/*
 * Comedi driver for Keithley DAS-1700/DAS-1800 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.
 */

/*
 * 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
 *
 * Configuration options:
 *   [0] - I/O port base address
 *   [1] - IRQ (optional, required for analog input cmd support)
 *   [2] - DMA0 (optional, requires irq)
 *   [3] - DMA1 (optional, requires irq and dma0)
 *
 * analog input cmd triggers supported:
 *
 *   start_src          TRIG_NOW        command starts immediately
 *                      TRIG_EXT        command starts on external pin TGIN
 *
 *   scan_begin_src     TRIG_FOLLOW     paced/external scans start immediately
 *                      TRIG_TIMER      burst scans start periodically
 *                      TRIG_EXT        burst scans start on external pin XPCLK
 *
 *   scan_end_src       TRIG_COUNT      scan ends after last channel
 *
 *   convert_src        TRIG_TIMER      paced/burst conversions are timed
 *                      TRIG_EXT        conversions on external pin XPCLK
 *                                      (requires scan_begin_src == TRIG_FOLLOW)
 *
 *   stop_src           TRIG_COUNT      command stops after stop_arg scans
 *                      TRIG_EXT        command stops on external pin TGIN
 *                      TRIG_NONE       command runs until canceled
 *
 * If TRIG_EXT is used for both the start_src and stop_src, the first TGIN
 * trigger starts the command, and the second trigger will stop it. If only
 * one is TRIG_EXT, the first trigger will either stop or start the command.
 * The external pin TGIN is normally set for negative edge triggering. It
 * can be set to positive edge with the CR_INVERT flag. If TRIG_EXT is used
 * for both the start_src and stop_src they must have the same polarity.
 *
 * Minimum conversion speed is limited to 64 microseconds (convert_arg <= 64000)
 * for 'burst' scans. This limitation does not apply for 'paced' scans. The
 * maximum conversion speed is limited by the board (convert_arg >= ai_speed).
 * Maximum conversion speeds are not always achievable depending on the
 * board setup (see user manual).
 *
 * NOTES:
 * Only the DAS-1801ST has been tested by me.
 * Unipolar and bipolar ranges cannot be mixed in the channel/gain list.
 *
 * The waveform analog output on the 'ao' cards is not supported.
 * If you need it, send me (Frank Hess) an email.
 */

#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/io.h>

#include "../comedidev.h"

#include "comedi_isadma.h"
#include "comedi_8254.h"

/* misc. defines */
#define DAS1800_SIZE           16       /* uses 16 io addresses */
#define FIFO_SIZE              1024     /*  1024 sample fifo */
#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   TGPL                    0x40
#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
#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
#define   INT                     0x1
#define   DMATC                   0x2
#define   CT0TC                   0x8
#define   OVF                     0x10
#define   FHF                     0x20
#define   FNE                     0x40
#define   CVEN                    0x80
#define   CVEN_MASK               0x40
#define   CLEAR_INTR_MASK         (CVEN_MASK | 0x1f)
#define DAS1800_BURST_LENGTH    0x8
#define DAS1800_BURST_RATE      0x9
#define DAS1800_QRAM_ADDRESS    0xa
#define DAS1800_COUNTER         0xc

#define IOBASE2                   0x400

static const struct comedi_lrange das1801_ai_range = {
        8, {
                BIP_RANGE(5),           /* bipolar gain = 1 */
                BIP_RANGE(1),           /* bipolar gain = 10 */
                BIP_RANGE(0.1),         /* bipolar gain = 50 */
                BIP_RANGE(0.02),        /* bipolar gain = 250 */
                UNI_RANGE(5),           /* unipolar gain = 1 */
                UNI_RANGE(1),           /* unipolar gain = 10 */
                UNI_RANGE(0.1),         /* unipolar gain = 50 */
                UNI_RANGE(0.02)         /* unipolar gain = 250 */
        }
};

static const struct comedi_lrange das1802_ai_range = {
        8, {
                BIP_RANGE(10),          /* bipolar gain = 1 */
                BIP_RANGE(5),           /* bipolar gain = 2 */
                BIP_RANGE(2.5),         /* bipolar gain = 4 */
                BIP_RANGE(1.25),        /* bipolar gain = 8 */
                UNI_RANGE(10),          /* unipolar gain = 1 */
                UNI_RANGE(5),           /* unipolar gain = 2 */
                UNI_RANGE(2.5),         /* unipolar gain = 4 */
                UNI_RANGE(1.25)         /* unipolar gain = 8 */
        }
};

/*
 * The waveform analog outputs on the 'ao' boards are not currently
 * supported. They have a comedi_lrange of:
 * { 2, { BIP_RANGE(10), BIP_RANGE(5) } }
 */

enum das1800_boardid {
        BOARD_DAS1701ST,
        BOARD_DAS1701ST_DA,
        BOARD_DAS1702ST,
        BOARD_DAS1702ST_DA,
        BOARD_DAS1702HR,
        BOARD_DAS1702HR_DA,
        BOARD_DAS1701AO,
        BOARD_DAS1702AO,
        BOARD_DAS1801ST,
        BOARD_DAS1801ST_DA,
        BOARD_DAS1802ST,
        BOARD_DAS1802ST_DA,
        BOARD_DAS1802HR,
        BOARD_DAS1802HR_DA,
        BOARD_DAS1801HC,
        BOARD_DAS1802HC,
        BOARD_DAS1801AO,
        BOARD_DAS1802AO
};

/* board probe id values (hi byte of the digital input register) */
#define DAS1800_ID_ST_DA                0x3
#define DAS1800_ID_HR_DA                0x4
#define DAS1800_ID_AO                   0x5
#define DAS1800_ID_HR                   0x6
#define DAS1800_ID_ST                   0x7
#define DAS1800_ID_HC                   0x8

struct das1800_board {
        const char *name;
        unsigned char id;
        unsigned int ai_speed;
        unsigned int is_01_series:1;
};

static const struct das1800_board das1800_boards[] = {
        [BOARD_DAS1701ST] = {
                .name           = "das-1701st",
                .id             = DAS1800_ID_ST,
                .ai_speed       = 6250,
                .is_01_series   = 1,
        },
        [BOARD_DAS1701ST_DA] = {
                .name           = "das-1701st-da",
                .id             = DAS1800_ID_ST_DA,
                .ai_speed       = 6250,
                .is_01_series   = 1,
        },
        [BOARD_DAS1702ST] = {
                .name           = "das-1702st",
                .id             = DAS1800_ID_ST,
                .ai_speed       = 6250,
        },
        [BOARD_DAS1702ST_DA] = {
                .name           = "das-1702st-da",
                .id             = DAS1800_ID_ST_DA,
                .ai_speed       = 6250,
        },
        [BOARD_DAS1702HR] = {
                .name           = "das-1702hr",
                .id             = DAS1800_ID_HR,
                .ai_speed       = 20000,
        },
        [BOARD_DAS1702HR_DA] = {
                .name           = "das-1702hr-da",
                .id             = DAS1800_ID_HR_DA,
                .ai_speed       = 20000,
        },
        [BOARD_DAS1701AO] = {
                .name           = "das-1701ao",
                .id             = DAS1800_ID_AO,
                .ai_speed       = 6250,
                .is_01_series   = 1,
        },
        [BOARD_DAS1702AO] = {
                .name           = "das-1702ao",
                .id             = DAS1800_ID_AO,
                .ai_speed       = 6250,
        },
        [BOARD_DAS1801ST] = {
                .name           = "das-1801st",
                .id             = DAS1800_ID_ST,
                .ai_speed       = 3000,
                .is_01_series   = 1,
        },
        [BOARD_DAS1801ST_DA] = {
                .name           = "das-1801st-da",
                .id             = DAS1800_ID_ST_DA,
                .ai_speed       = 3000,
                .is_01_series   = 1,
        },
        [BOARD_DAS1802ST] = {
                .name           = "das-1802st",
                .id             = DAS1800_ID_ST,
                .ai_speed       = 3000,
        },
        [BOARD_DAS1802ST_DA] = {
                .name           = "das-1802st-da",
                .id             = DAS1800_ID_ST_DA,
                .ai_speed       = 3000,
        },
        [BOARD_DAS1802HR] = {
                .name           = "das-1802hr",
                .id             = DAS1800_ID_HR,
                .ai_speed       = 10000,
        },
        [BOARD_DAS1802HR_DA] = {
                .name           = "das-1802hr-da",
                .id             = DAS1800_ID_HR_DA,
                .ai_speed       = 10000,
        },
        [BOARD_DAS1801HC] = {
                .name           = "das-1801hc",
                .id             = DAS1800_ID_HC,
                .ai_speed       = 3000,
                .is_01_series   = 1,
        },
        [BOARD_DAS1802HC] = {
                .name           = "das-1802hc",
                .id             = DAS1800_ID_HC,
                .ai_speed       = 3000,
        },
        [BOARD_DAS1801AO] = {
                .name           = "das-1801ao",
                .id             = DAS1800_ID_AO,
                .ai_speed       = 3000,
                .is_01_series   = 1,
        },
        [BOARD_DAS1802AO] = {
                .name           = "das-1802ao",
                .id             = DAS1800_ID_AO,
                .ai_speed       = 3000,
        },
};

struct das1800_private {
        struct comedi_isadma *dma;
        int irq_dma_bits;
        int dma_bits;
        unsigned short *fifo_buf;
        unsigned long iobase2;
        bool ai_is_unipolar;
};

static void das1800_ai_munge(struct comedi_device *dev,
                             struct comedi_subdevice *s,
                             void *data, unsigned int num_bytes,
                             unsigned int start_chan_index)
{
        struct das1800_private *devpriv = dev->private;
        unsigned short *array = data;
        unsigned int num_samples = comedi_bytes_to_samples(s, num_bytes);
        unsigned int i;

        if (devpriv->ai_is_unipolar)
                return;

        for (i = 0; i < num_samples; i++)
                array[i] = comedi_offset_munge(s, array[i]);
}

static void das1800_handle_fifo_half_full(struct comedi_device *dev,
                                          struct comedi_subdevice *s)
{
        struct das1800_private *devpriv = dev->private;
        unsigned int nsamples = comedi_nsamples_left(s, FIFO_SIZE / 2);

        insw(dev->iobase + DAS1800_FIFO, devpriv->fifo_buf, nsamples);
        comedi_buf_write_samples(s, devpriv->fifo_buf, nsamples);
}

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

        while (inb(dev->iobase + DAS1800_STATUS) & FNE) {
                dpnt = inw(dev->iobase + DAS1800_FIFO);
                comedi_buf_write_samples(s, &dpnt, 1);

                if (cmd->stop_src == TRIG_COUNT &&
                    s->async->scans_done >= cmd->stop_arg)
                        break;
        }
}

static void das1800_flush_dma_channel(struct comedi_device *dev,
                                      struct comedi_subdevice *s,
                                      struct comedi_isadma_desc *desc)
{
        unsigned int residue = comedi_isadma_disable(desc->chan);
        unsigned int nbytes = desc->size - residue;
        unsigned int nsamples;

        /*  figure out how many points to read */
        nsamples = comedi_bytes_to_samples(s, nbytes);
        nsamples = comedi_nsamples_left(s, nsamples);

        comedi_buf_write_samples(s, desc->virt_addr, nsamples);
}

static void das1800_flush_dma(struct comedi_device *dev,
                              struct comedi_subdevice *s)
{
        struct das1800_private *devpriv = dev->private;
        struct comedi_isadma *dma = devpriv->dma;
        struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];
        const int dual_dma = devpriv->irq_dma_bits & DMA_DUAL;

        das1800_flush_dma_channel(dev, s, desc);

        if (dual_dma) {
                /*  switch to other channel and flush it */
                dma->cur_dma = 1 - dma->cur_dma;
                desc = &dma->desc[dma->cur_dma];
                das1800_flush_dma_channel(dev, s, desc);
        }

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

static void das1800_handle_dma(struct comedi_device *dev,
                               struct comedi_subdevice *s, unsigned int status)
{
        struct das1800_private *devpriv = dev->private;
        struct comedi_isadma *dma = devpriv->dma;
        struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];
        const int dual_dma = devpriv->irq_dma_bits & DMA_DUAL;

        das1800_flush_dma_channel(dev, s, desc);

        /* re-enable dma channel */
        comedi_isadma_program(desc);

        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)
                        dma->cur_dma = 1 - dma->cur_dma;
        }
}

static int das1800_ai_cancel(struct comedi_device *dev,
                             struct comedi_subdevice *s)
{
        struct das1800_private *devpriv = dev->private;
        struct comedi_isadma *dma = devpriv->dma;
        struct comedi_isadma_desc *desc;
        int i;

        /* disable and stop conversions */
        outb(0x0, dev->iobase + DAS1800_STATUS);
        outb(0x0, dev->iobase + DAS1800_CONTROL_B);
        outb(0x0, dev->iobase + DAS1800_CONTROL_A);

        if (dma) {
                for (i = 0; i < 2; i++) {
                        desc = &dma->desc[i];
                        if (desc->chan)
                                comedi_isadma_disable(desc->chan);
                }
        }

        return 0;
}

static void das1800_ai_handler(struct comedi_device *dev)
{
        struct das1800_private *devpriv = dev->private;
        struct comedi_subdevice *s = dev->read_subdev;
        struct comedi_async *async = s->async;
        struct comedi_cmd *cmd = &async->cmd;
        unsigned int status = inb(dev->iobase + DAS1800_STATUS);

        /* select adc register (spinlock is already held) */
        outb(ADC, dev->iobase + DAS1800_SELECT);

        /* get samples with dma, fifo, or polled as necessary */
        if (devpriv->irq_dma_bits & DMA_ENABLED)
                das1800_handle_dma(dev, s, status);
        else if (status & FHF)
                das1800_handle_fifo_half_full(dev, s);
        else if (status & FNE)
                das1800_handle_fifo_not_empty(dev, s);

        /* if the card's fifo has overflowed */
        if (status & OVF) {
                /*  clear OVF interrupt bit */
                outb(CLEAR_INTR_MASK & ~OVF, dev->iobase + DAS1800_STATUS);
                dev_err(dev->class_dev, "FIFO overflow\n");
                async->events |= COMEDI_CB_ERROR;
                comedi_handle_events(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);
                /* get all remaining samples before quitting */
                if (devpriv->irq_dma_bits & DMA_ENABLED)
                        das1800_flush_dma(dev, s);
                else
                        das1800_handle_fifo_not_empty(dev, s);
                async->events |= COMEDI_CB_EOA;
        } else if (cmd->stop_src == TRIG_COUNT &&
                   async->scans_done >= cmd->stop_arg) {
                async->events |= COMEDI_CB_EOA;
        }

        comedi_handle_events(dev, s);
}

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

        /*
         * Protects the indirect addressing selected by DAS1800_SELECT
         * in das1800_ai_handler() also prevents race with das1800_interrupt().
         */
        spin_lock_irqsave(&dev->spinlock, flags);

        das1800_ai_handler(dev);

        spin_unlock_irqrestore(&dev->spinlock, flags);

        return comedi_buf_n_bytes_ready(s);
}

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

        if (!dev->attached) {
                dev_err(dev->class_dev, "premature interrupt\n");
                return IRQ_HANDLED;
        }

        /*
         * Protects the indirect addressing selected by DAS1800_SELECT
         * in das1800_ai_handler() also prevents race with das1800_ai_poll().
         */
        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;
}

static int das1800_ai_fixup_paced_timing(struct comedi_device *dev,
                                         struct comedi_cmd *cmd)
{
        unsigned int arg = cmd->convert_arg;

        /*
         * Paced mode:
         *      scan_begin_src is TRIG_FOLLOW
         *      convert_src is TRIG_TIMER
         *
         * The convert_arg sets the pacer sample acquisition time.
         * The max acquisition speed is limited to the boards
         * 'ai_speed' (this was already verified). The min speed is
         * limited by the cascaded 8254 timer.
         */
        comedi_8254_cascade_ns_to_timer(dev->pacer, &arg, cmd->flags);
        return comedi_check_trigger_arg_is(&cmd->convert_arg, arg);
}

static int das1800_ai_fixup_burst_timing(struct comedi_device *dev,
                                         struct comedi_cmd *cmd)
{
        unsigned int arg = cmd->convert_arg;
        int err = 0;

        /*
         * Burst mode:
         *      scan_begin_src is TRIG_TIMER or TRIG_EXT
         *      convert_src is TRIG_TIMER
         *
         * The convert_arg sets burst sample acquisition time.
         * The max acquisition speed is limited to the boards
         * 'ai_speed' (this was already verified). The min speed is
         * limiited to 64 microseconds,
         */
        err |= comedi_check_trigger_arg_max(&arg, 64000);

        /* round to microseconds then verify */
        switch (cmd->flags & CMDF_ROUND_MASK) {
        case CMDF_ROUND_NEAREST:
        default:
                arg = DIV_ROUND_CLOSEST(arg, 1000);
                break;
        case CMDF_ROUND_DOWN:
                arg = arg / 1000;
                break;
        case CMDF_ROUND_UP:
                arg = DIV_ROUND_UP(arg, 1000);
                break;
        }
        err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg * 1000);

        /*
         * The pacer can be used to set the scan sample rate. The max scan
         * speed is limited by the conversion speed and the number of channels
         * to convert. The min speed is limited by the cascaded 8254 timer.
         */
        if (cmd->scan_begin_src == TRIG_TIMER) {
                arg = cmd->convert_arg * cmd->chanlist_len;
                err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg, arg);

                arg = cmd->scan_begin_arg;
                comedi_8254_cascade_ns_to_timer(dev->pacer, &arg, cmd->flags);
                err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, arg);
        }

        return err;
}

static int das1800_ai_check_chanlist(struct comedi_device *dev,
                                     struct comedi_subdevice *s,
                                     struct comedi_cmd *cmd)
{
        unsigned int range = CR_RANGE(cmd->chanlist[0]);
        bool unipolar0 = comedi_range_is_unipolar(s, range);
        int i;

        for (i = 1; i < cmd->chanlist_len; i++) {
                range = CR_RANGE(cmd->chanlist[i]);

                if (unipolar0 != comedi_range_is_unipolar(s, range)) {
                        dev_dbg(dev->class_dev,
                                "unipolar and bipolar ranges cannot be mixed in the chanlist\n");
                        return -EINVAL;
                }
        }

        return 0;
}

static int das1800_ai_cmdtest(struct comedi_device *dev,
                              struct comedi_subdevice *s,
                              struct comedi_cmd *cmd)
{
        const struct das1800_board *board = dev->board_ptr;
        int err = 0;

        /* Step 1 : check if triggers are trivially valid */

        err |= comedi_check_trigger_src(&cmd->start_src, TRIG_NOW | TRIG_EXT);
        err |= comedi_check_trigger_src(&cmd->scan_begin_src,
                                        TRIG_FOLLOW | TRIG_TIMER | TRIG_EXT);
        err |= comedi_check_trigger_src(&cmd->convert_src,
                                        TRIG_TIMER | TRIG_EXT);
        err |= comedi_check_trigger_src(&cmd->scan_end_src, TRIG_COUNT);
        err |= comedi_check_trigger_src(&cmd->stop_src,
                                        TRIG_COUNT | TRIG_EXT | TRIG_NONE);

        if (err)
                return 1;

        /* Step 2a : make sure trigger sources are unique */

        err |= comedi_check_trigger_is_unique(cmd->start_src);
        err |= comedi_check_trigger_is_unique(cmd->scan_begin_src);
        err |= comedi_check_trigger_is_unique(cmd->convert_src);
        err |= comedi_check_trigger_is_unique(cmd->stop_src);

        /* Step 2b : and mutually compatible */

        /* burst scans must use timed conversions */
        if (cmd->scan_begin_src != TRIG_FOLLOW &&
            cmd->convert_src != TRIG_TIMER)
                err |= -EINVAL;

        /* the external pin TGIN must use the same polarity */
        if (cmd->start_src == TRIG_EXT && cmd->stop_src == TRIG_EXT)
                err |= comedi_check_trigger_arg_is(&cmd->start_arg,
                                                   cmd->stop_arg);

        if (err)
                return 2;

        /* Step 3: check if arguments are trivially valid */

        if (cmd->start_arg == TRIG_NOW)
                err |= comedi_check_trigger_arg_is(&cmd->start_arg, 0);

        if (cmd->convert_src == TRIG_TIMER) {
                err |= comedi_check_trigger_arg_min(&cmd->convert_arg,
                                                    board->ai_speed);
        }

        err |= comedi_check_trigger_arg_min(&cmd->chanlist_len, 1);
        err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
                                           cmd->chanlist_len);

        switch (cmd->stop_src) {
        case TRIG_COUNT:
                err |= comedi_check_trigger_arg_min(&cmd->stop_arg, 1);
                break;
        case TRIG_NONE:
                err |= comedi_check_trigger_arg_is(&cmd->stop_arg, 0);
                break;
        default:
                break;
        }

        if (err)
                return 3;

        /* Step 4: fix up any arguments */

        if (cmd->convert_src == TRIG_TIMER) {
                if (cmd->scan_begin_src == TRIG_FOLLOW)
                        err |= das1800_ai_fixup_paced_timing(dev, cmd);
                else /* TRIG_TIMER or TRIG_EXT */
                        err |= das1800_ai_fixup_burst_timing(dev, cmd);
        }

        if (err)
                return 4;

        /* Step 5: check channel list if it exists */
        if (cmd->chanlist && cmd->chanlist_len > 0)
                err |= das1800_ai_check_chanlist(dev, s, cmd);

        if (err)
                return 5;

        return 0;
}

static unsigned char das1800_ai_chanspec_bits(struct comedi_subdevice *s,
                                              unsigned int chanspec)
{
        unsigned int range = CR_RANGE(chanspec);
        unsigned int aref = CR_AREF(chanspec);
        unsigned char bits;

        bits = UQEN;
        if (aref != AREF_DIFF)
                bits |= SD;
        if (aref == AREF_COMMON)
                bits |= CMEN;
        if (comedi_range_is_unipolar(s, range))
                bits |= UB;

        return bits;
}

static unsigned int das1800_ai_transfer_size(struct comedi_device *dev,
                                             struct comedi_subdevice *s,
                                             unsigned int maxbytes,
                                             unsigned int ns)
{
        struct comedi_cmd *cmd = &s->async->cmd;
        unsigned int max_samples = comedi_bytes_to_samples(s, maxbytes);
        unsigned int samples;

        samples = max_samples;

        /* for timed modes, make dma buffer fill in 'ns' time */
        switch (cmd->scan_begin_src) {
        case TRIG_FOLLOW:       /* not in burst mode */
                if (cmd->convert_src == TRIG_TIMER)
                        samples = ns / cmd->convert_arg;
                break;
        case TRIG_TIMER:
                samples = ns / (cmd->scan_begin_arg * cmd->chanlist_len);
                break;
        }

        /* limit samples to what is remaining in the command */
        samples = comedi_nsamples_left(s, samples);

        if (samples > max_samples)
                samples = max_samples;
        if (samples < 1)
                samples = 1;

        return comedi_samples_to_bytes(s, samples);
}

static void das1800_ai_setup_dma(struct comedi_device *dev,
                                 struct comedi_subdevice *s)
{
        struct das1800_private *devpriv = dev->private;
        struct comedi_isadma *dma = devpriv->dma;
        struct comedi_isadma_desc *desc;
        unsigned int bytes;

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

        dma->cur_dma = 0;
        desc = &dma->desc[0];

        /* determine a dma transfer size to fill buffer in 0.3 sec */
        bytes = das1800_ai_transfer_size(dev, s, desc->maxsize, 300000000);

        desc->size = bytes;
        comedi_isadma_program(desc);

        /* set up dual dma if appropriate */
        if (devpriv->irq_dma_bits & DMA_DUAL) {
                desc = &dma->desc[1];
                desc->size = bytes;
                comedi_isadma_program(desc);
        }
}

static void das1800_ai_set_chanlist(struct comedi_device *dev,
                                    unsigned int *chanlist, unsigned int len)
{
        unsigned long flags;
        unsigned int i;

        /* protects the indirect addressing selected by DAS1800_SELECT */
        spin_lock_irqsave(&dev->spinlock, flags);

        /* select QRAM register and set start address */
        outb(QRAM, dev->iobase + DAS1800_SELECT);
        outb(len - 1, dev->iobase + DAS1800_QRAM_ADDRESS);

        /* make channel / gain list */
        for (i = 0; i < len; i++) {
                unsigned int chan = CR_CHAN(chanlist[i]);
                unsigned int range = CR_RANGE(chanlist[i]);
                unsigned short val;

                val = chan | ((range & 0x3) << 8);
                outw(val, dev->iobase + DAS1800_QRAM);
        }

        /* finish write to QRAM */
        outb(len - 1, dev->iobase + DAS1800_QRAM_ADDRESS);

        spin_unlock_irqrestore(&dev->spinlock, flags);
}

static int das1800_ai_cmd(struct comedi_device *dev,
                          struct comedi_subdevice *s)
{
        struct das1800_private *devpriv = dev->private;
        int control_a, control_c;
        struct comedi_async *async = s->async;
        const struct comedi_cmd *cmd = &async->cmd;
        unsigned int range0 = CR_RANGE(cmd->chanlist[0]);

        /*
         * Disable dma on CMDF_WAKE_EOS, or CMDF_PRIORITY (because dma in
         * handler is unsafe at hard real-time priority).
         */
        if (cmd->flags & (CMDF_WAKE_EOS | CMDF_PRIORITY))
                devpriv->irq_dma_bits &= ~DMA_ENABLED;
        else
                devpriv->irq_dma_bits |= devpriv->dma_bits;
        /*  interrupt on end of conversion for CMDF_WAKE_EOS */
        if (cmd->flags & CMDF_WAKE_EOS) {
                /*  interrupt fifo not empty */
                devpriv->irq_dma_bits &= ~FIMD;
        } else {
                /*  interrupt fifo half full */
                devpriv->irq_dma_bits |= FIMD;
        }

        das1800_ai_cancel(dev, s);

        devpriv->ai_is_unipolar = comedi_range_is_unipolar(s, range0);

        control_a = FFEN;
        if (cmd->stop_src == TRIG_EXT)
                control_a |= ATEN;
        if (cmd->start_src == TRIG_EXT)
                control_a |= TGEN | CGSL;
        else /* TRIG_NOW */
                control_a |= CGEN;
        if (control_a & (ATEN | TGEN)) {
                if ((cmd->start_arg & CR_INVERT) || (cmd->stop_arg & CR_INVERT))
                        control_a |= TGPL;
        }

        control_c = das1800_ai_chanspec_bits(s, cmd->chanlist[0]);
        /* set clock source to internal or external */
        if (cmd->scan_begin_src == TRIG_FOLLOW) {
                /* not in burst mode */
                if (cmd->convert_src == TRIG_TIMER) {
                        /* trig on cascaded counters */
                        control_c |= IPCLK;
                } else { /* TRIG_EXT */
                        /* trig on falling edge of external trigger */
                        control_c |= XPCLK;
                }
        } else if (cmd->scan_begin_src == TRIG_TIMER) {
                /* burst mode with internal pacer clock */
                control_c |= BMDE | IPCLK;
        } else { /* TRIG_EXT */
                /* burst mode with external trigger */
                control_c |= BMDE | XPCLK;
        }

        das1800_ai_set_chanlist(dev, cmd->chanlist, cmd->chanlist_len);

        /* setup cascaded counters for conversion/scan frequency */
        if ((cmd->scan_begin_src == TRIG_FOLLOW ||
             cmd->scan_begin_src == TRIG_TIMER) &&
            cmd->convert_src == TRIG_TIMER) {
                comedi_8254_update_divisors(dev->pacer);
                comedi_8254_pacer_enable(dev->pacer, 1, 2, true);
        }

        /* setup counter 0 for 'about triggering' */
        if (cmd->stop_src == TRIG_EXT)
                comedi_8254_load(dev->pacer, 0, 1, I8254_MODE0 | I8254_BINARY);

        das1800_ai_setup_dma(dev, s);
        outb(control_c, dev->iobase + DAS1800_CONTROL_C);
        /*  set conversion rate and length for burst mode */
        if (control_c & BMDE) {
                outb(cmd->convert_arg / 1000 - 1,       /* microseconds - 1 */
                     dev->iobase + DAS1800_BURST_RATE);
                outb(cmd->chanlist_len - 1, dev->iobase + DAS1800_BURST_LENGTH);
        }

        /* enable and start conversions */
        outb(devpriv->irq_dma_bits, dev->iobase + DAS1800_CONTROL_B);
        outb(control_a, dev->iobase + DAS1800_CONTROL_A);
        outb(CVEN, dev->iobase + DAS1800_STATUS);

        return 0;
}

static int das1800_ai_eoc(struct comedi_device *dev,
                          struct comedi_subdevice *s,
                          struct comedi_insn *insn,
                          unsigned long context)
{
        unsigned char status;

        status = inb(dev->iobase + DAS1800_STATUS);
        if (status & FNE)
                return 0;
        return -EBUSY;
}

static int das1800_ai_insn_read(struct comedi_device *dev,
                                struct comedi_subdevice *s,
                                struct comedi_insn *insn,
                                unsigned int *data)
{
        unsigned int range = CR_RANGE(insn->chanspec);
        bool is_unipolar = comedi_range_is_unipolar(s, range);
        int ret = 0;
        int n;
        unsigned short dpnt;
        unsigned long flags;

        outb(das1800_ai_chanspec_bits(s, insn->chanspec),
             dev->iobase + DAS1800_CONTROL_C);          /* software pacer */
        outb(CVEN, dev->iobase + DAS1800_STATUS);       /* enable conversions */
        outb(0x0, dev->iobase + DAS1800_CONTROL_A);     /* reset fifo */
        outb(FFEN, dev->iobase + DAS1800_CONTROL_A);

        das1800_ai_set_chanlist(dev, &insn->chanspec, 1);

        /* protects the indirect addressing selected by DAS1800_SELECT */
        spin_lock_irqsave(&dev->spinlock, flags);

        /* select ai fifo register */
        outb(ADC, dev->iobase + DAS1800_SELECT);

        for (n = 0; n < insn->n; n++) {
                /* trigger conversion */
                outb(0, dev->iobase + DAS1800_FIFO);

                ret = comedi_timeout(dev, s, insn, das1800_ai_eoc, 0);
                if (ret)
                        break;

                dpnt = inw(dev->iobase + DAS1800_FIFO);
                if (!is_unipolar)
                        dpnt = comedi_offset_munge(s, dpnt);
                data[n] = dpnt;
        }
        spin_unlock_irqrestore(&dev->spinlock, flags);

        return ret ? ret : insn->n;
}

static int das1800_ao_insn_write(struct comedi_device *dev,
                                 struct comedi_subdevice *s,
                                 struct comedi_insn *insn,
                                 unsigned int *data)
{
        unsigned int chan = CR_CHAN(insn->chanspec);
        unsigned int update_chan = s->n_chan - 1;
        unsigned long flags;

        int i;

        /* protects the indirect addressing selected by DAS1800_SELECT */
        spin_lock_irqsave(&dev->spinlock, flags);

        for (i = 0; i < insn->n; i++) {
                unsigned int val = data[i];

                s->readback[chan] = val;

                val = comedi_offset_munge(s, val);

                /* load this channel (and update if it's the last channel) */
                outb(DAC(chan), dev->iobase + DAS1800_SELECT);
                outw(val, dev->iobase + DAS1800_DAC);

                /* update all channels */
                if (chan != update_chan) {
                        val = comedi_offset_munge(s, s->readback[update_chan]);

                        outb(DAC(update_chan), dev->iobase + DAS1800_SELECT);
                        outw(val, dev->iobase + DAS1800_DAC);
                }
        }
        spin_unlock_irqrestore(&dev->spinlock, flags);

        return insn->n;
}

static int das1800_di_insn_bits(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 insn->n;
}

static int das1800_do_insn_bits(struct comedi_device *dev,
                                struct comedi_subdevice *s,
                                struct comedi_insn *insn,
                                unsigned int *data)
{
        if (comedi_dio_update_state(s, data))
                outb(s->state, dev->iobase + DAS1800_DIGITAL);

        data[1] = s->state;

        return insn->n;
}

static void das1800_init_dma(struct comedi_device *dev,
                             struct comedi_devconfig *it)
{
        struct das1800_private *devpriv = dev->private;
        unsigned int *dma_chan;

        /*
         * it->options[2] is DMA channel 0
         * it->options[3] is DMA channel 1
         *
         * Encode the DMA channels into 2 digit hexadecimal for switch.
         */
        dma_chan = &it->options[2];

        switch ((dma_chan[0] & 0x7) | (dma_chan[1] << 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:
                return;
        }

        /* DMA can use 1 or 2 buffers, each with a separate channel */
        devpriv->dma = comedi_isadma_alloc(dev, dma_chan[1] ? 2 : 1,
                                           dma_chan[0], dma_chan[1],
                                           DMA_BUF_SIZE, COMEDI_ISADMA_READ);
        if (!devpriv->dma)
                devpriv->dma_bits = 0;
}

static void das1800_free_dma(struct comedi_device *dev)
{
        struct das1800_private *devpriv = dev->private;

        if (devpriv)
                comedi_isadma_free(devpriv->dma);
}

static int das1800_probe(struct comedi_device *dev)
{
        const struct das1800_board *board = dev->board_ptr;
        unsigned char id;

        id = (inb(dev->iobase + DAS1800_DIGITAL) >> 4) & 0xf;

        /*
         * The dev->board_ptr will be set by comedi_device_attach() if the
         * board name provided by the user matches a board->name in this
         * driver. If so, this function sanity checks the id to verify that
         * the board is correct.
         */
        if (board) {
                if (board->id == id)
                        return 0;
                dev_err(dev->class_dev,
                        "probed id does not match board id (0x%x != 0x%x)\n",
                        id, board->id);
                return -ENODEV;
        }

         /*
          * If the dev->board_ptr is not set, the user is trying to attach
          * an unspecified board to this driver. In this case the id is used
          * to 'probe' for the dev->board_ptr.
          */
        switch (id) {
        case DAS1800_ID_ST_DA:
                /* das-1701st-da, das-1702st-da, das-1801st-da, das-1802st-da */
                board = &das1800_boards[BOARD_DAS1801ST_DA];
                break;
        case DAS1800_ID_HR_DA:
                /* das-1702hr-da, das-1802hr-da */
                board = &das1800_boards[BOARD_DAS1802HR_DA];
                break;
        case DAS1800_ID_AO:
                /* das-1701ao, das-1702ao, das-1801ao, das-1802ao */
                board = &das1800_boards[BOARD_DAS1801AO];
                break;
        case DAS1800_ID_HR:
                /*  das-1702hr, das-1802hr */
                board = &das1800_boards[BOARD_DAS1802HR];
                break;
        case DAS1800_ID_ST:
                /* das-1701st, das-1702st, das-1801st, das-1802st */
                board = &das1800_boards[BOARD_DAS1801ST];
                break;
        case DAS1800_ID_HC:
                /* das-1801hc, das-1802hc */
                board = &das1800_boards[BOARD_DAS1801HC];
                break;
        default:
                dev_err(dev->class_dev, "invalid probe id 0x%x\n", id);
                return -ENODEV;
        }
        dev->board_ptr = board;
        dev->board_name = board->name;
        dev_warn(dev->class_dev,
                 "probed id 0x%0x: %s series (not recommended)\n",
                 id, board->name);
        return 0;
}

static int das1800_attach(struct comedi_device *dev,
                          struct comedi_devconfig *it)
{
        const struct das1800_board *board;
        struct das1800_private *devpriv;
        struct comedi_subdevice *s;
        unsigned int irq = it->options[1];
        bool is_16bit;
        int ret;
        int i;

        devpriv = comedi_alloc_devpriv(dev, sizeof(*devpriv));
        if (!devpriv)
                return -ENOMEM;

        ret = comedi_request_region(dev, it->options[0], DAS1800_SIZE);
        if (ret)
                return ret;

        ret = das1800_probe(dev);
        if (ret)
                return ret;
        board = dev->board_ptr;

        is_16bit = board->id == DAS1800_ID_HR || board->id == DAS1800_ID_HR_DA;

        /* waveform 'ao' boards have additional io ports */
        if (board->id == DAS1800_ID_AO) {
                unsigned long iobase2 = dev->iobase + IOBASE2;

                ret = __comedi_request_region(dev, iobase2, DAS1800_SIZE);
                if (ret)
                        return ret;
                devpriv->iobase2 = iobase2;
        }

        if (irq == 3 || irq == 5 || irq == 7 || irq == 10 || irq == 11 ||
            irq == 15) {
                ret = request_irq(irq, das1800_interrupt, 0,
                                  dev->board_name, dev);
                if (ret == 0) {
                        dev->irq = irq;

                        switch (irq) {
                        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;
                        }
                }
        }

        /* an irq and one dma channel is required to use dma */
        if (dev->irq & it->options[2])
                das1800_init_dma(dev, it);

        devpriv->fifo_buf = kmalloc_array(FIFO_SIZE,
                                          sizeof(*devpriv->fifo_buf),
                                          GFP_KERNEL);
        if (!devpriv->fifo_buf)
                return -ENOMEM;

        dev->pacer = comedi_8254_init(dev->iobase + DAS1800_COUNTER,
                                      I8254_OSC_BASE_5MHZ, I8254_IO8, 0);
        if (!dev->pacer)
                return -ENOMEM;

        ret = comedi_alloc_subdevices(dev, 4);
        if (ret)
                return ret;

        /*
         * Analog Input subdevice
         *
         * The "hc" type boards have 64 analog input channels and a 64
         * entry QRAM fifo.
         *
         * All the other board types have 16 on-board channels. Each channel
         * can be expanded to 16 channels with the addition of an EXP-1800
         * expansion board for a total of 256 channels. The QRAM fifo on
         * these boards has 256 entries.
         *
         * From the datasheets it's not clear what the comedi channel to
         * actual physical channel mapping is when EXP-1800 boards are used.
         */
        s = &dev->subdevices[0];
        s->type         = COMEDI_SUBD_AI;
        s->subdev_flags = SDF_READABLE | SDF_DIFF | SDF_GROUND;
        if (board->id != DAS1800_ID_HC)
                s->subdev_flags |= SDF_COMMON;
        s->n_chan       = (board->id == DAS1800_ID_HC) ? 64 : 256;
        s->maxdata      = is_16bit ? 0xffff : 0x0fff;
        s->range_table  = board->is_01_series ? &das1801_ai_range
                                              : &das1802_ai_range;
        s->insn_read    = das1800_ai_insn_read;
        if (dev->irq) {
                dev->read_subdev = s;
                s->subdev_flags |= SDF_CMD_READ;
                s->len_chanlist = s->n_chan;
                s->do_cmd       = das1800_ai_cmd;
                s->do_cmdtest   = das1800_ai_cmdtest;
                s->poll         = das1800_ai_poll;
                s->cancel       = das1800_ai_cancel;
                s->munge        = das1800_ai_munge;
        }

        /* Analog Output subdevice */
        s = &dev->subdevices[1];
        if (board->id == DAS1800_ID_ST_DA || board->id == DAS1800_ID_HR_DA) {
                s->type         = COMEDI_SUBD_AO;
                s->subdev_flags = SDF_WRITABLE;
                s->n_chan       = (board->id == DAS1800_ID_ST_DA) ? 4 : 2;
                s->maxdata      = is_16bit ? 0xffff : 0x0fff;
                s->range_table  = &range_bipolar10;
                s->insn_write   = das1800_ao_insn_write;

                ret = comedi_alloc_subdev_readback(s);
                if (ret)
                        return ret;

                /* initialize all channels to 0V */
                for (i = 0; i < s->n_chan; i++) {
                        /* spinlock is not necessary during the attach */
                        outb(DAC(i), dev->iobase + DAS1800_SELECT);
                        outw(0, dev->iobase + DAS1800_DAC);
                }
        } else if (board->id == DAS1800_ID_AO) {
                /*
                 * 'ao' boards have waveform analog outputs that are not
                 * currently supported.
                 */
                s->type         = COMEDI_SUBD_UNUSED;
        } else {
                s->type         = COMEDI_SUBD_UNUSED;
        }

        /* Digital Input subdevice */
        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_insn_bits;

        /* Digital Output subdevice */
        s = &dev->subdevices[3];
        s->type         = COMEDI_SUBD_DO;
        s->subdev_flags = SDF_WRITABLE;
        s->n_chan       = (board->id == DAS1800_ID_HC) ? 8 : 4;
        s->maxdata      = 1;
        s->range_table  = &range_digital;
        s->insn_bits    = das1800_do_insn_bits;

        das1800_ai_cancel(dev, dev->read_subdev);

        /*  initialize digital out channels */
        outb(0, dev->iobase + DAS1800_DIGITAL);

        return 0;
};

static void das1800_detach(struct comedi_device *dev)
{
        struct das1800_private *devpriv = dev->private;

        das1800_free_dma(dev);
        if (devpriv) {
                kfree(devpriv->fifo_buf);
                if (devpriv->iobase2)
                        release_region(devpriv->iobase2, DAS1800_SIZE);
        }
        comedi_legacy_detach(dev);
}

static struct comedi_driver das1800_driver = {
        .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),
};
module_comedi_driver(das1800_driver);

MODULE_AUTHOR("Comedi http://www.comedi.org");
MODULE_DESCRIPTION("Comedi driver for DAS1800 compatible ISA boards");
MODULE_LICENSE("GPL");