Implement FIFO_FLAG_INIT, cherry pick to 4.0

Author: tyler-gilbert

include/device/fifo.h

@@ -16,19 +16,15 @@ typedef union {
   u32 atomic_access; // read head and tail in one operation
 } fifo_atomic_position_t;
 
-typedef struct MCU_PACK {
+typedef struct {
   volatile fifo_atomic_position_t atomic_position; // 4 bytes
   devfs_transfer_handler_t transfer_handler;       // 8 bytes
   volatile u32 o_flags;                            // 4 bytes
 } fifo_state_t;
 
-/*! \brief FIFO Configuration
- * \details This structure defines the static FIFO configuration.
- *
- */
 typedef struct MCU_PACK {
-  u32 size /*! \brief The size of the buffer (only size-1 is usable) */;
-  char *buffer /*! \brief A pointer to the buffer */;
+  u32 size;
+  char *buffer;
 } fifo_config_t;
 
 int fifo_open(const devfs_handle_t *handle) MCU_ROOT_EXEC_CODE;

src/device/fifo.c

@@ -1,6 +1,5 @@
 // Copyright 2011-2021 Tyler Gilbert and Stratify Labs, Inc; see LICENSE.md
 
-
 #include <errno.h>
 #include <fcntl.h>
 #include <stddef.h>
@@ -247,9 +246,17 @@ int fifo_close(const devfs_handle_t *handle) {
   return fifo_close_local(config, state);
 }
 
-int fifo_open_local(const fifo_config_t *config, fifo_state_t *state) { return 0; }
+int fifo_open_local(const fifo_config_t *config, fifo_state_t *state) {
+  MCU_UNUSED_ARGUMENT(config);
+  MCU_UNUSED_ARGUMENT(state);
+  return 0;
+}
 
-int fifo_close_local(const fifo_config_t *config, fifo_state_t *state) { return 0; }
+int fifo_close_local(const fifo_config_t *config, fifo_state_t *state) {
+  MCU_UNUSED_ARGUMENT(config);
+  MCU_UNUSED_ARGUMENT(state);
+  return 0;
+}
 
 int fifo_ioctl_local(
   const fifo_config_t *config,
@@ -288,6 +295,14 @@ int fifo_ioctl_local(
     fifo_data_transmitted(config, state); // something might be waiting to write the fifo
     return 0;
   case I_FIFO_SETATTR:
+
+    if( attr->o_flags & FIFO_FLAG_INIT ){
+      state->transfer_handler.read = NULL;
+      state->transfer_handler.write = NULL;
+      fifo_flush(state);
+      fifo_data_transmitted(config, state); // something might be waiting to write the fifo
+    }
+
     if (attr->o_flags & FIFO_FLAG_SET_WRITEBLOCK) {
       if (attr->o_flags & FIFO_FLAG_IS_OVERFLOW) {
         fifo_set_writeblock(state, 0);
@@ -301,6 +316,7 @@ int fifo_ioctl_local(
       fifo_data_transmitted(config, state); // something might be waiting to write the
                                             // fifo
     }
+
     return 0;
   }
   return SYSFS_SET_RETURN(EINVAL);