diff options
Diffstat (limited to 'src/common/tusb_fifo.h')
| -rw-r--r-- | src/common/tusb_fifo.h | 40 |
1 files changed, 19 insertions, 21 deletions
diff --git a/src/common/tusb_fifo.h b/src/common/tusb_fifo.h index f72ff295b..2f60ec2f4 100644 --- a/src/common/tusb_fifo.h +++ b/src/common/tusb_fifo.h @@ -69,8 +69,8 @@ extern "C" { * | 0 | 1 | W | 3 | 4 | R | * * - Number of items in the fifo can be determined in either cases: - * - case W > R: Count = W - R - * - case W < R: Count = 2*depth - (R - W) + * - case W >= R: Count = W - R + * - case W < R: Count = 2*depth - (R - W) * * In non-overwritable mode, computed Count (in above 2 cases) is at most equal to depth. * However, in over-writable mode, write index can be repeatedly increased and count can be @@ -82,10 +82,10 @@ extern "C" { * ------------------------- * | R | 1 | 2 | 3 | W | 5 | * - * - Double Overflowed i.e index is out of allowed range [0,2*depth) e.g: + * - Double Overflowed i.e index is out of allowed range [0,2*depth) + * This occurs when we continue to write after 1st overflowed to 2nd overflowed. e.g: * write(3), write(1), write(2) - * Continue to write after overflowed to 2nd overflowed. - * We must prevent 2nd overflowed since it will cause incorrect computed of count, in above example + * This must be prevented since it will cause unrecoverable state, in above example * if not handled the fifo will be empty instead of continue-to-be full. Since we must not modify * read index in write() function, which cause race condition. We will re-position write index so that * after data is written it is a full fifo i.e W = depth - R @@ -106,17 +106,16 @@ extern "C" { */ typedef struct { - uint8_t* buffer ; ///< buffer pointer - uint16_t depth ; ///< max items - uint16_t item_size ; ///< size of each item + uint8_t* buffer ; // buffer pointer + uint16_t depth ; // max items - bool overwritable ; + struct TU_ATTR_PACKED { + uint16_t item_size : 15; // size of each item + bool overwritable : 1 ; // ovwerwritable when full + }; - uint16_t non_used_index_space ; ///< required for non-power-of-two buffer length - //uint16_t max_pointer_idx ; ///< maximum absolute pointer index - - volatile uint16_t wr_idx ; ///< write index - volatile uint16_t rd_idx ; ///< read index + volatile uint16_t wr_idx ; // write index + volatile uint16_t rd_idx ; // read index #if OSAL_MUTEX_REQUIRED osal_mutex_t mutex_wr; @@ -133,13 +132,12 @@ typedef struct void * ptr_wrap ; ///< wrapped part start pointer } tu_fifo_buffer_info_t; -#define TU_FIFO_INIT(_buffer, _depth, _type, _overwritable) \ -{ \ - .buffer = _buffer, \ - .depth = _depth, \ - .item_size = sizeof(_type), \ - .overwritable = _overwritable, \ - .non_used_index_space = (uint16_t)(UINT16_MAX - (2*(_depth)-1)), \ +#define TU_FIFO_INIT(_buffer, _depth, _type, _overwritable) \ +{ \ + .buffer = _buffer, \ + .depth = _depth, \ + .item_size = sizeof(_type), \ + .overwritable = _overwritable, \ } #define TU_FIFO_DEF(_name, _depth, _type, _overwritable) \ |