serial-u16550.c

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/*
 *   serial.c
 *   Copyright (c) by Jaroslav Kysela <[email protected]>,
 *                    Isaku Yamahata <[email protected]>,
 *            George Hansper <[email protected]>,
 *            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 [email protected] 
 *      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/module.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 bool 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 bool 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(KERN_WARNING
                   "%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(KERN_WARNING
                   "%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,
                0, "Serial MIDI", uart)) {
            snd_printk(KERN_WARNING
                   "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(KERN_ERR
               "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(KERN_ERR
               "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(KERN_ERR
               "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 [%s] at %#lx, irq %d",
        card->shortname,
        adaptor_names[uart->adaptor],
        uart->base,
        uart->irq);

    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,
        .owner  = THIS_MODULE,
    },
};

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)