gsm_bts_send_c0_power_red(): check if BTS is online first

... and print a proper error message instead of "not supported".  We
don't know for sure whether it's supported before the BTS is connected.

Change-Id: I080aa7ef331b76918ae48d555eea6e4290c57120
Related: SYS#6435
---
M src/osmo-bsc/bsc_vty.c
M src/osmo-bsc/bts.c
M src/osmo-bsc/bts_ctrl.c
3 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/src/osmo-bsc/bsc_vty.c b/src/osmo-bsc/bsc_vty.c
index f1bd7c4..34676a2 100644
--- a/src/osmo-bsc/bsc_vty.c
+++ b/src/osmo-bsc/bsc_vty.c
@@ -1426,18 +1426,22 @@
 	}
 
 	rc = gsm_bts_set_c0_power_red(bts, red);
-	if (rc == -ENOTSUP) {
+	switch (rc) {
+	case 0: /* success */
+		return CMD_SUCCESS;
+	case -ENOTCONN:
+		vty_out(vty, "%% BTS%u is offline%s", bts_nr, VTY_NEWLINE);
+		return CMD_WARNING;
+	case -ENOTSUP:
 		vty_out(vty, "%% BCCH carrier power reduction operation mode "
 			"is not supported for BTS%u%s", bts_nr, VTY_NEWLINE);
 		return CMD_WARNING;
-	} else if (rc != 0) {
+	default:
 		vty_out(vty, "%% Failed to %sable BCCH carrier power reduction "
 			"operation mode for BTS%u%s", red ? "en" : "dis",
 			bts_nr, VTY_NEWLINE);
 		return CMD_WARNING;
 	}
-
-	return CMD_SUCCESS;
 }
 
 /* this command is now hidden, as it's a low-level debug hack, and people should
diff --git a/src/osmo-bsc/bts.c b/src/osmo-bsc/bts.c
index be0516d..1ef9cca 100644
--- a/src/osmo-bsc/bts.c
+++ b/src/osmo-bsc/bts.c
@@ -981,6 +981,8 @@
 /* Send the given C0 power reduction value to the BTS */
 int gsm_bts_send_c0_power_red(const struct gsm_bts *bts, const uint8_t red)
 {
+	if (!bts_is_online(bts))
+		return -ENOTCONN;
 	if (!osmo_bts_has_feature(&bts->features, BTS_FEAT_BCCH_POWER_RED))
 		return -ENOTSUP;
 	if (bts->model->power_ctrl_send_c0_power_red == NULL)
diff --git a/src/osmo-bsc/bts_ctrl.c b/src/osmo-bsc/bts_ctrl.c
index a971fab..5ac1e0d 100644
--- a/src/osmo-bsc/bts_ctrl.c
+++ b/src/osmo-bsc/bts_ctrl.c
@@ -497,15 +497,19 @@
 	int rc;
 
 	rc = gsm_bts_set_c0_power_red(bts, red);
-	if (rc == -ENOTSUP) {
+	switch (rc) {
+	case 0: /* success */
+		return get_bts_c0_power_red(cmd, data);
+	case -ENOTCONN:
+		cmd->reply = "BTS is offline";
+		return CTRL_CMD_ERROR;
+	case -ENOTSUP:
 		cmd->reply = "BCCH carrier power reduction is not supported";
 		return CTRL_CMD_ERROR;
-	} else if (rc != 0) {
+	default:
 		cmd->reply = "Failed to enable BCCH carrier power reduction";
 		return CTRL_CMD_ERROR;
 	}
-
-	return get_bts_c0_power_red(cmd, data);
 }
 
 CTRL_CMD_DEFINE(bts_c0_power_red, "c0-power-reduction");

