scpi-pps: Optimize channel selection.

This avoids sending a channel selection command to the device if
the channel we're working on is already on the same underlying
output channel.

diff --git a/src/hardware/scpi-pps/protocol.c b/src/hardware/scpi-pps/protocol.c
index 667ce46ae29242d7546fa8e831cd3d1a9f2a44d7..13133b5b8c5808ad459d9d7b653dc79369b2e35a 100644 (file)
--- a/src/hardware/scpi-pps/protocol.c
+++ b/src/hardware/scpi-pps/protocol.c
@@ -103,7 +103,7 @@ SR_PRIV int scpi_cmd_resp(const struct sr_dev_inst *sdi, GVariant **gvar,
 SR_PRIV int select_channel(const struct sr_dev_inst *sdi, struct sr_channel *ch)
 {
        struct dev_context *devc;
-       struct pps_channel *pch;
+       struct pps_channel *cur_pch, *new_pch;
        int ret;
 
        if (g_slist_length(sdi->channels) == 1)
@@ -113,13 +113,40 @@ SR_PRIV int select_channel(const struct sr_dev_inst *sdi, struct sr_channel *ch)
        if (ch == devc->cur_channel)
                return SR_OK;
 
-       pch = ch->priv;
-       if ((ret = scpi_cmd(sdi, SCPI_CMD_SELECT_CHANNEL, pch->hwname)) == SR_OK)
+       new_pch = ch->priv;
+       if (devc->cur_channel) {
+               cur_pch = devc->cur_channel->priv;
+               if (cur_pch->hw_output_idx == new_pch->hw_output_idx) {
+                       /* Same underlying output channel. */
+                       devc->cur_channel = ch;
+                       return SR_OK;
+               }
+       }
+
+       if ((ret = scpi_cmd(sdi, SCPI_CMD_SELECT_CHANNEL, new_pch->hwname)) == SR_OK)
                devc->cur_channel = ch;
 
        return ret;
 }
 
+SR_PRIV struct sr_channel *next_enabled_channel(const struct sr_dev_inst *sdi,
+               struct sr_channel *cur_channel)
+{
+       struct sr_channel *next_channel;
+       GSList *l;
+
+       next_channel = cur_channel;
+       do {
+               l = g_slist_find(sdi->channels, next_channel);
+               if (l && l->next)
+                       next_channel = l->next->data;
+               else
+                       next_channel = sdi->channels->data;
+       } while (!next_channel->enabled);
+
+       return next_channel;
+}
+
 SR_PRIV int scpi_pps_receive_data(int fd, int revents, void *cb_data)
 {
        struct dev_context *devc;
@@ -129,7 +156,6 @@ SR_PRIV int scpi_pps_receive_data(int fd, int revents, void *cb_data)
        struct sr_channel *next_channel;
        struct sr_scpi_dev_inst *scpi;
        struct pps_channel *pch;
-       GSList *l;
        float f;
        int cmd;
 
@@ -165,17 +191,8 @@ SR_PRIV int scpi_pps_receive_data(int fd, int revents, void *cb_data)
        }
 
        if (g_slist_length(sdi->channels) > 1) {
-               /* Find next enabled channel. */
-               next_channel = devc->cur_channel;
-               do {
-                       l = g_slist_find(sdi->channels, next_channel);
-                       if (l->next)
-                               next_channel = l->next->data;
-                       else
-                               next_channel = sdi->channels->data;
-               } while (!next_channel->enabled);
-               select_channel(sdi, next_channel);
-               if (devc->cur_channel != next_channel) {
+               next_channel = next_enabled_channel(sdi, devc->cur_channel);
+               if (select_channel(sdi, next_channel) != SR_OK) {
                        sr_err("Failed to select channel %s", next_channel->name);
                        return FALSE;
                }
@@ -190,7 +207,7 @@ SR_PRIV int scpi_pps_receive_data(int fd, int revents, void *cb_data)
                cmd = SCPI_CMD_GET_MEAS_POWER;
        else
                return SR_ERR;
-       scpi_cmd(sdi, cmd, pch->hwname);
+       scpi_cmd(sdi, cmd);
 
        return TRUE;
 }

diff --git a/src/hardware/scpi-pps/protocol.h b/src/hardware/scpi-pps/protocol.h
index 8a810af7f32ce67aaf362794b881cf2e35e77cf6..189f1ed95d5c5643c3f7c1fcbf83745dd1dbfb4c 100644 (file)
--- a/src/hardware/scpi-pps/protocol.h
+++ b/src/hardware/scpi-pps/protocol.h
@@ -153,6 +153,8 @@ SR_PRIV int scpi_cmd(const struct sr_dev_inst *sdi, int command, ...);
 SR_PRIV int scpi_cmd_resp(const struct sr_dev_inst *sdi, GVariant **gvar,
                const GVariantType *gvtype, int command, ...);
 SR_PRIV int select_channel(const struct sr_dev_inst *sdi, struct sr_channel *ch);
+SR_PRIV struct sr_channel *next_enabled_channel(const struct sr_dev_inst *sdi,
+               struct sr_channel *cur_channel);
 SR_PRIV int scpi_pps_receive_data(int fd, int revents, void *cb_data);
 
 #endif