// SPDX-License-Identifier: GPL-2.0+
/*
 * dt282x.c
 * Comedi driver for Data Translation DT2821 series
 *
 * COMEDI - Linux Control and Measurement Device Interface
 * Copyright (C) 1997-8 David A. Schleef <ds@schleef.org>
 */

/*
 * Driver: dt282x
 * Description: Data Translation DT2821 series (including DT-EZ)
 * Author: ds
 * Devices: [Data Translation] DT2821 (dt2821), DT2821-F-16SE (dt2821-f),
 *   DT2821-F-8DI (dt2821-f), DT2821-G-16SE (dt2821-g),
 *   DT2821-G-8DI (dt2821-g), DT2823 (dt2823), DT2824-PGH (dt2824-pgh),
 *   DT2824-PGL (dt2824-pgl), DT2825 (dt2825), DT2827 (dt2827),
 *   DT2828 (dt2828), DT2928 (dt2829), DT21-EZ (dt21-ez), DT23-EZ (dt23-ez),
 *   DT24-EZ (dt24-ez), DT24-EZ-PGL (dt24-ez-pgl)
 * Status: complete
 * Updated: Wed, 22 Aug 2001 17:11:34 -0700
 *
 * Configuration options:
 *   [0] - I/O port base address
 *   [1] - IRQ (optional, required for async command support)
 *   [2] - DMA 1 (optional, required for async command support)
 *   [3] - DMA 2 (optional, required for async command support)
 *   [4] - AI jumpered for 0=single ended, 1=differential
 *   [5] - AI jumpered for 0=straight binary, 1=2's complement
 *   [6] - AO 0 data format (deprecated, see below)
 *   [7] - AO 1 data format (deprecated, see below)
 *   [8] - AI jumpered for 0=[-10,10]V, 1=[0,10], 2=[-5,5], 3=[0,5]
 *   [9] - AO channel 0 range (deprecated, see below)
 *   [10]- AO channel 1 range (deprecated, see below)
 *
 * Notes:
 *   - AO commands might be broken.
 *   - If you try to run a command on both the AI and AO subdevices
 *     simultaneously, bad things will happen.  The driver needs to
 *     be fixed to check for this situation and return an error.
 *   - AO range is not programmable. The AO subdevice has a range_table
 *     containing all the possible analog output ranges. Use the range
 *     that matches your board configuration to convert between data
 *     values and physical units. The format of the data written to the
 *     board is handled automatically based on the unipolar/bipolar
 *     range that is selected.
 */

#include <linux/module.h>
#include <linux/delay.h>
#include <linux/gfp.h>
#include <linux/interrupt.h>
#include <linux/io.h>

#include "../comedidev.h"

#include "comedi_isadma.h"

/*
 * Register map
 */
#define DT2821_ADCSR_REG		0x00
#define DT2821_ADCSR_ADERR		BIT(15)
#define DT2821_ADCSR_ADCLK		BIT(9)
#define DT2821_ADCSR_MUXBUSY		BIT(8)
#define DT2821_ADCSR_ADDONE		BIT(7)
#define DT2821_ADCSR_IADDONE		BIT(6)
#define DT2821_ADCSR_GS(x)		(((x) & 0x3) << 4)
#define DT2821_ADCSR_CHAN(x)		(((x) & 0xf) << 0)
#define DT2821_CHANCSR_REG		0x02
#define DT2821_CHANCSR_LLE		BIT(15)
#define DT2821_CHANCSR_TO_PRESLA(x)	(((x) >> 8) & 0xf)
#define DT2821_CHANCSR_NUMB(x)		((((x) - 1) & 0xf) << 0)
#define DT2821_ADDAT_REG		0x04
#define DT2821_DACSR_REG		0x06
#define DT2821_DACSR_DAERR		BIT(15)
#define DT2821_DACSR_YSEL(x)		((x) << 9)
#define DT2821_DACSR_SSEL		BIT(8)
#define DT2821_DACSR_DACRDY		BIT(7)
#define DT2821_DACSR_IDARDY		BIT(6)
#define DT2821_DACSR_DACLK		BIT(5)
#define DT2821_DACSR_HBOE		BIT(1)
#define DT2821_DACSR_LBOE		BIT(0)
#define DT2821_DADAT_REG		0x08
#define DT2821_DIODAT_REG		0x0a
#define DT2821_SUPCSR_REG		0x0c
#define DT2821_SUPCSR_DMAD		BIT(15)
#define DT2821_SUPCSR_ERRINTEN		BIT(14)
#define DT2821_SUPCSR_CLRDMADNE		BIT(13)
#define DT2821_SUPCSR_DDMA		BIT(12)
#define DT2821_SUPCSR_DS(x)		(((x) & 0x3) << 10)
#define DT2821_SUPCSR_DS_PIO		DT2821_SUPCSR_DS(0)
#define DT2821_SUPCSR_DS_AD_CLK		DT2821_SUPCSR_DS(1)
#define DT2821_SUPCSR_DS_DA_CLK		DT2821_SUPCSR_DS(2)
#define DT2821_SUPCSR_DS_AD_TRIG	DT2821_SUPCSR_DS(3)
#define DT2821_SUPCSR_BUFFB		BIT(9)
#define DT2821_SUPCSR_SCDN		BIT(8)
#define DT2821_SUPCSR_DACON		BIT(7)
#define DT2821_SUPCSR_ADCINIT		BIT(6)
#define DT2821_SUPCSR_DACINIT		BIT(5)
#define DT2821_SUPCSR_PRLD		BIT(4)
#define DT2821_SUPCSR_STRIG		BIT(3)
#define DT2821_SUPCSR_XTRIG		BIT(2)
#define DT2821_SUPCSR_XCLK		BIT(1)
#define DT2821_SUPCSR_BDINIT		BIT(0)
#define DT2821_TMRCTR_REG		0x0e
#define DT2821_TMRCTR_PRESCALE(x)	(((x) & 0xf) << 8)
#define DT2821_TMRCTR_DIVIDER(x)	((255 - ((x) & 0xff)) << 0)

/* Pacer Clock */
#define DT2821_OSC_BASE		250	/* 4 MHz (in nanoseconds) */
#define DT2821_PRESCALE(x)	BIT(x)
#define DT2821_PRESCALE_MAX	15
#define DT2821_DIVIDER_MAX	255
#define DT2821_OSC_MAX		(DT2821_OSC_BASE *			\
				 DT2821_PRESCALE(DT2821_PRESCALE_MAX) *	\
				 DT2821_DIVIDER_MAX)

static const struct comedi_lrange range_dt282x_ai_lo_bipolar = {
	4, {
		BIP_RANGE(10),
		BIP_RANGE(5),
		BIP_RANGE(2.5),
		BIP_RANGE(1.25)
	}
};

static const struct comedi_lrange range_dt282x_ai_lo_unipolar = {
	4, {
		UNI_RANGE(10),
		UNI_RANGE(5),
		UNI_RANGE(2.5),
		UNI_RANGE(1.25)
	}
};

static const struct comedi_lrange range_dt282x_ai_5_bipolar = {
	4, {
		BIP_RANGE(5),
		BIP_RANGE(2.5),
		BIP_RANGE(1.25),
		BIP_RANGE(0.625)
	}
};

static const struct comedi_lrange range_dt282x_ai_5_unipolar = {
	4, {
		UNI_RANGE(5),
		UNI_RANGE(2.5),
		UNI_RANGE(1.25),
		UNI_RANGE(0.625)
	}
};

static const struct comedi_lrange range_dt282x_ai_hi_bipolar = {
	4, {
		BIP_RANGE(10),
		BIP_RANGE(1),
		BIP_RANGE(0.1),
		BIP_RANGE(0.02)
	}
};

static const struct comedi_lrange range_dt282x_ai_hi_unipolar = {
	4, {
		UNI_RANGE(10),
		UNI_RANGE(1),
		UNI_RANGE(0.1),
		UNI_RANGE(0.02)
	}
};

/*
 * The Analog Output range is set per-channel using jumpers on the board.
 * All of these ranges may not be available on some DT2821 series boards.
 * The default jumper setting has both channels set for +/-10V output.
 */
static const struct comedi_lrange dt282x_ao_range = {
	5, {
		BIP_RANGE(10),
		BIP_RANGE(5),
		BIP_RANGE(2.5),
		UNI_RANGE(10),
		UNI_RANGE(5),
	}
};

struct dt282x_board {
	const char *name;
	unsigned int ai_maxdata;
	int adchan_se;
	int adchan_di;
	int ai_speed;
	int ispgl;
	int dachan;
	unsigned int ao_maxdata;
};

static const struct dt282x_board boardtypes[] = {
	{
		.name		= "dt2821",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 20000,
		.dachan		= 2,
		.ao_maxdata	= 0x0fff,
	}, {
		.name		= "dt2821-f",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 6500,
		.dachan		= 2,
		.ao_maxdata	= 0x0fff,
	}, {
		.name		= "dt2821-g",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 4000,
		.dachan		= 2,
		.ao_maxdata	= 0x0fff,
	}, {
		.name		= "dt2823",
		.ai_maxdata	= 0xffff,
		.adchan_di	= 4,
		.ai_speed	= 10000,
		.dachan		= 2,
		.ao_maxdata	= 0xffff,
	}, {
		.name		= "dt2824-pgh",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 20000,
	}, {
		.name		= "dt2824-pgl",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 20000,
		.ispgl		= 1,
	}, {
		.name		= "dt2825",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 20000,
		.ispgl		= 1,
		.dachan		= 2,
		.ao_maxdata	= 0x0fff,
	}, {
		.name		= "dt2827",
		.ai_maxdata	= 0xffff,
		.adchan_di	= 4,
		.ai_speed	= 10000,
		.dachan		= 2,
		.ao_maxdata	= 0x0fff,
	}, {
		.name		= "dt2828",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 4,
		.ai_speed	= 10000,
		.dachan		= 2,
		.ao_maxdata	= 0x0fff,
	}, {
		.name		= "dt2829",
		.ai_maxdata	= 0xffff,
		.adchan_se	= 8,
		.ai_speed	= 33250,
		.dachan		= 2,
		.ao_maxdata	= 0xffff,
	}, {
		.name		= "dt21-ez",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 10000,
		.dachan		= 2,
		.ao_maxdata	= 0x0fff,
	}, {
		.name		= "dt23-ez",
		.ai_maxdata	= 0xffff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 10000,
	}, {
		.name		= "dt24-ez",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 10000,
	}, {
		.name		= "dt24-ez-pgl",
		.ai_maxdata	= 0x0fff,
		.adchan_se	= 16,
		.adchan_di	= 8,
		.ai_speed	= 10000,
		.ispgl		= 1,
	},
};

struct dt282x_private {
	struct comedi_isadma *dma;
	unsigned int ad_2scomp:1;
	unsigned int divisor;
	int dacsr;	/* software copies of registers */
	int adcsr;
	int supcsr;
	int ntrig;
	int nread;
	int dma_dir;
};

static int dt282x_prep_ai_dma(struct comedi_device *dev, int dma_index, int n)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_isadma *dma = devpriv->dma;
	struct comedi_isadma_desc *desc = &dma->desc[dma_index];

	if (!devpriv->ntrig)
		return 0;

	if (n == 0)
		n = desc->maxsize;
	if (n > devpriv->ntrig * 2)
		n = devpriv->ntrig * 2;
	devpriv->ntrig -= n / 2;

	desc->size = n;
	comedi_isadma_set_mode(desc, devpriv->dma_dir);

	comedi_isadma_program(desc);

	return n;
}

static int dt282x_prep_ao_dma(struct comedi_device *dev, int dma_index, int n)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_isadma *dma = devpriv->dma;
	struct comedi_isadma_desc *desc = &dma->desc[dma_index];

	desc->size = n;
	comedi_isadma_set_mode(desc, devpriv->dma_dir);

	comedi_isadma_program(desc);

	return n;
}

static void dt282x_disable_dma(struct comedi_device *dev)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_isadma *dma = devpriv->dma;
	struct comedi_isadma_desc *desc;
	int i;

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

static unsigned int dt282x_ns_to_timer(unsigned int *ns, unsigned int flags)
{
	unsigned int prescale, base, divider;

	for (prescale = 0; prescale <= DT2821_PRESCALE_MAX; prescale++) {
		if (prescale == 1)	/* 0 and 1 are both divide by 1 */
			continue;
		base = DT2821_OSC_BASE * DT2821_PRESCALE(prescale);
		switch (flags & CMDF_ROUND_MASK) {
		case CMDF_ROUND_NEAREST:
		default:
			divider = DIV_ROUND_CLOSEST(*ns, base);
			break;
		case CMDF_ROUND_DOWN:
			divider = (*ns) / base;
			break;
		case CMDF_ROUND_UP:
			divider = DIV_ROUND_UP(*ns, base);
			break;
		}
		if (divider <= DT2821_DIVIDER_MAX)
			break;
	}
	if (divider > DT2821_DIVIDER_MAX) {
		prescale = DT2821_PRESCALE_MAX;
		divider = DT2821_DIVIDER_MAX;
		base = DT2821_OSC_BASE * DT2821_PRESCALE(prescale);
	}
	*ns = divider * base;
	return DT2821_TMRCTR_PRESCALE(prescale) |
	       DT2821_TMRCTR_DIVIDER(divider);
}

static void dt282x_munge(struct comedi_device *dev,
			 struct comedi_subdevice *s,
			 unsigned short *buf,
			 unsigned int nbytes)
{
	struct dt282x_private *devpriv = dev->private;
	unsigned int val;
	int i;

	if (nbytes % 2)
		dev_err(dev->class_dev,
			"bug! odd number of bytes from dma xfer\n");

	for (i = 0; i < nbytes / 2; i++) {
		val = buf[i];
		val &= s->maxdata;
		if (devpriv->ad_2scomp)
			val = comedi_offset_munge(s, val);

		buf[i] = val;
	}
}

static unsigned int dt282x_ao_setup_dma(struct comedi_device *dev,
					struct comedi_subdevice *s,
					int cur_dma)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_isadma *dma = devpriv->dma;
	struct comedi_isadma_desc *desc = &dma->desc[cur_dma];
	unsigned int nsamples = comedi_bytes_to_samples(s, desc->maxsize);
	unsigned int nbytes;

	nbytes = comedi_buf_read_samples(s, desc->virt_addr, nsamples);
	if (nbytes)
		dt282x_prep_ao_dma(dev, cur_dma, nbytes);
	else
		dev_err(dev->class_dev, "AO underrun\n");

	return nbytes;
}

static void dt282x_ao_dma_interrupt(struct comedi_device *dev,
				    struct comedi_subdevice *s)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_isadma *dma = devpriv->dma;
	struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];

	outw(devpriv->supcsr | DT2821_SUPCSR_CLRDMADNE,
	     dev->iobase + DT2821_SUPCSR_REG);

	comedi_isadma_disable(desc->chan);

	if (!dt282x_ao_setup_dma(dev, s, dma->cur_dma))
		s->async->events |= COMEDI_CB_OVERFLOW;

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

static void dt282x_ai_dma_interrupt(struct comedi_device *dev,
				    struct comedi_subdevice *s)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_isadma *dma = devpriv->dma;
	struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];
	unsigned int nsamples = comedi_bytes_to_samples(s, desc->size);
	int ret;

	outw(devpriv->supcsr | DT2821_SUPCSR_CLRDMADNE,
	     dev->iobase + DT2821_SUPCSR_REG);

	comedi_isadma_disable(desc->chan);

	dt282x_munge(dev, s, desc->virt_addr, desc->size);
	ret = comedi_buf_write_samples(s, desc->virt_addr, nsamples);
	if (ret != desc->size)
		return;

	devpriv->nread -= nsamples;
	if (devpriv->nread < 0) {
		dev_info(dev->class_dev, "nread off by one\n");
		devpriv->nread = 0;
	}
	if (!devpriv->nread) {
		s->async->events |= COMEDI_CB_EOA;
		return;
	}
#if 0
	/* clear the dual dma flag, making this the last dma segment */
	/* XXX probably wrong */
	if (!devpriv->ntrig) {
		devpriv->supcsr &= ~DT2821_SUPCSR_DDMA;
		outw(devpriv->supcsr, dev->iobase + DT2821_SUPCSR_REG);
	}
#endif
	/* restart the channel */
	dt282x_prep_ai_dma(dev, dma->cur_dma, 0);

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

static irqreturn_t dt282x_interrupt(int irq, void *d)
{
	struct comedi_device *dev = d;
	struct dt282x_private *devpriv = dev->private;
	struct comedi_subdevice *s = dev->read_subdev;
	struct comedi_subdevice *s_ao = dev->write_subdev;
	unsigned int supcsr, adcsr, dacsr;
	int handled = 0;

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

	adcsr = inw(dev->iobase + DT2821_ADCSR_REG);
	dacsr = inw(dev->iobase + DT2821_DACSR_REG);
	supcsr = inw(dev->iobase + DT2821_SUPCSR_REG);
	if (supcsr & DT2821_SUPCSR_DMAD) {
		if (devpriv->dma_dir == COMEDI_ISADMA_READ)
			dt282x_ai_dma_interrupt(dev, s);
		else
			dt282x_ao_dma_interrupt(dev, s_ao);
		handled = 1;
	}
	if (adcsr & DT2821_ADCSR_ADERR) {
		if (devpriv->nread != 0) {
			dev_err(dev->class_dev, "A/D error\n");
			s->async->events |= COMEDI_CB_ERROR;
		}
		handled = 1;
	}
	if (dacsr & DT2821_DACSR_DAERR) {
		dev_err(dev->class_dev, "D/A error\n");
		s_ao->async->events |= COMEDI_CB_ERROR;
		handled = 1;
	}
#if 0
	if (adcsr & DT2821_ADCSR_ADDONE) {
		unsigned short data;

		data = inw(dev->iobase + DT2821_ADDAT_REG);
		data &= s->maxdata;
		if (devpriv->ad_2scomp)
			data = comedi_offset_munge(s, data);

		comedi_buf_write_samples(s, &data, 1);

		devpriv->nread--;
		if (!devpriv->nread) {
			s->async->events |= COMEDI_CB_EOA;
		} else {
			if (supcsr & DT2821_SUPCSR_SCDN)
				outw(devpriv->supcsr | DT2821_SUPCSR_STRIG,
				     dev->iobase + DT2821_SUPCSR_REG);
		}
		handled = 1;
	}
#endif
	comedi_handle_events(dev, s);
	if (s_ao)
		comedi_handle_events(dev, s_ao);

	return IRQ_RETVAL(handled);
}

static void dt282x_load_changain(struct comedi_device *dev, int n,
				 unsigned int *chanlist)
{
	struct dt282x_private *devpriv = dev->private;
	int i;

	outw(DT2821_CHANCSR_LLE | DT2821_CHANCSR_NUMB(n),
	     dev->iobase + DT2821_CHANCSR_REG);
	for (i = 0; i < n; i++) {
		unsigned int chan = CR_CHAN(chanlist[i]);
		unsigned int range = CR_RANGE(chanlist[i]);

		outw(devpriv->adcsr |
		     DT2821_ADCSR_GS(range) |
		     DT2821_ADCSR_CHAN(chan),
		     dev->iobase + DT2821_ADCSR_REG);
	}
	outw(DT2821_CHANCSR_NUMB(n), dev->iobase + DT2821_CHANCSR_REG);
}

static int dt282x_ai_timeout(struct comedi_device *dev,
			     struct comedi_subdevice *s,
			     struct comedi_insn *insn,
			     unsigned long context)
{
	unsigned int status;

	status = inw(dev->iobase + DT2821_ADCSR_REG);
	switch (context) {
	case DT2821_ADCSR_MUXBUSY:
		if ((status & DT2821_ADCSR_MUXBUSY) == 0)
			return 0;
		break;
	case DT2821_ADCSR_ADDONE:
		if (status & DT2821_ADCSR_ADDONE)
			return 0;
		break;
	default:
		return -EINVAL;
	}
	return -EBUSY;
}

/*
 *    Performs a single A/D conversion.
 *      - Put channel/gain into channel-gain list
 *      - preload multiplexer
 *      - trigger conversion and wait for it to finish
 */
static int dt282x_ai_insn_read(struct comedi_device *dev,
			       struct comedi_subdevice *s,
			       struct comedi_insn *insn,
			       unsigned int *data)
{
	struct dt282x_private *devpriv = dev->private;
	unsigned int val;
	int ret;
	int i;

	/* XXX should we really be enabling the ad clock here? */
	devpriv->adcsr = DT2821_ADCSR_ADCLK;
	outw(devpriv->adcsr, dev->iobase + DT2821_ADCSR_REG);

	dt282x_load_changain(dev, 1, &insn->chanspec);

	outw(devpriv->supcsr | DT2821_SUPCSR_PRLD,
	     dev->iobase + DT2821_SUPCSR_REG);
	ret = comedi_timeout(dev, s, insn,
			     dt282x_ai_timeout, DT2821_ADCSR_MUXBUSY);
	if (ret)
		return ret;

	for (i = 0; i < insn->n; i++) {
		outw(devpriv->supcsr | DT2821_SUPCSR_STRIG,
		     dev->iobase + DT2821_SUPCSR_REG);

		ret = comedi_timeout(dev, s, insn,
				     dt282x_ai_timeout, DT2821_ADCSR_ADDONE);
		if (ret)
			return ret;

		val = inw(dev->iobase + DT2821_ADDAT_REG);
		val &= s->maxdata;
		if (devpriv->ad_2scomp)
			val = comedi_offset_munge(s, val);

		data[i] = val;
	}

	return i;
}

static int dt282x_ai_cmdtest(struct comedi_device *dev,
			     struct comedi_subdevice *s,
			     struct comedi_cmd *cmd)
{
	const struct dt282x_board *board = dev->board_ptr;
	struct dt282x_private *devpriv = dev->private;
	int err = 0;
	unsigned int arg;

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

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

	if (err)
		return 1;

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

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

	/* Step 2b : and mutually compatible */

	if (err)
		return 2;

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

	err |= comedi_check_trigger_arg_is(&cmd->start_arg, 0);
	err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, 0);
	err |= comedi_check_trigger_arg_max(&cmd->convert_arg, DT2821_OSC_MAX);
	err |= comedi_check_trigger_arg_min(&cmd->convert_arg, board->ai_speed);
	err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
					   cmd->chanlist_len);

	if (cmd->stop_src == TRIG_COUNT)
		err |= comedi_check_trigger_arg_min(&cmd->stop_arg, 1);
	else	/* TRIG_EXT | TRIG_NONE */
		err |= comedi_check_trigger_arg_is(&cmd->stop_arg, 0);

	if (err)
		return 3;

	/* step 4: fix up any arguments */

	arg = cmd->convert_arg;
	devpriv->divisor = dt282x_ns_to_timer(&arg, cmd->flags);
	err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg);

	if (err)
		return 4;

	return 0;
}

static int dt282x_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_isadma *dma = devpriv->dma;
	struct comedi_cmd *cmd = &s->async->cmd;
	int ret;

	dt282x_disable_dma(dev);

	outw(devpriv->divisor, dev->iobase + DT2821_TMRCTR_REG);

	devpriv->supcsr = DT2821_SUPCSR_ERRINTEN;
	if (cmd->scan_begin_src == TRIG_FOLLOW)
		devpriv->supcsr = DT2821_SUPCSR_DS_AD_CLK;
	else
		devpriv->supcsr = DT2821_SUPCSR_DS_AD_TRIG;
	outw(devpriv->supcsr |
	     DT2821_SUPCSR_CLRDMADNE |
	     DT2821_SUPCSR_BUFFB |
	     DT2821_SUPCSR_ADCINIT,
	     dev->iobase + DT2821_SUPCSR_REG);

	devpriv->ntrig = cmd->stop_arg * cmd->scan_end_arg;
	devpriv->nread = devpriv->ntrig;

	devpriv->dma_dir = COMEDI_ISADMA_READ;
	dma->cur_dma = 0;
	dt282x_prep_ai_dma(dev, 0, 0);
	if (devpriv->ntrig) {
		dt282x_prep_ai_dma(dev, 1, 0);
		devpriv->supcsr |= DT2821_SUPCSR_DDMA;
		outw(devpriv->supcsr, dev->iobase + DT2821_SUPCSR_REG);
	}

	devpriv->adcsr = 0;

	dt282x_load_changain(dev, cmd->chanlist_len, cmd->chanlist);

	devpriv->adcsr = DT2821_ADCSR_ADCLK | DT2821_ADCSR_IADDONE;
	outw(devpriv->adcsr, dev->iobase + DT2821_ADCSR_REG);

	outw(devpriv->supcsr | DT2821_SUPCSR_PRLD,
	     dev->iobase + DT2821_SUPCSR_REG);
	ret = comedi_timeout(dev, s, NULL,
			     dt282x_ai_timeout, DT2821_ADCSR_MUXBUSY);
	if (ret)
		return ret;

	if (cmd->scan_begin_src == TRIG_FOLLOW) {
		outw(devpriv->supcsr | DT2821_SUPCSR_STRIG,
		     dev->iobase + DT2821_SUPCSR_REG);
	} else {
		devpriv->supcsr |= DT2821_SUPCSR_XTRIG;
		outw(devpriv->supcsr, dev->iobase + DT2821_SUPCSR_REG);
	}

	return 0;
}

static int dt282x_ai_cancel(struct comedi_device *dev,
			    struct comedi_subdevice *s)
{
	struct dt282x_private *devpriv = dev->private;

	dt282x_disable_dma(dev);

	devpriv->adcsr = 0;
	outw(devpriv->adcsr, dev->iobase + DT2821_ADCSR_REG);

	devpriv->supcsr = 0;
	outw(devpriv->supcsr | DT2821_SUPCSR_ADCINIT,
	     dev->iobase + DT2821_SUPCSR_REG);

	return 0;
}

static int dt282x_ao_insn_write(struct comedi_device *dev,
				struct comedi_subdevice *s,
				struct comedi_insn *insn,
				unsigned int *data)
{
	struct dt282x_private *devpriv = dev->private;
	unsigned int chan = CR_CHAN(insn->chanspec);
	unsigned int range = CR_RANGE(insn->chanspec);
	int i;

	devpriv->dacsr |= DT2821_DACSR_SSEL | DT2821_DACSR_YSEL(chan);

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

		s->readback[chan] = val;

		if (comedi_range_is_bipolar(s, range))
			val = comedi_offset_munge(s, val);

		outw(devpriv->dacsr, dev->iobase + DT2821_DACSR_REG);

		outw(val, dev->iobase + DT2821_DADAT_REG);

		outw(devpriv->supcsr | DT2821_SUPCSR_DACON,
		     dev->iobase + DT2821_SUPCSR_REG);
	}

	return insn->n;
}

static int dt282x_ao_cmdtest(struct comedi_device *dev,
			     struct comedi_subdevice *s,
			     struct comedi_cmd *cmd)
{
	struct dt282x_private *devpriv = dev->private;
	int err = 0;
	unsigned int arg;

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

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

	if (err)
		return 1;

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

	err |= comedi_check_trigger_is_unique(cmd->stop_src);

	/* Step 2b : and mutually compatible */

	if (err)
		return 2;

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

	err |= comedi_check_trigger_arg_is(&cmd->start_arg, 0);
	err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg, 5000);
	err |= comedi_check_trigger_arg_is(&cmd->convert_arg, 0);
	err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
					   cmd->chanlist_len);

	if (cmd->stop_src == TRIG_COUNT)
		err |= comedi_check_trigger_arg_min(&cmd->stop_arg, 1);
	else	/* TRIG_EXT | TRIG_NONE */
		err |= comedi_check_trigger_arg_is(&cmd->stop_arg, 0);

	if (err)
		return 3;

	/* step 4: fix up any arguments */

	arg = cmd->scan_begin_arg;
	devpriv->divisor = dt282x_ns_to_timer(&arg, cmd->flags);
	err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, arg);

	if (err)
		return 4;

	return 0;
}

static int dt282x_ao_inttrig(struct comedi_device *dev,
			     struct comedi_subdevice *s,
			     unsigned int trig_num)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_cmd *cmd = &s->async->cmd;

	if (trig_num != cmd->start_src)
		return -EINVAL;

	if (!dt282x_ao_setup_dma(dev, s, 0))
		return -EPIPE;

	if (!dt282x_ao_setup_dma(dev, s, 1))
		return -EPIPE;

	outw(devpriv->supcsr | DT2821_SUPCSR_STRIG,
	     dev->iobase + DT2821_SUPCSR_REG);
	s->async->inttrig = NULL;

	return 1;
}

static int dt282x_ao_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
{
	struct dt282x_private *devpriv = dev->private;
	struct comedi_isadma *dma = devpriv->dma;
	struct comedi_cmd *cmd = &s->async->cmd;

	dt282x_disable_dma(dev);

	devpriv->supcsr = DT2821_SUPCSR_ERRINTEN |
			  DT2821_SUPCSR_DS_DA_CLK |
			  DT2821_SUPCSR_DDMA;
	outw(devpriv->supcsr |
	     DT2821_SUPCSR_CLRDMADNE |
	     DT2821_SUPCSR_BUFFB |
	     DT2821_SUPCSR_DACINIT,
	     dev->iobase + DT2821_SUPCSR_REG);

	devpriv->ntrig = cmd->stop_arg * cmd->chanlist_len;
	devpriv->nread = devpriv->ntrig;

	devpriv->dma_dir = COMEDI_ISADMA_WRITE;
	dma->cur_dma = 0;

	outw(devpriv->divisor, dev->iobase + DT2821_TMRCTR_REG);

	/* clear all bits but the DIO direction bits */
	devpriv->dacsr &= (DT2821_DACSR_LBOE | DT2821_DACSR_HBOE);

	devpriv->dacsr |= (DT2821_DACSR_SSEL |
			   DT2821_DACSR_DACLK |
			   DT2821_DACSR_IDARDY);
	outw(devpriv->dacsr, dev->iobase + DT2821_DACSR_REG);

	s->async->inttrig = dt282x_ao_inttrig;

	return 0;
}

static int dt282x_ao_cancel(struct comedi_device *dev,
			    struct comedi_subdevice *s)
{
	struct dt282x_private *devpriv = dev->private;

	dt282x_disable_dma(dev);

	/* clear all bits but the DIO direction bits */
	devpriv->dacsr &= (DT2821_DACSR_LBOE | DT2821_DACSR_HBOE);

	outw(devpriv->dacsr, dev->iobase + DT2821_DACSR_REG);

	devpriv->supcsr = 0;
	outw(devpriv->supcsr | DT2821_SUPCSR_DACINIT,
	     dev->iobase + DT2821_SUPCSR_REG);

	return 0;
}

static int dt282x_dio_insn_bits(struct comedi_device *dev,
				struct comedi_subdevice *s,
				struct comedi_insn *insn,
				unsigned int *data)
{
	if (comedi_dio_update_state(s, data))
		outw(s->state, dev->iobase + DT2821_DIODAT_REG);

	data[1] = inw(dev->iobase + DT2821_DIODAT_REG);

	return insn->n;
}

static int dt282x_dio_insn_config(struct comedi_device *dev,
				  struct comedi_subdevice *s,
				  struct comedi_insn *insn,
				  unsigned int *data)
{
	struct dt282x_private *devpriv = dev->private;
	unsigned int chan = CR_CHAN(insn->chanspec);
	unsigned int mask;
	int ret;

	if (chan < 8)
		mask = 0x00ff;
	else
		mask = 0xff00;

	ret = comedi_dio_insn_config(dev, s, insn, data, mask);
	if (ret)
		return ret;

	devpriv->dacsr &= ~(DT2821_DACSR_LBOE | DT2821_DACSR_HBOE);
	if (s->io_bits & 0x00ff)
		devpriv->dacsr |= DT2821_DACSR_LBOE;
	if (s->io_bits & 0xff00)
		devpriv->dacsr |= DT2821_DACSR_HBOE;

	outw(devpriv->dacsr, dev->iobase + DT2821_DACSR_REG);

	return insn->n;
}

static const struct comedi_lrange *const ai_range_table[] = {
	&range_dt282x_ai_lo_bipolar,
	&range_dt282x_ai_lo_unipolar,
	&range_dt282x_ai_5_bipolar,
	&range_dt282x_ai_5_unipolar
};

static const struct comedi_lrange *const ai_range_pgl_table[] = {
	&range_dt282x_ai_hi_bipolar,
	&range_dt282x_ai_hi_unipolar
};

static const struct comedi_lrange *opt_ai_range_lkup(int ispgl, int x)
{
	if (ispgl) {
		if (x < 0 || x >= 2)
			x = 0;
		return ai_range_pgl_table[x];
	}

	if (x < 0 || x >= 4)
		x = 0;
	return ai_range_table[x];
}

static void dt282x_alloc_dma(struct comedi_device *dev,
			     struct comedi_devconfig *it)
{
	struct dt282x_private *devpriv = dev->private;
	unsigned int irq_num = it->options[1];
	unsigned int dma_chan[2];

	if (it->options[2] < it->options[3]) {
		dma_chan[0] = it->options[2];
		dma_chan[1] = it->options[3];
	} else {
		dma_chan[0] = it->options[3];
		dma_chan[1] = it->options[2];
	}

	if (!irq_num || dma_chan[0] == dma_chan[1] ||
	    dma_chan[0] < 5 || dma_chan[0] > 7 ||
	    dma_chan[1] < 5 || dma_chan[1] > 7)
		return;

	if (request_irq(irq_num, dt282x_interrupt, 0, dev->board_name, dev))
		return;

	/* DMA uses two 4K buffers with separate DMA channels */
	devpriv->dma = comedi_isadma_alloc(dev, 2, dma_chan[0], dma_chan[1],
					   PAGE_SIZE, 0);
	if (!devpriv->dma)
		free_irq(irq_num, dev);
	else
		dev->irq = irq_num;
}

static void dt282x_free_dma(struct comedi_device *dev)
{
	struct dt282x_private *devpriv = dev->private;

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

static int dt282x_initialize(struct comedi_device *dev)
{
	/* Initialize board */
	outw(DT2821_SUPCSR_BDINIT, dev->iobase + DT2821_SUPCSR_REG);
	inw(dev->iobase + DT2821_ADCSR_REG);

	/*
	 * At power up, some registers are in a well-known state.
	 * Check them to see if a DT2821 series board is present.
	 */
	if (((inw(dev->iobase + DT2821_ADCSR_REG) & 0xfff0) != 0x7c00) ||
	    ((inw(dev->iobase + DT2821_CHANCSR_REG) & 0xf0f0) != 0x70f0) ||
	    ((inw(dev->iobase + DT2821_DACSR_REG) & 0x7c93) != 0x7c90) ||
	    ((inw(dev->iobase + DT2821_SUPCSR_REG) & 0xf8ff) != 0x0000) ||
	    ((inw(dev->iobase + DT2821_TMRCTR_REG) & 0xff00) != 0xf000)) {
		dev_err(dev->class_dev, "board not found\n");
		return -EIO;
	}
	return 0;
}

static int dt282x_attach(struct comedi_device *dev, struct comedi_devconfig *it)
{
	const struct dt282x_board *board = dev->board_ptr;
	struct dt282x_private *devpriv;
	struct comedi_subdevice *s;
	int ret;

	ret = comedi_request_region(dev, it->options[0], 0x10);
	if (ret)
		return ret;

	ret = dt282x_initialize(dev);
	if (ret)
		return ret;

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

	/* an IRQ and 2 DMA channels are required for async command support */
	dt282x_alloc_dma(dev, it);

	ret = comedi_alloc_subdevices(dev, 3);
	if (ret)
		return ret;

	/* Analog Input subdevice */
	s = &dev->subdevices[0];
	s->type		= COMEDI_SUBD_AI;
	s->subdev_flags	= SDF_READABLE;
	if ((it->options[4] && board->adchan_di) || board->adchan_se == 0) {
		s->subdev_flags	|= SDF_DIFF;
		s->n_chan	= board->adchan_di;
	} else {
		s->subdev_flags	|= SDF_COMMON;
		s->n_chan	= board->adchan_se;
	}
	s->maxdata	= board->ai_maxdata;

	s->range_table = opt_ai_range_lkup(board->ispgl, it->options[8]);
	devpriv->ad_2scomp = it->options[5] ? 1 : 0;

	s->insn_read	= dt282x_ai_insn_read;
	if (dev->irq) {
		dev->read_subdev = s;
		s->subdev_flags	|= SDF_CMD_READ;
		s->len_chanlist	= s->n_chan;
		s->do_cmdtest	= dt282x_ai_cmdtest;
		s->do_cmd	= dt282x_ai_cmd;
		s->cancel	= dt282x_ai_cancel;
	}

	/* Analog Output subdevice */
	s = &dev->subdevices[1];
	if (board->dachan) {
		s->type		= COMEDI_SUBD_AO;
		s->subdev_flags	= SDF_WRITABLE;
		s->n_chan	= board->dachan;
		s->maxdata	= board->ao_maxdata;
		/* ranges are per-channel, set by jumpers on the board */
		s->range_table	= &dt282x_ao_range;
		s->insn_write	= dt282x_ao_insn_write;
		if (dev->irq) {
			dev->write_subdev = s;
			s->subdev_flags	|= SDF_CMD_WRITE;
			s->len_chanlist	= s->n_chan;
			s->do_cmdtest	= dt282x_ao_cmdtest;
			s->do_cmd	= dt282x_ao_cmd;
			s->cancel	= dt282x_ao_cancel;
		}

		ret = comedi_alloc_subdev_readback(s);
		if (ret)
			return ret;
	} else {
		s->type		= COMEDI_SUBD_UNUSED;
	}

	/* Digital I/O subdevice */
	s = &dev->subdevices[2];
	s->type		= COMEDI_SUBD_DIO;
	s->subdev_flags	= SDF_READABLE | SDF_WRITABLE;
	s->n_chan	= 16;
	s->maxdata	= 1;
	s->range_table	= &range_digital;
	s->insn_bits	= dt282x_dio_insn_bits;
	s->insn_config	= dt282x_dio_insn_config;

	return 0;
}

static void dt282x_detach(struct comedi_device *dev)
{
	dt282x_free_dma(dev);
	comedi_legacy_detach(dev);
}

static struct comedi_driver dt282x_driver = {
	.driver_name	= "dt282x",
	.module		= THIS_MODULE,
	.attach		= dt282x_attach,
	.detach		= dt282x_detach,
	.board_name	= &boardtypes[0].name,
	.num_names	= ARRAY_SIZE(boardtypes),
	.offset		= sizeof(struct dt282x_board),
};
module_comedi_driver(dt282x_driver);

MODULE_AUTHOR("Comedi http://www.comedi.org");
MODULE_DESCRIPTION("Comedi driver for Data Translation DT2821 series");
MODULE_LICENSE("GPL");