ABB semaphore protection overhaul The ABB semaphone protection logic that came with TCS211 from TI was broken in several ways: * Some semaphore-protected functions were called from Application_Initialize() context. NU_Obtain_Semaphore() called with NU_SUSPEND fails with NU_INVALID_SUSPEND in this context, but the return value wasn't checked, and NU_Release_Semaphore() would be called unconditionally at the end. The latter call would increment the semaphore count past 1, making the semaphore no longer binary and thus no longer effective for resource protection. The fix is to check the return value from NU_Obtain_Semaphore() and skip the NU_Release_Semaphore() call if the semaphore wasn't properly obtained. * Some SPI hardware manipulation was being done before entering the semaphore- protected critical section. The fix is to reorder the code: first obtain the semaphore, then do everything else. * In the corner case of L1/DSP recovery, l1_abb_power_on() would call some non-semaphore-protected ABB & SPI init functions. The fix is to skip those calls in the case of recovery. * A few additional corner cases existed, all of which are fixed by making ABB semaphore protection 100% consistent for all ABB functions and code paths. There is still one remaining problem of priority inversion: suppose a low- priority task calls an ABB function, and some medium-priority task just happens to preempt right in the middle of that semaphore-protected ABB operation. Then the high-priority SPI task is locked out for a non-deterministic time until that medium-priority task finishes its work and goes back to sleep. This priority inversion problem remains outstanding for now.

/**
 * @file	tty_api.h
 *
 * API Definition for TTY SWE.
 *
 * @author	Frederic Turgis (f-turgis@ti.com) & Gerard Cauvy (g-cauvy@ti.com)
 * @version 0.1
 */

/*
 * History:
 *
 * 	Date       	Modification
 *  ------------------------------------
 *  01/27/2003	Create
 *
 * (C) Copyright 2003 by Texas Instruments Incorporated, All Rights Reserved
 */

#ifndef __TTY_API_H_
#define __TTY_API_H_

#include "rvm/rvm_gen.h"		/* Generic RVM types and functions. */

/* TTY entity (Background Task) is highly linked to the Audio entity. */
#include "audio/audio_api.h"

#ifdef __cplusplus
extern "C"
{
#endif

typedef struct
{
  UINT8  Mode;
  UINT16 ThresholdRead;
  UINT16 ThreshHoldWrite;
}
T_AUDIO_TTY_CONFIG_PARAMETER;

#define TTY_STOP      (0)
#define TTY_EXT_START (1)

T_AUDIO_RET audio_tty_set_config (T_AUDIO_TTY_CONFIG_PARAMETER *parameter,
                                  T_RV_RETURN *return_path);

#define AUDIO_TTY_STATUS_MSG (0x00F2 | AUDIO_EVENT_EXTERN | AUDIO_EVENTS_MASK)

typedef struct
{
  T_RV_HDR  os_hdr;
  INT8      status;
}
T_AUDIO_TTY_STATUS;

#ifdef __cplusplus
}
#endif


#endif /*__TTY_API_H_*/