From: Frank Mori Hess <fmhess@users.sourceforge.net>
Date: Thu, 19 Feb 2009 17:51:15 +0000 (-0800)
Subject: Staging: comedi: add das1800 driver
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=a69cc3a9fae82f3620d7242fe5bfaedd24b65df5;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

Staging: comedi: add das1800 driver

Driver for Keitley das1700/das1800 series boards

From: Frank Mori Hess <fmhess@users.sourceforge.net>
Cc: David Schleef <ds@schleef.org>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/drivers/staging/comedi/drivers/das1800.c b/drivers/staging/comedi/drivers/das1800.c
new file mode 100644
index 000000000000..9c106965a429
--- /dev/null
+++ b/drivers/staging/comedi/drivers/das1800.c
@@ -0,0 +1,1758 @@
+/*
+    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 "../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(comedi_device * dev, comedi_devconfig * it);
+static int das1800_detach(comedi_device * dev);
+static int das1800_probe(comedi_device * dev);
+static int das1800_cancel(comedi_device * dev, comedi_subdevice * s);
+static irqreturn_t das1800_interrupt(int irq, void *d PT_REGS_ARG);
+static int das1800_ai_poll(comedi_device * dev, comedi_subdevice * s);
+static void das1800_ai_handler(comedi_device * dev);
+static void das1800_handle_dma(comedi_device * dev, comedi_subdevice * s,
+	unsigned int status);
+static void das1800_flush_dma(comedi_device * dev, comedi_subdevice * s);
+static void das1800_flush_dma_channel(comedi_device * dev, comedi_subdevice * s,
+	unsigned int channel, uint16_t * buffer);
+static void das1800_handle_fifo_half_full(comedi_device * dev,
+	comedi_subdevice * s);
+static void das1800_handle_fifo_not_empty(comedi_device * dev,
+	comedi_subdevice * s);
+static int das1800_ai_do_cmdtest(comedi_device * dev, comedi_subdevice * s,
+	comedi_cmd * cmd);
+static int das1800_ai_do_cmd(comedi_device * dev, comedi_subdevice * s);
+static int das1800_ai_rinsn(comedi_device * dev, comedi_subdevice * s,
+	comedi_insn * insn, lsampl_t * data);
+static int das1800_ao_winsn(comedi_device * dev, comedi_subdevice * s,
+	comedi_insn * insn, lsampl_t * data);
+static int das1800_di_rbits(comedi_device * dev, comedi_subdevice * s,
+	comedi_insn * insn, lsampl_t * data);
+static int das1800_do_wbits(comedi_device * dev, comedi_subdevice * s,
+	comedi_insn * insn, lsampl_t * data);
+
+static int das1800_set_frequency(comedi_device * dev);
+static unsigned int burst_convert_arg(unsigned int convert_arg, int round_mode);
+static unsigned int suggest_transfer_size(comedi_cmd * cmd);
+
+// analog input ranges
+static const 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 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),
+		}
+};
+
+typedef struct das1800_board_struct {
+	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 comedi_lrange *range_ai;	/* available input ranges */
+} das1800_board;
+
+/* Warning: the maximum conversion speeds listed below are
+ * not always achievable depending on board setup (see
+ * user manual.)
+ */
+static const 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 das1800_board *)dev->board_ptr)
+
+typedef struct {
+	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 */
+} das1800_private;
+
+#define devpriv ((das1800_private *)dev->private)
+
+// analog out range for boards with basic analog out
+static const comedi_lrange range_ao_1 = {
+	1,
+	{
+			RANGE(-10, 10),
+		}
+};
+
+// analog out range for 'ao' boards
+/*
+static const comedi_lrange range_ao_2 = {
+	2,
+	{
+		RANGE(-10, 10),
+		RANGE(-5, 5),
+	}
+};
+*/
+
+static comedi_driver driver_das1800 = {
+      driver_name:"das1800",
+      module:THIS_MODULE,
+      attach:das1800_attach,
+      detach:das1800_detach,
+      num_names:sizeof(das1800_boards) / sizeof(das1800_board),
+      board_name:&das1800_boards[0].name,
+      offset:sizeof(das1800_board),
+};
+
+/*
+ * A convenient macro that defines init_module() and cleanup_module(),
+ * as necessary.
+ */
+COMEDI_INITCLEANUP(driver_das1800);
+
+static int das1800_init_dma(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(comedi_device * dev, comedi_devconfig * it)
+{
+	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(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 (comedi_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(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)
+		comedi_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(comedi_device * dev)
+{
+	int id;
+	int board;
+
+	id = (inb(dev->iobase + DAS1800_DIGITAL) >> 4) & 0xf;	/* get id bits */
+	board = ((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(comedi_device * dev, comedi_subdevice * s)
+{
+	unsigned long flags;
+
+	// prevent race with interrupt handler
+	comedi_spin_lock_irqsave(&dev->spinlock, flags);
+	das1800_ai_handler(dev);
+	comedi_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 PT_REGS_ARG)
+{
+	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(comedi_device * dev)
+{
+	comedi_subdevice *s = dev->subdevices + 0;	/* analog input subdevice */
+	comedi_async *async = s->async;
+	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(comedi_device * dev, 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 comedi_device * dev,
+	uint16_t sample)
+{
+	sample += 1 << (thisboard->resolution - 1);
+	return sample;
+}
+
+static void munge_data(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(comedi_device * dev, comedi_subdevice * s,
+	unsigned int channel, uint16_t * buffer)
+{
+	unsigned int num_bytes, num_samples;
+	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(sampl_t);
+
+	/* 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(comedi_device * dev, 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(comedi_device * dev,
+	comedi_subdevice * s)
+{
+	int numPoints = 0;	/* number of points to read */
+	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(comedi_device * dev,
+	comedi_subdevice * s)
+{
+	sampl_t dpnt;
+	int unipolar;
+	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(comedi_device * dev, 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(comedi_device * dev, comedi_subdevice * s,
+	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(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(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(comedi_device * dev, 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(comedi_device * dev, 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(comedi_device * dev, 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
+	comedi_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 */
+	comedi_spin_unlock_irqrestore(&dev->spinlock, irq_flags);
+
+	return;
+}
+
+// analog input do_cmd
+static int das1800_ai_do_cmd(comedi_device * dev, comedi_subdevice * s)
+{
+	int ret;
+	int control_a, control_c;
+	comedi_async *async = s->async;
+	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(comedi_device * dev, comedi_subdevice * s,
+	comedi_insn * insn, lsampl_t * 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);
+	comedi_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;
+	}
+	comedi_spin_unlock_irqrestore(&dev->spinlock, irq_flags);
+
+	return n;
+}
+
+/* writes to an analog output channel */
+static int das1800_ao_winsn(comedi_device * dev, comedi_subdevice * s,
+	comedi_insn * insn, lsampl_t * 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
+	comedi_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);
+	}
+	comedi_spin_unlock_irqrestore(&dev->spinlock, irq_flags);
+
+	return 1;
+}
+
+/* reads from digital input channels */
+static int das1800_di_rbits(comedi_device * dev, comedi_subdevice * s,
+	comedi_insn * insn, lsampl_t * data)
+{
+
+	data[1] = inb(dev->iobase + DAS1800_DIGITAL) & 0xf;
+	data[0] = 0;
+
+	return 2;
+}
+
+/* writes to digital output channels */
+static int das1800_do_wbits(comedi_device * dev, comedi_subdevice * s,
+	comedi_insn * insn, lsampl_t * data)
+{
+	lsampl_t 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(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(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;
+}