Tuner step increment/decrement will select the next highest or next
lowest service frequency.  There are a total of three possible
frequencies from analog_freqs_khz given a broadcast type and system.

Opcodes implemented:
   - <Tuner Step Increment>
   - <Tuner Step Decrement>

Signed-off-by: Jiunn Chang <c0d1n61at3 at gmail.com>
---
  utils/cec-follower/cec-tuner.cpp | 47 ++++++++++++++++++++++++++++++--
  1 file changed, 44 insertions(+), 3 deletions(-)

diff --git a/utils/cec-follower/cec-tuner.cpp b/utils/cec-follower/cec-tuner.cpp
index acc3fd00..1a9b9d90 100644
--- a/utils/cec-follower/cec-tuner.cpp
+++ b/utils/cec-follower/cec-tuner.cpp

@@ -135,6 +135,22 @@ static bool analog_set_tuner_dev_info(struct node *node, struct cec_msg *msg)
  	return false;
  }
  
+static int analog_find_freq_index(struct cec_op_tuner_device_info *info)
+{
+	if (info->analog.ana_freq == 0)
+		return -1;
+
+	int ana_freq_khz = (info->analog.ana_freq * 625) / 10;
+
+	for (int i = 0; i < NUM_ANALOG_FREQS; i++) {
+		int freq = analog_freqs_khz[info->analog.ana_bcast_type][info->analog.bcast_system][i];
+
+		if (ana_freq_khz == freq)
+			return i;
+	}
+	return -1;
+}
+
  void process_tuner_record_timer_msgs(struct node *node, struct cec_msg &msg, unsigned me)
  {
  	bool is_bcast = cec_msg_is_broadcast(&msg);

@@ -178,12 +194,37 @@ void process_tuner_record_timer_msgs(struct node *node, struct cec_msg &msg, uns
  		return;
  
  	case CEC_MSG_SELECT_DIGITAL_SERVICE:
-	case CEC_MSG_TUNER_STEP_DECREMENT:
-	case CEC_MSG_TUNER_STEP_INCREMENT:
-		if (!cec_has_tuner(1 << me))
+	case CEC_MSG_TUNER_STEP_DECREMENT: {
+		if (!cec_has_tuner(1 << me) && !cec_has_tv(1 << me))
  			break;
+
+		struct cec_op_tuner_device_info *info = &node->state.tuner_dev_info;
+		int freq_idx = analog_find_freq_index(info);
+		int idx = (freq_idx == 0) ? NUM_ANALOG_FREQS : freq_idx;
+
+		if (info->is_analog) {
+			int freq = analog_freqs_khz[info->analog.ana_bcast_type][info->analog.bcast_system][--idx];
+