ -358,20 +580,30 @@ SR_PRIV int sr_scpi_read_complete(struct sr_scpi_dev_inst *scpi)
  */
 SR_PRIV int sr_scpi_close(struct sr_scpi_dev_inst *scpi)
 {
-	return scpi->close(scpi);
+	int ret;
+
+	g_mutex_lock(&scpi->scpi_mutex);
+	ret = scpi->close(scpi);
+	g_mutex_unlock(&scpi->scpi_mutex);
+	g_mutex_clear(&scpi->scpi_mutex);
+
+	return ret;
 }
 
 /**
  * Free SCPI device.
  *
- * @param scpi Previously initialized SCPI device structure.
- *
- * @return SR_OK on success, SR_ERR on failure.
+ * @param scpi Previously initialized SCPI device structure. If NULL,
+ *             this function does nothing.
  */
 SR_PRIV void sr_scpi_free(struct sr_scpi_dev_inst *scpi)
 {
+	if (!scpi)
+		return;
+
 	scpi->free(scpi->priv);
 	g_free(scpi->priv);
+	g_free(scpi->actual_channel_name);
 	g_free(scpi);
 }
 
@@ -388,8 +620,10 @@ SR_PRIV int sr_scpi_get_string(struct sr_scpi_dev_inst *scpi,
 			       const char *command, char **scpi_response)
 {
 	GString *response;
-	response = g_string_sized_new(1024);
 
+	*scpi_response = NULL;
+
+	response = g_string_sized_new(1024);
 	if (sr_scpi_get_data(scpi, command, &response) != SR_OK) {
 		if (response)
 			g_string_free(response, TRUE);
@@ -412,53 +646,38 @@ SR_PRIV int sr_scpi_get_string(struct sr_scpi_dev_inst *scpi,
 	return SR_OK;
 }
 
-SR_PRIV int sr_scpi_get_data(struct sr_scpi_dev_inst *scpi,
-			     const char *command, GString **scpi_response)
+/**
+ * Do a non-blocking read of up to the allocated length, and
+ * check if a timeout has occured.
+ *
+ * @param scpi Previously initialised SCPI device structure.
+ * @param response Buffer to which the response is appended.
+ * @param abs_timeout_us Absolute timeout in microseconds
+ *
+ * @return read length on success, SR_ERR* on failure.
+ */
+SR_PRIV int sr_scpi_read_response(struct sr_scpi_dev_inst *scpi,
+				  GString *response, gint64 abs_timeout_us)
 {
-	int len;
-	GString *response;
-	gint64 laststart;
-	unsigned int elapsed_ms;
-	unsigned int offset;
-	int space;
-
-	if (command) {
-		if (sr_scpi_send(scpi, command) != SR_OK)
-			return SR_ERR;
-	}
-
-	if (sr_scpi_read_begin(scpi) != SR_OK)
-		return SR_ERR;
+	int ret;
 
-	laststart = g_get_monotonic_time();
+	g_mutex_lock(&scpi->scpi_mutex);
+	ret = scpi_read_response(scpi, response, abs_timeout_us);
+	g_mutex_unlock(&scpi->scpi_mutex);
 
-	response = *scpi_response;
+	return ret;
+}
 
-	offset = response->len;
+SR_PRIV int sr_scpi_get_data(struct sr_scpi_dev_inst *scpi,
+			     const char *command, GString **scpi_response)
+{
+	int ret;
 
-	while (!sr_scpi_read_complete(scpi)) {
-		space = response->allocated_len - response->len;
-		if (space < 128) {
-			g_string_set_size(response, response->len + 1024);
-			space = response->allocated_len - response->len;
-		}
-		len = sr_scpi_read_data(scpi, &response->str[offset], space);
-		if (len < 0) {
-			sr_err("Incompletely read SCPI response.");
-			return SR_ERR;
-		} else if (len > 0) {
-			laststart = g_get_monotonic_time();
-		}
-		offset += len;
-		g_string_set_size(response, offset);
-		elapsed_ms = (g_get_monotonic_time() - laststart) / 1000;
-		if (elapsed_ms >= scpi->read_timeout_ms) {
-			sr_err("Timed out waiting for SCPI response.");
-			return SR_ERR;
-		}
-	}
+	g_mutex_lock(&scpi->scpi_mutex);
+	ret = scpi_get_data(scpi, command, scpi_response);
+	g_mutex_unlock(&scpi->scpi_mutex);
 
-	return SR_OK;
+	return ret;
 }
 
 /**
@@ -507,6 +726,7 @@ SR_PRIV int sr_scpi_get_int(struct sr_scpi_dev_inst *scpi,
 			    const char *command, int *scpi_response)
 {
 	int ret;
+	struct sr_rational ret_rational;
 	char *response;
 
 	response = NULL;
@@ -515,10 +735,14 @@ SR_PRIV int sr_scpi_get_int(struct sr_scpi_dev_inst *scpi,
 	if (ret != SR_OK && !response)
 		return ret;
 
-	if (sr_atoi(response, scpi_response) == SR_OK)
-		ret = SR_OK;
-	else
+	ret = sr_parse_rational(response, &ret_rational);
+	if (ret == SR_OK && (ret_rational.p % ret_rational.q) == 0) {
+		*scpi_response = ret_rational.p / ret_rational.q;
+	} else {
+		sr_dbg("get_int: non-integer rational=%" PRId64 "/%" PRIu64,
+			ret_rational.p, ret_rational.q);
 		ret = SR_ERR_DATA;
+	}
 
 	g_free(response);
 
@@ -579,7 +803,7 @@ SR_PRIV int sr_scpi_get_double(struct sr_scpi_dev_inst *scpi,
 	if (ret != SR_OK && !response)
 		return ret;
 
-	if (sr_atod(response, scpi_response) == SR_OK)
+	if (sr_atod_ascii(response, scpi_response) == SR_OK)
 		ret = SR_OK;
 	else
 		ret = SR_ERR_DATA;
@@ -603,6 +827,7 @@ SR_PRIV int sr_scpi_get_opc(struct sr_scpi_dev_inst *scpi)
 	gboolean opc;
 
 	for (i = 0; i < SCPI_READ_RETRIES; i++) {
+		opc = FALSE;
 		sr_scpi_get_bool(scpi, SCPI_CMD_OPC, &opc);
 		if (opc)
 			return SR_OK;
@@ -634,6 +859,7 @@ SR_PRIV int sr_scpi_get_floatv(struct sr_scpi_dev_inst *scpi,
 	gchar **ptr, **tokens;
 	GArray *response_array;
 
+	*scpi_response = NULL;
 	response = NULL;
 	tokens = NULL;
 
@@ -660,7 +886,6 @@ SR_PRIV int sr_scpi_get_floatv(struct sr_scpi_dev_inst *scpi,
 
 	if (ret != SR_OK && response_array->len == 0) {
 		g_array_free(response_array, TRUE);
-		*scpi_response = NULL;
 		return SR_ERR_DATA;
 	}
 
@@ -690,6 +915,7 @@ SR_PRIV int sr_scpi_get_uint8v(struct sr_scpi_dev_inst *scpi,
 	gchar **ptr, **tokens;
 	GArray *response_array;
 
+	*scpi_response = NULL;
 	response = NULL;
 	tokens = NULL;
 
@@ -716,7 +942,6 @@ SR_PRIV int sr_scpi_get_uint8v(struct sr_scpi_dev_inst *scpi,
 
 	if (response_array->len == 0) {
 		g_array_free(response_array, TRUE);
-		*scpi_response = NULL;
 		return SR_ERR_DATA;
 	}
 
@@ -743,23 +968,44 @@ SR_PRIV int sr_scpi_get_block(struct sr_scpi_dev_inst *scpi,
 {
 	int ret;
 	GString* response;
+	gsize oldlen;
 	char buf[10];
 	long llen;
 	long datalen;
+	gint64 timeout;
+
+	*scpi_response = NULL;
+
+	g_mutex_lock(&scpi->scpi_mutex);
+
+	if (command)
+		if (scpi_send(scpi, command) != SR_OK) {
+			g_mutex_unlock(&scpi->scpi_mutex);
+			return SR_ERR;
+		}
+
+	if (sr_scpi_read_begin(scpi) != SR_OK) {
+		g_mutex_unlock(&scpi->scpi_mutex);
+		return SR_ERR;
+	}
 
 	/*
 	 * Assume an initial maximum length, optionally gets adjusted below.
 	 * Prepare a NULL return value for when error paths will be taken.
 	 */
 	response = g_string_sized_new(1024);
-	*scpi_response = NULL;
+
+	timeout = g_get_monotonic_time() + scpi->read_timeout_us;
 
 	/* Get (the first chunk of) the response. */
-	ret = sr_scpi_get_data(scpi, command, &response);
-	if (ret != SR_OK) {
-		g_string_free(response, TRUE);
-		return ret;
-	}
+	do {
+		ret = scpi_read_response(scpi, response, timeout);
+		if (ret < 0) {
+			g_mutex_unlock(&scpi->scpi_mutex);
+			g_string_free(response, TRUE);
+			return ret;
+		}
+	} while (response->len < 2);
 
 	/*
 	 * SCPI protocol data blocks are preceeded with a length spec.
@@ -773,6 +1019,7 @@ SR_PRIV int sr_scpi_get_block(struct sr_scpi_dev_inst *scpi,
 	 * the input buffer, leaving just the data bytes.
 	 */
 	if (response->str[0] != '#') {
+		g_mutex_unlock(&scpi->scpi_mutex);
 		g_string_free(response, TRUE);
 		return SR_ERR_DATA;
 	}
@@ -780,41 +1027,67 @@ SR_PRIV int sr_scpi_get_block(struct sr_scpi_dev_inst *scpi,
 	buf[1] = '\0';
 	ret = sr_atol(buf, &llen);
 	if ((ret != SR_OK) || (llen == 0)) {
+		g_mutex_unlock(&scpi->scpi_mutex);
 		g_string_free(response, TRUE);
 		return ret;
 	}
+
+	while (response->len < (unsigned long)(2 + llen)) {
+		ret = scpi_read_response(scpi, response, timeout);
+		if (ret < 0) {
+			g_mutex_unlock(&scpi->scpi_mutex);
+			g_string_free(response, TRUE);
+			return ret;
+		}
+	}
+
 	memcpy(buf, &response->str[2], llen);
 	buf[llen] = '\0';
 	ret = sr_atol(buf, &datalen);
 	if ((ret != SR_OK) || (datalen == 0)) {
+		g_mutex_unlock(&scpi->scpi_mutex);
 		g_string_free(response, TRUE);
 		return ret;
 	}
 	g_string_erase(response, 0, 2 + llen);
 
 	/*
-	 * If the initially assumed length does not cover the data block
-	 * length, then re-allocate the buffer size to the now known
-	 * length, and keep reading more chunks of response data.
+	 * Re-allocate the buffer size to the now known length
+	 * and keep reading more chunks of response data.
 	 */
-	if (response->len < (unsigned long)(datalen)) {
-		int oldlen = response->len;
-		g_string_set_size(response, datalen);
-		g_string_set_size(response, oldlen);
-	}
-	while (response->len < (unsigned long)(datalen)) {
-		ret = sr_scpi_get_data(scpi, NULL, &response);
-		if (ret != SR_OK) {
-			g_string_free(response, TRUE);
-			return ret;
-		}
+	oldlen = response->len;
+	g_string_set_size(response, datalen);
+	g_string_set_size(response, oldlen);
+
+	if (oldlen < (unsigned long)(datalen)) {
+		do {
+			oldlen = response->len;
+			ret = scpi_read_response(scpi, response, timeout);
+
+			/* On timeout truncate the buffer and send the partial response
+			 * instead of getting stuck on timeouts...
+			 */
+			if (ret == SR_ERR_TIMEOUT) {
+				datalen = oldlen;
+				break;
+			}
+			if (ret < 0) {
+				g_mutex_unlock(&scpi->scpi_mutex);
+				g_string_free(response, TRUE);
+				return ret;
+			}
+			if (ret > 0)
+				timeout = g_get_monotonic_time() + scpi->read_timeout_us;
+		} while (response->len < (unsigned long)(datalen));
 	}
 
+	g_mutex_unlock(&scpi->scpi_mutex);
+
 	/* Convert received data to byte array. */
 	*scpi_response = g_byte_array_new_take(
 		(guint8*)g_string_free(response, FALSE), datalen);
 
-	return ret;
+	return SR_OK;
 }
 
 /**
@@ -835,7 +1108,9 @@ SR_PRIV int sr_scpi_get_hw_id(struct sr_scpi_dev_inst *scpi,
 	char *response;
 	gchar **tokens;
 	struct sr_scpi_hw_info *hw_info;
+	gchar *idn_substr;
 
+	*scpi_response = NULL;
 	response = NULL;
 	tokens = NULL;
 
@@ -843,30 +1118,46 @@ SR_PRIV int sr_scpi_get_hw_id(struct sr_scpi_dev_inst *scpi,
 	if (ret != SR_OK && !response)
 		return ret;
 
-	sr_info("Got IDN string: '%s'", response);
-
 	/*
 	 * The response to a '*IDN?' is specified by the SCPI spec. It contains
 	 * a comma-separated list containing the manufacturer name, instrument
 	 * model, serial number of the instrument and the firmware version.
+	 *
+	 * BEWARE! Although strictly speaking a smaller field count is invalid,
+	 * this implementation also accepts IDN responses with one field less,
+	 * and assumes that the serial number is missing. Some GWInstek DMMs
+	 * were found to do this. Keep warning about this condition, which may
+	 * need more consideration later.
 	 */
 	tokens = g_strsplit(response, ",", 0);
-
-	for (num_tokens = 0; tokens[num_tokens] != NULL; num_tokens++);
-
-	if (num_tokens < 4) {
-		sr_dbg("IDN response not according to spec: %80.s.", response);
+	num_tokens = g_strv_length(tokens);
+	if (num_tokens < 3) {
+		sr_dbg("IDN response not according to spec: '%s'", response);
 		g_strfreev(tokens);
 		g_free(response);
 		return SR_ERR_DATA;
 	}
+	if (num_tokens < 4) {
+		sr_warn("Short IDN response, assume missing serial number.");
+	}
 	g_free(response);
 
 	hw_info = g_malloc0(sizeof(struct sr_scpi_hw_info));
-	hw_info->manufacturer = g_strstrip(g_strdup(tokens[0]));
+
+	idn_substr = g_strstr_len(tokens[0], -1, "IDN ");
+	if (idn_substr == NULL)
+		hw_info->manufacturer = g_strstrip(g_strdup(tokens[0]));
+	else
+		hw_info->manufacturer = g_strstrip(g_strdup(idn_substr + 4));
+
 	hw_info->model = g_strstrip(g_strdup(tokens[1]));
-	hw_info->serial_number = g_strstrip(g_strdup(tokens[2]));
-	hw_info->firmware_version = g_strstrip(g_strdup(tokens[3]));
+	if (num_tokens < 4) {
+		hw_info->serial_number = g_strdup("Unknown");
+		hw_info->firmware_version = g_strstrip(g_strdup(tokens[2]));
+	} else {
+		hw_info->serial_number = g_strstrip(g_strdup(tokens[2]));
+		hw_info->firmware_version = g_strstrip(g_strdup(tokens[3]));
+	}
 
 	g_strfreev(tokens);
 
@@ -878,17 +1169,216 @@ SR_PRIV int sr_scpi_get_hw_id(struct sr_scpi_dev_inst *scpi,
 /**
  * Free a sr_scpi_hw_info struct.
  *
- * @param hw_info Pointer to the struct to free.
- *
- * This function is safe to call with a NULL pointer.
+ * @param hw_info Pointer to the struct to free. If NULL, this
+ *                function does nothing.
  */
 SR_PRIV void sr_scpi_hw_info_free(struct sr_scpi_hw_info *hw_info)
 {
-	if (hw_info) {
-		g_free(hw_info->manufacturer);
-		g_free(hw_info->model);
-		g_free(hw_info->serial_number);
-		g_free(hw_info->firmware_version);
-		g_free(hw_info);
+	if (!hw_info)
+		return;
+
+	g_free(hw_info->manufacturer);
+	g_free(hw_info->model);
+	g_free(hw_info->serial_number);
+	g_free(hw_info->firmware_version);
+	g_free(hw_info);
+}
+
+/**
+ * Remove potentially enclosing pairs of quotes, un-escape content.
+ * This implementation modifies the caller's buffer when quotes are found
+ * and doubled quote characters need to get removed from the content.
+ *
+ * @param[in, out] s	The SCPI string to check and un-quote.
+ *
+ * @return The start of the un-quoted string.
+ */
+SR_PRIV const char *sr_scpi_unquote_string(char *s)
+{
+	size_t s_len;
+	char quotes[3];
+	char *rdptr;
+
+	/* Immediately bail out on invalid or short input. */
+	if (!s || !*s)
+		return s;
+	s_len = strlen(s);
+	if (s_len < 2)
+		return s;
+
+	/* Check for matching quote characters front and back. */
+	if (s[0] != '\'' && s[0] != '"')
+		return s;
+	if (s[0] != s[s_len - 1])
+		return s;
+
+	/* Need to strip quotes, and un-double quote chars inside. */
+	quotes[0] = quotes[1] = *s;
+	quotes[2] = '\0';
+	s[s_len - 1] = '\0';
+	s++;
+	rdptr = s;
+	while ((rdptr = strstr(rdptr, quotes)) != NULL) {
+		memmove(rdptr, rdptr + 1, strlen(rdptr));
+		rdptr++;
+	}
+
+	return s;
+}
+
+SR_PRIV const char *sr_vendor_alias(const char *raw_vendor)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(scpi_vendors); i++) {
+		if (!g_ascii_strcasecmp(raw_vendor, scpi_vendors[i][0]))
+			return scpi_vendors[i][1];
+	}
+
+	return raw_vendor;
+}
+
+SR_PRIV const char *sr_scpi_cmd_get(const struct scpi_command *cmdtable,
+		int command)
+{
+	unsigned int i;
+	const char *cmd;
+
+	if (!cmdtable)
+		return NULL;
+
+	cmd = NULL;
+	for (i = 0; cmdtable[i].string; i++) {
+		if (cmdtable[i].command == command) {
+			cmd = cmdtable[i].string;
+			break;
+		}
+	}
+
+	return cmd;
+}
+
+SR_PRIV int sr_scpi_cmd(const struct sr_dev_inst *sdi,
+		const struct scpi_command *cmdtable,
+		int channel_command, const char *channel_name,
+		int command, ...)
+{
+	struct sr_scpi_dev_inst *scpi;
+	va_list args;
+	int ret;
+	const char *channel_cmd;
+	const char *cmd;
+
+	scpi = sdi->conn;
+
+	if (!(cmd = sr_scpi_cmd_get(cmdtable, command))) {
+		/* Device does not implement this command, that's OK. */
+		return SR_OK;
+	}
+
+	g_mutex_lock(&scpi->scpi_mutex);
+
+	/* Select channel. */
+	channel_cmd = sr_scpi_cmd_get(cmdtable, channel_command);
+	if (channel_cmd && channel_name &&
+			g_strcmp0(channel_name, scpi->actual_channel_name)) {
+		sr_spew("sr_scpi_cmd(): new channel = %s", channel_name);
+		g_free(scpi->actual_channel_name);
+		scpi->actual_channel_name = g_strdup(channel_name);
+		ret = scpi_send(scpi, channel_cmd, channel_name);
+		if (ret != SR_OK)
+			return ret;
+	}
+
+	va_start(args, command);
+	ret = scpi_send_variadic(scpi, cmd, args);
+	va_end(args);
+
+	g_mutex_unlock(&scpi->scpi_mutex);
+
+	return ret;
+}
+
+SR_PRIV int sr_scpi_cmd_resp(const struct sr_dev_inst *sdi,
+		const struct scpi_command *cmdtable,
+		int channel_command, const char *channel_name,
+		GVariant **gvar, const GVariantType *gvtype, int command, ...)
+{
+	struct sr_scpi_dev_inst *scpi;
+	va_list args;
+	const char *channel_cmd;
+	const char *cmd;
+	GString *response;
+	char *s;
+	gboolean b;
+	double d;
+	int ret;
+
+	scpi = sdi->conn;
+
+	if (!(cmd = sr_scpi_cmd_get(cmdtable, command))) {
+		/* Device does not implement this command. */
+		return SR_ERR_NA;
+	}
+
+	g_mutex_lock(&scpi->scpi_mutex);
+
+	/* Select channel. */
+	channel_cmd = sr_scpi_cmd_get(cmdtable, channel_command);
+	if (channel_cmd && channel_name &&
+			g_strcmp0(channel_name, scpi->actual_channel_name)) {
+		sr_spew("sr_scpi_cmd_get(): new channel = %s", channel_name);
+		g_free(scpi->actual_channel_name);
+		scpi->actual_channel_name = g_strdup(channel_name);
+		ret = scpi_send(scpi, channel_cmd, channel_name);
+		if (ret != SR_OK)
+			return ret;
+	}
+
+	va_start(args, command);
+	ret = scpi_send_variadic(scpi, cmd, args);
+	va_end(args);
+	if (ret != SR_OK) {
+		g_mutex_unlock(&scpi->scpi_mutex);
+		return ret;
+	}
+
+	response = g_string_sized_new(1024);
+	ret = scpi_get_data(scpi, NULL, &response);
+	if (ret != SR_OK) {
+		g_mutex_unlock(&scpi->scpi_mutex);
+		if (response)
+			g_string_free(response, TRUE);
+		return ret;
+	}
+
+	g_mutex_unlock(&scpi->scpi_mutex);
+
+	/* Get rid of trailing linefeed if present */
+	if (response->len >= 1 && response->str[response->len - 1] == '\n')
+		g_string_truncate(response, response->len - 1);
+
+	/* Get rid of trailing carriage return if present */
+	if (response->len >= 1 && response->str[response->len - 1] == '\r')
+		g_string_truncate(response, response->len - 1);
+
+	s = g_string_free(response, FALSE);
+
+	ret = SR_OK;
+	if (g_variant_type_equal(gvtype, G_VARIANT_TYPE_BOOLEAN)) {
+		if ((ret = parse_strict_bool(s, &b)) == SR_OK)
+			*gvar = g_variant_new_boolean(b);
+	} else if (g_variant_type_equal(gvtype, G_VARIANT_TYPE_DOUBLE)) {
+		if ((ret = sr_atod_ascii(s, &d)) == SR_OK)
+			*gvar = g_variant_new_double(d);
+	} else if (g_variant_type_equal(gvtype, G_VARIANT_TYPE_STRING)) {
+		*gvar = g_variant_new_string(s);
+	} else {
+		sr_err("Unable to convert to desired GVariant type.");
+		ret = SR_ERR_NA;
 	}
+
+	g_free(s);
+
+	return ret;
 }