midi host: skip rx data with all zeroes

Author: hathach

examples/host/midi_rx/src/main.c

@@ -110,7 +110,7 @@ void tuh_midi_rx_cb(uint8_t idx, uint32_t xferred_bytes) {
   uint8_t cable_num = 0;
   uint32_t bytes_read = tuh_midi_stream_read(idx, &cable_num, buffer, sizeof(buffer));
 
-  printf("Cable %u rx %lu bytes: ", cable_num, bytes_read);
+  printf("Cable %u rx: ", cable_num);
   for (uint32_t i = 0; i < bytes_read; i++) {
     printf("%02X ", buffer[i]);
   }

src/class/midi/midi_host.c

@@ -166,23 +166,24 @@ bool midih_xfer_cb(uint8_t dev_addr, uint8_t ep_addr, xfer_result_t result, uint
   (void) result;
   const uint8_t idx = get_idx_by_ep_addr(dev_addr, ep_addr);
   TU_VERIFY(idx < CFG_TUH_MIDI);
-  midih_interface_t *p_midi_host = &_midi_host[idx];
+  midih_interface_t *p_midi = &_midi_host[idx];
 
-  if (ep_addr == p_midi_host->ep_stream.rx.ep_addr) {
+  if (ep_addr == p_midi->ep_stream.rx.ep_addr) {
     // receive new data, put it into FIFO and invoke callback if available
-    if (xferred_bytes) {
-      tu_edpt_stream_read_xfer_complete(&p_midi_host->ep_stream.rx, xferred_bytes);
+    // Note: some devices send back all zero packets even if there is no data ready
+    if (xferred_bytes && !tu_mem_is_zero(p_midi->ep_stream.rx.ep_buf, xferred_bytes)) {
+      tu_edpt_stream_read_xfer_complete(&p_midi->ep_stream.rx, xferred_bytes);
       tuh_midi_rx_cb(idx, xferred_bytes);
     }
 
-    tu_edpt_stream_read_xfer(dev_addr, &p_midi_host->ep_stream.rx); // prepare for next transfer
-  } else if (ep_addr == p_midi_host->ep_stream.tx.ep_addr) {
+    tu_edpt_stream_read_xfer(dev_addr, &p_midi->ep_stream.rx); // prepare for next transfer
+  } else if (ep_addr == p_midi->ep_stream.tx.ep_addr) {
     tuh_midi_tx_cb(idx, xferred_bytes);
 
-    if (0 == tu_edpt_stream_write_xfer(dev_addr, &p_midi_host->ep_stream.tx)) {
+    if (0 == tu_edpt_stream_write_xfer(dev_addr, &p_midi->ep_stream.tx)) {
       // If there is no data left, a ZLP should be sent if
       // xferred_bytes is multiple of EP size and not zero
-      tu_edpt_stream_write_zlp_if_needed(dev_addr, &p_midi_host->ep_stream.tx, xferred_bytes);
+      tu_edpt_stream_write_zlp_if_needed(dev_addr, &p_midi->ep_stream.tx, xferred_bytes);
     }
   }
 

src/common/tusb_common.h

@@ -120,6 +120,22 @@ TU_ATTR_ALWAYS_INLINE static inline int tu_memcpy_s(void *dest, size_t destsz, c
   return 0;
 }
 
+TU_ATTR_ALWAYS_INLINE static inline bool tu_mem_is_zero(const void *buffer, size_t size) {
+  const uint8_t* buf8 = (const uint8_t*) buffer;
+  for (size_t i = 0; i < size; i++) {
+    if (buf8[i] != 0) { return false; }
+  }
+  return true;
+}
+
+TU_ATTR_ALWAYS_INLINE static inline bool tu_mem_is_ff(const void *buffer, size_t size) {
+  const uint8_t* buf8 = (const uint8_t*) buffer;
+  for (size_t i = 0; i < size; i++) {
+    if (buf8[i] != 0xff) { return false; }
+  }
+  return true;
+}
+
 
 //------------- Bytes -------------//
 TU_ATTR_ALWAYS_INLINE static inline uint32_t tu_u32(uint8_t b3, uint8_t b2, uint8_t b1, uint8_t b0) {
@@ -181,8 +197,7 @@ TU_ATTR_ALWAYS_INLINE static inline uint32_t tu_round_up(uint32_t v, uint32_t f)
 
 // log2 of a value is its MSB's position
 // TODO use clz TODO remove
-static inline uint8_t tu_log2(uint32_t value)
-{
+TU_ATTR_ALWAYS_INLINE static inline uint8_t tu_log2(uint32_t value) {
   uint8_t result = 0;
   while (value >>= 1) { result++; }
   return result;
@@ -193,8 +208,7 @@ static inline uint8_t tu_log2(uint32_t value)
 //   return sizeof(uint32_t) * CHAR_BIT - __builtin_clz(x) - 1;
 //}
 
-static inline bool tu_is_power_of_two(uint32_t value)
-{
+TU_ATTR_ALWAYS_INLINE static inline bool tu_is_power_of_two(uint32_t value) {
    return (value != 0) && ((value & (value - 1)) == 0);
 }
 
@@ -205,27 +219,23 @@ static inline bool tu_is_power_of_two(uint32_t value)
 typedef struct { uint16_t val; } TU_ATTR_PACKED tu_unaligned_uint16_t;
 typedef struct { uint32_t val; } TU_ATTR_PACKED tu_unaligned_uint32_t;
 
-TU_ATTR_ALWAYS_INLINE static inline uint32_t tu_unaligned_read32(const void* mem)
-{
-  tu_unaligned_uint32_t const* ua32 = (tu_unaligned_uint32_t const*) mem;
+TU_ATTR_ALWAYS_INLINE static inline uint32_t tu_unaligned_read32(const void *mem) {
+  tu_unaligned_uint32_t const *ua32 = (tu_unaligned_uint32_t const *) mem;
   return ua32->val;
 }
 
-TU_ATTR_ALWAYS_INLINE static inline void tu_unaligned_write32(void* mem, uint32_t value)
-{
-  tu_unaligned_uint32_t* ua32 = (tu_unaligned_uint32_t*) mem;
+TU_ATTR_ALWAYS_INLINE static inline void tu_unaligned_write32(void *mem, uint32_t value) {
+  tu_unaligned_uint32_t *ua32 = (tu_unaligned_uint32_t *) mem;
   ua32->val = value;
 }
 
-TU_ATTR_ALWAYS_INLINE static inline uint16_t tu_unaligned_read16(const void* mem)
-{
-  tu_unaligned_uint16_t const* ua16 = (tu_unaligned_uint16_t const*) mem;
+TU_ATTR_ALWAYS_INLINE static inline uint16_t tu_unaligned_read16(const void *mem) {
+  tu_unaligned_uint16_t const *ua16 = (tu_unaligned_uint16_t const *) mem;
   return ua16->val;
 }
 
-TU_ATTR_ALWAYS_INLINE static inline void tu_unaligned_write16(void* mem, uint16_t value)
-{
-  tu_unaligned_uint16_t* ua16 = (tu_unaligned_uint16_t*) mem;
+TU_ATTR_ALWAYS_INLINE static inline void tu_unaligned_write16(void *mem, uint16_t value) {
+  tu_unaligned_uint16_t *ua16 = (tu_unaligned_uint16_t *) mem;
   ua16->val = value;
 }