rdtech-um: tone down and extend diagnostics messages

Reflect tested conditions in diagnostics messages, and tell more
conditions apart where possible. Take the user's perspective in these
messages.

Address programming style while we are here: Prefer read_u16be() over
RB16() for robustness. Use intermediate variables to avoid repeated
converter calls. Transparently advance over the received data length
(the read size and the separated increment had no perceivable relation
in the source code).

diff --git a/src/hardware/rdtech-um/protocol.c b/src/hardware/rdtech-um/protocol.c
index e2afc67d8a9f4c2117212485ed8450de3f865fc0..e4e4c6055101bb42a60008aa47668042969708c1 100644 (file)
--- a/src/hardware/rdtech-um/protocol.c
+++ b/src/hardware/rdtech-um/protocol.c
@@ -119,6 +119,7 @@ SR_PRIV const struct rdtech_um_profile *rdtech_um_probe(struct sr_serial_dev_ins
        uint8_t request;
        uint8_t buf[RDTECH_UM_BUFSIZE];
        int len;
+       uint16_t model_id;
 
        request = UM_CMD_POLL;
        if (serial_write_blocking(serial, &request, sizeof(request),
@@ -133,14 +134,15 @@ SR_PRIV const struct rdtech_um_profile *rdtech_um_probe(struct sr_serial_dev_ins
                return NULL;
        }
 
-       p = find_profile(RB16(&buf[0]));
+       model_id = read_u16be(&buf[0]);
+       p = find_profile(model_id);
        if (!p) {
-               sr_err("Unrecognized UM device (0x%.4" PRIx16 ")!", RB16(&buf[0]));
+               sr_err("Unrecognized UM device (0x%.4" PRIx16 ").", model_id);
                return NULL;
        }
 
        if (!p->csum_ok(buf, len)) {
-               sr_err("Probe response contains illegal checksum or end marker.\n");
+               sr_err("Probe response fails checksum verification.");
                return NULL;
        }
 
@@ -209,8 +211,7 @@ static void recv_poll_data(struct sr_dev_inst *sdi, struct sr_serial_dev_inst *s
                len = serial_read_nonblocking(serial, devc->buf + devc->buflen, 1);
                if (len < 1)
                        return;
-
-               devc->buflen++;
+               devc->buflen += len;
 
                /* Check if the poll model ID matches the profile. */
                if (devc->buflen == 2 && RB16(devc->buf) != p->model_id) {
@@ -222,11 +223,12 @@ static void recv_poll_data(struct sr_dev_inst *sdi, struct sr_serial_dev_inst *s
                }
        }
 
-       if (devc->buflen == UM_POLL_LEN && p->csum_ok(devc->buf, devc->buflen))
-               handle_poll_data(sdi);
+       if (devc->buflen != UM_POLL_LEN)
+               sr_warn("Skipping packet, unexpected receive length.");
+       else if (!p->csum_ok(devc->buf, devc->buflen))
+               sr_warn("Skipping packet, checksum verification failed.");
        else
-               sr_warn("Skipping packet with illegal checksum / end marker.");
-
+               handle_poll_data(sdi);
        devc->buflen = 0;
 }