serial.c

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/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2010-2012 Bert Vermeulen <bert@biot.com>
 * Copyright (C) 2010-2012 Uwe Hermann <uwe@hermann-uwe.de>
 * Copyright (C) 2012 Alexandru Gagniuc <mr.nuke.me@gmail.com>
 * Copyright (C) 2014 Uffe Jakobsen <uffe@uffe.org>
 *
 * 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 <string.h>
#include <stdlib.h>
#include <glib.h>
#include <glib/gstdio.h>
#include <libserialport.h>
#include <libsigrok/libsigrok.h>
#include "libsigrok-internal.h"
#ifdef G_OS_WIN32
#include <windows.h> /* for HANDLE */
#endif

/** @cond PRIVATE */
#define LOG_PREFIX "serial"
/** @endcond */

/**
 * @file
 *
 * Serial port handling.
 */

/**
 * @defgroup grp_serial Serial port handling
 *
 * Serial port handling functions.
 *
 * @{
 */

/**
 * Open the specified serial port.
 *
 * @param serial Previously initialized serial port structure.
 * @param[in] flags Flags to use when opening the serial port. Possible flags
 *              include SERIAL_RDWR, SERIAL_RDONLY.
 *
 * If the serial structure contains a serialcomm string, it will be
 * passed to serial_set_paramstr() after the port is opened.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int serial_open(struct sr_serial_dev_inst *serial, int flags)
{
        int ret;
        char *error;
        int sp_flags = 0;

        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
        }

        sr_spew("Opening serial port '%s' (flags %d).", serial->port, flags);

        sp_get_port_by_name(serial->port, &serial->data);

        if (flags & SERIAL_RDWR)
                sp_flags = (SP_MODE_READ | SP_MODE_WRITE);
        else if (flags & SERIAL_RDONLY)
                sp_flags = SP_MODE_READ;

        ret = sp_open(serial->data, sp_flags);

        switch (ret) {
        case SP_ERR_ARG:
                sr_err("Attempt to open serial port with invalid parameters.");
                return SR_ERR_ARG;
        case SP_ERR_FAIL:
                error = sp_last_error_message();
                sr_err("Error opening port (%d): %s.",
                        sp_last_error_code(), error);
                sp_free_error_message(error);
                return SR_ERR;
        }

        if (serial->serialcomm)
                return serial_set_paramstr(serial, serial->serialcomm);
        else
                return SR_OK;
}

/**
 * Close the specified serial port.
 *
 * @param serial Previously initialized serial port structure.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int serial_close(struct sr_serial_dev_inst *serial)
{
        int ret;
        char *error;

        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
        }

        if (!serial->data) {
                sr_dbg("Cannot close unopened serial port %s.", serial->port);
                return SR_ERR;
        }

        sr_spew("Closing serial port %s.", serial->port);

        ret = sp_close(serial->data);

        switch (ret) {
        case SP_ERR_ARG:
                sr_err("Attempt to close an invalid serial port.");
                return SR_ERR_ARG;
        case SP_ERR_FAIL:
                error = sp_last_error_message();
                sr_err("Error closing port (%d): %s.",
                        sp_last_error_code(), error);
                sp_free_error_message(error);
                return SR_ERR;
        }

        sp_free_port(serial->data);
        serial->data = NULL;

        return SR_OK;
}

/**
 * Flush serial port buffers.
 *
 * @param serial Previously initialized serial port structure.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int serial_flush(struct sr_serial_dev_inst *serial)
{
        int ret;
        char *error;

        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
        }

        if (!serial->data) {
                sr_dbg("Cannot flush unopened serial port %s.", serial->port);
                return SR_ERR;
        }

        sr_spew("Flushing serial port %s.", serial->port);

        ret = sp_flush(serial->data, SP_BUF_BOTH);

        switch (ret) {
        case SP_ERR_ARG:
                sr_err("Attempt to flush an invalid serial port.");
                return SR_ERR_ARG;
        case SP_ERR_FAIL:
                error = sp_last_error_message();
                sr_err("Error flushing port (%d): %s.",
                        sp_last_error_code(), error);
                sp_free_error_message(error);
                return SR_ERR;
        }

        return SR_OK;
}

/**
 * Drain serial port buffers.
 *
 * @param serial Previously initialized serial port structure.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int serial_drain(struct sr_serial_dev_inst *serial)
{
        int ret;
        char *error;

        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
        }

        if (!serial->data) {
                sr_dbg("Cannot drain unopened serial port %s.", serial->port);
                return SR_ERR;
        }

        sr_spew("Draining serial port %s.", serial->port);

        ret = sp_drain(serial->data);

        if (ret == SP_ERR_FAIL) {
                error = sp_last_error_message();
                sr_err("Error draining port (%d): %s.",
                        sp_last_error_code(), error);
                sp_free_error_message(error);
                return SR_ERR;
        }

        return SR_OK;
}

static int _serial_write(struct sr_serial_dev_inst *serial,
                const void *buf, size_t count, int nonblocking, unsigned int timeout_ms)
{
        ssize_t ret;
        char *error;

        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
        }

        if (!serial->data) {
                sr_dbg("Cannot use unopened serial port %s.", serial->port);
                return SR_ERR;
        }

        if (nonblocking)
                ret = sp_nonblocking_write(serial->data, buf, count);
        else
                ret = sp_blocking_write(serial->data, buf, count, timeout_ms);

        switch (ret) {
        case SP_ERR_ARG:
                sr_err("Attempted serial port write with invalid arguments.");
                return SR_ERR_ARG;
        case SP_ERR_FAIL:
                error = sp_last_error_message();
                sr_err("Write error (%d): %s.", sp_last_error_code(), error);
                sp_free_error_message(error);
                return SR_ERR;
        }

        sr_spew("Wrote %zd/%zu bytes.", ret, count);

        return ret;
}

/**
 * Write a number of bytes to the specified serial port, blocking until finished.
 *
 * @param serial Previously initialized serial port structure.
 * @param[in] buf Buffer containing the bytes to write.
 * @param[in] count Number of bytes to write.
 * @param[in] timeout_ms Timeout in ms, or 0 for no timeout.
 *
 * @retval SR_ERR_ARG Invalid argument.
 * @retval SR_ERR Other error.
 * @retval other The number of bytes written. If this is less than the number
 * specified in the call, the timeout was reached.
 *
 * @private
 */
SR_PRIV int serial_write_blocking(struct sr_serial_dev_inst *serial,
                const void *buf, size_t count, unsigned int timeout_ms)
{
        return _serial_write(serial, buf, count, 0, timeout_ms);
}

/**
 * Write a number of bytes to the specified serial port, return immediately.
 *
 * @param serial Previously initialized serial port structure.
 * @param[in] buf Buffer containing the bytes to write.
 * @param[in] count Number of bytes to write.
 *
 * @retval SR_ERR_ARG Invalid argument.
 * @retval SR_ERR Other error.
 * @retval other The number of bytes written.
 *
 * @private
 */
SR_PRIV int serial_write_nonblocking(struct sr_serial_dev_inst *serial,
                const void *buf, size_t count)
{
        return _serial_write(serial, buf, count, 1, 0);
}

static int _serial_read(struct sr_serial_dev_inst *serial, void *buf,
                size_t count, int nonblocking, unsigned int timeout_ms)
{
        ssize_t ret;
        char *error;

        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
        }

        if (!serial->data) {
                sr_dbg("Cannot use unopened serial port %s.", serial->port);
                return SR_ERR;
        }

        if (nonblocking)
                ret = sp_nonblocking_read(serial->data, buf, count);
        else
                ret = sp_blocking_read(serial->data, buf, count, timeout_ms);

        switch (ret) {
        case SP_ERR_ARG:
                sr_err("Attempted serial port read with invalid arguments.");
                return SR_ERR_ARG;
        case SP_ERR_FAIL:
                error = sp_last_error_message();
                sr_err("Read error (%d): %s.", sp_last_error_code(), error);
                sp_free_error_message(error);
                return SR_ERR;
        }

        if (ret > 0)
                sr_spew("Read %zd/%zu bytes.", ret, count);

        return ret;
}

/**
 * Read a number of bytes from the specified serial port, block until finished.
 *
 * @param serial Previously initialized serial port structure.
 * @param buf Buffer where to store the bytes that are read.
 * @param[in] count The number of bytes to read.
 * @param[in] timeout_ms Timeout in ms, or 0 for no timeout.
 *
 * @retval SR_ERR_ARG Invalid argument.
 * @retval SR_ERR     Other error.
 * @retval other      The number of bytes read. If this is less than the number
 * requested, the timeout was reached.
 *
 * @private
 */
SR_PRIV int serial_read_blocking(struct sr_serial_dev_inst *serial, void *buf,
                size_t count, unsigned int timeout_ms)
{
        return _serial_read(serial, buf, count, 0, timeout_ms);
}

/**
 * Try to read up to @a count bytes from the specified serial port, return
 * immediately with what's available.
 *
 * @param serial Previously initialized serial port structure.
 * @param buf Buffer where to store the bytes that are read.
 * @param[in] count The number of bytes to read.
 *
 * @retval SR_ERR_ARG Invalid argument.
 * @retval SR_ERR     Other error.
 * @retval other      The number of bytes read.
 *
 * @private
 */
SR_PRIV int serial_read_nonblocking(struct sr_serial_dev_inst *serial, void *buf,
                size_t count)
{
        return _serial_read(serial, buf, count, 1, 0);
}

/**
 * Set serial parameters for the specified serial port.
 *
 * @param serial Previously initialized serial port structure.
 * @param[in] baudrate The baudrate to set.
 * @param[in] bits The number of data bits to use (5, 6, 7 or 8).
 * @param[in] parity The parity setting to use (0 = none, 1 = even, 2 = odd).
 * @param[in] stopbits The number of stop bits to use (1 or 2).
 * @param[in] flowcontrol The flow control settings to use (0 = none,
 *                      1 = RTS/CTS, 2 = XON/XOFF).
 * @param[in] rts Status of RTS line (0 or 1; required by some interfaces).
 * @param[in] dtr Status of DTR line (0 or 1; required by some interfaces).
 *
 * @retval SR_OK Success.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int serial_set_params(struct sr_serial_dev_inst *serial, int baudrate,
                              int bits, int parity, int stopbits,
                              int flowcontrol, int rts, int dtr)
{
        int ret;
        char *error;
        struct sp_port_config *config;

        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
        }

        if (!serial->data) {
                sr_dbg("Cannot configure unopened serial port %s.", serial->port);
                return SR_ERR;
        }

        sr_spew("Setting serial parameters on port %s.", serial->port);

        sp_new_config(&config);
        sp_set_config_baudrate(config, baudrate);
        sp_set_config_bits(config, bits);
        switch (parity) {
        case 0:
                sp_set_config_parity(config, SP_PARITY_NONE);
                break;
        case 1:
                sp_set_config_parity(config, SP_PARITY_EVEN);
                break;
        case 2:
                sp_set_config_parity(config, SP_PARITY_ODD);
                break;
        default:
                return SR_ERR_ARG;
        }
        sp_set_config_stopbits(config, stopbits);
        sp_set_config_rts(config, flowcontrol == 1 ? SP_RTS_FLOW_CONTROL : rts);
        sp_set_config_cts(config, flowcontrol == 1 ? SP_CTS_FLOW_CONTROL : SP_CTS_IGNORE);
        sp_set_config_dtr(config, dtr);
        sp_set_config_dsr(config, SP_DSR_IGNORE);
        sp_set_config_xon_xoff(config, flowcontrol == 2 ? SP_XONXOFF_INOUT : SP_XONXOFF_DISABLED);

        ret = sp_set_config(serial->data, config);
        sp_free_config(config);

        switch (ret) {
        case SP_ERR_ARG:
                sr_err("Invalid arguments for setting serial port parameters.");
                return SR_ERR_ARG;
        case SP_ERR_FAIL:
                error = sp_last_error_message();
                sr_err("Error setting serial port parameters (%d): %s.",
                        sp_last_error_code(), error);
                sp_free_error_message(error);
                return SR_ERR;
        }

        return SR_OK;
}

/**
 * Set serial parameters for the specified serial port from parameter string.
 *
 * @param serial Previously initialized serial port structure.
 * @param[in] paramstr A serial communication parameters string of the form
 * "<baudrate>/<bits><parity><stopbits>{/<option>}".\n
 *  Examples: "9600/8n1", "600/7o2/dtr=1/rts=0" or "460800/8n1/flow=2".\n
 * <baudrate>=integer Baud rate.\n
 * <bits>=5|6|7|8 Number of data bits.\n
 * <parity>=n|e|o None, even, odd.\n
 * <stopbits>=1|2 One or two stop bits.\n
 * Options:\n
 * dtr=0|1 Set DTR off resp. on.\n
 * flow=0|1|2 Flow control. 0 for none, 1 for RTS/CTS, 2 for XON/XOFF.\n
 * rts=0|1 Set RTS off resp. on.\n
 * Please note that values and combinations of these parameters must be
 * supported by the concrete serial interface hardware and the drivers for it.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int serial_set_paramstr(struct sr_serial_dev_inst *serial,
                const char *paramstr)
{
/** @cond PRIVATE */
#define SERIAL_COMM_SPEC "^(\\d+)/([5678])([neo])([12])(.*)$"
/** @endcond */

        GRegex *reg;
        GMatchInfo *match;
        int speed, databits, parity, stopbits, flow, rts, dtr, i;
        char *mstr, **opts, **kv;

        speed = databits = parity = stopbits = flow = 0;
        rts = dtr = -1;
        sr_spew("Parsing parameters from \"%s\".", paramstr);
        reg = g_regex_new(SERIAL_COMM_SPEC, 0, 0, NULL);
        if (g_regex_match(reg, paramstr, 0, &match)) {
                if ((mstr = g_match_info_fetch(match, 1)))
                        speed = strtoul(mstr, NULL, 10);
                g_free(mstr);
                if ((mstr = g_match_info_fetch(match, 2)))
                        databits = strtoul(mstr, NULL, 10);
                g_free(mstr);
                if ((mstr = g_match_info_fetch(match, 3))) {
                        switch (mstr[0]) {
                        case 'n':
                                parity = SP_PARITY_NONE;
                                break;
                        case 'e':
                                parity = SP_PARITY_EVEN;
                                break;
                        case 'o':
                                parity = SP_PARITY_ODD;
                                break;
                        }
                }
                g_free(mstr);
                if ((mstr = g_match_info_fetch(match, 4)))
                        stopbits = strtoul(mstr, NULL, 10);
                g_free(mstr);
                if ((mstr = g_match_info_fetch(match, 5)) && mstr[0] != '\0') {
                        if (mstr[0] != '/') {
                                sr_dbg("missing separator before extra options");
                                speed = 0;
                        } else {
                                /* A set of "key=value" options separated by / */
                                opts = g_strsplit(mstr + 1, "/", 0);
                                for (i = 0; opts[i]; i++) {
                                        kv = g_strsplit(opts[i], "=", 2);
                                        if (!strncmp(kv[0], "rts", 3)) {
                                                if (kv[1][0] == '1')
                                                        rts = 1;
                                                else if (kv[1][0] == '0')
                                                        rts = 0;
                                                else {
                                                        sr_dbg("invalid value for rts: %c", kv[1][0]);
                                                        speed = 0;
                                                }
                                        } else if (!strncmp(kv[0], "dtr", 3)) {
                                                if (kv[1][0] == '1')
                                                        dtr = 1;
                                                else if (kv[1][0] == '0')
                                                        dtr = 0;
                                                else {
                                                        sr_dbg("invalid value for dtr: %c", kv[1][0]);
                                                        speed = 0;
                                                }
                                        } else if (!strncmp(kv[0], "flow", 4)) {
                                                if (kv[1][0] == '0')
                                                        flow = 0;
                                                else if (kv[1][0] == '1')
                                                        flow = 1;
                                                else if (kv[1][0] == '2')
                                                        flow = 2;
                                                else {
                                                        sr_dbg("invalid value for flow: %c", kv[1][0]);
                                                        speed = 0;
                                                }
                                        }
                                        g_strfreev(kv);
                                }
                                g_strfreev(opts);
                        }
                }
                g_free(mstr);
        }
        g_match_info_unref(match);
        g_regex_unref(reg);

        if (speed) {
                return serial_set_params(serial, speed, databits, parity,
                                         stopbits, flow, rts, dtr);
        } else {
                sr_dbg("Could not infer speed from parameter string.");
                return SR_ERR_ARG;
        }
}

/**
 * Read a line from the specified serial port.
 *
 * @param serial Previously initialized serial port structure.
 * @param buf Buffer where to store the bytes that are read.
 * @param buflen Size of the buffer.
 * @param[in] timeout_ms How long to wait for a line to come in.
 *
 * Reading stops when CR of LR is found, which is stripped from the buffer.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int serial_readline(struct sr_serial_dev_inst *serial, char **buf,
                int *buflen, gint64 timeout_ms)
{
        gint64 start, remaining;
        int maxlen, len;

        if (!serial) {
                sr_dbg("Invalid serial port.");
                return SR_ERR;
        }

        if (!serial->data) {
                sr_dbg("Cannot use unopened serial port %s.", serial->port);
                return -1;
        }

        start = g_get_monotonic_time();
        remaining = timeout_ms;

        maxlen = *buflen;
        *buflen = len = 0;
        while (1) {
                len = maxlen - *buflen - 1;
                if (len < 1)
                        break;
                len = sp_blocking_read(serial->data, *buf + *buflen, 1, remaining);
                if (len > 0) {
                        *buflen += len;
                        *(*buf + *buflen) = '\0';
                        if (*buflen > 0 && (*(*buf + *buflen - 1) == '\r'
                                        || *(*buf + *buflen - 1) == '\n')) {
                                /* Strip CR/LF and terminate. */
                                *(*buf + --*buflen) = '\0';
                                break;
                        }
                }
                /* Reduce timeout by time elapsed. */
                remaining = timeout_ms - ((g_get_monotonic_time() - start) / 1000);
                if (remaining <= 0)
                        /* Timeout */
                        break;
                if (len < 1)
                        g_usleep(2000);
        }
        if (*buflen)
                sr_dbg("Received %d: '%s'.", *buflen, *buf);

        return SR_OK;
}

/**
 * Try to find a valid packet in a serial data stream.
 *
 * @param serial Previously initialized serial port structure.
 * @param buf Buffer containing the bytes to write.
 * @param buflen Size of the buffer.
 * @param[in] packet_size Size, in bytes, of a valid packet.
 * @param is_valid Callback that assesses whether the packet is valid or not.
 * @param[in] timeout_ms The timeout after which, if no packet is detected, to
 *                   abort scanning.
 * @param[in] baudrate The baudrate of the serial port. This parameter is not
 *                 critical, but it helps fine tune the serial port polling
 *                 delay.
 *
 * @retval SR_OK Valid packet was found within the given timeout.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int serial_stream_detect(struct sr_serial_dev_inst *serial,
                                 uint8_t *buf, size_t *buflen,
                                 size_t packet_size,
                                 packet_valid_callback is_valid,
                                 uint64_t timeout_ms, int baudrate)
{
        uint64_t start, time, byte_delay_us;
        size_t ibuf, i, maxlen;
        ssize_t len;

        maxlen = *buflen;

        sr_dbg("Detecting packets on %s (timeout = %" PRIu64
               "ms, baudrate = %d).", serial->port, timeout_ms, baudrate);

        if (maxlen < (packet_size / 2) ) {
                sr_err("Buffer size must be at least twice the packet size.");
                return SR_ERR;
        }

        /* Assume 8n1 transmission. That is 10 bits for every byte. */
        byte_delay_us = 10 * ((1000 * 1000) / baudrate);
        start = g_get_monotonic_time();

        i = ibuf = len = 0;
        while (ibuf < maxlen) {
                len = serial_read_nonblocking(serial, &buf[ibuf], 1);
                if (len > 0) {
                        ibuf += len;
                } else if (len == 0) {
                        /* No logging, already done in serial_read(). */
                } else {
                        /* Error reading byte, but continuing anyway. */
                }

                time = g_get_monotonic_time() - start;
                time /= 1000;

                if ((ibuf - i) >= packet_size) {
                        /* We have at least a packet's worth of data. */
                        if (is_valid(&buf[i])) {
                                sr_spew("Found valid %zu-byte packet after "
                                        "%" PRIu64 "ms.", (ibuf - i), time);
                                *buflen = ibuf;
                                return SR_OK;
                        } else {
                                sr_spew("Got %zu bytes, but not a valid "
                                        "packet.", (ibuf - i));
                        }
                        /* Not a valid packet. Continue searching. */
                        i++;
                }
                if (time >= timeout_ms) {
                        /* Timeout */
                        sr_dbg("Detection timed out after %" PRIu64 "ms.", time);
                        break;
                }
                if (len < 1)
                        g_usleep(byte_delay_us);
        }

        *buflen = ibuf;

        sr_err("Didn't find a valid packet (read %zu bytes).", *buflen);

        return SR_ERR;
}

/**
 * Extract the serial device and options from the options linked list.
 *
 * @param options List of options passed from the command line.
 * @param serial_device Pointer where to store the extracted serial device.
 * @param serial_options Pointer where to store the optional extracted serial
 * options.
 *
 * @return SR_OK if a serial_device is found, SR_ERR if no device is found. The
 * returned string should not be freed by the caller.
 *
 * @private
 */
SR_PRIV int sr_serial_extract_options(GSList *options, const char **serial_device,
                                      const char **serial_options)
{
        GSList *l;
        struct sr_config *src;

        *serial_device = NULL;

        for (l = options; l; l = l->next) {
                src = l->data;
                switch (src->key) {
                case SR_CONF_CONN:
                        *serial_device = g_variant_get_string(src->data, NULL);
                        sr_dbg("Parsed serial device: %s.", *serial_device);
                        break;
                case SR_CONF_SERIALCOMM:
                        *serial_options = g_variant_get_string(src->data, NULL);
                        sr_dbg("Parsed serial options: %s.", *serial_options);
                        break;
                }
        }

        if (!*serial_device) {
                sr_dbg("No serial device specified.");
                return SR_ERR;
        }

        return SR_OK;
}

/** @cond PRIVATE */
#ifdef G_OS_WIN32
typedef HANDLE event_handle;
#else
typedef int event_handle;
#endif
/** @endcond */

/** @private */
SR_PRIV int serial_source_add(struct sr_session *session,
                struct sr_serial_dev_inst *serial, int events, int timeout,
                sr_receive_data_callback cb, void *cb_data)
{
        struct sp_event_set *event_set;
        gintptr poll_fd;
        unsigned int poll_events;
        enum sp_event mask = 0;

        if ((events & (G_IO_IN|G_IO_ERR)) && (events & G_IO_OUT)) {
                sr_err("Cannot poll input/error and output simultaneously.");
                return SR_ERR_ARG;
        }

        if (sp_new_event_set(&event_set) != SP_OK)
                return SR_ERR;

        if (events & G_IO_IN)
                mask |= SP_EVENT_RX_READY;
        if (events & G_IO_OUT)
                mask |= SP_EVENT_TX_READY;
        if (events & G_IO_ERR)
                mask |= SP_EVENT_ERROR;

        if (sp_add_port_events(event_set, serial->data, mask) != SP_OK) {
                sp_free_event_set(event_set);
                return SR_ERR;
        }
        if (event_set->count != 1) {
                sr_err("Unexpected number (%u) of event handles to poll.",
                        event_set->count);
                sp_free_event_set(event_set);
                return SR_ERR;
        }

        poll_fd = (gintptr) ((event_handle *)event_set->handles)[0];
        mask = event_set->masks[0];

        sp_free_event_set(event_set);

        poll_events = 0;
        if (mask & SP_EVENT_RX_READY)
                poll_events |= G_IO_IN;
        if (mask & SP_EVENT_TX_READY)
                poll_events |= G_IO_OUT;
        if (mask & SP_EVENT_ERROR)
                poll_events |= G_IO_ERR;
        /*
         * Using serial->data as the key for the event source is not quite
         * proper, as it makes it impossible to create another event source
         * for the same serial port. However, these fixed keys will soon be
         * removed from the API anyway, so this is OK for now.
         */
        return sr_session_fd_source_add(session, serial->data,
                        poll_fd, poll_events, timeout, cb, cb_data);
}

/** @private */
SR_PRIV int serial_source_remove(struct sr_session *session,
                struct sr_serial_dev_inst *serial)
{
        return sr_session_source_remove_internal(session, serial->data);
}

/**
 * Create/allocate a new sr_serial_port structure.
 *
 * @param name The OS dependent name of the serial port. Must not be NULL.
 * @param description An end user friendly description for the serial port.
 *                    Can be NULL (in that case the empty string is used
 *                    as description).
 *
 * @return The newly allocated sr_serial_port struct.
 */
static struct sr_serial_port *sr_serial_new(const char *name,
                const char *description)
{
        struct sr_serial_port *serial;

        if (!name)
                return NULL;

        serial = g_malloc(sizeof(struct sr_serial_port));
        serial->name = g_strdup(name);
        serial->description = g_strdup(description ? description : "");

        return serial;
}

/**
 * Free a previously allocated sr_serial_port structure.
 *
 * @param serial The sr_serial_port struct to free. Must not be NULL.
 */
SR_API void sr_serial_free(struct sr_serial_port *serial)
{
        if (!serial)
                return;
        g_free(serial->name);
        g_free(serial->description);
        g_free(serial);
}

/**
 * List available serial devices.
 *
 * @return A GSList of strings containing the path of the serial devices or
 *         NULL if no serial device is found. The returned list must be freed
 *         by the caller.
 */
SR_API GSList *sr_serial_list(const struct sr_dev_driver *driver)
{
        GSList *tty_devs = NULL;
        struct sp_port **ports;
        struct sr_serial_port *port;
        int i;

        /* Currently unused, but will be used by some drivers later on. */
        (void)driver;

        if (sp_list_ports(&ports) != SP_OK)
                return NULL;

        for (i = 0; ports[i]; i++) {
                port = sr_serial_new(sp_get_port_name(ports[i]),
                                     sp_get_port_description(ports[i]));
                tty_devs = g_slist_append(tty_devs, port);
        }

        sp_free_port_list(ports);

        return tty_devs;
}

/**
 * Find USB serial devices via the USB vendor ID and product ID.
 *
 * @param[in] vendor_id Vendor ID of the USB device.
 * @param[in] product_id Product ID of the USB device.
 *
 * @return A GSList of strings containing the path of the serial device or
 *         NULL if no serial device is found. The returned list must be freed
 *         by the caller.
 *
 * @private
 */
SR_PRIV GSList *sr_serial_find_usb(uint16_t vendor_id, uint16_t product_id)
{
        GSList *tty_devs = NULL;
        struct sp_port **ports;
        int i, vid, pid;

        if (sp_list_ports(&ports) != SP_OK)
                return NULL;

        for (i = 0; ports[i]; i++)
                if (sp_get_port_transport(ports[i]) == SP_TRANSPORT_USB &&
                    sp_get_port_usb_vid_pid(ports[i], &vid, &pid) == SP_OK &&
                    vid == vendor_id && pid == product_id) {
                        tty_devs = g_slist_prepend(tty_devs,
                                        g_strdup(sp_get_port_name(ports[i])));
                }

        sp_free_port_list(ports);

        return tty_devs;
}

/** @private */
SR_PRIV int serial_timeout(struct sr_serial_dev_inst *port, int num_bytes)
{
        struct sp_port_config *config;
        int timeout_ms, bits, baud, tmp;

        /* Default to 1s. */
        timeout_ms = 1000;

        if (sp_new_config(&config) < 0)
                return timeout_ms;

        bits = baud = 0;
        do {
                if (sp_get_config(port->data, config) < 0)
                        break;

                /* Start bit. */
                bits = 1;
                if (sp_get_config_bits(config, &tmp) < 0)
                        break;
                bits += tmp;
                if (sp_get_config_stopbits(config, &tmp) < 0)
                        break;
                bits += tmp;
                if (sp_get_config_baudrate(config, &tmp) < 0)
                        break;
                baud = tmp;
        } while (FALSE);

        if (bits && baud) {
                /* Throw in 10ms for misc OS overhead. */
                timeout_ms = 10;
                timeout_ms += ((1000.0 / baud) * bits) * num_bytes;
        }

        sp_free_config(config);

        return timeout_ms;
}

/** @} */