hp-3457a: only probe when conn= was specified, to not break SCPI devices

[libsigrok.git] / src / hardware / hp-3457a / api.c

diff --git a/src/hardware/hp-3457a/api.c b/src/hardware/hp-3457a/api.c
index 5325224e5e8207e7593b5a0c55765e20866be7e2..4cfc2d758b54e79625609d408ef0f506d028a5b7 100644 (file)
--- a/src/hardware/hp-3457a/api.c
+++ b/src/hardware/hp-3457a/api.c
@@ -127,6 +127,14 @@ static struct sr_dev_inst *probe_device(struct sr_scpi_dev_inst *scpi)
        struct sr_dev_inst *sdi;
        struct dev_context *devc;
 
+       /*
+        * The device cannot get identified by means of SCPI queries.
+        * Neither shall non-SCPI requests get emitted before reliable
+        * identification of the device. Assume that we only get here
+        * when user specs led us to believe it's safe to communicate
+        * to the expected kind of device.
+        */
+
        /*
         * This command ensures we receive an EOI after every response, so that
         * we don't wait the entire timeout after the response is received.
@@ -138,13 +146,15 @@ static struct sr_dev_inst *probe_device(struct sr_scpi_dev_inst *scpi)
        if ((ret != SR_OK) || !response)
                return NULL;
 
-       if (strcmp(response, "HP3457A"))
+       if (strcmp(response, "HP3457A") != 0) {
+               g_free(response);
                return NULL;
+       }
 
        g_free(response);
 
-       devc = g_malloc0(sizeof(struct dev_context));
-       sdi = g_malloc0(sizeof(struct sr_dev_inst));
+       devc = g_malloc0(sizeof(*devc));
+       sdi = g_malloc0(sizeof(*sdi));
        sdi->vendor = g_strdup("Hewlett-Packard");
        sdi->model = g_strdup("3457A");
        sdi->version = get_revision(scpi);
@@ -168,6 +178,14 @@ static struct sr_dev_inst *probe_device(struct sr_scpi_dev_inst *scpi)
 
 static GSList *scan(struct sr_dev_driver *di, GSList *options)
 {
+       const char *conn;
+
+       /* Only scan for a device when conn= was specified. */
+       conn = NULL;
+       (void)sr_serial_extract_options(options, &conn, NULL);
+       if (!conn)
+               return NULL;
+
        return sr_scpi_scan(di->context, options, probe_device);
 }
 
@@ -359,8 +377,13 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
                return SR_ERR_ARG;
        }
 
-       devc->current_channel = devc->active_channels->data;
        devc->num_active_channels = g_slist_length(devc->active_channels);
+       if (!devc->num_active_channels) {
+               sr_err("Need at least one active channel!");
+               g_slist_free(devc->active_channels);
+               return SR_ERR_ARG;
+       }
+       devc->current_channel = devc->active_channels->data;
 
        hp_3457a_select_input(sdi, front_selected ? CONN_FRONT : CONN_REAR);