bpp.c

底层驱动开发

        /* Wait for Event 2: Peripheral responds as a 1284 device. */
      rc = wait_for(BPP_GP_PError|BPP_GP_Select|BPP_GP_nFault,
                BPP_GP_nAck,
                TIME_PResponse,
                minor);

      if (rc == -1) return -ETIMEDOUT;

        /* Event 3: latch extensibility request */
      set_pins(BPP_PP_nSelectIn|BPP_PP_nInit, minor);

        /* ... quick nap while peripheral ponders the byte i'm sending...*/
      snooze(1, minor);

        /* Event 4: restore strobe, to ACK peripheral's response. */
      set_pins(BPP_PP_nSelectIn|BPP_PP_nAutoFd|BPP_PP_nStrobe|BPP_PP_nInit, minor);

        /* Wait for Event 6: Peripheral latches response bits */
      rc = wait_for(BPP_GP_nAck, 0, TIME_PSetup+TIME_PResponse, minor);
      if (rc == -1) return -EIO;

        /* A 1284 device cannot refuse nibble mode */
      if (mode == DEFAULT_NIBBLE) return 0;

      if (pins & BPP_GP_Select) return 0;

      return -EPROTONOSUPPORT;
}

static int terminate(unsigned minor)
{
      int rc;

        /* Event 22: Request termination of 1284 mode */
      set_pins(BPP_PP_nAutoFd|BPP_PP_nStrobe|BPP_PP_nInit, minor);

        /* Wait for Events 23 and 24: ACK termination request. */
      rc = wait_for(BPP_GP_Busy|BPP_GP_nFault,
                BPP_GP_nAck,
                TIME_PSetup+TIME_PResponse,
                minor);

      instances[minor].direction = 0;
      instances[minor].mode = COMPATIBILITY;

      if (rc == -1) {
          return -EIO;
      }

        /* Event 25: Handshake by lowering nAutoFd */
      set_pins(BPP_PP_nStrobe|BPP_PP_nInit, minor);

        /* Event 26: Peripheral wiggles lines... */

        /* Event 27: Peripheral sets nAck HIGH to ack handshake */
      rc = wait_for(BPP_GP_nAck, 0, TIME_PResponse, minor);
      if (rc == -1) {
          set_pins(BPP_PP_nAutoFd|BPP_PP_nStrobe|BPP_PP_nInit, minor);
          return -EIO;
      }

        /* Event 28: Finish phase by raising nAutoFd */
      set_pins(BPP_PP_nAutoFd|BPP_PP_nStrobe|BPP_PP_nInit, minor);

      return 0;
}

static DEFINE_SPINLOCK(bpp_open_lock);

/*
 * Allow only one process to open the device at a time.
 */
static int bpp_open(struct inode *inode, struct file *f)
{
      unsigned minor = iminor(inode);
      int ret;

      spin_lock(&bpp_open_lock);
      ret = 0;
      if (minor >= BPP_NO) {
	      ret = -ENODEV;
      } else {
	      if (! instances[minor].present) {
		      ret = -ENODEV;
	      } else {
		      if (instances[minor].opened) 
			      ret = -EBUSY;
		      else
			      instances[minor].opened = 1;
	      }
      }
      spin_unlock(&bpp_open_lock);

      return ret;
}

/*
 * When the process closes the device, this method is called to clean
 * up and reset the hardware. Always leave the device in compatibility
 * mode as this is a reasonable place to clean up from messes made by
 * ioctls, or other mayhem.
 */
static int bpp_release(struct inode *inode, struct file *f)
{
      unsigned minor = iminor(inode);

      spin_lock(&bpp_open_lock);
      instances[minor].opened = 0;

      if (instances[minor].mode != COMPATIBILITY)
	      terminate(minor);

      spin_unlock(&bpp_open_lock);

      return 0;
}

static long read_nibble(unsigned minor, char __user *c, unsigned long cnt)
{
      unsigned long remaining = cnt;
      long rc;

      while (remaining > 0) {
          unsigned char byte = 0;
          int pins;

          /* Event 7: request nibble */
          set_pins(BPP_PP_nSelectIn|BPP_PP_nStrobe, minor);

          /* Wait for event 9: Peripher strobes first nibble */
          pins = wait_for(0, BPP_GP_nAck, TIME_IDLE_LIMIT, minor);
          if (pins == -1) return -ETIMEDOUT;

          /* Event 10: I handshake nibble */
          set_pins(BPP_PP_nSelectIn|BPP_PP_nStrobe|BPP_PP_nAutoFd, minor);
          if (pins & BPP_GP_nFault) byte |= 0x01;
          if (pins & BPP_GP_Select) byte |= 0x02;
          if (pins & BPP_GP_PError) byte |= 0x04;
          if (pins & BPP_GP_Busy)   byte |= 0x08;

          /* Wait for event 11: Peripheral handshakes nibble */
          rc = wait_for(BPP_GP_nAck, 0, TIME_PResponse, minor);

          /* Event 7: request nibble */
          set_pins(BPP_PP_nSelectIn|BPP_PP_nStrobe, minor);

          /* Wait for event 9: Peripher strobes first nibble */
          pins = wait_for(0, BPP_GP_nAck, TIME_PResponse, minor);
          if (rc == -1) return -ETIMEDOUT;

          /* Event 10: I handshake nibble */
          set_pins(BPP_PP_nSelectIn|BPP_PP_nStrobe|BPP_PP_nAutoFd, minor);
          if (pins & BPP_GP_nFault) byte |= 0x10;
          if (pins & BPP_GP_Select) byte |= 0x20;
          if (pins & BPP_GP_PError) byte |= 0x40;
          if (pins & BPP_GP_Busy)   byte |= 0x80;

          if (put_user(byte, c))
		  return -EFAULT;
          c += 1;
          remaining -= 1;

          /* Wait for event 11: Peripheral handshakes nibble */
          rc = wait_for(BPP_GP_nAck, 0, TIME_PResponse, minor);
          if (rc == -1) return -EIO;
      }

      return cnt - remaining;
}

static long read_ecp(unsigned minor, char __user *c, unsigned long cnt)
{
      unsigned long remaining;
      long rc;

        /* Turn ECP mode from forward to reverse if needed. */
      if (! instances[minor].direction) {
          unsigned short pins = get_pins(minor);

            /* Event 38: Turn the bus around */
          instances[minor].direction = 0x20;
          pins &= ~BPP_PP_nAutoFd;
          set_pins(pins, minor);

            /* Event 39: Set pins for reverse mode. */
          snooze(TIME_PSetup, minor);
          set_pins(BPP_PP_nStrobe|BPP_PP_nSelectIn, minor);

            /* Wait for event 40: Peripheral ready to be strobed */
          rc = wait_for(0, BPP_GP_PError, TIME_PResponse, minor);
          if (rc == -1) return -ETIMEDOUT;
      }

      remaining = cnt;

      while (remaining > 0) {

            /* If there is a run length for a repeated byte, repeat */
            /* that byte a few times. */
          if (instances[minor].run_length && !instances[minor].run_flag) {

              char buffer[128];
              unsigned idx;
              unsigned repeat = remaining < instances[minor].run_length
                                     ? remaining
                               : instances[minor].run_length;

              for (idx = 0 ;  idx < repeat ;  idx += 1)
                buffer[idx] = instances[minor].repeat_byte;

              if (copy_to_user(c, buffer, repeat))
		      return -EFAULT;
              remaining -= repeat;
              c += repeat;
              instances[minor].run_length -= repeat;
          }

          if (remaining == 0) break;


            /* Wait for Event 43: Data active on the bus. */
          rc = wait_for(0, BPP_GP_nAck, TIME_IDLE_LIMIT, minor);
          if (rc == -1) break;

          if (rc & BPP_GP_Busy) {
                /* OK, this is data. read it in. */
              unsigned char byte = bpp_inb(base_addrs[minor]);
              if (put_user(byte, c))
		      return -EFAULT;
              c += 1;
              remaining -= 1;

              if (instances[minor].run_flag) {
                  instances[minor].repeat_byte = byte;
                  instances[minor].run_flag = 0;
              }

          } else {
              unsigned char byte = bpp_inb(base_addrs[minor]);
              if (byte & 0x80) {
                  printk("bpp%d: "
                         "Ignoring ECP channel %u from device.\n",
                         minor, byte & 0x7f);
              } else {
                  instances[minor].run_length = byte;
                  instances[minor].run_flag = 1;
              }
          }

            /* Event 44: I got it. */
          set_pins(BPP_PP_nStrobe|BPP_PP_nAutoFd|BPP_PP_nSelectIn, minor);

            /* Wait for event 45: peripheral handshake */
          rc = wait_for(BPP_GP_nAck, 0, TIME_PResponse, minor);
          if (rc == -1) return -ETIMEDOUT;

             /* Event 46: Finish handshake */
          set_pins(BPP_PP_nStrobe|BPP_PP_nSelectIn, minor);

      }


      return cnt - remaining;
}

static ssize_t bpp_read(struct file *f, char __user *c, size_t cnt, loff_t * ppos)
{
      long rc;
      unsigned minor = iminor(f->f_dentry->d_inode);
      if (minor >= BPP_NO) return -ENODEV;
      if (!instances[minor].present) return -ENODEV;

      switch (instances[minor].mode) {

        default:
          if (instances[minor].mode != COMPATIBILITY)
            terminate(minor);

          if (instances[minor].enhanced) {
              /* For now, do all reads with ECP-RLE mode */
              unsigned short pins;

              rc = negotiate(DEFAULT_ECP, minor);
              if (rc < 0) break;

              instances[minor].mode = ECP_RLE;

              /* Event 30: set nAutoFd low to setup for ECP mode */
              pins = get_pins(minor);
              pins &= ~BPP_PP_nAutoFd;
              set_pins(pins, minor);

              /* Wait for Event 31: peripheral ready */
              rc = wait_for(BPP_GP_PError, 0, TIME_PResponse, minor);
              if (rc == -1) return -ETIMEDOUT;

              rc = read_ecp(minor, c, cnt);

          } else {
              rc = negotiate(DEFAULT_NIBBLE, minor);
              if (rc < 0) break;

              instances[minor].mode = NIBBLE;

              rc = read_nibble(minor, c, cnt);
          }
          break;

        case NIBBLE:
          rc = read_nibble(minor, c, cnt);
          break;

        case ECP:
        case ECP_RLE:
          rc = read_ecp(minor, c, cnt);
          break;

      }


      return rc;
}

/*
 * Compatibility mode handshaking is a matter of writing data,
 * strobing it, and waiting for the printer to stop being busy.
 */
static long write_compat(unsigned minor, const char __user *c, unsigned long cnt)
{
      long rc;
      unsigned short pins = get_pins(minor);

      unsigned long remaining = cnt;


      while (remaining > 0) {
            unsigned char byte;

            if (get_user(byte, c))
		    return -EFAULT;
            c += 1;

            rc = wait_for(BPP_GP_nAck, BPP_GP_Busy, TIME_IDLE_LIMIT, minor);
            if (rc == -1) return -ETIMEDOUT;

            bpp_outb_p(byte, base_addrs[minor]);
            remaining -= 1;
          /* snooze(1, minor); */

          pins &= ~BPP_PP_nStrobe;
          set_pins(pins, minor);

          rc = wait_for(BPP_GP_Busy, 0, TIME_PResponse, minor);