/*
    comedi/drivers/das1800.c
    Driver for Keitley das1700/das1800 series boards
    Copyright (C) 2000 Frank Mori Hess <fmhess@users.sourceforge.net>

    COMEDI - Linux Control and Measurement Device Interface
    Copyright (C) 2000 David A. Schleef <ds@schleef.org>

    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., 675 Mass Ave, Cambridge, MA 02139, USA.

************************************************************************
*/
/*
Driver: das1800
Description: Keithley Metrabyte DAS1800 (& compatibles)
Author: Frank Mori Hess <fmhess@users.sourceforge.net>
Devices: [Keithley Metrabyte] DAS-1701ST (das-1701st),
  DAS-1701ST-DA (das-1701st-da), DAS-1701/AO (das-1701ao),
  DAS-1702ST (das-1702st), DAS-1702ST-DA (das-1702st-da),
  DAS-1702HR (das-1702hr), DAS-1702HR-DA (das-1702hr-da),
  DAS-1702/AO (das-1702ao), DAS-1801ST (das-1801st),
  DAS-1801ST-DA (das-1801st-da), DAS-1801HC (das-1801hc),
  DAS-1801AO (das-1801ao), DAS-1802ST (das-1802st),
  DAS-1802ST-DA (das-1802st-da), DAS-1802HR (das-1802hr),
  DAS-1802HR-DA (das-1802hr-da), DAS-1802HC (das-1802hc),
  DAS-1802AO (das-1802ao)
Status: works

The waveform analog output on the 'ao' cards is not supported.
If you need it, send me (Frank Hess) an email.

Configuration options:
  [0] - I/O port base address
  [1] - IRQ (optional, required for timed or externally triggered conversions)
  [2] - DMA0 (optional, requires irq)
  [3] - DMA1 (optional, requires irq and dma0)
*/
/*

This driver supports the following Keithley boards:

das-1701st
das-1701st-da
das-1701ao
das-1702st
das-1702st-da
das-1702hr
das-1702hr-da
das-1702ao
das-1801st
das-1801st-da
das-1801hc
das-1801ao
das-1802st
das-1802st-da
das-1802hr
das-1802hr-da
das-1802hc
das-1802ao

Options:
        [0] - base io address
        [1] - irq (optional, required for timed or externally triggered conversions)
        [2] - dma0 (optional, requires irq)
        [3] - dma1 (optional, requires irq and dma0)

irq can be omitted, although the cmd interface will not work without it.

analog input cmd triggers supported:
        start_src:      TRIG_NOW | TRIG_EXT
        scan_begin_src: TRIG_FOLLOW | TRIG_TIMER | TRIG_EXT
        scan_end_src:   TRIG_COUNT
        convert_src:    TRIG_TIMER | TRIG_EXT (TRIG_EXT requires scan_begin_src == TRIG_FOLLOW)
        stop_src:       TRIG_COUNT | TRIG_EXT | TRIG_NONE

scan_begin_src triggers TRIG_TIMER and TRIG_EXT use the card's
'burst mode' which limits the valid conversion time to 64 microseconds
(convert_arg <= 64000).  This limitation does not apply if scan_begin_src
is TRIG_FOLLOW.

NOTES:
Only the DAS-1801ST has been tested by me.
Unipolar and bipolar ranges cannot be mixed in the channel/gain list.

TODO:
        Make it automatically allocate irq and dma channels if they are not specified
        Add support for analog out on 'ao' cards
        read insn for analog out
*/

#include <linux/interrupt.h>
#include "../comedidev.h"

#include <linux/ioport.h>
#include <asm/dma.h>

#include "8253.h"
#include "comedi_fc.h"

/* misc. defines */
#define DAS1800_SIZE           16       /* uses 16 io addresses */
#define FIFO_SIZE              1024     /*  1024 sample fifo */
#define TIMER_BASE             200      /*  5 Mhz master clock */
#define UNIPOLAR               0x4      /*  bit that determines whether input range is uni/bipolar */
#define DMA_BUF_SIZE           0x1ff00  /*  size in bytes of dma buffers */

/* Registers for the das1800 */
#define DAS1800_FIFO            0x0
#define DAS1800_QRAM            0x0
#define DAS1800_DAC             0x0
#define DAS1800_SELECT          0x2
#define   ADC                     0x0
#define   QRAM                    0x1
#define   DAC(a)                  (0x2 + a)
#define DAS1800_DIGITAL         0x3
#define DAS1800_CONTROL_A       0x4
#define   FFEN                    0x1
#define   CGEN                    0x4
#define   CGSL                    0x8
#define   TGEN                    0x10
#define   TGSL                    0x20
#define   ATEN                    0x80
#define DAS1800_CONTROL_B       0x5
#define   DMA_CH5                 0x1
#define   DMA_CH6                 0x2
#define   DMA_CH7                 0x3
#define   DMA_CH5_CH6             0x5
#define   DMA_CH6_CH7             0x6
#define   DMA_CH7_CH5             0x7
#define   DMA_ENABLED             0x3   /* mask used to determine if dma is enabled */
#define   DMA_DUAL                0x4
#define   IRQ3                    0x8
#define   IRQ5                    0x10
#define   IRQ7                    0x18
#define   IRQ10                   0x28
#define   IRQ11                   0x30
#define   IRQ15                   0x38
#define   FIMD                    0x40
#define DAS1800_CONTROL_C       0X6
#define   IPCLK                   0x1
#define   XPCLK                   0x3
#define   BMDE                    0x4
#define   CMEN                    0x8
#define   UQEN                    0x10
#define   SD                      0x40
#define   UB                      0x80
#define DAS1800_STATUS          0x7
/* bits that prevent interrupt status bits (and CVEN) from being cleared on write */
#define   CLEAR_INTR_MASK         (CVEN_MASK | 0x1f)
#define   INT                     0x1
#define   DMATC                   0x2
#define   CT0TC                   0x8
#define   OVF                     0x10
#define   FHF                     0x20
#define   FNE                     0x40
#define   CVEN_MASK               0x40  /*  masks CVEN on write */
#define   CVEN                    0x80
#define DAS1800_BURST_LENGTH    0x8
#define DAS1800_BURST_RATE      0x9
#define DAS1800_QRAM_ADDRESS    0xa
#define DAS1800_COUNTER         0xc

#define IOBASE2                   0x400 /* offset of additional ioports used on 'ao' cards */

enum {
        das1701st, das1701st_da, das1702st, das1702st_da, das1702hr,
        das1702hr_da,
        das1701ao, das1702ao, das1801st, das1801st_da, das1802st, das1802st_da,
        das1802hr, das1802hr_da, das1801hc, das1802hc, das1801ao, das1802ao
};

static int das1800_attach(struct comedi_device *dev,
                          struct comedi_devconfig *it);
static int das1800_detach(struct comedi_device *dev);
static int das1800_probe(struct comedi_device *dev);
static int das1800_cancel(struct comedi_device *dev,
                          struct comedi_subdevice *s);
static irqreturn_t das1800_interrupt(int irq, void *d);
static int das1800_ai_poll(struct comedi_device *dev,
                           struct comedi_subdevice *s);
static void das1800_ai_handler(struct comedi_device *dev);
static void das1800_handle_dma(struct comedi_device *dev,
                               struct comedi_subdevice *s, unsigned int status);
static void das1800_flush_dma(struct comedi_device *dev,
                              struct comedi_subdevice *s);
static void das1800_flush_dma_channel(struct comedi_device *dev,
                                      struct comedi_subdevice *s,
                                      unsigned int channel, uint16_t * buffer);
static void das1800_handle_fifo_half_full(struct comedi_device *dev,
                                          struct comedi_subdevice *s);
static void das1800_handle_fifo_not_empty(struct comedi_device *dev,
                                          struct comedi_subdevice *s);
static int das1800_ai_do_cmdtest(struct comedi_device *dev,
                                 struct comedi_subdevice *s,
                                 struct comedi_cmd *cmd);
static int das1800_ai_do_cmd(struct comedi_device *dev,
                             struct comedi_subdevice *s);
static int das1800_ai_rinsn(struct comedi_device *dev,
                            struct comedi_subdevice *s,
                            struct comedi_insn *insn, unsigned int *data);
static int das1800_ao_winsn(struct comedi_device *dev,
                            struct comedi_subdevice *s,
                            struct comedi_insn *insn, unsigned int *data);
static int das1800_di_rbits(struct comedi_device *dev,
                            struct comedi_subdevice *s,
                            struct comedi_insn *insn, unsigned int *data);
static int das1800_do_wbits(struct comedi_device *dev,
                            struct comedi_subdevice *s,
                            struct comedi_insn *insn, unsigned int *data);

static int das1800_set_frequency(struct comedi_device *dev);
static unsigned int burst_convert_arg(unsigned int convert_arg, int round_mode);
static unsigned int suggest_transfer_size(struct comedi_cmd *cmd);

/* analog input ranges */
static const struct comedi_lrange range_ai_das1801 = {
        8,
        {
         RANGE(-5, 5),
         RANGE(-1, 1),
         RANGE(-0.1, 0.1),
         RANGE(-0.02, 0.02),
         RANGE(0, 5),
         RANGE(0, 1),
         RANGE(0, 0.1),
         RANGE(0, 0.02),
         }
};

static const struct comedi_lrange range_ai_das1802 = {
        8,
        {
         RANGE(-10, 10),
         RANGE(-5, 5),
         RANGE(-2.5, 2.5),
         RANGE(-1.25, 1.25),
         RANGE(0, 10),
         RANGE(0, 5),
         RANGE(0, 2.5),
         RANGE(0, 1.25),
         }
};

struct das1800_board {
        const char *name;
        int ai_speed;           /* max conversion period in nanoseconds */
        int resolution;         /* bits of ai resolution */
        int qram_len;           /* length of card's channel / gain queue */
        int common;             /* supports AREF_COMMON flag */
        int do_n_chan;          /* number of digital output channels */
        int ao_ability;         /* 0 == no analog out, 1 == basic analog out, 2 == waveform analog out */
        int ao_n_chan;          /* number of analog out channels */
        const struct comedi_lrange *range_ai;   /* available input ranges */
};

/* Warning: the maximum conversion speeds listed below are
 * not always achievable depending on board setup (see
 * user manual.)
 */
static const struct das1800_board das1800_boards[] = {
        {
         .name = "das-1701st",
         .ai_speed = 6250,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 0,
         .ao_n_chan = 0,
         .range_ai = &range_ai_das1801,
         },
        {
         .name = "das-1701st-da",
         .ai_speed = 6250,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 1,
         .ao_n_chan = 4,
         .range_ai = &range_ai_das1801,
         },
        {
         .name = "das-1702st",
         .ai_speed = 6250,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 0,
         .ao_n_chan = 0,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1702st-da",
         .ai_speed = 6250,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 1,
         .ao_n_chan = 4,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1702hr",
         .ai_speed = 20000,
         .resolution = 16,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 0,
         .ao_n_chan = 0,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1702hr-da",
         .ai_speed = 20000,
         .resolution = 16,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 1,
         .ao_n_chan = 2,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1701ao",
         .ai_speed = 6250,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 2,
         .ao_n_chan = 2,
         .range_ai = &range_ai_das1801,
         },
        {
         .name = "das-1702ao",
         .ai_speed = 6250,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 2,
         .ao_n_chan = 2,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1801st",
         .ai_speed = 3000,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 0,
         .ao_n_chan = 0,
         .range_ai = &range_ai_das1801,
         },
        {
         .name = "das-1801st-da",
         .ai_speed = 3000,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 0,
         .ao_n_chan = 4,
         .range_ai = &range_ai_das1801,
         },
        {
         .name = "das-1802st",
         .ai_speed = 3000,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 0,
         .ao_n_chan = 0,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1802st-da",
         .ai_speed = 3000,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 1,
         .ao_n_chan = 4,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1802hr",
         .ai_speed = 10000,
         .resolution = 16,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 0,
         .ao_n_chan = 0,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1802hr-da",
         .ai_speed = 10000,
         .resolution = 16,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 1,
         .ao_n_chan = 2,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1801hc",
         .ai_speed = 3000,
         .resolution = 12,
         .qram_len = 64,
         .common = 0,
         .do_n_chan = 8,
         .ao_ability = 1,
         .ao_n_chan = 2,
         .range_ai = &range_ai_das1801,
         },
        {
         .name = "das-1802hc",
         .ai_speed = 3000,
         .resolution = 12,
         .qram_len = 64,
         .common = 0,
         .do_n_chan = 8,
         .ao_ability = 1,
         .ao_n_chan = 2,
         .range_ai = &range_ai_das1802,
         },
        {
         .name = "das-1801ao",
         .ai_speed = 3000,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 2,
         .ao_n_chan = 2,
         .range_ai = &range_ai_das1801,
         },
        {
         .name = "das-1802ao",
         .ai_speed = 3000,
         .resolution = 12,
         .qram_len = 256,
         .common = 1,
         .do_n_chan = 4,
         .ao_ability = 2,
         .ao_n_chan = 2,
         .range_ai = &range_ai_das1802,
         },
};

/*
 * Useful for shorthand access to the particular board structure
 */
#define thisboard ((const struct das1800_board *)dev->board_ptr)

struct das1800_private {
        volatile unsigned int count;    /* number of data points left to be taken */
        unsigned int divisor1;  /* value to load into board's counter 1 for timed conversions */
        unsigned int divisor2;  /* value to load into board's counter 2 for timed conversions */
        int do_bits;            /* digital output bits */
        int irq_dma_bits;       /* bits for control register b */
        /* dma bits for control register b, stored so that dma can be
         * turned on and off */
        int dma_bits;
        unsigned int dma0;      /* dma channels used */
        unsigned int dma1;
        volatile unsigned int dma_current;      /* dma channel currently in use */
        uint16_t *ai_buf0;      /* pointers to dma buffers */
        uint16_t *ai_buf1;
        uint16_t *dma_current_buf;      /* pointer to dma buffer currently being used */
        unsigned int dma_transfer_size; /* size of transfer currently used, in bytes */
        unsigned long iobase2;  /* secondary io address used for analog out on 'ao' boards */
        short ao_update_bits;   /* remembers the last write to the 'update' dac */
};

#define devpriv ((struct das1800_private *)dev->private)

/* analog out range for boards with basic analog out */
static const struct comedi_lrange range_ao_1 = {
        1,
        {
         RANGE(-10, 10),
         }
};

/* analog out range for 'ao' boards */
/*
static const struct comedi_lrange range_ao_2 = {
        2,
        {
                RANGE(-10, 10),
                RANGE(-5, 5),
        }
};
*/

static struct comedi_driver driver_das1800 = {
        .driver_name = "das1800",
        .module = THIS_MODULE,
        .attach = das1800_attach,
        .detach = das1800_detach,
        .num_names = ARRAY_SIZE(das1800_boards),
        .board_name = &das1800_boards[0].name,
        .offset = sizeof(struct das1800_board),
};

/*
 * A convenient macro that defines init_module() and cleanup_module(),
 * as necessary.
 */
COMEDI_INITCLEANUP(driver_das1800);

static int das1800_init_dma(struct comedi_device *dev, unsigned int dma0,
                            unsigned int dma1)
{
        unsigned long flags;

        /*  need an irq to do dma */
        if (dev->irq && dma0) {
                /* encode dma0 and dma1 into 2 digit hexadecimal for switch */
                switch ((dma0 & 0x7) | (dma1 << 4)) {
                case 0x5:       /*  dma0 == 5 */
                        devpriv->dma_bits |= DMA_CH5;
                        break;
                case 0x6:       /*  dma0 == 6 */
                        devpriv->dma_bits |= DMA_CH6;
                        break;
                case 0x7:       /*  dma0 == 7 */
                        devpriv->dma_bits |= DMA_CH7;
                        break;
                case 0x65:      /*  dma0 == 5, dma1 == 6 */
                        devpriv->dma_bits |= DMA_CH5_CH6;
                        break;
                case 0x76:      /*  dma0 == 6, dma1 == 7 */
                        devpriv->dma_bits |= DMA_CH6_CH7;
                        break;
                case 0x57:      /*  dma0 == 7, dma1 == 5 */
                        devpriv->dma_bits |= DMA_CH7_CH5;
                        break;
                default:
                        printk(" only supports dma channels 5 through 7\n"
                               " Dual dma only allows the following combinations:\n"
                               " dma 5,6 / 6,7 / or 7,5\n");
                        return -EINVAL;
                        break;
                }
                if (request_dma(dma0, driver_das1800.driver_name)) {
                        printk(" failed to allocate dma channel %i\n", dma0);
                        return -EINVAL;
                }
                devpriv->dma0 = dma0;
                devpriv->dma_current = dma0;
                if (dma1) {
                        if (request_dma(dma1, driver_das1800.driver_name)) {
                                printk(" failed to allocate dma channel %i\n",
                                       dma1);
                                return -EINVAL;
                        }
                        devpriv->dma1 = dma1;
                }
                devpriv->ai_buf0 = kmalloc(DMA_BUF_SIZE, GFP_KERNEL | GFP_DMA);
                if (devpriv->ai_buf0 == NULL)
                        return -ENOMEM;
                devpriv->dma_current_buf = devpriv->ai_buf0;
                if (dma1) {
                        devpriv->ai_buf1 =
                            kmalloc(DMA_BUF_SIZE, GFP_KERNEL | GFP_DMA);
                        if (devpriv->ai_buf1 == NULL)
                                return -ENOMEM;
                }
                flags = claim_dma_lock();
                disable_dma(devpriv->dma0);
                set_dma_mode(devpriv->dma0, DMA_MODE_READ);
                if (dma1) {
                        disable_dma(devpriv->dma1);
                        set_dma_mode(devpriv->dma1, DMA_MODE_READ);
                }
                release_dma_lock(flags);
        }
        return 0;
}

static int das1800_attach(struct comedi_device *dev,
                          struct comedi_devconfig *it)
{
        struct comedi_subdevice *s;
        unsigned long iobase = it->options[0];
        unsigned int irq = it->options[1];
        unsigned int dma0 = it->options[2];
        unsigned int dma1 = it->options[3];
        unsigned long iobase2;
        int board;
        int retval;

        /* allocate and initialize dev->private */
        if (alloc_private(dev, sizeof(struct das1800_private)) < 0)
                return -ENOMEM;

        printk("comedi%d: %s: io 0x%lx", dev->minor, driver_das1800.driver_name,
               iobase);
        if (irq) {
                printk(", irq %u", irq);
                if (dma0) {
                        printk(", dma %u", dma0);
                        if (dma1)
                                printk(" and %u", dma1);
                }
        }
        printk("\n");

        if (iobase == 0) {
                printk(" io base address required\n");
                return -EINVAL;
        }

        /* check if io addresses are available */
        if (!request_region(iobase, DAS1800_SIZE, driver_das1800.driver_name)) {
                printk
                    (" I/O port conflict: failed to allocate ports 0x%lx to 0x%lx\n",
                     iobase, iobase + DAS1800_SIZE - 1);
                return -EIO;
        }
        dev->iobase = iobase;

        board = das1800_probe(dev);
        if (board < 0) {
                printk(" unable to determine board type\n");
                return -ENODEV;
        }

        dev->board_ptr = das1800_boards + board;
        dev->board_name = thisboard->name;

        /*  if it is an 'ao' board with fancy analog out then we need extra io ports */
        if (thisboard->ao_ability == 2) {
                iobase2 = iobase + IOBASE2;
                if (!request_region(iobase2, DAS1800_SIZE,
                                    driver_das1800.driver_name)) {
                        printk
                            (" I/O port conflict: failed to allocate ports 0x%lx to 0x%lx\n",
                             iobase2, iobase2 + DAS1800_SIZE - 1);
                        return -EIO;
                }
                devpriv->iobase2 = iobase2;
        }

        /* grab our IRQ */
        if (irq) {
                if (request_irq(irq, das1800_interrupt, 0,
                                driver_das1800.driver_name, dev)) {
                        printk(" unable to allocate irq %u\n", irq);
                        return -EINVAL;
                }
        }
        dev->irq = irq;

        /*  set bits that tell card which irq to use */
        switch (irq) {
        case 0:
                break;
        case 3:
                devpriv->irq_dma_bits |= 0x8;
                break;
        case 5:
                devpriv->irq_dma_bits |= 0x10;
                break;
        case 7:
                devpriv->irq_dma_bits |= 0x18;
                break;
        case 10:
                devpriv->irq_dma_bits |= 0x28;
                break;
        case 11:
                devpriv->irq_dma_bits |= 0x30;
                break;
        case 15:
                devpriv->irq_dma_bits |= 0x38;
                break;
        default:
                printk(" irq out of range\n");
                return -EINVAL;
                break;
        }

        retval = das1800_init_dma(dev, dma0, dma1);
        if (retval < 0)
                return retval;

        if (devpriv->ai_buf0 == NULL) {
                devpriv->ai_buf0 =
                    kmalloc(FIFO_SIZE * sizeof(uint16_t), GFP_KERNEL);
                if (devpriv->ai_buf0 == NULL)
                        return -ENOMEM;
        }

        if (alloc_subdevices(dev, 4) < 0)
                return -ENOMEM;

        /* analog input subdevice */
        s = dev->subdevices + 0;
        dev->read_subdev = s;
        s->type = COMEDI_SUBD_AI;
        s->subdev_flags = SDF_READABLE | SDF_DIFF | SDF_GROUND | SDF_CMD_READ;
        if (thisboard->common)
                s->subdev_flags |= SDF_COMMON;
        s->n_chan = thisboard->qram_len;
        s->len_chanlist = thisboard->qram_len;
        s->maxdata = (1 << thisboard->resolution) - 1;
        s->range_table = thisboard->range_ai;
        s->do_cmd = das1800_ai_do_cmd;
        s->do_cmdtest = das1800_ai_do_cmdtest;
        s->insn_read = das1800_ai_rinsn;
        s->poll = das1800_ai_poll;
        s->cancel = das1800_cancel;

        /* analog out */
        s = dev->subdevices + 1;
        if (thisboard->ao_ability == 1) {
                s->type = COMEDI_SUBD_AO;
                s->subdev_flags = SDF_WRITABLE;
                s->n_chan = thisboard->ao_n_chan;
                s->maxdata = (1 << thisboard->resolution) - 1;
                s->range_table = &range_ao_1;
                s->insn_write = das1800_ao_winsn;
        } else {
                s->type = COMEDI_SUBD_UNUSED;
        }

        /* di */
        s = dev->subdevices + 2;
        s->type = COMEDI_SUBD_DI;
        s->subdev_flags = SDF_READABLE;
        s->n_chan = 4;
        s->maxdata = 1;
        s->range_table = &range_digital;
        s->insn_bits = das1800_di_rbits;

        /* do */
        s = dev->subdevices + 3;
        s->type = COMEDI_SUBD_DO;
        s->subdev_flags = SDF_WRITABLE | SDF_READABLE;
        s->n_chan = thisboard->do_n_chan;
        s->maxdata = 1;
        s->range_table = &range_digital;
        s->insn_bits = das1800_do_wbits;

        das1800_cancel(dev, dev->read_subdev);

        /*  initialize digital out channels */
        outb(devpriv->do_bits, dev->iobase + DAS1800_DIGITAL);

        /*  initialize analog out channels */
        if (thisboard->ao_ability == 1) {
                /*  select 'update' dac channel for baseAddress + 0x0 */
                outb(DAC(thisboard->ao_n_chan - 1),
                     dev->iobase + DAS1800_SELECT);
                outw(devpriv->ao_update_bits, dev->iobase + DAS1800_DAC);
        }

        return 0;
};

static int das1800_detach(struct comedi_device *dev)
{
        /* only free stuff if it has been allocated by _attach */
        if (dev->iobase)
                release_region(dev->iobase, DAS1800_SIZE);
        if (dev->irq)
                free_irq(dev->irq, dev);
        if (dev->private) {
                if (devpriv->iobase2)
                        release_region(devpriv->iobase2, DAS1800_SIZE);
                if (devpriv->dma0)
                        free_dma(devpriv->dma0);
                if (devpriv->dma1)
                        free_dma(devpriv->dma1);
                if (devpriv->ai_buf0)
                        kfree(devpriv->ai_buf0);
                if (devpriv->ai_buf1)
                        kfree(devpriv->ai_buf1);
        }

        printk("comedi%d: %s: remove\n", dev->minor,
               driver_das1800.driver_name);

        return 0;
};

/* probes and checks das-1800 series board type
 */
static int das1800_probe(struct comedi_device *dev)
{
        int id;
        int board;

        id = (inb(dev->iobase + DAS1800_DIGITAL) >> 4) & 0xf;   /* get id bits */
        board = ((struct das1800_board *)dev->board_ptr) - das1800_boards;

        switch (id) {
        case 0x3:
                if (board == das1801st_da || board == das1802st_da ||
                    board == das1701st_da || board == das1702st_da) {
                        printk(" Board model: %s\n",
                               das1800_boards[board].name);
                        return board;
                }
                printk
                    (" Board model (probed, not recommended): das-1800st-da series\n");
                return das1801st;
                break;
        case 0x4:
                if (board == das1802hr_da || board == das1702hr_da) {
                        printk(" Board model: %s\n",
                               das1800_boards[board].name);
                        return board;
                }
                printk
                    (" Board model (probed, not recommended): das-1802hr-da\n");
                return das1802hr;
                break;
        case 0x5:
                if (board == das1801ao || board == das1802ao ||
                    board == das1701ao || board == das1702ao) {
                        printk(" Board model: %s\n",
                               das1800_boards[board].name);
                        return board;
                }
                printk
                    (" Board model (probed, not recommended): das-1800ao series\n");
                return das1801ao;
                break;
        case 0x6:
                if (board == das1802hr || board == das1702hr) {
                        printk(" Board model: %s\n",
                               das1800_boards[board].name);
                        return board;
                }
                printk(" Board model (probed, not recommended): das-1802hr\n");
                return das1802hr;
                break;
        case 0x7:
                if (board == das1801st || board == das1802st ||
                    board == das1701st || board == das1702st) {
                        printk(" Board model: %s\n",
                               das1800_boards[board].name);
                        return board;
                }
                printk
                    (" Board model (probed, not recommended): das-1800st series\n");
                return das1801st;
                break;
        case 0x8:
                if (board == das1801hc || board == das1802hc) {
                        printk(" Board model: %s\n",
                               das1800_boards[board].name);
                        return board;
                }
                printk
                    (" Board model (probed, not recommended): das-1800hc series\n");
                return das1801hc;
                break;
        default:
                printk
                    (" Board model: probe returned 0x%x (unknown, please report)\n",
                     id);
                return board;
                break;
        }
        return -1;
}

static int das1800_ai_poll(struct comedi_device *dev,
                           struct comedi_subdevice *s)
{
        unsigned long flags;

        /*  prevent race with interrupt handler */
        spin_lock_irqsave(&dev->spinlock, flags);
        das1800_ai_handler(dev);
        spin_unlock_irqrestore(&dev->spinlock, flags);

        return s->async->buf_write_count - s->async->buf_read_count;
}

static irqreturn_t das1800_interrupt(int irq, void *d)
{
        struct comedi_device *dev = d;
        unsigned int status;

        if (dev->attached == 0) {
                comedi_error(dev, "premature interrupt");
                return IRQ_HANDLED;
        }

        /* Prevent race with das1800_ai_poll() on multi processor systems.
         * Also protects indirect addressing in das1800_ai_handler */
        spin_lock(&dev->spinlock);
        status = inb(dev->iobase + DAS1800_STATUS);

        /* if interrupt was not caused by das-1800 */
        if (!(status & INT)) {
                spin_unlock(&dev->spinlock);
                return IRQ_NONE;
        }
        /* clear the interrupt status bit INT */
        outb(CLEAR_INTR_MASK & ~INT, dev->iobase + DAS1800_STATUS);
        /*  handle interrupt */
        das1800_ai_handler(dev);

        spin_unlock(&dev->spinlock);
        return IRQ_HANDLED;
}

/* the guts of the interrupt handler, that is shared with das1800_ai_poll */
static void das1800_ai_handler(struct comedi_device *dev)
{
        struct comedi_subdevice *s = dev->subdevices + 0;       /* analog input subdevice */
        struct comedi_async *async = s->async;
        struct comedi_cmd *cmd = &async->cmd;
        unsigned int status = inb(dev->iobase + DAS1800_STATUS);

        async->events = 0;
        /*  select adc for base address + 0 */
        outb(ADC, dev->iobase + DAS1800_SELECT);
        /*  dma buffer full */
        if (devpriv->irq_dma_bits & DMA_ENABLED) {
                /*  look for data from dma transfer even if dma terminal count hasn't happened yet */
                das1800_handle_dma(dev, s, status);
        } else if (status & FHF) {      /*  if fifo half full */
                das1800_handle_fifo_half_full(dev, s);
        } else if (status & FNE) {      /*  if fifo not empty */
                das1800_handle_fifo_not_empty(dev, s);
        }

        async->events |= COMEDI_CB_BLOCK;
        /* if the card's fifo has overflowed */
        if (status & OVF) {
                /*  clear OVF interrupt bit */
                outb(CLEAR_INTR_MASK & ~OVF, dev->iobase + DAS1800_STATUS);
                comedi_error(dev, "DAS1800 FIFO overflow");
                das1800_cancel(dev, s);
                async->events |= COMEDI_CB_ERROR | COMEDI_CB_EOA;
                comedi_event(dev, s);
                return;
        }
        /*  stop taking data if appropriate */
        /* stop_src TRIG_EXT */
        if (status & CT0TC) {
                /*  clear CT0TC interrupt bit */
                outb(CLEAR_INTR_MASK & ~CT0TC, dev->iobase + DAS1800_STATUS);
                /*  make sure we get all remaining data from board before quitting */
                if (devpriv->irq_dma_bits & DMA_ENABLED)
                        das1800_flush_dma(dev, s);
                else
                        das1800_handle_fifo_not_empty(dev, s);
                das1800_cancel(dev, s); /* disable hardware conversions */
                async->events |= COMEDI_CB_EOA;
        } else if (cmd->stop_src == TRIG_COUNT && devpriv->count == 0) {        /*  stop_src TRIG_COUNT */
                das1800_cancel(dev, s); /* disable hardware conversions */
                async->events |= COMEDI_CB_EOA;
        }

        comedi_event(dev, s);

        return;
}

static void das1800_handle_dma(struct comedi_device *dev,
                               struct comedi_subdevice *s, unsigned int status)
{
        unsigned long flags;
        const int dual_dma = devpriv->irq_dma_bits & DMA_DUAL;

        flags = claim_dma_lock();
        das1800_flush_dma_channel(dev, s, devpriv->dma_current,
                                  devpriv->dma_current_buf);
        /*  re-enable  dma channel */
        set_dma_addr(devpriv->dma_current,

                     virt_to_bus(devpriv->dma_current_buf));
        set_dma_count(devpriv->dma_current, devpriv->dma_transfer_size);
        enable_dma(devpriv->dma_current);
        release_dma_lock(flags);

        if (status & DMATC) {
                /*  clear DMATC interrupt bit */
                outb(CLEAR_INTR_MASK & ~DMATC, dev->iobase + DAS1800_STATUS);
                /*  switch dma channels for next time, if appropriate */
                if (dual_dma) {
                        /*  read data from the other channel next time */
                        if (devpriv->dma_current == devpriv->dma0) {
                                devpriv->dma_current = devpriv->dma1;
                                devpriv->dma_current_buf = devpriv->ai_buf1;
                        } else {
                                devpriv->dma_current = devpriv->dma0;
                                devpriv->dma_current_buf = devpriv->ai_buf0;
                        }
                }
        }

        return;
}

static inline uint16_t munge_bipolar_sample(const struct comedi_device *dev,
                                            uint16_t sample)
{
        sample += 1 << (thisboard->resolution - 1);
        return sample;
}

static void munge_data(struct comedi_device *dev, uint16_t * array,
                       unsigned int num_elements)
{
        unsigned int i;
        int unipolar;

        /* see if card is using a unipolar or bipolar range so we can munge data correctly */
        unipolar = inb(dev->iobase + DAS1800_CONTROL_C) & UB;

        /* convert to unsigned type if we are in a bipolar mode */
        if (!unipolar) {
                for (i = 0; i < num_elements; i++) {
                        array[i] = munge_bipolar_sample(dev, array[i]);
                }
        }
}

/* Utility function used by das1800_flush_dma() and das1800_handle_dma().
 * Assumes dma lock is held */
static void das1800_flush_dma_channel(struct comedi_device *dev,
                                      struct comedi_subdevice *s,
                                      unsigned int channel, uint16_t * buffer)
{
        unsigned int num_bytes, num_samples;
        struct comedi_cmd *cmd = &s->async->cmd;

        disable_dma(channel);

        /* clear flip-flop to make sure 2-byte registers
         * get set correctly */
        clear_dma_ff(channel);

        /*  figure out how many points to read */
        num_bytes = devpriv->dma_transfer_size - get_dma_residue(channel);
        num_samples = num_bytes / sizeof(short);

        /* if we only need some of the points */
        if (cmd->stop_src == TRIG_COUNT && devpriv->count < num_samples)
                num_samples = devpriv->count;

        munge_data(dev, buffer, num_samples);
        cfc_write_array_to_buffer(s, buffer, num_bytes);
        if (s->async->cmd.stop_src == TRIG_COUNT)
                devpriv->count -= num_samples;

        return;
}

/* flushes remaining data from board when external trigger has stopped aquisition
 * and we are using dma transfers */
static void das1800_flush_dma(struct comedi_device *dev,
                              struct comedi_subdevice *s)
{
        unsigned long flags;
        const int dual_dma = devpriv->irq_dma_bits & DMA_DUAL;

        flags = claim_dma_lock();
        das1800_flush_dma_channel(dev, s, devpriv->dma_current,
                                  devpriv->dma_current_buf);

        if (dual_dma) {
                /*  switch to other channel and flush it */
                if (devpriv->dma_current == devpriv->dma0) {
                        devpriv->dma_current = devpriv->dma1;
                        devpriv->dma_current_buf = devpriv->ai_buf1;
                } else {
                        devpriv->dma_current = devpriv->dma0;
                        devpriv->dma_current_buf = devpriv->ai_buf0;
                }
                das1800_flush_dma_channel(dev, s, devpriv->dma_current,
                                          devpriv->dma_current_buf);
        }

        release_dma_lock(flags);

        /*  get any remaining samples in fifo */
        das1800_handle_fifo_not_empty(dev, s);

        return;
}

static void das1800_handle_fifo_half_full(struct comedi_device *dev,
                                          struct comedi_subdevice *s)
{
        int numPoints = 0;      /* number of points to read */
        struct comedi_cmd *cmd = &s->async->cmd;

        numPoints = FIFO_SIZE / 2;
        /* if we only need some of the points */
        if (cmd->stop_src == TRIG_COUNT && devpriv->count < numPoints)
                numPoints = devpriv->count;
        insw(dev->iobase + DAS1800_FIFO, devpriv->ai_buf0, numPoints);
        munge_data(dev, devpriv->ai_buf0, numPoints);
        cfc_write_array_to_buffer(s, devpriv->ai_buf0,
                                  numPoints * sizeof(devpriv->ai_buf0[0]));
        if (cmd->stop_src == TRIG_COUNT)
                devpriv->count -= numPoints;
        return;
}

static void das1800_handle_fifo_not_empty(struct comedi_device *dev,
                                          struct comedi_subdevice *s)
{
        short dpnt;
        int unipolar;
        struct comedi_cmd *cmd = &s->async->cmd;

        unipolar = inb(dev->iobase + DAS1800_CONTROL_C) & UB;

        while (inb(dev->iobase + DAS1800_STATUS) & FNE) {
                if (cmd->stop_src == TRIG_COUNT && devpriv->count == 0)
                        break;
                dpnt = inw(dev->iobase + DAS1800_FIFO);
                /* convert to unsigned type if we are in a bipolar mode */
                if (!unipolar) ;
                dpnt = munge_bipolar_sample(dev, dpnt);
                cfc_write_to_buffer(s, dpnt);
                if (cmd->stop_src == TRIG_COUNT)
                        devpriv->count--;
        }

        return;
}

static int das1800_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
{
        outb(0x0, dev->iobase + DAS1800_STATUS);        /* disable conversions */
        outb(0x0, dev->iobase + DAS1800_CONTROL_B);     /* disable interrupts and dma */
        outb(0x0, dev->iobase + DAS1800_CONTROL_A);     /* disable and clear fifo and stop triggering */
        if (devpriv->dma0)
                disable_dma(devpriv->dma0);
        if (devpriv->dma1)
                disable_dma(devpriv->dma1);
        return 0;
}

/* test analog input cmd */
static int das1800_ai_do_cmdtest(struct comedi_device *dev,
                                 struct comedi_subdevice *s,
                                 struct comedi_cmd *cmd)
{
        int err = 0;
        int tmp;
        unsigned int tmp_arg;
        int i;
        int unipolar;

        /* step 1: make sure trigger sources are trivially valid */

        tmp = cmd->start_src;
        cmd->start_src &= TRIG_NOW | TRIG_EXT;
        if (!cmd->start_src || tmp != cmd->start_src)
                err++;

        tmp = cmd->scan_begin_src;
        cmd->scan_begin_src &= TRIG_FOLLOW | TRIG_TIMER | TRIG_EXT;
        if (!cmd->scan_begin_src || tmp != cmd->scan_begin_src)
                err++;

        tmp = cmd->convert_src;
        cmd->convert_src &= TRIG_TIMER | TRIG_EXT;
        if (!cmd->convert_src || tmp != cmd->convert_src)
                err++;

        tmp = cmd->scan_end_src;
        cmd->scan_end_src &= TRIG_COUNT;
        if (!cmd->scan_end_src || tmp != cmd->scan_end_src)
                err++;

        tmp = cmd->stop_src;
        cmd->stop_src &= TRIG_COUNT | TRIG_EXT | TRIG_NONE;
        if (!cmd->stop_src || tmp != cmd->stop_src)
                err++;

        if (err)
                return 1;

        /* step 2: make sure trigger sources are unique and mutually compatible */

        /*  uniqueness check */
        if (cmd->start_src != TRIG_NOW && cmd->start_src != TRIG_EXT)
                err++;
        if (cmd->scan_begin_src != TRIG_FOLLOW &&
            cmd->scan_begin_src != TRIG_TIMER &&
            cmd->scan_begin_src != TRIG_EXT)
                err++;
        if (cmd->convert_src != TRIG_TIMER && cmd->convert_src != TRIG_EXT)
                err++;
        if (cmd->stop_src != TRIG_COUNT &&
            cmd->stop_src != TRIG_NONE && cmd->stop_src != TRIG_EXT)
                err++;
        /* compatibility check */
        if (cmd->scan_begin_src != TRIG_FOLLOW &&
            cmd->convert_src != TRIG_TIMER)
                err++;

        if (err)
                return 2;

        /* step 3: make sure arguments are trivially compatible */

        if (cmd->start_arg != 0) {
                cmd->start_arg = 0;
                err++;
        }
        if (cmd->convert_src == TRIG_TIMER) {
                if (cmd->convert_arg < thisboard->ai_speed) {
                        cmd->convert_arg = thisboard->ai_speed;
                        err++;
                }
        }
        if (!cmd->chanlist_len) {
                cmd->chanlist_len = 1;
                err++;
        }
        if (cmd->scan_end_arg != cmd->chanlist_len) {
                cmd->scan_end_arg = cmd->chanlist_len;
                err++;
        }

        switch (cmd->stop_src) {
        case TRIG_COUNT:
                if (!cmd->stop_arg) {
                        cmd->stop_arg = 1;
                        err++;
                }
                break;
        case TRIG_NONE:
                if (cmd->stop_arg != 0) {
                        cmd->stop_arg = 0;
                        err++;
                }
                break;
        default:
                break;
        }

        if (err)
                return 3;

        /* step 4: fix up any arguments */

        if (cmd->convert_src == TRIG_TIMER) {
                /*  if we are not in burst mode */
                if (cmd->scan_begin_src == TRIG_FOLLOW) {
                        tmp_arg = cmd->convert_arg;
                        /* calculate counter values that give desired timing */
                        i8253_cascade_ns_to_timer_2div(TIMER_BASE,
                                                       &(devpriv->divisor1),
                                                       &(devpriv->divisor2),
                                                       &(cmd->convert_arg),
                                                       cmd->
                                                       flags & TRIG_ROUND_MASK);
                        if (tmp_arg != cmd->convert_arg)
                                err++;
                }
                /*  if we are in burst mode */
                else {
                        /*  check that convert_arg is compatible */
                        tmp_arg = cmd->convert_arg;
                        cmd->convert_arg =
                            burst_convert_arg(cmd->convert_arg,
                                              cmd->flags & TRIG_ROUND_MASK);
                        if (tmp_arg != cmd->convert_arg)
                                err++;

                        if (cmd->scan_begin_src == TRIG_TIMER) {
                                /*  if scans are timed faster than conversion rate allows */
                                if (cmd->convert_arg * cmd->chanlist_len >
                                    cmd->scan_begin_arg) {
                                        cmd->scan_begin_arg =
                                            cmd->convert_arg *
                                            cmd->chanlist_len;
                                        err++;
                                }
                                tmp_arg = cmd->scan_begin_arg;
                                /* calculate counter values that give desired timing */
                                i8253_cascade_ns_to_timer_2div(TIMER_BASE,
                                                               &(devpriv->
                                                                 divisor1),
                                                               &(devpriv->
                                                                 divisor2),
                                                               &(cmd->
                                                                 scan_begin_arg),
                                                               cmd->
                                                               flags &
                                                               TRIG_ROUND_MASK);
                                if (tmp_arg != cmd->scan_begin_arg)
                                        err++;
                        }
                }
        }

        if (err)
                return 4;

        /*  make sure user is not trying to mix unipolar and bipolar ranges */
        if (cmd->chanlist) {
                unipolar = CR_RANGE(cmd->chanlist[0]) & UNIPOLAR;
                for (i = 1; i < cmd->chanlist_len; i++) {
                        if (unipolar != (CR_RANGE(cmd->chanlist[i]) & UNIPOLAR)) {
                                comedi_error(dev,
                                             "unipolar and bipolar ranges cannot be mixed in the chanlist");
                                err++;
                                break;
                        }
                }
        }

        if (err)
                return 5;

        return 0;
}

/* analog input cmd interface */

/* first, some utility functions used in the main ai_do_cmd() */

/* returns appropriate bits for control register a, depending on command */
static int control_a_bits(struct comedi_cmd cmd)
{
        int control_a;

        control_a = FFEN;       /* enable fifo */
        if (cmd.stop_src == TRIG_EXT) {
                control_a |= ATEN;
        }
        switch (cmd.start_src) {
        case TRIG_EXT:
                control_a |= TGEN | CGSL;
                break;
        case TRIG_NOW:
                control_a |= CGEN;
                break;
        default:
                break;
        }

        return control_a;
}

/* returns appropriate bits for control register c, depending on command */
static int control_c_bits(struct comedi_cmd cmd)
{
        int control_c;
        int aref;

        /* set clock source to internal or external, select analog reference,
         * select unipolar / bipolar
         */
        aref = CR_AREF(cmd.chanlist[0]);
        control_c = UQEN;       /* enable upper qram addresses */
        if (aref != AREF_DIFF)
                control_c |= SD;
        if (aref == AREF_COMMON)
                control_c |= CMEN;
        /* if a unipolar range was selected */
        if (CR_RANGE(cmd.chanlist[0]) & UNIPOLAR)
                control_c |= UB;
        switch (cmd.scan_begin_src) {
        case TRIG_FOLLOW:       /*  not in burst mode */
                switch (cmd.convert_src) {
                case TRIG_TIMER:
                        /* trig on cascaded counters */
                        control_c |= IPCLK;
                        break;
                case TRIG_EXT:
                        /* trig on falling edge of external trigger */
                        control_c |= XPCLK;
                        break;
                default:
                        break;
                }
                break;
        case TRIG_TIMER:
                /*  burst mode with internal pacer clock */
                control_c |= BMDE | IPCLK;
                break;
        case TRIG_EXT:
                /*  burst mode with external trigger */
                control_c |= BMDE | XPCLK;
                break;
        default:
                break;
        }

        return control_c;
}

/* sets up counters */
static int setup_counters(struct comedi_device *dev, struct comedi_cmd cmd)
{
        /*  setup cascaded counters for conversion/scan frequency */
        switch (cmd.scan_begin_src) {
        case TRIG_FOLLOW:       /*  not in burst mode */
                if (cmd.convert_src == TRIG_TIMER) {
                        /* set conversion frequency */
                        i8253_cascade_ns_to_timer_2div(TIMER_BASE,
                                                       &(devpriv->divisor1),
                                                       &(devpriv->divisor2),
                                                       &(cmd.convert_arg),
                                                       cmd.
                                                       flags & TRIG_ROUND_MASK);
                        if (das1800_set_frequency(dev) < 0) {
                                return -1;
                        }
                }
                break;
        case TRIG_TIMER:        /*  in burst mode */
                /* set scan frequency */
                i8253_cascade_ns_to_timer_2div(TIMER_BASE, &(devpriv->divisor1),
                                               &(devpriv->divisor2),
                                               &(cmd.scan_begin_arg),
                                               cmd.flags & TRIG_ROUND_MASK);
                if (das1800_set_frequency(dev) < 0) {
                        return -1;
                }
                break;
        default:
                break;
        }

        /*  setup counter 0 for 'about triggering' */
        if (cmd.stop_src == TRIG_EXT) {
                /*  load counter 0 in mode 0 */
                i8254_load(dev->iobase + DAS1800_COUNTER, 0, 0, 1, 0);
        }

        return 0;
}

/* sets up dma */
static void setup_dma(struct comedi_device *dev, struct comedi_cmd cmd)
{
        unsigned long lock_flags;
        const int dual_dma = devpriv->irq_dma_bits & DMA_DUAL;

        if ((devpriv->irq_dma_bits & DMA_ENABLED) == 0)
                return;

        /* determine a reasonable dma transfer size */
        devpriv->dma_transfer_size = suggest_transfer_size(&cmd);
        lock_flags = claim_dma_lock();
        disable_dma(devpriv->dma0);
        /* clear flip-flop to make sure 2-byte registers for
         * count and address get set correctly */
        clear_dma_ff(devpriv->dma0);
        set_dma_addr(devpriv->dma0, virt_to_bus(devpriv->ai_buf0));
        /*  set appropriate size of transfer */
        set_dma_count(devpriv->dma0, devpriv->dma_transfer_size);
        devpriv->dma_current = devpriv->dma0;
        devpriv->dma_current_buf = devpriv->ai_buf0;
        enable_dma(devpriv->dma0);
        /*  set up dual dma if appropriate */
        if (dual_dma) {
                disable_dma(devpriv->dma1);
                /* clear flip-flop to make sure 2-byte registers for
                 * count and address get set correctly */
                clear_dma_ff(devpriv->dma1);
                set_dma_addr(devpriv->dma1, virt_to_bus(devpriv->ai_buf1));
                /*  set appropriate size of transfer */
                set_dma_count(devpriv->dma1, devpriv->dma_transfer_size);
                enable_dma(devpriv->dma1);
        }
        release_dma_lock(lock_flags);

        return;
}

/* programs channel/gain list into card */
static void program_chanlist(struct comedi_device *dev, struct comedi_cmd cmd)
{
        int i, n, chan_range;
        unsigned long irq_flags;
        const int range_mask = 0x3;     /* masks unipolar/bipolar bit off range */
        const int range_bitshift = 8;

        n = cmd.chanlist_len;
        /*  spinlock protects indirect addressing */
        spin_lock_irqsave(&dev->spinlock, irq_flags);
        outb(QRAM, dev->iobase + DAS1800_SELECT);       /* select QRAM for baseAddress + 0x0 */
        outb(n - 1, dev->iobase + DAS1800_QRAM_ADDRESS);        /*set QRAM address start */
        /* make channel / gain list */
        for (i = 0; i < n; i++) {
                chan_range =
                    CR_CHAN(cmd.
                            chanlist[i]) | ((CR_RANGE(cmd.chanlist[i]) &
                                             range_mask) << range_bitshift);
                outw(chan_range, dev->iobase + DAS1800_QRAM);
        }
        outb(n - 1, dev->iobase + DAS1800_QRAM_ADDRESS);        /*finish write to QRAM */
        spin_unlock_irqrestore(&dev->spinlock, irq_flags);

        return;
}

/* analog input do_cmd */
static int das1800_ai_do_cmd(struct comedi_device *dev,
                             struct comedi_subdevice *s)
{
        int ret;
        int control_a, control_c;
        struct comedi_async *async = s->async;
        struct comedi_cmd cmd = async->cmd;

        if (!dev->irq) {
                comedi_error(dev,
                             "no irq assigned for das-1800, cannot do hardware conversions");
                return -1;
        }

        /* disable dma on TRIG_WAKE_EOS, or TRIG_RT
         * (because dma in handler is unsafe at hard real-time priority) */
        if (cmd.flags & (TRIG_WAKE_EOS | TRIG_RT)) {
                devpriv->irq_dma_bits &= ~DMA_ENABLED;
        } else {
                devpriv->irq_dma_bits |= devpriv->dma_bits;
        }
        /*  interrupt on end of conversion for TRIG_WAKE_EOS */
        if (cmd.flags & TRIG_WAKE_EOS) {
                /*  interrupt fifo not empty */
                devpriv->irq_dma_bits &= ~FIMD;
        } else {
                /*  interrupt fifo half full */
                devpriv->irq_dma_bits |= FIMD;
        }
        /*  determine how many conversions we need */
        if (cmd.stop_src == TRIG_COUNT) {
                devpriv->count = cmd.stop_arg * cmd.chanlist_len;
        }

        das1800_cancel(dev, s);

        /*  determine proper bits for control registers */
        control_a = control_a_bits(cmd);
        control_c = control_c_bits(cmd);

        /* setup card and start */
        program_chanlist(dev, cmd);
        ret = setup_counters(dev, cmd);
        if (ret < 0) {
                comedi_error(dev, "Error setting up counters");
                return ret;
        }
        setup_dma(dev, cmd);
        outb(control_c, dev->iobase + DAS1800_CONTROL_C);
        /*  set conversion rate and length for burst mode */
        if (control_c & BMDE) {
                /*  program conversion period with number of microseconds minus 1 */
                outb(cmd.convert_arg / 1000 - 1,
                     dev->iobase + DAS1800_BURST_RATE);
                outb(cmd.chanlist_len - 1, dev->iobase + DAS1800_BURST_LENGTH);
        }
        outb(devpriv->irq_dma_bits, dev->iobase + DAS1800_CONTROL_B);   /*  enable irq/dma */
        outb(control_a, dev->iobase + DAS1800_CONTROL_A);       /* enable fifo and triggering */
        outb(CVEN, dev->iobase + DAS1800_STATUS);       /* enable conversions */

        return 0;
}

/* read analog input */
static int das1800_ai_rinsn(struct comedi_device *dev,
                            struct comedi_subdevice *s,
                            struct comedi_insn *insn, unsigned int *data)
{
        int i, n;
        int chan, range, aref, chan_range;
        int timeout = 1000;
        short dpnt;
        int conv_flags = 0;
        unsigned long irq_flags;

        /* set up analog reference and unipolar / bipolar mode */
        aref = CR_AREF(insn->chanspec);
        conv_flags |= UQEN;
        if (aref != AREF_DIFF)
                conv_flags |= SD;
        if (aref == AREF_COMMON)
                conv_flags |= CMEN;
        /* if a unipolar range was selected */
        if (CR_RANGE(insn->chanspec) & UNIPOLAR)
                conv_flags |= UB;

        outb(conv_flags, dev->iobase + DAS1800_CONTROL_C);      /* software conversion enabled */
        outb(CVEN, dev->iobase + DAS1800_STATUS);       /* enable conversions */
        outb(0x0, dev->iobase + DAS1800_CONTROL_A);     /* reset fifo */
        outb(FFEN, dev->iobase + DAS1800_CONTROL_A);

        chan = CR_CHAN(insn->chanspec);
        /* mask of unipolar/bipolar bit from range */
        range = CR_RANGE(insn->chanspec) & 0x3;
        chan_range = chan | (range << 8);
        spin_lock_irqsave(&dev->spinlock, irq_flags);
        outb(QRAM, dev->iobase + DAS1800_SELECT);       /* select QRAM for baseAddress + 0x0 */
        outb(0x0, dev->iobase + DAS1800_QRAM_ADDRESS);  /* set QRAM address start */
        outw(chan_range, dev->iobase + DAS1800_QRAM);
        outb(0x0, dev->iobase + DAS1800_QRAM_ADDRESS);  /*finish write to QRAM */
        outb(ADC, dev->iobase + DAS1800_SELECT);        /* select ADC for baseAddress + 0x0 */

        for (n = 0; n < insn->n; n++) {
                /* trigger conversion */
                outb(0, dev->iobase + DAS1800_FIFO);
                for (i = 0; i < timeout; i++) {
                        if (inb(dev->iobase + DAS1800_STATUS) & FNE)
                                break;
                }
                if (i == timeout) {
                        comedi_error(dev, "timeout");
                        return -ETIME;
                }
                dpnt = inw(dev->iobase + DAS1800_FIFO);
                /* shift data to offset binary for bipolar ranges */
                if ((conv_flags & UB) == 0)
                        dpnt += 1 << (thisboard->resolution - 1);
                data[n] = dpnt;
        }
        spin_unlock_irqrestore(&dev->spinlock, irq_flags);

        return n;
}

/* writes to an analog output channel */
static int das1800_ao_winsn(struct comedi_device *dev,
                            struct comedi_subdevice *s,
                            struct comedi_insn *insn, unsigned int *data)
{
        int chan = CR_CHAN(insn->chanspec);
/* int range = CR_RANGE(insn->chanspec); */
        int update_chan = thisboard->ao_n_chan - 1;
        short output;
        unsigned long irq_flags;

        /*   card expects two's complement data */
        output = data[0] - (1 << (thisboard->resolution - 1));
        /*  if the write is to the 'update' channel, we need to remember its value */
        if (chan == update_chan)
                devpriv->ao_update_bits = output;
        /*  write to channel */
        spin_lock_irqsave(&dev->spinlock, irq_flags);
        outb(DAC(chan), dev->iobase + DAS1800_SELECT);  /* select dac channel for baseAddress + 0x0 */
        outw(output, dev->iobase + DAS1800_DAC);
        /*  now we need to write to 'update' channel to update all dac channels */
        if (chan != update_chan) {
                outb(DAC(update_chan), dev->iobase + DAS1800_SELECT);   /* select 'update' channel for baseAddress + 0x0 */
                outw(devpriv->ao_update_bits, dev->iobase + DAS1800_DAC);
        }
        spin_unlock_irqrestore(&dev->spinlock, irq_flags);

        return 1;
}

/* reads from digital input channels */
static int das1800_di_rbits(struct comedi_device *dev,
                            struct comedi_subdevice *s,
                            struct comedi_insn *insn, unsigned int *data)
{

        data[1] = inb(dev->iobase + DAS1800_DIGITAL) & 0xf;
        data[0] = 0;

        return 2;
}

/* writes to digital output channels */
static int das1800_do_wbits(struct comedi_device *dev,
                            struct comedi_subdevice *s,
                            struct comedi_insn *insn, unsigned int *data)
{
        unsigned int wbits;

        /*  only set bits that have been masked */
        data[0] &= (1 << s->n_chan) - 1;
        wbits = devpriv->do_bits;
        wbits &= ~data[0];
        wbits |= data[0] & data[1];
        devpriv->do_bits = wbits;

        outb(devpriv->do_bits, dev->iobase + DAS1800_DIGITAL);

        data[1] = devpriv->do_bits;

        return 2;
}

/* loads counters with divisor1, divisor2 from private structure */
static int das1800_set_frequency(struct comedi_device *dev)
{
        int err = 0;

        /*  counter 1, mode 2 */
        if (i8254_load(dev->iobase + DAS1800_COUNTER, 0, 1, devpriv->divisor1,
                       2))
                err++;
        /*  counter 2, mode 2 */
        if (i8254_load(dev->iobase + DAS1800_COUNTER, 0, 2, devpriv->divisor2,
                       2))
                err++;
        if (err)
                return -1;

        return 0;
}

/* converts requested conversion timing to timing compatible with
 * hardware, used only when card is in 'burst mode'
 */
static unsigned int burst_convert_arg(unsigned int convert_arg, int round_mode)
{
        unsigned int micro_sec;

        /*  in burst mode, the maximum conversion time is 64 microseconds */
        if (convert_arg > 64000)
                convert_arg = 64000;

        /*  the conversion time must be an integral number of microseconds */
        switch (round_mode) {
        case TRIG_ROUND_NEAREST:
        default:
                micro_sec = (convert_arg + 500) / 1000;
                break;
        case TRIG_ROUND_DOWN:
                micro_sec = convert_arg / 1000;
                break;
        case TRIG_ROUND_UP:
                micro_sec = (convert_arg - 1) / 1000 + 1;
                break;
        }

        /*  return number of nanoseconds */
        return micro_sec * 1000;
}

/* utility function that suggests a dma transfer size based on the conversion period 'ns' */
static unsigned int suggest_transfer_size(struct comedi_cmd *cmd)
{
        unsigned int size = DMA_BUF_SIZE;
        static const int sample_size = 2;       /*  size in bytes of one sample from board */
        unsigned int fill_time = 300000000;     /*  target time in nanoseconds for filling dma buffer */
        unsigned int max_size;  /*  maximum size we will allow for a transfer */

        /*  make dma buffer fill in 0.3 seconds for timed modes */
        switch (cmd->scan_begin_src) {
        case TRIG_FOLLOW:       /*  not in burst mode */
                if (cmd->convert_src == TRIG_TIMER)
                        size = (fill_time / cmd->convert_arg) * sample_size;
                break;
        case TRIG_TIMER:
                size = (fill_time / (cmd->scan_begin_arg * cmd->chanlist_len)) *
                    sample_size;
                break;
        default:
                size = DMA_BUF_SIZE;
                break;
        }

        /*  set a minimum and maximum size allowed */
        max_size = DMA_BUF_SIZE;
        /*  if we are taking limited number of conversions, limit transfer size to that */
        if (cmd->stop_src == TRIG_COUNT &&
            cmd->stop_arg * cmd->chanlist_len * sample_size < max_size)
                max_size = cmd->stop_arg * cmd->chanlist_len * sample_size;

        if (size > max_size)
                size = max_size;
        if (size < sample_size)
                size = sample_size;

        return size;
}