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serial-u16550.c

/*
 *   serial.c
 *   Copyright (c) by Jaroslav Kysela <perex@perex.cz>,
 *                    Isaku Yamahata <yamahata@private.email.ne.jp>,
 *                George Hansper <ghansper@apana.org.au>,
 *                Hannu Savolainen
 *
 *   This code is based on the code from ALSA 0.5.9, but heavily rewritten.
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * Sat Mar 31 17:27:57 PST 2001 tim.mann@compaq.com 
 *      Added support for the Midiator MS-124T and for the MS-124W in
 *      Single Addressed (S/A) or Multiple Burst (M/B) mode, with
 *      power derived either parasitically from the serial port or
 *      from a separate power supply.
 *
 *      More documentation can be found in serial-u16550.txt.
 */

#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/moduleparam.h>
#include <sound/core.h>
#include <sound/rawmidi.h>
#include <sound/initval.h>

#include <linux/serial_reg.h>
#include <linux/jiffies.h>

#include <asm/io.h>

MODULE_DESCRIPTION("MIDI serial u16550");
MODULE_LICENSE("GPL");
MODULE_SUPPORTED_DEVICE("{{ALSA, MIDI serial u16550}}");

#define SNDRV_SERIAL_SOUNDCANVAS 0 /* Roland Soundcanvas; F5 NN selects part */
#define SNDRV_SERIAL_MS124T 1      /* Midiator MS-124T */
#define SNDRV_SERIAL_MS124W_SA 2   /* Midiator MS-124W in S/A mode */
#define SNDRV_SERIAL_MS124W_MB 3   /* Midiator MS-124W in M/B mode */
#define SNDRV_SERIAL_GENERIC 4     /* Generic Interface */
#define SNDRV_SERIAL_MAX_ADAPTOR SNDRV_SERIAL_GENERIC
static char *adaptor_names[] = {
      "Soundcanvas",
        "MS-124T",
      "MS-124W S/A",
      "MS-124W M/B",
      "Generic"
};

#define SNDRV_SERIAL_NORMALBUFF 0 /* Normal blocking buffer operation */
#define SNDRV_SERIAL_DROPBUFF   1 /* Non-blocking discard operation */

static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;    /* Index 0-MAX */
static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;     /* ID for this card */
static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE; /* Enable this card */
static long port[SNDRV_CARDS] = SNDRV_DEFAULT_PORT; /* 0x3f8,0x2f8,0x3e8,0x2e8 */
static int irq[SNDRV_CARDS] = SNDRV_DEFAULT_IRQ;      /* 3,4,5,7,9,10,11,14,15 */
static int speed[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 38400}; /* 9600,19200,38400,57600,115200 */
static int base[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 115200}; /* baud base */
static int outs[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 1};    /* 1 to 16 */
static int ins[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 1};    /* 1 to 16 */
static int adaptor[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = SNDRV_SERIAL_SOUNDCANVAS};
static int droponfull[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS -1)] = SNDRV_SERIAL_NORMALBUFF };

module_param_array(index, int, NULL, 0444);
MODULE_PARM_DESC(index, "Index value for Serial MIDI.");
module_param_array(id, charp, NULL, 0444);
MODULE_PARM_DESC(id, "ID string for Serial MIDI.");
module_param_array(enable, bool, NULL, 0444);
MODULE_PARM_DESC(enable, "Enable UART16550A chip.");
module_param_array(port, long, NULL, 0444);
MODULE_PARM_DESC(port, "Port # for UART16550A chip.");
module_param_array(irq, int, NULL, 0444);
MODULE_PARM_DESC(irq, "IRQ # for UART16550A chip.");
module_param_array(speed, int, NULL, 0444);
MODULE_PARM_DESC(speed, "Speed in bauds.");
module_param_array(base, int, NULL, 0444);
MODULE_PARM_DESC(base, "Base for divisor in bauds.");
module_param_array(outs, int, NULL, 0444);
MODULE_PARM_DESC(outs, "Number of MIDI outputs.");
module_param_array(ins, int, NULL, 0444);
MODULE_PARM_DESC(ins, "Number of MIDI inputs.");
module_param_array(droponfull, bool, NULL, 0444);
MODULE_PARM_DESC(droponfull, "Flag to enable drop-on-full buffer mode");

module_param_array(adaptor, int, NULL, 0444);
MODULE_PARM_DESC(adaptor, "Type of adaptor.");

/*#define SNDRV_SERIAL_MS124W_MB_NOCOMBO 1*/  /* Address outs as 0-3 instead of bitmap */

#define SNDRV_SERIAL_MAX_OUTS 16          /* max 64, min 16 */
#define SNDRV_SERIAL_MAX_INS  16          /* max 64, min 16 */

#define TX_BUFF_SIZE          (1<<15)           /* Must be 2^n */
#define TX_BUFF_MASK          (TX_BUFF_SIZE - 1)

#define SERIAL_MODE_NOT_OPENED            (0)
#define SERIAL_MODE_INPUT_OPEN            (1 << 0)
#define SERIAL_MODE_OUTPUT_OPEN           (1 << 1)
#define SERIAL_MODE_INPUT_TRIGGERED (1 << 2)
#define SERIAL_MODE_OUTPUT_TRIGGERED      (1 << 3)

struct snd_uart16550 {
      struct snd_card *card;
      struct snd_rawmidi *rmidi;
      struct snd_rawmidi_substream *midi_output[SNDRV_SERIAL_MAX_OUTS];
      struct snd_rawmidi_substream *midi_input[SNDRV_SERIAL_MAX_INS];

      int filemode;           /* open status of file */

      spinlock_t open_lock;

      int irq;

      unsigned long base;
      struct resource *res_base;

      unsigned int speed;
      unsigned int speed_base;
      unsigned char divisor;

      unsigned char old_divisor_lsb;
      unsigned char old_divisor_msb;
      unsigned char old_line_ctrl_reg;

      /* parameter for using of write loop */
      short int fifo_limit;   /* used in uart16550 */
        short int fifo_count; /* used in uart16550 */

      /* type of adaptor */
      int adaptor;

      /* inputs */
      int prev_in;
      unsigned char rstatus;

      /* outputs */
      int prev_out;
      unsigned char prev_status[SNDRV_SERIAL_MAX_OUTS];

      /* write buffer and its writing/reading position */
      unsigned char tx_buff[TX_BUFF_SIZE];
      int buff_in_count;
        int buff_in;
        int buff_out;
        int drop_on_full;

      /* wait timer */
      unsigned int timer_running:1;
      struct timer_list buffer_timer;

};

static struct platform_device *devices[SNDRV_CARDS];

static inline void snd_uart16550_add_timer(struct snd_uart16550 *uart)
{
      if (!uart->timer_running) {
            /* timer 38600bps * 10bit * 16byte */
            uart->buffer_timer.expires = jiffies + (HZ+255)/256;
            uart->timer_running = 1;
            add_timer(&uart->buffer_timer);
      }
}

static inline void snd_uart16550_del_timer(struct snd_uart16550 *uart)
{
      if (uart->timer_running) {
            del_timer(&uart->buffer_timer);
            uart->timer_running = 0;
      }
}

/* This macro is only used in snd_uart16550_io_loop */
static inline void snd_uart16550_buffer_output(struct snd_uart16550 *uart)
{
      unsigned short buff_out = uart->buff_out;
      if (uart->buff_in_count > 0) {
            outb(uart->tx_buff[buff_out], uart->base + UART_TX);
            uart->fifo_count++;
            buff_out++;
            buff_out &= TX_BUFF_MASK;
            uart->buff_out = buff_out;
            uart->buff_in_count--;
      }
}

/* This loop should be called with interrupts disabled
 * We don't want to interrupt this, 
 * as we're already handling an interrupt 
 */
static void snd_uart16550_io_loop(struct snd_uart16550 * uart)
{
      unsigned char c, status;
      int substream;

      /* recall previous stream */
      substream = uart->prev_in;

      /* Read Loop */
      while ((status = inb(uart->base + UART_LSR)) & UART_LSR_DR) {
            /* while receive data ready */
            c = inb(uart->base + UART_RX);

            /* keep track of last status byte */
            if (c & 0x80)
                  uart->rstatus = c;

            /* handle stream switch */
            if (uart->adaptor == SNDRV_SERIAL_GENERIC) {
                  if (uart->rstatus == 0xf5) {
                        if (c <= SNDRV_SERIAL_MAX_INS && c > 0)
                              substream = c - 1;
                        if (c != 0xf5)
                              /* prevent future bytes from being
                                 interpreted as streams */
                              uart->rstatus = 0;
                  } else if ((uart->filemode & SERIAL_MODE_INPUT_OPEN)
                           && uart->midi_input[substream])
                        snd_rawmidi_receive(uart->midi_input[substream],
                                        &c, 1);
            } else if ((uart->filemode & SERIAL_MODE_INPUT_OPEN) &&
                     uart->midi_input[substream])
                  snd_rawmidi_receive(uart->midi_input[substream], &c, 1);

            if (status & UART_LSR_OE)
                  snd_printk("%s: Overrun on device at 0x%lx\n",
                         uart->rmidi->name, uart->base);
      }

      /* remember the last stream */
      uart->prev_in = substream;

      /* no need of check SERIAL_MODE_OUTPUT_OPEN because if not,
         buffer is never filled. */
      /* Check write status */
      if (status & UART_LSR_THRE)
            uart->fifo_count = 0;
      if (uart->adaptor == SNDRV_SERIAL_MS124W_SA
         || uart->adaptor == SNDRV_SERIAL_GENERIC) {
            /* Can't use FIFO, must send only when CTS is true */
            status = inb(uart->base + UART_MSR);
            while (uart->fifo_count == 0 && (status & UART_MSR_CTS) &&
                   uart->buff_in_count > 0) {
                   snd_uart16550_buffer_output(uart);
                   status = inb(uart->base + UART_MSR);
            }
      } else {
            /* Write loop */
            while (uart->fifo_count < uart->fifo_limit /* Can we write ? */
                   && uart->buff_in_count > 0)  /* Do we want to? */
                  snd_uart16550_buffer_output(uart);
      }
      if (uart->irq < 0 && uart->buff_in_count > 0)
            snd_uart16550_add_timer(uart);
}

/* NOTES ON SERVICING INTERUPTS
 * ---------------------------
 * After receiving a interrupt, it is important to indicate to the UART that
 * this has been done. 
 * For a Rx interrupt, this is done by reading the received byte.
 * For a Tx interrupt this is done by either:
 * a) Writing a byte
 * b) Reading the IIR
 * It is particularly important to read the IIR if a Tx interrupt is received
 * when there is no data in tx_buff[], as in this case there no other
 * indication that the interrupt has been serviced, and it remains outstanding
 * indefinitely. This has the curious side effect that and no further interrupts
 * will be generated from this device AT ALL!!.
 * It is also desirable to clear outstanding interrupts when the device is
 * opened/closed.
 *
 *
 * Note that some devices need OUT2 to be set before they will generate
 * interrupts at all. (Possibly tied to an internal pull-up on CTS?)
 */
static irqreturn_t snd_uart16550_interrupt(int irq, void *dev_id)
{
      struct snd_uart16550 *uart;

      uart = dev_id;
      spin_lock(&uart->open_lock);
      if (uart->filemode == SERIAL_MODE_NOT_OPENED) {
            spin_unlock(&uart->open_lock);
            return IRQ_NONE;
      }
      /* indicate to the UART that the interrupt has been serviced */
      inb(uart->base + UART_IIR);
      snd_uart16550_io_loop(uart);
      spin_unlock(&uart->open_lock);
      return IRQ_HANDLED;
}

/* When the polling mode, this function calls snd_uart16550_io_loop. */
static void snd_uart16550_buffer_timer(unsigned long data)
{
      unsigned long flags;
      struct snd_uart16550 *uart;

      uart = (struct snd_uart16550 *)data;
      spin_lock_irqsave(&uart->open_lock, flags);
      snd_uart16550_del_timer(uart);
      snd_uart16550_io_loop(uart);
      spin_unlock_irqrestore(&uart->open_lock, flags);
}

/*
 *  this method probes, if an uart sits on given port
 *  return 0 if found
 *  return negative error if not found
 */
static int __devinit snd_uart16550_detect(struct snd_uart16550 *uart)
{
      unsigned long io_base = uart->base;
      int ok;
      unsigned char c;

      /* Do some vague tests for the presence of the uart */
      if (io_base == 0 || io_base == SNDRV_AUTO_PORT) {
            return -ENODEV;   /* Not configured */
      }

      uart->res_base = request_region(io_base, 8, "Serial MIDI");
      if (uart->res_base == NULL) {
            snd_printk(KERN_ERR "u16550: can't grab port 0x%lx\n", io_base);
            return -EBUSY;
      }

      /* uart detected unless one of the following tests should fail */
      ok = 1;
      /* 8 data-bits, 1 stop-bit, parity off, DLAB = 0 */
      outb(UART_LCR_WLEN8, io_base + UART_LCR); /* Line Control Register */
      c = inb(io_base + UART_IER);
      /* The top four bits of the IER should always == 0 */
      if ((c & 0xf0) != 0)
            ok = 0;           /* failed */

      outb(0xaa, io_base + UART_SCR);
      /* Write arbitrary data into the scratch reg */
      c = inb(io_base + UART_SCR);
      /* If it comes back, it's OK */
      if (c != 0xaa)
            ok = 0;           /* failed */

      outb(0x55, io_base + UART_SCR);
      /* Write arbitrary data into the scratch reg */
      c = inb(io_base + UART_SCR);
      /* If it comes back, it's OK */
      if (c != 0x55)
            ok = 0;           /* failed */

      return ok;
}

static void snd_uart16550_do_open(struct snd_uart16550 * uart)
{
      char byte;

      /* Initialize basic variables */
      uart->buff_in_count = 0;
      uart->buff_in = 0;
      uart->buff_out = 0;
      uart->fifo_limit = 1;
      uart->fifo_count = 0;
      uart->timer_running = 0;

      outb(UART_FCR_ENABLE_FIFO     /* Enable FIFO's (if available) */
           | UART_FCR_CLEAR_RCVR    /* Clear receiver FIFO */
           | UART_FCR_CLEAR_XMIT    /* Clear transmitter FIFO */
           | UART_FCR_TRIGGER_4     /* Set FIFO trigger at 4-bytes */
      /* NOTE: interrupt generated after T=(time)4-bytes
       * if less than UART_FCR_TRIGGER bytes received
       */
           ,uart->base + UART_FCR); /* FIFO Control Register */

      if ((inb(uart->base + UART_IIR) & 0xf0) == 0xc0)
            uart->fifo_limit = 16;
      if (uart->divisor != 0) {
            uart->old_line_ctrl_reg = inb(uart->base + UART_LCR);
            outb(UART_LCR_DLAB      /* Divisor latch access bit */
                 ,uart->base + UART_LCR); /* Line Control Register */
            uart->old_divisor_lsb = inb(uart->base + UART_DLL);
            uart->old_divisor_msb = inb(uart->base + UART_DLM);

            outb(uart->divisor
                 ,uart->base + UART_DLL); /* Divisor Latch Low */
            outb(0
                 ,uart->base + UART_DLM); /* Divisor Latch High */
            /* DLAB is reset to 0 in next outb() */
      }
      /* Set serial parameters (parity off, etc) */
      outb(UART_LCR_WLEN8     /* 8 data-bits */
           | 0          /* 1 stop-bit */
           | 0          /* parity off */
           | 0          /* DLAB = 0 */
           ,uart->base + UART_LCR); /* Line Control Register */

      switch (uart->adaptor) {
      default:
            outb(UART_MCR_RTS /* Set Request-To-Send line active */
                 | UART_MCR_DTR     /* Set Data-Terminal-Ready line active */
                 | UART_MCR_OUT2    /* Set OUT2 - not always required, but when
                               * it is, it is ESSENTIAL for enabling interrupts
                         */
                 ,uart->base + UART_MCR); /* Modem Control Register */
            break;
      case SNDRV_SERIAL_MS124W_SA:
      case SNDRV_SERIAL_MS124W_MB:
            /* MS-124W can draw power from RTS and DTR if they
               are in opposite states. */ 
            outb(UART_MCR_RTS | (0&UART_MCR_DTR) | UART_MCR_OUT2,
                 uart->base + UART_MCR);
            break;
      case SNDRV_SERIAL_MS124T:
            /* MS-124T can draw power from RTS and/or DTR (preferably
               both) if they are both asserted. */
            outb(UART_MCR_RTS | UART_MCR_DTR | UART_MCR_OUT2,
                 uart->base + UART_MCR);
            break;
      }

      if (uart->irq < 0) {
            byte = (0 & UART_IER_RDI)     /* Disable Receiver data interrupt */
                |(0 & UART_IER_THRI)      /* Disable Transmitter holding register empty interrupt */
                ;
      } else if (uart->adaptor == SNDRV_SERIAL_MS124W_SA) {
            byte = UART_IER_RDI     /* Enable Receiver data interrupt */
                | UART_IER_MSI      /* Enable Modem status interrupt */
                ;
      } else if (uart->adaptor == SNDRV_SERIAL_GENERIC) {
            byte = UART_IER_RDI     /* Enable Receiver data interrupt */
                | UART_IER_MSI      /* Enable Modem status interrupt */
                | UART_IER_THRI     /* Enable Transmitter holding register empty interrupt */
                ;
      } else {
            byte = UART_IER_RDI     /* Enable Receiver data interrupt */
                | UART_IER_THRI     /* Enable Transmitter holding register empty interrupt */
                ;
      }
      outb(byte, uart->base + UART_IER);  /* Interrupt enable Register */

      inb(uart->base + UART_LSR);   /* Clear any pre-existing overrun indication */
      inb(uart->base + UART_IIR);   /* Clear any pre-existing transmit interrupt */
      inb(uart->base + UART_RX);    /* Clear any pre-existing receive interrupt */
}

static void snd_uart16550_do_close(struct snd_uart16550 * uart)
{
      if (uart->irq < 0)
            snd_uart16550_del_timer(uart);

      /* NOTE: may need to disable interrupts before de-registering out handler.
       * For now, the consequences are harmless.
       */

      outb((0 & UART_IER_RDI)       /* Disable Receiver data interrupt */
           |(0 & UART_IER_THRI)     /* Disable Transmitter holding register empty interrupt */
           ,uart->base + UART_IER); /* Interrupt enable Register */

      switch (uart->adaptor) {
      default:
            outb((0 & UART_MCR_RTS)       /* Deactivate Request-To-Send line  */
                 |(0 & UART_MCR_DTR)      /* Deactivate Data-Terminal-Ready line */
                 |(0 & UART_MCR_OUT2)     /* Deactivate OUT2 */
                 ,uart->base + UART_MCR); /* Modem Control Register */
        break;
      case SNDRV_SERIAL_MS124W_SA:
      case SNDRV_SERIAL_MS124W_MB:
            /* MS-124W can draw power from RTS and DTR if they
               are in opposite states; leave it powered. */ 
            outb(UART_MCR_RTS | (0&UART_MCR_DTR) | (0&UART_MCR_OUT2),
                 uart->base + UART_MCR);
            break;
      case SNDRV_SERIAL_MS124T:
            /* MS-124T can draw power from RTS and/or DTR (preferably
               both) if they are both asserted; leave it powered. */
            outb(UART_MCR_RTS | UART_MCR_DTR | (0&UART_MCR_OUT2),
                 uart->base + UART_MCR);
            break;
      }

      inb(uart->base + UART_IIR);   /* Clear any outstanding interrupts */

      /* Restore old divisor */
      if (uart->divisor != 0) {
            outb(UART_LCR_DLAB            /* Divisor latch access bit */
                 ,uart->base + UART_LCR); /* Line Control Register */
            outb(uart->old_divisor_lsb
                 ,uart->base + UART_DLL); /* Divisor Latch Low */
            outb(uart->old_divisor_msb
                 ,uart->base + UART_DLM); /* Divisor Latch High */
            /* Restore old LCR (data bits, stop bits, parity, DLAB) */
            outb(uart->old_line_ctrl_reg
                 ,uart->base + UART_LCR); /* Line Control Register */
      }
}

static int snd_uart16550_input_open(struct snd_rawmidi_substream *substream)
{
      unsigned long flags;
      struct snd_uart16550 *uart = substream->rmidi->private_data;

      spin_lock_irqsave(&uart->open_lock, flags);
      if (uart->filemode == SERIAL_MODE_NOT_OPENED)
            snd_uart16550_do_open(uart);
      uart->filemode |= SERIAL_MODE_INPUT_OPEN;
      uart->midi_input[substream->number] = substream;
      spin_unlock_irqrestore(&uart->open_lock, flags);
      return 0;
}

static int snd_uart16550_input_close(struct snd_rawmidi_substream *substream)
{
      unsigned long flags;
      struct snd_uart16550 *uart = substream->rmidi->private_data;

      spin_lock_irqsave(&uart->open_lock, flags);
      uart->filemode &= ~SERIAL_MODE_INPUT_OPEN;
      uart->midi_input[substream->number] = NULL;
      if (uart->filemode == SERIAL_MODE_NOT_OPENED)
            snd_uart16550_do_close(uart);
      spin_unlock_irqrestore(&uart->open_lock, flags);
      return 0;
}

static void snd_uart16550_input_trigger(struct snd_rawmidi_substream *substream,
                              int up)
{
      unsigned long flags;
      struct snd_uart16550 *uart = substream->rmidi->private_data;

      spin_lock_irqsave(&uart->open_lock, flags);
      if (up)
            uart->filemode |= SERIAL_MODE_INPUT_TRIGGERED;
      else
            uart->filemode &= ~SERIAL_MODE_INPUT_TRIGGERED;
      spin_unlock_irqrestore(&uart->open_lock, flags);
}

static int snd_uart16550_output_open(struct snd_rawmidi_substream *substream)
{
      unsigned long flags;
      struct snd_uart16550 *uart = substream->rmidi->private_data;

      spin_lock_irqsave(&uart->open_lock, flags);
      if (uart->filemode == SERIAL_MODE_NOT_OPENED)
            snd_uart16550_do_open(uart);
      uart->filemode |= SERIAL_MODE_OUTPUT_OPEN;
      uart->midi_output[substream->number] = substream;
      spin_unlock_irqrestore(&uart->open_lock, flags);
      return 0;
};

static int snd_uart16550_output_close(struct snd_rawmidi_substream *substream)
{
      unsigned long flags;
      struct snd_uart16550 *uart = substream->rmidi->private_data;

      spin_lock_irqsave(&uart->open_lock, flags);
      uart->filemode &= ~SERIAL_MODE_OUTPUT_OPEN;
      uart->midi_output[substream->number] = NULL;
      if (uart->filemode == SERIAL_MODE_NOT_OPENED)
            snd_uart16550_do_close(uart);
      spin_unlock_irqrestore(&uart->open_lock, flags);
      return 0;
};

static inline int snd_uart16550_buffer_can_write(struct snd_uart16550 *uart,
                                     int Num)
{
      if (uart->buff_in_count + Num < TX_BUFF_SIZE)
            return 1;
      else
            return 0;
}

static inline int snd_uart16550_write_buffer(struct snd_uart16550 *uart,
                                   unsigned char byte)
{
      unsigned short buff_in = uart->buff_in;
      if (uart->buff_in_count < TX_BUFF_SIZE) {
            uart->tx_buff[buff_in] = byte;
            buff_in++;
            buff_in &= TX_BUFF_MASK;
            uart->buff_in = buff_in;
            uart->buff_in_count++;
            if (uart->irq < 0) /* polling mode */
                  snd_uart16550_add_timer(uart);
            return 1;
      } else
            return 0;
}

static int snd_uart16550_output_byte(struct snd_uart16550 *uart,
                             struct snd_rawmidi_substream *substream,
                             unsigned char midi_byte)
{
      if (uart->buff_in_count == 0                    /* Buffer empty? */
          && ((uart->adaptor != SNDRV_SERIAL_MS124W_SA &&
          uart->adaptor != SNDRV_SERIAL_GENERIC) ||
            (uart->fifo_count == 0                  /* FIFO empty? */
             && (inb(uart->base + UART_MSR) & UART_MSR_CTS)))) { /* CTS? */

              /* Tx Buffer Empty - try to write immediately */
            if ((inb(uart->base + UART_LSR) & UART_LSR_THRE) != 0) {
                    /* Transmitter holding register (and Tx FIFO) empty */
                    uart->fifo_count = 1;
                  outb(midi_byte, uart->base + UART_TX);
            } else {
                    if (uart->fifo_count < uart->fifo_limit) {
                          uart->fifo_count++;
                        outb(midi_byte, uart->base + UART_TX);
                  } else {
                          /* Cannot write (buffer empty) -
                         * put char in buffer */
                        snd_uart16550_write_buffer(uart, midi_byte);
                  }
            }
      } else {
            if (!snd_uart16550_write_buffer(uart, midi_byte)) {
                  snd_printk("%s: Buffer overrun on device at 0x%lx\n",
                           uart->rmidi->name, uart->base);
                  return 0;
            }
      }

      return 1;
}

static void snd_uart16550_output_write(struct snd_rawmidi_substream *substream)
{
      unsigned long flags;
      unsigned char midi_byte, addr_byte;
      struct snd_uart16550 *uart = substream->rmidi->private_data;
      char first;
      static unsigned long lasttime = 0;
      
      /* Interrupts are disabled during the updating of the tx_buff,
       * since it is 'bad' to have two processes updating the same
       * variables (ie buff_in & buff_out)
       */

      spin_lock_irqsave(&uart->open_lock, flags);

      if (uart->irq < 0)      /* polling */
            snd_uart16550_io_loop(uart);

      if (uart->adaptor == SNDRV_SERIAL_MS124W_MB) {
            while (1) {
                  /* buffer full? */
                  /* in this mode we need two bytes of space */
                  if (uart->buff_in_count > TX_BUFF_SIZE - 2)
                        break;
                  if (snd_rawmidi_transmit(substream, &midi_byte, 1) != 1)
                        break;
#ifdef SNDRV_SERIAL_MS124W_MB_NOCOMBO
                  /* select exactly one of the four ports */
                  addr_byte = (1 << (substream->number + 4)) | 0x08;
#else
                  /* select any combination of the four ports */
                  addr_byte = (substream->number << 4) | 0x08;
                  /* ...except none */
                  if (addr_byte == 0x08)
                        addr_byte = 0xf8;
#endif
                  snd_uart16550_output_byte(uart, substream, addr_byte);
                  /* send midi byte */
                  snd_uart16550_output_byte(uart, substream, midi_byte);
            }
      } else {
            first = 0;
            while (snd_rawmidi_transmit_peek(substream, &midi_byte, 1) == 1) {
                  /* Also send F5 after 3 seconds with no data
                   * to handle device disconnect */
                  if (first == 0 &&
                      (uart->adaptor == SNDRV_SERIAL_SOUNDCANVAS ||
                       uart->adaptor == SNDRV_SERIAL_GENERIC) &&
                      (uart->prev_out != substream->number ||
                       time_after(jiffies, lasttime + 3*HZ))) {

                        if (snd_uart16550_buffer_can_write(uart, 3)) {
                              /* Roland Soundcanvas part selection */
                              /* If this substream of the data is
                               * different previous substream
                               * in this uart, send the change part
                               * event
                               */
                              uart->prev_out = substream->number;
                              /* change part */
                              snd_uart16550_output_byte(uart, substream,
                                                  0xf5);
                              /* data */
                              snd_uart16550_output_byte(uart, substream,
                                                  uart->prev_out + 1);
                              /* If midi_byte is a data byte,
                               * send the previous status byte */
                              if (midi_byte < 0x80 &&
                                  uart->adaptor == SNDRV_SERIAL_SOUNDCANVAS)
                                    snd_uart16550_output_byte(uart, substream, uart->prev_status[uart->prev_out]);
                        } else if (!uart->drop_on_full)
                              break;

                  }

                  /* send midi byte */
                  if (!snd_uart16550_output_byte(uart, substream, midi_byte) &&
                      !uart->drop_on_full )
                        break;

                  if (midi_byte >= 0x80 && midi_byte < 0xf0)
                        uart->prev_status[uart->prev_out] = midi_byte;
                  first = 1;

                  snd_rawmidi_transmit_ack( substream, 1 );
            }
            lasttime = jiffies;
      }
      spin_unlock_irqrestore(&uart->open_lock, flags);
}

static void snd_uart16550_output_trigger(struct snd_rawmidi_substream *substream,
                               int up)
{
      unsigned long flags;
      struct snd_uart16550 *uart = substream->rmidi->private_data;

      spin_lock_irqsave(&uart->open_lock, flags);
      if (up)
            uart->filemode |= SERIAL_MODE_OUTPUT_TRIGGERED;
      else
            uart->filemode &= ~SERIAL_MODE_OUTPUT_TRIGGERED;
      spin_unlock_irqrestore(&uart->open_lock, flags);
      if (up)
            snd_uart16550_output_write(substream);
}

static struct snd_rawmidi_ops snd_uart16550_output =
{
      .open =           snd_uart16550_output_open,
      .close =    snd_uart16550_output_close,
      .trigger =  snd_uart16550_output_trigger,
};

static struct snd_rawmidi_ops snd_uart16550_input =
{
      .open =           snd_uart16550_input_open,
      .close =    snd_uart16550_input_close,
      .trigger =  snd_uart16550_input_trigger,
};

static int snd_uart16550_free(struct snd_uart16550 *uart)
{
      if (uart->irq >= 0)
            free_irq(uart->irq, uart);
      release_and_free_resource(uart->res_base);
      kfree(uart);
      return 0;
};

static int snd_uart16550_dev_free(struct snd_device *device)
{
      struct snd_uart16550 *uart = device->device_data;
      return snd_uart16550_free(uart);
}

static int __devinit snd_uart16550_create(struct snd_card *card,
                               unsigned long iobase,
                               int irq,
                               unsigned int speed,
                               unsigned int base,
                               int adaptor,
                               int droponfull,
                               struct snd_uart16550 **ruart)
{
      static struct snd_device_ops ops = {
            .dev_free = snd_uart16550_dev_free,
      };
      struct snd_uart16550 *uart;
      int err;


      if ((uart = kzalloc(sizeof(*uart), GFP_KERNEL)) == NULL)
            return -ENOMEM;
      uart->adaptor = adaptor;
      uart->card = card;
      spin_lock_init(&uart->open_lock);
      uart->irq = -1;
      uart->base = iobase;
      uart->drop_on_full = droponfull;

      if ((err = snd_uart16550_detect(uart)) <= 0) {
            printk(KERN_ERR "no UART detected at 0x%lx\n", iobase);
            snd_uart16550_free(uart);
            return -ENODEV;
      }

      if (irq >= 0 && irq != SNDRV_AUTO_IRQ) {
            if (request_irq(irq, snd_uart16550_interrupt,
                        IRQF_DISABLED, "Serial MIDI", uart)) {
                  snd_printk("irq %d busy. Using Polling.\n", irq);
            } else {
                  uart->irq = irq;
            }
      }
      uart->divisor = base / speed;
      uart->speed = base / (unsigned int)uart->divisor;
      uart->speed_base = base;
      uart->prev_out = -1;
      uart->prev_in = 0;
      uart->rstatus = 0;
      memset(uart->prev_status, 0x80, sizeof(unsigned char) * SNDRV_SERIAL_MAX_OUTS);
      init_timer(&uart->buffer_timer);
      uart->buffer_timer.function = snd_uart16550_buffer_timer;
      uart->buffer_timer.data = (unsigned long)uart;
      uart->timer_running = 0;

      /* Register device */
      if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, uart, &ops)) < 0) {
            snd_uart16550_free(uart);
            return err;
      }

      switch (uart->adaptor) {
      case SNDRV_SERIAL_MS124W_SA:
      case SNDRV_SERIAL_MS124W_MB:
            /* MS-124W can draw power from RTS and DTR if they
               are in opposite states. */ 
            outb(UART_MCR_RTS | (0&UART_MCR_DTR), uart->base + UART_MCR);
            break;
      case SNDRV_SERIAL_MS124T:
            /* MS-124T can draw power from RTS and/or DTR (preferably
               both) if they are asserted. */
            outb(UART_MCR_RTS | UART_MCR_DTR, uart->base + UART_MCR);
            break;
      default:
            break;
      }

      if (ruart)
            *ruart = uart;

      return 0;
}

static void __devinit snd_uart16550_substreams(struct snd_rawmidi_str *stream)
{
      struct snd_rawmidi_substream *substream;

      list_for_each_entry(substream, &stream->substreams, list) {
            sprintf(substream->name, "Serial MIDI %d", substream->number + 1);
      }
}

static int __devinit snd_uart16550_rmidi(struct snd_uart16550 *uart, int device,
                              int outs, int ins,
                              struct snd_rawmidi **rmidi)
{
      struct snd_rawmidi *rrawmidi;
      int err;

      err = snd_rawmidi_new(uart->card, "UART Serial MIDI", device,
                        outs, ins, &rrawmidi);
      if (err < 0)
            return err;
      snd_rawmidi_set_ops(rrawmidi, SNDRV_RAWMIDI_STREAM_INPUT,
                      &snd_uart16550_input);
      snd_rawmidi_set_ops(rrawmidi, SNDRV_RAWMIDI_STREAM_OUTPUT,
                      &snd_uart16550_output);
      strcpy(rrawmidi->name, "Serial MIDI");
      snd_uart16550_substreams(&rrawmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT]);
      snd_uart16550_substreams(&rrawmidi->streams[SNDRV_RAWMIDI_STREAM_INPUT]);
      rrawmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT |
                         SNDRV_RAWMIDI_INFO_INPUT |
                         SNDRV_RAWMIDI_INFO_DUPLEX;
      rrawmidi->private_data = uart;
      if (rmidi)
            *rmidi = rrawmidi;
      return 0;
}

static int __devinit snd_serial_probe(struct platform_device *devptr)
{
      struct snd_card *card;
      struct snd_uart16550 *uart;
      int err;
      int dev = devptr->id;

      switch (adaptor[dev]) {
      case SNDRV_SERIAL_SOUNDCANVAS:
            ins[dev] = 1;
            break;
      case SNDRV_SERIAL_MS124T:
      case SNDRV_SERIAL_MS124W_SA:
            outs[dev] = 1;
            ins[dev] = 1;
            break;
      case SNDRV_SERIAL_MS124W_MB:
            outs[dev] = 16;
            ins[dev] = 1;
            break;
      case SNDRV_SERIAL_GENERIC:
            break;
      default:
            snd_printk("Adaptor type is out of range 0-%d (%d)\n",
                     SNDRV_SERIAL_MAX_ADAPTOR, adaptor[dev]);
            return -ENODEV;
      }

      if (outs[dev] < 1 || outs[dev] > SNDRV_SERIAL_MAX_OUTS) {
            snd_printk("Count of outputs is out of range 1-%d (%d)\n",
                     SNDRV_SERIAL_MAX_OUTS, outs[dev]);
            return -ENODEV;
      }

      if (ins[dev] < 1 || ins[dev] > SNDRV_SERIAL_MAX_INS) {
            snd_printk("Count of inputs is out of range 1-%d (%d)\n",
                     SNDRV_SERIAL_MAX_INS, ins[dev]);
            return -ENODEV;
      }

      err  = snd_card_create(index[dev], id[dev], THIS_MODULE, 0, &card);
      if (err < 0)
            return err;

      strcpy(card->driver, "Serial");
      strcpy(card->shortname, "Serial MIDI (UART16550A)");

      if ((err = snd_uart16550_create(card,
                              port[dev],
                              irq[dev],
                              speed[dev],
                              base[dev],
                              adaptor[dev],
                              droponfull[dev],
                              &uart)) < 0)
            goto _err;

      err = snd_uart16550_rmidi(uart, 0, outs[dev], ins[dev], &uart->rmidi);
      if (err < 0)
            goto _err;

      sprintf(card->longname, "%s at 0x%lx, irq %d speed %d div %d outs %d ins %d adaptor %s droponfull %d",
            card->shortname,
            uart->base,
            uart->irq,
            uart->speed,
            (int)uart->divisor,
            outs[dev],
            ins[dev],
            adaptor_names[uart->adaptor],
            uart->drop_on_full);

      snd_card_set_dev(card, &devptr->dev);

      if ((err = snd_card_register(card)) < 0)
            goto _err;

      platform_set_drvdata(devptr, card);
      return 0;

 _err:
      snd_card_free(card);
      return err;
}

static int __devexit snd_serial_remove(struct platform_device *devptr)
{
      snd_card_free(platform_get_drvdata(devptr));
      platform_set_drvdata(devptr, NULL);
      return 0;
}

#define SND_SERIAL_DRIVER     "snd_serial_u16550"

static struct platform_driver snd_serial_driver = {
      .probe            = snd_serial_probe,
      .remove           = __devexit_p( snd_serial_remove),
      .driver           = {
            .name = SND_SERIAL_DRIVER
      },
};

static void snd_serial_unregister_all(void)
{
      int i;

      for (i = 0; i < ARRAY_SIZE(devices); ++i)
            platform_device_unregister(devices[i]);
      platform_driver_unregister(&snd_serial_driver);
}

static int __init alsa_card_serial_init(void)
{
      int i, cards, err;

      if ((err = platform_driver_register(&snd_serial_driver)) < 0)
            return err;

      cards = 0;
      for (i = 0; i < SNDRV_CARDS; i++) {
            struct platform_device *device;
            if (! enable[i])
                  continue;
            device = platform_device_register_simple(SND_SERIAL_DRIVER,
                                           i, NULL, 0);
            if (IS_ERR(device))
                  continue;
            if (!platform_get_drvdata(device)) {
                  platform_device_unregister(device);
                  continue;
            }
            devices[i] = device;
            cards++;
      }
      if (! cards) {
#ifdef MODULE
            printk(KERN_ERR "serial midi soundcard not found or device busy\n");
#endif
            snd_serial_unregister_all();
            return -ENODEV;
      }
      return 0;
}

static void __exit alsa_card_serial_exit(void)
{
      snd_serial_unregister_all();
}

module_init(alsa_card_serial_init)
module_exit(alsa_card_serial_exit)

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