Final cleanup.

1 files changed, 16 insertions, 3 deletions

diff --git a/src/common/tusb_fifo.h b/src/common/tusb_fifo.h
index 56491c37b..66888ef19 100644
--- a/src/common/tusb_fifo.h
+++ b/src/common/tusb_fifo.h
@@ -31,6 +31,15 @@
 #ifndef _TUSB_FIFO_H_
 #define _TUSB_FIFO_H_
 
+// Due to the use of unmasked pointers, this FIFO does not suffer from loosing
+// one item slice. Furthermore, write and read operations are completely
+// decoupled as write and read functions do not modify a common state. Henceforth,
+// writing or reading from the FIFO within an ISR is safe as long as no other
+// process (thread or ISR) interferes.
+// Also, this FIFO is ready to be used in combination with a DMA as the write and
+// read pointers can be updated from within a DMA ISR. Overflows are detectable
+// within a certain number (see tu_fifo_overflow()).
+
 // mutex is only needed for RTOS
 // for OS None, we don't get preempted
 #define CFG_FIFO_MUTEX      (CFG_TUSB_OS != OPT_OS_NONE)
@@ -76,8 +85,8 @@ typedef struct
       .depth                  = _depth,                               \
       .item_size              = sizeof(_type),                        \
       .overwritable           = _overwritable,                        \
-      .non_used_index_space   = (2^16-1) % _depth,                    \
-      .max_pointer_idx        = (2^16-1) - ((2^16-1) % _depth),       \
+      .non_used_index_space   = 0x10000 % _depth,                     \
+      .max_pointer_idx        = 0xFFFF - (0x10000 % _depth),          \
   }
 
 bool tu_fifo_clear(tu_fifo_t *f);
@@ -100,13 +109,17 @@ bool     tu_fifo_peek_at                (tu_fifo_t* f, uint16_t pos, void * p_bu
 uint16_t tu_fifo_peek_at_n              (tu_fifo_t* f, uint16_t pos, void * p_buffer, uint16_t n);
 
 uint16_t tu_fifo_count                  (tu_fifo_t* f);
-void     tu_fifo_correct_read_pointer   (tu_fifo_t* f);
 bool     tu_fifo_empty                  (tu_fifo_t* f);
 bool     tu_fifo_full                   (tu_fifo_t* f);
 uint16_t tu_fifo_remaining              (tu_fifo_t* f);
 bool     tu_fifo_overflow               (tu_fifo_t* f);
 void     tu_fifo_correct_read_pointer   (tu_fifo_t* f);
 
+// Pointer modifications intended to be used in combinations with DMAs.
+// USE WITH CARE - NO SAFTY CHECKS CONDUCTED HERE! NOT MUTEX PROTECTED!
+void     tu_fifo_advance_write_pointer  (tu_fifo_t *f, uint16_t n);
+void     tu_fifo_advance_read_pointer   (tu_fifo_t *f, uint16_t n);
+
 static inline bool tu_fifo_peek(tu_fifo_t* f, void * p_buffer)
 {
   return tu_fifo_peek_at(f, 0, p_buffer);