devantech-eth008: make request for digital output optional

[libsigrok.git] / src / hardware / devantech-eth008 / protocol.c

diff --git a/src/hardware/devantech-eth008/protocol.c b/src/hardware/devantech-eth008/protocol.c
index e2c3445a966a4e99551aa3300ab0f03351eb14a5..2e79717c9db05b45c590f6a4da9315813f67569f 100644 (file)
--- a/src/hardware/devantech-eth008/protocol.c
+++ b/src/hardware/devantech-eth008/protocol.c
@@ -291,33 +291,35 @@ SR_PRIV int devantech_eth008_cache_state(const struct sr_dev_inst *sdi)
        if (!devc)
                return SR_ERR_ARG;
 
-       /* Unconditionally get the state of digital output. */
-       rx_size = devc->model->width_do;
-       if (rx_size > sizeof(rsp))
-               return SR_ERR_NA;
+       /* Get the state of digital outputs when the model supports them. */
+       if (devc->model->ch_count_do) {
+               rx_size = devc->model->width_do;
+               if (rx_size > sizeof(rsp))
+                       return SR_ERR_NA;
 
-       wrptr = req;
-       write_u8_inc(&wrptr, CMD_DIGITAL_GET_OUTPUTS);
-       ret = send_then_recv(serial, req, wrptr - req, rsp, rx_size);
-       if (ret != SR_OK)
-               return ret;
-       rdptr = rsp;
+               wrptr = req;
+               write_u8_inc(&wrptr, CMD_DIGITAL_GET_OUTPUTS);
+               ret = send_then_recv(serial, req, wrptr - req, rsp, rx_size);
+               if (ret != SR_OK)
+                       return ret;
+               rdptr = rsp;
 
-       switch (rx_size) {
-       case 1:
-               have = read_u8_inc(&rdptr);
-               break;
-       case 2:
-               have = read_u16le_inc(&rdptr);
-               break;
-       case 3:
-               have = read_u24le_inc(&rdptr);
-               break;
-       default:
-               return SR_ERR_NA;
+               switch (rx_size) {
+               case 1:
+                       have = read_u8_inc(&rdptr);
+                       break;
+               case 2:
+                       have = read_u16le_inc(&rdptr);
+                       break;
+               case 3:
+                       have = read_u24le_inc(&rdptr);
+                       break;
+               default:
+                       return SR_ERR_NA;
+               }
+               have &= devc->mask_do;
+               devc->curr_do = have;
        }
-       have &= devc->mask_do;
-       devc->curr_do = have;
 
        /*
         * Get the state of digital inputs when the model supports them.