[libsigrok.git] / src / scpi / scpi.c

/*
 * 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
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <config.h>
#include <glib.h>
#include <string.h>
#include <libsigrok/libsigrok.h>
#include "libsigrok-internal.h"
#include "scpi.h"

#define LOG_PREFIX "scpi"

#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
 * a boolean-like value.
 *
 * @param str String to convert.
 * @param ret Pointer to a gboolean where the result of the conversion will be
 * stored.
 *
 * @return SR_OK on success, SR_ERR on failure.
 */
static int parse_strict_bool(const char *str, gboolean *ret)
{
        if (!str)
                return SR_ERR_ARG;

        if (!g_strcmp0(str, "1") ||
            !g_ascii_strncasecmp(str, "y", 1) ||
            !g_ascii_strncasecmp(str, "t", 1) ||
            !g_ascii_strncasecmp(str, "yes", 3) ||
            !g_ascii_strncasecmp(str, "true", 4) ||
            !g_ascii_strncasecmp(str, "on", 2)) {
                *ret = TRUE;
                return SR_OK;
        } else if (!g_strcmp0(str, "0") ||
                   !g_ascii_strncasecmp(str, "n", 1) ||
                   !g_ascii_strncasecmp(str, "f", 1) ||
                   !g_ascii_strncasecmp(str, "no", 2) ||
                   !g_ascii_strncasecmp(str, "false", 5) ||
                   !g_ascii_strncasecmp(str, "off", 3)) {
                *ret = FALSE;
                return SR_OK;
        }

        return SR_ERR;
}

SR_PRIV extern const struct sr_scpi_dev_inst scpi_serial_dev;
SR_PRIV extern const struct sr_scpi_dev_inst scpi_tcp_raw_dev;
SR_PRIV extern const struct sr_scpi_dev_inst scpi_tcp_rigol_dev;
SR_PRIV extern const struct sr_scpi_dev_inst scpi_usbtmc_libusb_dev;
SR_PRIV extern const struct sr_scpi_dev_inst scpi_vxi_dev;
SR_PRIV extern const struct sr_scpi_dev_inst scpi_visa_dev;
SR_PRIV extern const struct sr_scpi_dev_inst scpi_libgpib_dev;

static const struct sr_scpi_dev_inst *scpi_devs[] = {
        &scpi_tcp_raw_dev,
        &scpi_tcp_rigol_dev,
#ifdef HAVE_LIBUSB_1_0
        &scpi_usbtmc_libusb_dev,
#endif
#if HAVE_RPC
        &scpi_vxi_dev,
#endif
#ifdef HAVE_LIBREVISA
        &scpi_visa_dev,
#endif
#ifdef HAVE_LIBGPIB
        &scpi_libgpib_dev,
#endif
#ifdef HAVE_SERIAL_COMM
        &scpi_serial_dev, /* Must be last as it matches any resource. */
#endif
};

static struct sr_dev_inst *sr_scpi_scan_resource(struct drv_context *drvc,
                const char *resource, const char *serialcomm,
                struct sr_dev_inst *(*probe_device)(struct sr_scpi_dev_inst *scpi))
{
        struct sr_scpi_dev_inst *scpi;
        struct sr_dev_inst *sdi;

        if (!(scpi = scpi_dev_inst_new(drvc, resource, serialcomm)))
                return NULL;

        if (sr_scpi_open(scpi) != SR_OK) {
                sr_info("Couldn't open SCPI device.");
                sr_scpi_free(scpi);
                return NULL;
        };

        sdi = probe_device(scpi);

        sr_scpi_close(scpi);

        if (sdi)
                sdi->status = SR_ST_INACTIVE;
        else
                sr_scpi_free(scpi);

        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))
{
        GSList *resources, *l, *devices;
        struct sr_dev_inst *sdi;
        const char *resource = NULL;
        const char *serialcomm = NULL;
        gchar **res;
        unsigned i;

        for (l = options; l; l = l->next) {
                struct sr_config *src = l->data;
                switch (src->key) {
                case SR_CONF_CONN:
                        resource = g_variant_get_string(src->data, NULL);
                        break;
                case SR_CONF_SERIALCOMM:
                        serialcomm = g_variant_get_string(src->data, NULL);
                        break;
                }
        }

        devices = NULL;
        for (i = 0; i < ARRAY_SIZE(scpi_devs); i++) {
                if ((resource && strcmp(resource, scpi_devs[i]->prefix))
                    || !scpi_devs[i]->scan)
                        continue;
                resources = scpi_devs[i]->scan(drvc);
                for (l = resources; l; l = l->next) {
                        res = g_strsplit(l->data, ":", 2);
                        if (res[0] && (sdi = sr_scpi_scan_resource(drvc, res[0],
                                       serialcomm ? serialcomm : res[1], probe_device))) {
                                devices = g_slist_append(devices, sdi);
                                sdi->connection_id = g_strdup(l->data);
                        }
                        g_strfreev(res);
                }
                g_slist_free_full(resources, g_free);
        }

        if (!devices && resource) {
                sdi = sr_scpi_scan_resource(drvc, resource, serialcomm, probe_device);
                if (sdi)
                        devices = g_slist_append(NULL, sdi);
        }

        /* Tack a copy of the newly found devices onto the driver list. */
        if (devices)
                drvc->instances = g_slist_concat(drvc->instances, g_slist_copy(devices));

        return devices;
}

SR_PRIV struct sr_scpi_dev_inst *scpi_dev_inst_new(struct drv_context *drvc,
                const char *resource, const char *serialcomm)
{
        struct sr_scpi_dev_inst *scpi = NULL;
        const struct sr_scpi_dev_inst *scpi_dev;
        gchar **params;
        unsigned i;

        for (i = 0; i < ARRAY_SIZE(scpi_devs); i++) {
                scpi_dev = scpi_devs[i];
                if (!strncmp(resource, scpi_dev->prefix, strlen(scpi_dev->prefix))) {
                        sr_dbg("Opening %s device %s.", scpi_dev->name, resource);
                        scpi = g_malloc(sizeof(*scpi));
                        *scpi = *scpi_dev;
                        scpi->priv = g_malloc0(scpi->priv_size);
                        scpi->read_timeout_us = 1000 * 1000;
                        params = g_strsplit(resource, "/", 0);
                        if (scpi->dev_inst_new(scpi->priv, drvc, resource,
                                               params, serialcomm) != SR_OK) {
                                sr_scpi_free(scpi);
                                scpi = NULL;
                        }
                        g_strfreev(params);
                        break;
                }
        }

        return scpi;
}

/**
 * Open SCPI device.
 *
 * @param scpi Previously initialized SCPI device structure.
 *
 * @return SR_OK on success, SR_ERR on failure.
 */
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.
 *
 * @param session The session to add the event source to.
 * @param scpi Previously initialized SCPI device structure.
 * @param events Events to check for.
 * @param timeout Max time to wait before the callback is called, ignored if 0.
 * @param cb Callback function to add. Must not be NULL.
 * @param cb_data Data for the callback function. Can be NULL.
 *
 * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
 *         SR_ERR_MALLOC upon memory allocation errors.
 */
SR_PRIV int sr_scpi_source_add(struct sr_session *session,
                struct sr_scpi_dev_inst *scpi, int events, int timeout,
                sr_receive_data_callback cb, void *cb_data)
{
        return scpi->source_add(session, scpi->priv, events, timeout, cb, cb_data);
}

/**
 * Remove event source for an SCPI device.
 *
 * @param session The session to remove the event source from.
 * @param scpi Previously initialized SCPI device structure.
 *
 * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
 *         SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
 *         internal errors.
 */
SR_PRIV int sr_scpi_source_remove(struct sr_session *session,
                struct sr_scpi_dev_inst *scpi)
{
        return scpi->source_remove(session, scpi->priv);
}

/**
 * Send a SCPI command.
 *
 * @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.
 */
SR_PRIV int sr_scpi_send(struct sr_scpi_dev_inst *scpi,
                         const char *format, ...)
{
        va_list args;
        int ret;

        va_start(args, format);
        g_mutex_lock(&scpi->scpi_mutex);
        ret = scpi_send_variadic(scpi, format, args);
        g_mutex_unlock(&scpi->scpi_mutex);
        va_end(args);

        return ret;
}

/**
 * Send a SCPI command with a variadic argument list.
 *
 * @param scpi Previously initialized SCPI device structure.
 * @param format Format string.
 * @param args Argument list.
 *
 * @return SR_OK on success, SR_ERR on failure.
 */
SR_PRIV int sr_scpi_send_variadic(struct sr_scpi_dev_inst *scpi,
                         const char *format, va_list args)
{
        int ret;

        g_mutex_lock(&scpi->scpi_mutex);
        ret = scpi_send_variadic(scpi, format, args);
        g_mutex_unlock(&scpi->scpi_mutex);

        return ret;
}

/**
 * Begin receiving an SCPI reply.
 *
 * @param scpi Previously initialised SCPI device structure.
 *
 * @return SR_OK on success, SR_ERR on failure.
 */
SR_PRIV int sr_scpi_read_begin(struct sr_scpi_dev_inst *scpi)
{
        return scpi->read_begin(scpi->priv);
}

/**
 * Read part of a response from SCPI device.
 *
 * @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.
 */
SR_PRIV int sr_scpi_read_data(struct sr_scpi_dev_inst *scpi,
                        char *buf, int 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;
}

/**
 * Check whether a complete SCPI response has been received.
 *
 * @param scpi Previously initialised SCPI device structure.
 *
 * @return 1 if complete, 0 otherwise.
 */
SR_PRIV int sr_scpi_read_complete(struct sr_scpi_dev_inst *scpi)
{
        return scpi->read_complete(scpi->priv);
}

/**
 * Close SCPI device.
 *
 * @param scpi Previously initialized SCPI device structure.
 *
 * @return SR_OK on success, SR_ERR on failure.
 */
SR_PRIV int sr_scpi_close(struct sr_scpi_dev_inst *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. 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);
}

/**
 * Send a SCPI command, receive the reply and store the reply in scpi_response.
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param command The SCPI command to send to the device (can be NULL).
 * @param scpi_response Pointer where to store the SCPI response.
 *
 * @return SR_OK on success, SR_ERR* on failure.
 */
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);

        if (sr_scpi_get_data(scpi, command, &response) != SR_OK) {
                if (response)
                        g_string_free(response, TRUE);
                return SR_ERR;
        }

        /* 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);

        sr_spew("Got response: '%.70s', length %" G_GSIZE_FORMAT ".",
                response->str, response->len);

        *scpi_response = g_string_free(response, FALSE);

        return SR_OK;
}

/**
 * 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 ret;

        g_mutex_lock(&scpi->scpi_mutex);
        ret = scpi_read_response(scpi, response, abs_timeout_us);
        g_mutex_unlock(&scpi->scpi_mutex);

        return ret;
}

SR_PRIV int sr_scpi_get_data(struct sr_scpi_dev_inst *scpi,
                             const char *command, GString **scpi_response)
{
        int ret;

        g_mutex_lock(&scpi->scpi_mutex);
        ret = scpi_get_data(scpi, command, scpi_response);
        g_mutex_unlock(&scpi->scpi_mutex);

        return ret;
}

/**
 * Send a SCPI command, read the reply, parse it as a bool value and store the
 * result in scpi_response.
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param command The SCPI command to send to the device (can be NULL).
 * @param scpi_response Pointer where to store the parsed result.
 *
 * @return SR_OK on success, SR_ERR* on failure.
 */
SR_PRIV int sr_scpi_get_bool(struct sr_scpi_dev_inst *scpi,
                             const char *command, gboolean *scpi_response)
{
        int ret;
        char *response;

        response = NULL;

        ret = sr_scpi_get_string(scpi, command, &response);
        if (ret != SR_OK && !response)
                return ret;

        if (parse_strict_bool(response, scpi_response) == SR_OK)
                ret = SR_OK;
        else
                ret = SR_ERR_DATA;

        g_free(response);

        return ret;
}

/**
 * Send a SCPI command, read the reply, parse it as an integer and store the
 * result in scpi_response.
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param command The SCPI command to send to the device (can be NULL).
 * @param scpi_response Pointer where to store the parsed result.
 *
 * @return SR_OK on success, SR_ERR* on failure.
 */
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;

        ret = sr_scpi_get_string(scpi, command, &response);
        if (ret != SR_OK && !response)
                return ret;

        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);

        return ret;
}

/**
 * Send a SCPI command, read the reply, parse it as a float and store the
 * result in scpi_response.
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param command The SCPI command to send to the device (can be NULL).
 * @param scpi_response Pointer where to store the parsed result.
 *
 * @return SR_OK on success, SR_ERR* on failure.
 */
SR_PRIV int sr_scpi_get_float(struct sr_scpi_dev_inst *scpi,
                              const char *command, float *scpi_response)
{
        int ret;
        char *response;

        response = NULL;

        ret = sr_scpi_get_string(scpi, command, &response);
        if (ret != SR_OK && !response)
                return ret;

        if (sr_atof_ascii(response, scpi_response) == SR_OK)
                ret = SR_OK;
        else
                ret = SR_ERR_DATA;

        g_free(response);

        return ret;
}

/**
 * Send a SCPI command, read the reply, parse it as a double and store the
 * result in scpi_response.
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param command The SCPI command to send to the device (can be NULL).
 * @param scpi_response Pointer where to store the parsed result.
 *
 * @return SR_OK on success, SR_ERR* on failure.
 */
SR_PRIV int sr_scpi_get_double(struct sr_scpi_dev_inst *scpi,
                               const char *command, double *scpi_response)
{
        int ret;
        char *response;

        response = NULL;

        ret = sr_scpi_get_string(scpi, command, &response);
        if (ret != SR_OK && !response)
                return ret;

        if (sr_atod_ascii(response, scpi_response) == SR_OK)
                ret = SR_OK;
        else
                ret = SR_ERR_DATA;

        g_free(response);

        return ret;
}

/**
 * Send a SCPI *OPC? command, read the reply and return the result of the
 * command.
 *
 * @param scpi Previously initialised SCPI device structure.
 *
 * @return SR_OK on success, SR_ERR* on failure.
 */
SR_PRIV int sr_scpi_get_opc(struct sr_scpi_dev_inst *scpi)
{
        unsigned int i;
        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;
                g_usleep(SCPI_READ_RETRY_TIMEOUT_US);
        }

        return SR_ERR;
}

/**
 * Send a SCPI command, read the reply, parse it as comma separated list of
 * floats and store the as an result in scpi_response.
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param command The SCPI command to send to the device (can be NULL).
 * @param scpi_response Pointer where to store the parsed result.
 *
 * @return SR_OK upon successfully parsing all values, SR_ERR* upon a parsing
 *         error or upon no response. The allocated response must be freed by
 *         the caller in the case of an SR_OK as well as in the case of
 *         parsing error.
 */
SR_PRIV int sr_scpi_get_floatv(struct sr_scpi_dev_inst *scpi,
                               const char *command, GArray **scpi_response)
{
        int ret;
        float tmp;
        char *response;
        gchar **ptr, **tokens;
        GArray *response_array;

        response = NULL;
        tokens = NULL;

        ret = sr_scpi_get_string(scpi, command, &response);
        if (ret != SR_OK && !response)
                return ret;

        tokens = g_strsplit(response, ",", 0);
        ptr = tokens;

        response_array = g_array_sized_new(TRUE, FALSE, sizeof(float), 256);

        while (*ptr) {
                if (sr_atof_ascii(*ptr, &tmp) == SR_OK)
                        response_array = g_array_append_val(response_array,
                                                            tmp);
                else
                        ret = SR_ERR_DATA;

                ptr++;
        }
        g_strfreev(tokens);
        g_free(response);

        if (ret != SR_OK && response_array->len == 0) {
                g_array_free(response_array, TRUE);
                *scpi_response = NULL;
                return SR_ERR_DATA;
        }

        *scpi_response = response_array;

        return ret;
}

/**
 * Send a SCPI command, read the reply, parse it as comma separated list of
 * unsigned 8 bit integers and store the as an result in scpi_response.
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param command The SCPI command to send to the device (can be NULL).
 * @param scpi_response Pointer where to store the parsed result.
 *
 * @return SR_OK upon successfully parsing all values, SR_ERR* upon a parsing
 *         error or upon no response. The allocated response must be freed by
 *         the caller in the case of an SR_OK as well as in the case of
 *         parsing error.
 */
SR_PRIV int sr_scpi_get_uint8v(struct sr_scpi_dev_inst *scpi,
                               const char *command, GArray **scpi_response)
{
        int tmp, ret;
        char *response;
        gchar **ptr, **tokens;
        GArray *response_array;

        response = NULL;
        tokens = NULL;

        ret = sr_scpi_get_string(scpi, command, &response);
        if (ret != SR_OK && !response)
                return ret;

        tokens = g_strsplit(response, ",", 0);
        ptr = tokens;

        response_array = g_array_sized_new(TRUE, FALSE, sizeof(uint8_t), 256);

        while (*ptr) {
                if (sr_atoi(*ptr, &tmp) == SR_OK)
                        response_array = g_array_append_val(response_array,
                                                            tmp);
                else
                        ret = SR_ERR_DATA;

                ptr++;
        }
        g_strfreev(tokens);
        g_free(response);

        if (response_array->len == 0) {
                g_array_free(response_array, TRUE);
                *scpi_response = NULL;
                return SR_ERR_DATA;
        }

        *scpi_response = response_array;

        return ret;
}

/**
 * Send a SCPI command, read the reply, parse it as binary data with a
 * "definite length block" header and store the as an result in scpi_response.
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param command The SCPI command to send to the device (can be NULL).
 * @param scpi_response Pointer where to store the parsed result.
 *
 * @return SR_OK upon successfully parsing all values, SR_ERR* upon a parsing
 *         error or upon no response. The allocated response must be freed by
 *         the caller in the case of an SR_OK as well as in the case of
 *         parsing error.
 */
SR_PRIV int sr_scpi_get_block(struct sr_scpi_dev_inst *scpi,
                               const char *command, GByteArray **scpi_response)
{
        int ret;
        GString* response;
        gsize oldlen;
        char buf[10];
        long llen;
        long datalen;
        gint64 timeout;

        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);

        timeout = g_get_monotonic_time() + scpi->read_timeout_us;

        *scpi_response = NULL;

        /* Get (the first chunk of) the response. */
        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.
         * The length spec consists of a '#' marker, one digit which
         * specifies the character count of the length spec, and the
         * respective number of characters which specify the data block's
         * length. Raw data bytes follow (thus one must no longer assume
         * that the received input stream would be an ASCIIZ string).
         *
         * Get the data block length, and strip off the length spec from
         * 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;
        }
        buf[0] = response->str[1];
        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);

        /*
         * Re-allocate the buffer size to the now known length
         * and keep reading more chunks of response data.
         */
        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 SR_OK;
}

/**
 * Send the *IDN? SCPI command, receive the reply, parse it and store the
 * reply as a sr_scpi_hw_info structure in the supplied scpi_response pointer.
 *
 * The hw_info structure must be freed by the caller via sr_scpi_hw_info_free().
 *
 * @param scpi Previously initialised SCPI device structure.
 * @param scpi_response Pointer where to store the hw_info structure.
 *
 * @return SR_OK upon success, SR_ERR* on failure.
 */
SR_PRIV int sr_scpi_get_hw_id(struct sr_scpi_dev_inst *scpi,
                              struct sr_scpi_hw_info **scpi_response)
{
        int num_tokens, ret;
        char *response;
        gchar **tokens;
        struct sr_scpi_hw_info *hw_info;
        gchar *idn_substr;

        response = NULL;
        tokens = NULL;

        ret = sr_scpi_get_string(scpi, SCPI_CMD_IDN, &response);
        if (ret != SR_OK && !response)
                return ret;

        /*
         * 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);
        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));

        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]));
        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);

        *scpi_response = hw_info;

        return SR_OK;
}

/**
 * Free a sr_scpi_hw_info struct.
 *
 * @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)
                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;
}