4 files changed, 101 insertions, 38 deletions

diff --git a/quantum/encoder.c b/quantum/encoder.c
index 735eb1cd71..0a48ac9a07 100644
--- a/quantum/encoder.c
+++ b/quantum/encoder.c
@@ -15,34 +15,39 @@ __attribute__((weak)) bool should_process_encoder(void) {
 }
 
 static encoder_events_t encoder_events;
+static bool             signal_queue_drain = false;
 
 void encoder_init(void) {
     memset(&encoder_events, 0, sizeof(encoder_events));
     encoder_driver_init();
 }
 
-static bool encoder_handle_queue(void) {
-    bool changed = false;
-    while (encoder_events.tail != encoder_events.head) {
-        encoder_event_t event = encoder_events.queue[encoder_events.tail];
-        encoder_events.tail   = (encoder_events.tail + 1) % MAX_QUEUED_ENCODER_EVENTS;
+static void encoder_queue_drain(void) {
+    encoder_events.tail     = encoder_events.head;
+    encoder_events.dequeued = encoder_events.enqueued;
+}
 
+static bool encoder_handle_queue(void) {
+    bool    changed = false;
+    uint8_t index;
+    bool    clockwise;
+    while (encoder_dequeue_event(&index, &clockwise)) {
 #ifdef ENCODER_MAP_ENABLE
 
         // The delays below cater for Windows and its wonderful requirements.
-        action_exec(event.clockwise ? MAKE_ENCODER_CW_EVENT(event.index, true) : MAKE_ENCODER_CCW_EVENT(event.index, true));
+        action_exec(clockwise ? MAKE_ENCODER_CW_EVENT(index, true) : MAKE_ENCODER_CCW_EVENT(index, true));
 #    if ENCODER_MAP_KEY_DELAY > 0
         wait_ms(ENCODER_MAP_KEY_DELAY);
 #    endif // ENCODER_MAP_KEY_DELAY > 0
 
-        action_exec(event.clockwise ? MAKE_ENCODER_CW_EVENT(event.index, false) : MAKE_ENCODER_CCW_EVENT(event.index, false));
+        action_exec(clockwise ? MAKE_ENCODER_CW_EVENT(index, false) : MAKE_ENCODER_CCW_EVENT(index, false));
 #    if ENCODER_MAP_KEY_DELAY > 0
         wait_ms(ENCODER_MAP_KEY_DELAY);
 #    endif // ENCODER_MAP_KEY_DELAY > 0
 
 #else // ENCODER_MAP_ENABLE
 
-        encoder_update_kb(event.index, event.clockwise ? true : false);
+        encoder_update_kb(index, clockwise);
 
 #endif // ENCODER_MAP_ENABLE
 
@@ -61,6 +66,11 @@ bool encoder_task(void) {
     }
 #endif // SPLIT_KEYBOARD
 
+    if (signal_queue_drain) {
+        signal_queue_drain = false;
+        encoder_queue_drain();
+    }
+
     // Let the encoder driver produce events
     encoder_driver_task();
 
@@ -72,39 +82,71 @@ bool encoder_task(void) {
     return changed;
 }
 
-bool encoder_queue_event(uint8_t index, bool clockwise) {
+bool encoder_queue_full_advanced(encoder_events_t *events) {
+    return events->head == (events->tail - 1) % MAX_QUEUED_ENCODER_EVENTS;
+}
+
+bool encoder_queue_full(void) {
+    return encoder_queue_full_advanced(&encoder_events);
+}
+
+bool encoder_queue_empty_advanced(encoder_events_t *events) {
+    return events->head == events->tail;
+}
+
+bool encoder_queue_empty(void) {
+    return encoder_queue_empty_advanced(&encoder_events);
+}
+
+bool encoder_queue_event_advanced(encoder_events_t *events, uint8_t index, bool clockwise) {
     // Drop out if we're full
-    if ((encoder_events.head + 1) % MAX_QUEUED_ENCODER_EVENTS == encoder_events.tail) {
+    if (encoder_queue_full_advanced(events)) {
         return false;
     }
 
     // Append the event
-    encoder_event_t new_event                 = {.index = index, .clockwise = clockwise ? 1 : 0};
-    encoder_events.queue[encoder_events.head] = new_event;
+    encoder_event_t new_event   = {.index = index, .clockwise = clockwise ? 1 : 0};
+    events->queue[events->head] = new_event;
 
     // Increment the head index
-    encoder_events.head = (encoder_events.head + 1) % MAX_QUEUED_ENCODER_EVENTS;
+    events->head = (events->head + 1) % MAX_QUEUED_ENCODER_EVENTS;
+    events->enqueued++;
 
     return true;
 }
 
-void encoder_retrieve_events(encoder_events_t *events) {
-    memcpy(events, &encoder_events, sizeof(encoder_events));
+bool encoder_dequeue_event_advanced(encoder_events_t *events, uint8_t *index, bool *clockwise) {
+    if (encoder_queue_empty_advanced(events)) {
+        return false;
+    }
+
+    // Retrieve the event
+    encoder_event_t event = events->queue[events->tail];
+    *index                = event.index;
+    *clockwise            = event.clockwise;
+
+    // Increment the tail index
+    events->tail = (events->tail + 1) % MAX_QUEUED_ENCODER_EVENTS;
+    events->dequeued++;
+
+    return true;
 }
 
-#ifdef SPLIT_KEYBOARD
-void encoder_set_tail_index(uint8_t tail_index) {
-    encoder_events.tail = tail_index;
+bool encoder_queue_event(uint8_t index, bool clockwise) {
+    return encoder_queue_event_advanced(&encoder_events, index, clockwise);
 }
 
-void encoder_handle_slave_events(encoder_events_t *events) {
-    while (events->tail != events->head) {
-        encoder_event_t event = events->queue[events->tail];
-        events->tail          = (events->tail + 1) % MAX_QUEUED_ENCODER_EVENTS;
-        encoder_queue_event(event.index, event.clockwise ? true : false);
-    }
+bool encoder_dequeue_event(uint8_t *index, bool *clockwise) {
+    return encoder_dequeue_event_advanced(&encoder_events, index, clockwise);
+}
+
+void encoder_retrieve_events(encoder_events_t *events) {
+    memcpy(events, &encoder_events, sizeof(encoder_events));
+}
+
+void encoder_signal_queue_drain(void) {
+    signal_queue_drain = true;
 }
-#endif // SPLIT_KEYBOARD
 
 __attribute__((weak)) bool encoder_update_user(uint8_t index, bool clockwise) {
     return true;
diff --git a/quantum/encoder.h b/quantum/encoder.h
index 90414a43a0..317a91f1da 100644
--- a/quantum/encoder.h
+++ b/quantum/encoder.h
@@ -29,6 +29,7 @@ __attribute__((weak)) bool should_process_encoder(void);
 void encoder_init(void);
 bool encoder_task(void);
 bool encoder_queue_event(uint8_t index, bool clockwise);
+bool encoder_dequeue_event(uint8_t *index, bool *clockwise);
 
 bool encoder_update_kb(uint8_t index, bool clockwise);
 bool encoder_update_user(uint8_t index, bool clockwise);
@@ -82,6 +83,8 @@ typedef struct encoder_event_t {
 } encoder_event_t;
 
 typedef struct encoder_events_t {
+    uint8_t         enqueued;
+    uint8_t         dequeued;
     uint8_t         head;
     uint8_t         tail;
     encoder_event_t queue[MAX_QUEUED_ENCODER_EVENTS];
@@ -90,10 +93,12 @@ typedef struct encoder_events_t {
 // Get the current queued events
 void encoder_retrieve_events(encoder_events_t *events);
 
-#    ifdef SPLIT_KEYBOARD
-void encoder_set_tail_index(uint8_t tail_index);
-void encoder_handle_slave_events(encoder_events_t *events);
-#    endif // SPLIT_KEYBOARD
+// Encoder event queue management
+bool encoder_queue_event_advanced(encoder_events_t *events, uint8_t index, bool clockwise);
+bool encoder_dequeue_event_advanced(encoder_events_t *events, uint8_t *index, bool *clockwise);
+
+// Reset the queue to be empty
+void encoder_signal_queue_drain(void);
 
 #    ifdef ENCODER_MAP_ENABLE
 #        define NUM_DIRECTIONS 2
diff --git a/quantum/split_common/transaction_id_define.h b/quantum/split_common/transaction_id_define.h
index 05b3bf7b62..5bfbe2aec7 100644
--- a/quantum/split_common/transaction_id_define.h
+++ b/quantum/split_common/transaction_id_define.h
@@ -31,7 +31,7 @@ enum serial_transaction_id {
 #ifdef ENCODER_ENABLE
     GET_ENCODERS_CHECKSUM,
     GET_ENCODERS_DATA,
-    PUT_ENCODER_TAIL,
+    CMD_ENCODER_DRAIN,
 #endif // ENCODER_ENABLE
 
 #ifndef DISABLE_SYNC_TIMER
diff --git a/quantum/split_common/transactions.c b/quantum/split_common/transactions.c
index 2cfa83e7a3..33bc9e9f57 100644
--- a/quantum/split_common/transactions.c
+++ b/quantum/split_common/transactions.c
@@ -14,6 +14,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <stdint.h>
 #include <string.h>
 #include <stddef.h>
 
@@ -80,8 +81,12 @@
     { 0, 0, sizeof_member(split_shared_memory_t, member), offsetof(split_shared_memory_t, member), cb }
 #define trans_target2initiator_initializer(member) trans_target2initiator_initializer_cb(member, NULL)
 
+#define trans_initiator2target_cb(cb) \
+    { 0, 0, 0, 0, cb }
+
 #define transport_write(id, data, length) transport_execute_transaction(id, data, length, NULL, 0)
 #define transport_read(id, data, length) transport_execute_transaction(id, NULL, 0, data, length)
+#define transport_exec(id) transport_execute_transaction(id, NULL, 0, NULL, 0)
 
 #if defined(SPLIT_TRANSACTION_IDS_KB) || defined(SPLIT_TRANSACTION_IDS_USER)
 // Forward-declare the RPC callback handlers
@@ -234,14 +239,26 @@ static void master_matrix_handlers_slave(matrix_row_t master_matrix[], matrix_ro
 #ifdef ENCODER_ENABLE
 
 static bool encoder_handlers_master(matrix_row_t master_matrix[], matrix_row_t slave_matrix[]) {
-    static uint32_t  last_update = 0;
+    static uint32_t  last_update   = 0;
+    static uint8_t   last_checksum = 0;
     encoder_events_t temp_events;
 
     bool okay = read_if_checksum_mismatch(GET_ENCODERS_CHECKSUM, GET_ENCODERS_DATA, &last_update, &temp_events, &split_shmem->encoders.events, sizeof(temp_events));
     if (okay) {
-        encoder_handle_slave_events(&split_shmem->encoders.events);
-        transport_write(PUT_ENCODER_TAIL, &split_shmem->encoders.events.tail, sizeof(split_shmem->encoders.events.tail));
-        split_shmem->encoders.checksum = crc8(&split_shmem->encoders.events, sizeof(split_shmem->encoders.events));
+        if (last_checksum != split_shmem->encoders.checksum) {
+            bool    actioned = false;
+            uint8_t index;
+            bool    clockwise;
+            while (okay && encoder_dequeue_event_advanced(&split_shmem->encoders.events, &index, &clockwise)) {
+                okay &= encoder_queue_event(index, clockwise);
+                actioned = true;
+            }
+
+            if (actioned) {
+                okay &= transport_exec(CMD_ENCODER_DRAIN);
+            }
+            last_checksum = split_shmem->encoders.checksum;
+        }
     }
     return okay;
 }
@@ -253,9 +270,8 @@ static void encoder_handlers_slave(matrix_row_t master_matrix[], matrix_row_t sl
     split_shmem->encoders.checksum = crc8(&split_shmem->encoders.events, sizeof(split_shmem->encoders.events));
 }
 
-static void encoder_handlers_slave_reset(uint8_t initiator2target_buffer_size, const void *initiator2target_buffer, uint8_t target2initiator_buffer_size, void *target2initiator_buffer) {
-    uint8_t tail_index = *(uint8_t *)initiator2target_buffer;
-    encoder_set_tail_index(tail_index);
+static void encoder_handlers_slave_drain(uint8_t initiator2target_buffer_size, const void *initiator2target_buffer, uint8_t target2initiator_buffer_size, void *target2initiator_buffer) {
+    encoder_signal_queue_drain();
 }
 
 // clang-format off
@@ -264,7 +280,7 @@ static void encoder_handlers_slave_reset(uint8_t initiator2target_buffer_size, c
 #    define TRANSACTIONS_ENCODERS_REGISTRATIONS \
     [GET_ENCODERS_CHECKSUM] = trans_target2initiator_initializer(encoders.checksum), \
     [GET_ENCODERS_DATA]     = trans_target2initiator_initializer(encoders.events), \
-    [PUT_ENCODER_TAIL]      = trans_initiator2target_initializer_cb(encoders.events.tail, encoder_handlers_slave_reset),
+    [CMD_ENCODER_DRAIN]     = trans_initiator2target_cb(encoder_handlers_slave_drain),
 // clang-format on
 
 #else // ENCODER_ENABLE