#define TRUE  1
#define FALSE 0

/* defines for calls to SetI2C, ON -> +5V, OFF -> 0 V */
#define CLKON      0
#define CLKOFF     0x8
#define DATON      0
#define DATOFF     0x4

static void SetI2C(unsigned char Clock, unsigned char Data) {
/* set Clock and Data values */
  unsigned char remain;

  remain = inportb(QQS_PORT + 2) & 0x3; /* keep tuner & tt selection */
  outportb(QQS_PORT + 2, Clock | Data | remain);
}

static int GetI2C(void) {
/* return whether data is ON */
  return (inportb(QQS_PORT + 2) & 0x4) != 0;
}

static void StartI2C(void) {
/* set I2C to start condition */
  SetI2C(CLKON, DATOFF);
  SetI2C(CLKOFF, DATOFF);
}

static void StopI2C(void) {
/* (re)set I2C to stop condition */
  SetI2C(CLKON, DATOFF);
  SetI2C(CLKON, DATON);
}

static int SendByteI2C(unsigned char Byte) {
/* send byte to I2C, I2C must be in startcondition (clk = 0), return whether 
   success */
  unsigned char bit;
  int result;

  for (bit = 0x80; bit; bit >>= 1) {
    /* send a bit */
    SetI2C(CLKOFF, (Byte & bit) ? DATON : DATOFF);
    SetI2C(CLKON, (Byte & bit) ? DATON : DATOFF);
    udelay(110);
    SetI2C(CLKOFF, (Byte & bit) ? DATON : DATOFF);
  }
  /* get acknowledge */
  SetI2C(CLKOFF, DATON);
  SetI2C(CLKON, DATON);
  udelay(110);
  result = !GetI2C();  /* must return FALSE, tuner has set DATOFF */
  SetI2C(CLKOFF, DATOFF);
  return result;
} 

static void RecByteI2C(unsigned char* Byte) {
/* receive Byte from I2C, I2C must be in startcondition (clk = OFF) */
  unsigned char bit;

  *Byte = 0;
  for (bit = 0x80; bit; bit >>= 1)
  {
    /* receive a bit */
    SetI2C(CLKOFF, DATON);
    SetI2C(CLKON, DATON);
    udelay(110);
    if (GetI2C())
      *Byte |= bit;
  }
  SetI2C(CLKOFF, DATON);
} 

static int WriteI2C(int Count, unsigned char * Buffer) {
/* write Buffer[0..Count-1] to I2C, return whether success */
  StartI2C();
  while (Count-- > 0)
    if (!SendByteI2C(*Buffer++)) break;     /* not acknowledged */
  StopI2C();
  return Count < 0;
}

int InitTune(void) {
/* return whether I2C functions correctly. if TRUE tuner is initialized. */
  int result;

  SetI2C(CLKON, DATON);
  udelay(110);
  if (!GetI2C()) return FALSE;
  SetI2C(CLKON, DATOFF);
  udelay(110);
  result = !GetI2C();
  StopI2C();
  return result;
}

int GetStatus(unsigned char* Status) {
/* get status from tuner, return whether success */
  int result = TRUE;

  StartI2C();
  if ((result = SendByteI2C(0xc3)) == TRUE) RecByteI2C(Status);
  StopI2C();
  return result;
}

int SetFreq(unsigned long Freq) {
/* set tuner to given frequency Freq in Hz, return whether success.
   InitTune() must have been called before use. */

  unsigned char band, buffer[5];
  unsigned int divider;

  if (Freq < 46000000L || Freq > 870000000L) return FALSE;

  if      (Freq < 175250000L) band = 0xa0;     /* low band */
  else if (Freq < 455250000L) band = 0x90;     /* mid band */
  else                        band = 0x30;     /* high band */

  divider = (unsigned int)((Freq + 38900000L) / 62500L);
  buffer[0] = 0xc2;
  buffer[1] = (unsigned char)(divider >> 8);
  buffer[2] = (unsigned char)(divider & 0xff);
  buffer[3] = 0x8e; /* CP -> moderate tuning speed with quality */
  buffer[4] = band;
  return WriteI2C(5, buffer);
}

int SelectChannel(unsigned long freq) {
/* freq == 0 -> direct video,
   freq != 0 -> tune frequency freq on tuner.
   initializes tuner if neccesary, return whether success */

  unsigned char tuneremain;
  int status;
  tuneremain = inportb(QQS_PORT + 2) & 1;
                               /* keep tt interrupt on/off selection */
  if (freq == 0) {
    outportb(QQS_PORT + 2, tuneremain);              /* select video */
    printk ("QQS tuner off\n");
    return TRUE;
  }
  tuneremain |= 0x2;
  outportb(QQS_PORT + 2, tuneremain);                /* select tuner */
  status = SetFreq(freq);
  printk ("QQS tuner at %9d, status %2d\n", freq, status);
  return status;
}