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

Only scan for hp-3457a devices when the user specified which connection
to use. This avoids breaking SCPI devices by emitting non-standard
requests before reliable device identification.

diff --git a/src/hardware/hp-3457a/api.c b/src/hardware/hp-3457a/api.c
index f828cfd817f3743c7c764561c8ac8c5737285cff..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.
@@ -170,6 +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);
 }