Add alternate bitfield padding option

Adds configuration option CFG_TUSB_ALT_BIT_PACKING_ALIGNMENT, which
substitutes bitfield variable " : 0" padding syntax with an unused
variable of size equal to the remaining number of bits.

This change resolves aligned access issues for some platforms.

Default behavior is original if the option is not explicitly enabled.

1 files changed, 10 insertions, 2 deletions

diff --git a/src/host/ohci/ohci.h b/src/host/ohci/ohci.h
index bfcdaf9a3..76d6fff61 100644
--- a/src/host/ohci/ohci.h
+++ b/src/host/ohci/ohci.h
@@ -1,4 +1,4 @@
-/* 
+/*
  * The MIT License (MIT)
  *
  * Copyright (c) 2019 Ha Thach (tinyusb.org)
@@ -208,7 +208,11 @@ typedef volatile struct
       uint32_t interrupt_routing          : 1;
       uint32_t remote_wakeup_connected    : 1;
       uint32_t remote_wakeup_enale        : 1;
-      uint32_t : 0;
+#if CFG_TUSB_ALT_BIT_PACKING_ALIGNMENT
+      uint32_t unused                     : 21;
+#else
+      uint32_t                            : 0;
+#endif /* CFG_TUSB_ALT_BIT_PACKING_ALIGNMENT */
     }control_bit;
   };
 
@@ -276,7 +280,11 @@ typedef volatile struct
       uint32_t port_suspend_status_change         : 1;
       uint32_t port_over_current_indicator_change : 1;
       uint32_t port_reset_status_change           : 1;
+#if CFG_TUSB_ALT_BIT_PACKING_ALIGNMENT
+      uint32_t unused                             : 11;
+#else
       uint32_t                                    : 0;
+#endif /* CFG_TUSB_ALT_BIT_PACKING_ALIGNMENT */
     }rhport_status_bit[2];
   };
 }ohci_registers_t;