Contributors: 6
Author Tokens Token Proportion Commits Commit Proportion
Dave Penkler 6928 98.27% 15 57.69%
Michael Rubin 95 1.35% 6 23.08%
Nihar Chaithanya 18 0.26% 1 3.85%
Arnd Bergmann 6 0.09% 2 7.69%
Paul Retourné 2 0.03% 1 3.85%
Rohit Chavan 1 0.01% 1 3.85%
Total 7050 26 


// SPDX-License-Identifier: GPL-2.0

/*************************************************************************
 *  This code has been developed at the Institute of Sensor and Actuator  *
 *  Systems (Technical University of Vienna, Austria) to enable the GPIO  *
 *  lines (e.g. of a raspberry pi) to function as a GPIO master device	  *
 *									  *
 *  authors		 : Thomas Klima					  *
 *			   Marcello Carla'				  *
 *			   Dave Penkler					  *
 *									  *
 *  copyright		 : (C) 2016 Thomas Klima			  *
 *									  *
 *************************************************************************/

/*
 * limitations:
 *	works only on RPi
 *	cannot function as non-CIC system controller with SN7516x because
 *	SN75161B cannot simultaneously make ATN input with IFC and REN as
 *	outputs.
 * not implemented:
 *	parallel poll
 *	return2local
 *	device support (non master operation)
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define dev_fmt pr_fmt
#define NAME KBUILD_MODNAME

#define ENABLE_IRQ(IRQ, TYPE) irq_set_irq_type(IRQ, TYPE)
#define DISABLE_IRQ(IRQ) irq_set_irq_type(IRQ, IRQ_TYPE_NONE)

/*
 * Debug print levels:
 *  0 = load/unload info and errors that make the driver fail;
 *  1 = + warnings for unforeseen events that may break the current
 *	 operation and lead to a timeout, but do not affect the
 *       driver integrity (mainly unexpected interrupts);
 *  2 = + trace of function calls;
 *  3 = + trace of protocol codes;
 *  4 = + trace of interrupt operation.
 */
#define dbg_printk(level, frm, ...)					\
	do { if (debug >= (level))					\
			dev_dbg(board->gpib_dev, frm, ## __VA_ARGS__); } \
	while (0)

#define LINVAL gpiod_get_value(DAV),		\
		gpiod_get_value(NRFD),		\
		gpiod_get_value(NDAC),		\
		gpiod_get_value(SRQ)
#define LINFMT "DAV: %d	 NRFD:%d  NDAC: %d SRQ: %d"

#include "gpibP.h"
#include "gpib_state_machines.h"
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/gpio/machine.h>
#include <linux/gpio.h>
#include <linux/irq.h>

static int sn7516x_used = 1, sn7516x;
module_param(sn7516x_used, int, 0660);

#define PINMAP_0 "elektronomikon"
#define PINMAP_1 "gpib4pi-1.1"
#define PINMAP_2 "yoga"
static char *pin_map = PINMAP_0;
module_param(pin_map, charp, 0660);
MODULE_PARM_DESC(pin_map, " valid values: " PINMAP_0 " " PINMAP_1 " " PINMAP_2);

/**********************************************
 *  Signal pairing and pin wiring between the *
 *  Raspberry-Pi connector and the GPIB bus   *
 *					      *
 *		 signal		  pin wiring  *
 *	      GPIB  Pi-gpio	GPIB  ->  RPi *
 **********************************************
 */
enum lines_t {
	D01_pin_nr =  20,     /*   1  ->  38  */
	D02_pin_nr =  26,     /*   2  ->  37  */
	D03_pin_nr =  16,     /*   3  ->  36  */
	D04_pin_nr =  19,     /*   4  ->  35  */
	D05_pin_nr =  13,     /*  13  ->  33  */
	D06_pin_nr =  12,     /*  14  ->  32  */
	D07_pin_nr =   6,     /*  15  ->  31  */
	D08_pin_nr =   5,     /*  16  ->  29  */
	EOI_pin_nr =   9,     /*   5  ->  21  */
	DAV_pin_nr =  10,     /*   6  ->  19  */
	NRFD_pin_nr = 24,     /*   7  ->  18  */
	NDAC_pin_nr = 23,     /*   8  ->  16  */
	IFC_pin_nr =  22,     /*   9  ->  15  */
	SRQ_pin_nr =  11,     /*  10  ->  23  */
	_ATN_pin_nr = 25,     /*  11  ->  22  */
	REN_pin_nr =  27,     /*  17  ->  13  */
/*
 *  GROUND PINS
 *    12,18,19,20,21,22,23,24  => 14,20,25,30,34,39
 */

/*
 *  These lines are used to control the external
 *  SN75160/161 driver chips when used.
 *  When not used there is reduced fan out;
 *  currently tested with up to 4 devices.
 */

/*		 Pi GPIO	RPI   75161B 75160B   Description       */
	PE_pin_nr =    7,    /*	 26  ->	  nc	 11   Pullup Enable     */
	DC_pin_nr =    8,    /*	 24  ->	  12	 nc   Direction control */
	TE_pin_nr =   18,    /*	 12  ->	   2	  1   Talk Enable       */
	ACT_LED_pin_nr = 4,  /*	  7  ->	 LED  */

/* YOGA adapter uses different pinout to ease layout */
	YOGA_D03_pin_nr =  13,
	YOGA_D04_pin_nr =  12,
	YOGA_D05_pin_nr =  21,
	YOGA_D06_pin_nr =  19,
};

/*
 * GPIO descriptors and pins - WARNING: STRICTLY KEEP ITEMS ORDER
 */

#define GPIB_PINS 16
#define SN7516X_PINS 4
#define NUM_PINS (GPIB_PINS + SN7516X_PINS)

#define ACT_LED_ON do {						\
		if (ACT_LED)					\
			gpiod_direction_output(ACT_LED, 1);	\
	} while (0)
#define ACT_LED_OFF do {					\
		if (ACT_LED)					\
			gpiod_direction_output(ACT_LED, 0);	\
	} while (0)

static struct gpio_desc *all_descriptors[GPIB_PINS + SN7516X_PINS];

#define D01 all_descriptors[0]
#define D02 all_descriptors[1]
#define D03 all_descriptors[2]
#define D04 all_descriptors[3]
#define D05 all_descriptors[4]
#define D06 all_descriptors[5]
#define D07 all_descriptors[6]
#define D08 all_descriptors[7]

#define EOI all_descriptors[8]
#define NRFD all_descriptors[9]
#define IFC all_descriptors[10]
#define _ATN all_descriptors[11]
#define REN all_descriptors[12]
#define DAV all_descriptors[13]
#define NDAC all_descriptors[14]
#define SRQ all_descriptors[15]

#define PE all_descriptors[16]
#define DC all_descriptors[17]
#define TE all_descriptors[18]
#define ACT_LED all_descriptors[19]

/* YOGA dapter uses a global enable for the buffer chips, re-using the TE pin */
#define YOGA_ENABLE TE

static int gpios_vector[] = {
	D01_pin_nr,
	D02_pin_nr,
	D03_pin_nr,
	D04_pin_nr,
	D05_pin_nr,
	D06_pin_nr,
	D07_pin_nr,
	D08_pin_nr,

	EOI_pin_nr,
	NRFD_pin_nr,
	IFC_pin_nr,
	_ATN_pin_nr,
	REN_pin_nr,
	DAV_pin_nr,
	NDAC_pin_nr,
	SRQ_pin_nr,

	PE_pin_nr,
	DC_pin_nr,
	TE_pin_nr,
	ACT_LED_pin_nr
};

/* Lookup table for general GPIOs */

static struct gpiod_lookup_table gpib_gpio_table_1 = {
	// for bcm2835/6
	.dev_id = "",	 // device id of board device
	.table = {
		GPIO_LOOKUP_IDX("GPIO_GCLK",  U16_MAX, NULL,  4, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO5",	  U16_MAX, NULL,  5, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO6",	  U16_MAX, NULL,  6, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("SPI_CE1_N",  U16_MAX, NULL,  7, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("SPI_CE0_N",  U16_MAX, NULL,  8, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("SPI_MISO",	  U16_MAX, NULL,  9, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("SPI_MOSI",	  U16_MAX, NULL, 10, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("SPI_SCLK",	  U16_MAX, NULL, 11, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO12",	  U16_MAX, NULL, 12, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO13",	  U16_MAX, NULL, 13, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO16",	  U16_MAX, NULL, 16, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO17",	  U16_MAX, NULL, 17, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO18",	  U16_MAX, NULL, 18, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO19",	  U16_MAX, NULL, 19, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO20",	  U16_MAX, NULL, 20, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO21",	  U16_MAX, NULL, 21, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO22",	  U16_MAX, NULL, 22, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO23",	  U16_MAX, NULL, 23, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO24",	  U16_MAX, NULL, 24, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO25",	  U16_MAX, NULL, 25, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO26",	  U16_MAX, NULL, 26, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO27",	  U16_MAX, NULL, 27, GPIO_ACTIVE_HIGH),
		{ }
	},
};

static struct gpiod_lookup_table gpib_gpio_table_0 = {
	.dev_id = "",	 // device id of board device
	.table = {
		// for bcm27xx based pis (b b+ 2b 3b 3b+ 4 5)
		GPIO_LOOKUP_IDX("GPIO4",  U16_MAX, NULL,  4, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO5",  U16_MAX, NULL,  5, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO6",  U16_MAX, NULL,  6, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO7",  U16_MAX, NULL,  7, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO8",  U16_MAX, NULL,  8, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO9",  U16_MAX, NULL,  9, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO10", U16_MAX, NULL, 10, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO11", U16_MAX, NULL, 11, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO12", U16_MAX, NULL, 12, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO13", U16_MAX, NULL, 13, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO16", U16_MAX, NULL, 16, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO17", U16_MAX, NULL, 17, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO18", U16_MAX, NULL, 18, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO19", U16_MAX, NULL, 19, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO20", U16_MAX, NULL, 20, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO21", U16_MAX, NULL, 21, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO22", U16_MAX, NULL, 22, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO23", U16_MAX, NULL, 23, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO24", U16_MAX, NULL, 24, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO25", U16_MAX, NULL, 25, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO26", U16_MAX, NULL, 26, GPIO_ACTIVE_HIGH),
		GPIO_LOOKUP_IDX("GPIO27", U16_MAX, NULL, 27, GPIO_ACTIVE_HIGH),
		{ }
	},
};

static struct gpiod_lookup_table *lookup_tables[] = {
	&gpib_gpio_table_0,
	&gpib_gpio_table_1,
	NULL
};

/* struct which defines private_data for gpio driver */

struct bb_priv {
	int irq_NRFD;
	int irq_NDAC;
	int irq_DAV;
	int irq_SRQ;
	int dav_mode;	     /* dav  interrupt mode 0/1 -> edge/levels */
	int nrfd_mode;	     /* nrfd interrupt mode 0/1 -> edge/levels */
	int ndac_mode;	     /* nrfd interrupt mode 0/1 -> edge/levels */
	int dav_tx;	     /* keep trace of DAV status while sending */
	int dav_rx;	     /* keep trace of DAV status while receiving */
	u8 eos;	     // eos character
	short eos_flags;     // eos mode
	short eos_check;     /* eos check required in current operation ... */
	short eos_check_8;   /* ... with byte comparison */
	short eos_mask_7;    /* ... with 7 bit masked character */
	short int end;
	int request;
	int count;
	int direction;
	int t1_delay;
	u8 *rbuf;
	u8 *wbuf;
	int end_flag;
	int r_busy;	   /* 0==idle	1==busy	 */
	int w_busy;
	int write_done;
	int cmd;	   /* 1 = cmd write in	progress */
	size_t w_cnt;
	size_t length;
	u8 *w_buf;
	spinlock_t rw_lock; // protect mods to rw_lock
	int phase;
	int ndac_idle;
	int ndac_seq;
	int nrfd_idle;
	int nrfd_seq;
	int dav_seq;
	long all_irqs;
	int dav_idle;

	enum talker_function_state talker_state;
	enum listener_function_state listener_state;
};

static inline long usec_diff(struct timespec64 *a, struct timespec64 *b);
static void bb_buffer_print(struct gpib_board *board, unsigned char *buffer, size_t length,
			    int cmd, int eoi);
static void set_data_lines(u8 byte);
static u8 get_data_lines(void);
static void set_data_lines_input(void);
static void set_data_lines_output(void);
static inline int check_for_eos(struct bb_priv *priv, u8 byte);
static void set_atn(struct gpib_board *board, int atn_asserted);

static inline void SET_DIR_WRITE(struct bb_priv *priv);
static inline void SET_DIR_READ(struct bb_priv *priv);

#define DIR_READ 0
#define DIR_WRITE 1

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("GPIB helper functions for bitbanging I/O");

/****  global variables	 ****/
static int debug;
module_param(debug, int, 0644);

static char printable(char x)
{
	if (x < 32 || x > 126)
		return ' ';
	return x;
}

/***************************************************************************
 *									   *
 * READ									   *
 *									   *
 ***************************************************************************/

static int bb_read(struct gpib_board *board, u8 *buffer, size_t length,
		   int *end, size_t *bytes_read)
{
	struct bb_priv *priv = board->private_data;
	unsigned long flags;
	int retval = 0;

	ACT_LED_ON;
	SET_DIR_READ(priv);

	dbg_printk(2, "board: %p  lock %d  length: %zu\n",
		   board, mutex_is_locked(&board->user_mutex), length);

	priv->end = 0;
	priv->count = 0;
	priv->rbuf = buffer;
	if (length == 0)
		goto read_end;
	priv->request = length;
	priv->eos_check = (priv->eos_flags & REOS) == 0; /* do eos check */
	priv->eos_check_8 = priv->eos_flags & BIN;	 /* over 8 bits */
	priv->eos_mask_7 = priv->eos & 0x7f;		 /* with this 7 bit eos */

	dbg_printk(3, ".........." LINFMT "\n", LINVAL);

	spin_lock_irqsave(&priv->rw_lock, flags);
	priv->dav_mode = 1;
	priv->dav_rx = 1;
	ENABLE_IRQ(priv->irq_DAV, IRQ_TYPE_LEVEL_LOW);
	priv->end_flag = 0;
	gpiod_set_value(NRFD, 1); // ready for data
	priv->r_busy = 1;
	priv->phase = 100;
	spin_unlock_irqrestore(&priv->rw_lock, flags);

	/* wait for the interrupt routines finish their work */

	retval = wait_event_interruptible(board->wait,
					  (priv->end_flag || board->status & TIMO));

	dbg_printk(3, "awake from wait queue: %d\n", retval);

	if (retval == 0 && board->status & TIMO) {
		retval = -ETIMEDOUT;
		dbg_printk(1, "timeout\n");
	} else if (retval) {
		retval = -ERESTARTSYS;
	}

	DISABLE_IRQ(priv->irq_DAV);
	spin_lock_irqsave(&priv->rw_lock, flags);
	gpiod_set_value(NRFD, 0); // DIR_READ line state
	priv->r_busy = 0;
	spin_unlock_irqrestore(&priv->rw_lock, flags);

read_end:
	ACT_LED_OFF;
	*bytes_read = priv->count;
	*end = priv->end;
	priv->r_busy = 0;
	dbg_printk(2, "return: %d  eoi|eos: %d count: %d\n\n", retval, priv->end, priv->count);
	return retval;
}

/***************************************************************************
 *									   *
 *	READ interrupt routine (DAV line)				   *
 *									   *
 ***************************************************************************/

static irqreturn_t bb_DAV_interrupt(int irq, void *arg)
{
	struct gpib_board *board = arg;
	struct bb_priv *priv = board->private_data;
	int val;
	unsigned long flags;

	spin_lock_irqsave(&priv->rw_lock, flags);

	priv->all_irqs++;

	if (priv->dav_mode) {
		ENABLE_IRQ(priv->irq_DAV, IRQ_TYPE_EDGE_BOTH);
		priv->dav_mode = 0;
	}

	if (priv->r_busy == 0) {
		dbg_printk(1, "interrupt while idle after %d at %d\n",
			   priv->count, priv->phase);
		priv->dav_idle++;
		priv->phase = 200;
		goto dav_exit;	/* idle */
	}

	val = gpiod_get_value(DAV);
	if (val == priv->dav_rx) {
		dbg_printk(1, "out of order DAV interrupt %d/%d after %zu/%zu at %d cmd %d "
			   LINFMT ".\n", val, priv->dav_rx, priv->w_cnt, priv->length,
			   priv->phase, priv->cmd, LINVAL);
		priv->dav_seq++;
	}
	priv->dav_rx = val;

	dbg_printk(3, "> irq: %d  DAV: %d  st: %4lx dir: %d  busy: %d:%d\n",
		   irq, val, board->status, priv->direction, priv->r_busy, priv->w_busy);

	if (val == 0) {
		gpiod_set_value(NRFD, 0); // not ready for data
		priv->rbuf[priv->count++] = get_data_lines();
		priv->end = !gpiod_get_value(EOI);
		gpiod_set_value(NDAC, 1); // data accepted
		priv->end |= check_for_eos(priv, priv->rbuf[priv->count - 1]);
		priv->end_flag = ((priv->count >= priv->request) || priv->end);
		priv->phase = 210;
	} else {
		gpiod_set_value(NDAC, 0);	// data not accepted
		if (priv->end_flag) {
			priv->r_busy = 0;
			wake_up_interruptible(&board->wait);
			priv->phase = 220;
		} else {
			gpiod_set_value(NRFD, 1);     // ready for data
			priv->phase = 230;
		}
	}

dav_exit:
	spin_unlock_irqrestore(&priv->rw_lock, flags);
	dbg_printk(3, "< irq: %d  count %d\n", irq, priv->count);
	return IRQ_HANDLED;
}

/***************************************************************************
 *									   *
 * WRITE								   *
 *									   *
 ***************************************************************************/

static int bb_write(struct gpib_board *board, u8 *buffer, size_t length,
		    int send_eoi, size_t *bytes_written)
{
	unsigned long flags;
	int retval = 0;

	struct bb_priv *priv = board->private_data;

	ACT_LED_ON;

	priv->w_cnt = 0;
	priv->w_buf = buffer;
	dbg_printk(2, "board %p	lock %d	 length: %zu\n",
		   board, mutex_is_locked(&board->user_mutex), length);

	if (debug > 1)
		bb_buffer_print(board, buffer, length, priv->cmd, send_eoi);
	priv->count = 0;
	priv->phase = 300;

	if (length == 0)
		goto write_end;
	priv->end = send_eoi;
	priv->length = length;

	SET_DIR_WRITE(priv);

	dbg_printk(2, "Enabling interrupts - NRFD: %d   NDAC: %d\n",
		   gpiod_get_value(NRFD), gpiod_get_value(NDAC));

	if (gpiod_get_value(NRFD) && gpiod_get_value(NDAC)) { /* check for listener */
		retval = -ENOTCONN;
		goto write_end;
	}

	spin_lock_irqsave(&priv->rw_lock, flags);
	priv->w_busy = 1;	   /* make the interrupt routines active */
	priv->write_done = 0;
	priv->nrfd_mode = 1;
	priv->ndac_mode = 1;
	priv->dav_tx = 1;
	ENABLE_IRQ(priv->irq_NDAC, IRQ_TYPE_LEVEL_HIGH);
	ENABLE_IRQ(priv->irq_NRFD, IRQ_TYPE_LEVEL_HIGH);
	spin_unlock_irqrestore(&priv->rw_lock, flags);

	/* wait for the interrupt routines finish their work */

	retval = wait_event_interruptible(board->wait,
					  priv->write_done || (board->status & TIMO));

	dbg_printk(3, "awake from wait queue: %d\n", retval);

	if (retval == 0) {
		if (board->status & TIMO) {
			retval = -ETIMEDOUT;
			dbg_printk(1, "timeout after %zu/%zu at %d " LINFMT " eoi: %d\n",
				   priv->w_cnt, length, priv->phase, LINVAL, send_eoi);
		} else {
			retval = priv->w_cnt;
		}
	} else {
		retval = -ERESTARTSYS;
	}

	DISABLE_IRQ(priv->irq_NRFD);
	DISABLE_IRQ(priv->irq_NDAC);

	spin_lock_irqsave(&priv->rw_lock, flags);
	priv->w_busy = 0;
	gpiod_set_value(DAV, 1); // DIR_WRITE line state
	gpiod_set_value(EOI, 1); // De-assert EOI (in case)
	spin_unlock_irqrestore(&priv->rw_lock, flags);

write_end:
	*bytes_written = priv->w_cnt;
	ACT_LED_OFF;
	dbg_printk(2, "sent %zu bytes\r\n\r\n", *bytes_written);
	priv->phase = 310;
	return retval;
}

/***************************************************************************
 *									   *
 *	WRITE interrupt routine (NRFD line)				   *
 *									   *
 ***************************************************************************/

static irqreturn_t bb_NRFD_interrupt(int irq, void *arg)
{
	struct gpib_board *board = arg;
	struct bb_priv *priv = board->private_data;
	unsigned long flags;
	int nrfd;

	spin_lock_irqsave(&priv->rw_lock, flags);

	nrfd = gpiod_get_value(NRFD);
	priv->all_irqs++;

	dbg_printk(3, "> irq: %d  NRFD: %d   NDAC: %d	st: %4lx dir: %d  busy: %d:%d\n",
		   irq, nrfd, gpiod_get_value(NDAC), board->status, priv->direction,
		   priv->w_busy, priv->r_busy);

	if (priv->nrfd_mode) {
		ENABLE_IRQ(priv->irq_NRFD, IRQ_TYPE_EDGE_RISING);
		priv->nrfd_mode = 0;
	}

	if (priv->w_busy == 0) {
		dbg_printk(1, "interrupt while idle after %zu/%zu at %d\n",
			   priv->w_cnt, priv->length, priv->phase);
		priv->nrfd_idle++;
		goto nrfd_exit;	 /* idle */
	}
	if (nrfd == 0) {
		dbg_printk(1, "out of order interrupt after %zu/%zu at %d cmd %d " LINFMT ".\n",
			   priv->w_cnt, priv->length, priv->phase, priv->cmd, LINVAL);
		priv->phase = 400;
		priv->nrfd_seq++;
		goto nrfd_exit;
	}
	if (!priv->dav_tx) {
		dbg_printk(1, "DAV low after %zu/%zu cmd %d " LINFMT ". No action.\n",
			   priv->w_cnt, priv->length, priv->cmd, LINVAL);
		priv->dav_seq++;
		goto nrfd_exit;
	}

	if (priv->w_cnt >= priv->length) { // test for missed NDAC end of transfer
		dev_err(board->gpib_dev, "Unexpected NRFD exit\n");
		priv->write_done = 1;
		priv->w_busy = 0;
		wake_up_interruptible(&board->wait);
		goto nrfd_exit;
	}

	dbg_printk(3, "sending %zu\n", priv->w_cnt);

	set_data_lines(priv->w_buf[priv->w_cnt++]); // put the data on the lines

	if (priv->w_cnt == priv->length && priv->end) {
		dbg_printk(3, "Asserting EOI\n");
		gpiod_set_value(EOI, 0); // Assert EOI
	}

	gpiod_set_value(DAV, 0); // Data available
	priv->dav_tx = 0;
	priv->phase = 410;

nrfd_exit:
	spin_unlock_irqrestore(&priv->rw_lock, flags);

	return IRQ_HANDLED;
}

/***************************************************************************
 *									   *
 *	WRITE interrupt routine (NDAC line)				   *
 *									   *
 ***************************************************************************/

static irqreturn_t bb_NDAC_interrupt(int irq, void *arg)
{
	struct gpib_board *board = arg;
	struct bb_priv *priv = board->private_data;
	unsigned long flags;
	int ndac;

	spin_lock_irqsave(&priv->rw_lock, flags);

	ndac = gpiod_get_value(NDAC);
	priv->all_irqs++;
	dbg_printk(3, "> irq: %d  NRFD: %d   NDAC: %d	st: %4lx dir: %d  busy: %d:%d\n",
		   irq, gpiod_get_value(NRFD), ndac, board->status, priv->direction,
		   priv->w_busy, priv->r_busy);

	if (priv->ndac_mode) {
		ENABLE_IRQ(priv->irq_NDAC, IRQ_TYPE_EDGE_RISING);
		priv->ndac_mode = 0;
	}

	if (priv->w_busy == 0) {
		dbg_printk(1, "interrupt while idle.\n");
		priv->ndac_idle++;
		goto ndac_exit;
	}
	if (ndac == 0) {
		dbg_printk(1, "out of order interrupt at %zu:%d.\n", priv->w_cnt, priv->phase);
		priv->phase = 500;
		priv->ndac_seq++;
		goto ndac_exit;
	}
	if (priv->dav_tx) {
		dbg_printk(1, "DAV high after %zu/%zu cmd %d " LINFMT ". No action.\n",
			   priv->w_cnt, priv->length, priv->cmd, LINVAL);
		priv->dav_seq++;
		goto ndac_exit;
	}

	dbg_printk(3, "accepted %zu\n", priv->w_cnt - 1);

	gpiod_set_value(DAV, 1); // Data not available
	priv->dav_tx = 1;
	priv->phase = 510;

	if (priv->w_cnt >= priv->length) { // test for end of transfer
		priv->write_done = 1;
		priv->w_busy = 0;
		wake_up_interruptible(&board->wait);
	}

ndac_exit:
	spin_unlock_irqrestore(&priv->rw_lock, flags);
	return IRQ_HANDLED;
}

/***************************************************************************
 *									   *
 *	interrupt routine for SRQ line					   *
 *									   *
 ***************************************************************************/

static irqreturn_t bb_SRQ_interrupt(int irq, void *arg)
{
	struct gpib_board  *board = arg;

	int val = gpiod_get_value(SRQ);

	dbg_printk(3, "> %d   st: %4lx\n", val, board->status);

	if (!val)
		set_bit(SRQI_NUM, &board->status);  /* set_bit() is atomic */

	wake_up_interruptible(&board->wait);

	return IRQ_HANDLED;
}

static int bb_command(struct gpib_board *board, u8 *buffer,
		      size_t length, size_t *bytes_written)
{
	size_t ret;
	struct bb_priv *priv = board->private_data;
	int i;

	dbg_printk(2, "%p  %p\n", buffer, board->buffer);

	/* the _ATN line has already been asserted by bb_take_control() */

	priv->cmd = 1;

	ret = bb_write(board, buffer, length, 0, bytes_written); // no eoi

	for (i = 0; i < length; i++) {
		if (buffer[i] == UNT) {
			priv->talker_state = talker_idle;
		} else {
			if (buffer[i] == UNL) {
				priv->listener_state = listener_idle;
			} else {
				if (buffer[i] == (MTA(board->pad))) {
					priv->talker_state = talker_addressed;
					priv->listener_state = listener_idle;
				} else if (buffer[i] == (MLA(board->pad))) {
					priv->listener_state = listener_addressed;
					priv->talker_state = talker_idle;
				}
			}
		}
	}

	/* the _ATN line will be released by bb_go_to_stby */

	priv->cmd = 0;

	return ret;
}

/***************************************************************************
 *									   *
 *	Buffer print with decode for debug/trace			   *
 *									   *
 ***************************************************************************/

static char *cmd_string[32] = {
	"",    // 0x00
	"GTL", // 0x01
	"",    // 0x02
	"",    // 0x03
	"SDC", // 0x04
	"PPC", // 0x05
	"",    // 0x06
	"",    // 0x07
	"GET", // 0x08
	"TCT", // 0x09
	"",    // 0x0a
	"",    // 0x0b
	"",    // 0x0c
	"",    // 0x0d
	"",    // 0x0e
	"",    // 0x0f
	"",    // 0x10
	"LLO", // 0x11
	"",    // 0x12
	"",    // 0x13
	"DCL", // 0x14
	"PPU", // 0x15
	"",    // 0x16
	"",    // 0x17
	"SPE", // 0x18
	"SPD", // 0x19
	"",    // 0x1a
	"",    // 0x1b
	"",    // 0x1c
	"",    // 0x1d
	"",    // 0x1e
	"CFE"  // 0x1f
};

static void bb_buffer_print(struct gpib_board *board, unsigned char *buffer, size_t length,
			    int cmd, int eoi)
{
	int i;

	if (cmd) {
		dbg_printk(2, "<cmd len %zu>\n", length);
		for (i = 0; i < length; i++) {
			if (buffer[i] < 0x20) {
				dbg_printk(3, "0x%x=%s\n", buffer[i], cmd_string[buffer[i]]);
			} else if (buffer[i] == 0x3f) {
				dbg_printk(3, "0x%x=%s\n", buffer[i], "UNL");
			} else if (buffer[i] == 0x5f) {
				dbg_printk(3, "0x%x=%s\n", buffer[i], "UNT");
			} else	if (buffer[i] < 0x60) {
				dbg_printk(3, "0x%x=%s%d\n", buffer[i],
					   (buffer[i] & 0x40) ? "TLK" : "LSN", buffer[i] & 0x1F);
			} else {
				dbg_printk(3, "0x%x\n", buffer[i]);
			}
		}
	} else {
		dbg_printk(2, "<data len %zu %s>\n", length, (eoi) ? "w.EOI" : " ");
		for (i = 0; i < length; i++)
			dbg_printk(2, "%3d  0x%x->%c\n", i, buffer[i], printable(buffer[i]));
	}
}

/***************************************************************************
 *									   *
 * STATUS Management							   *
 *									   *
 ***************************************************************************/
static void set_atn(struct gpib_board *board, int atn_asserted)
{
	struct bb_priv *priv = board->private_data;

	if (priv->listener_state != listener_idle &&
	    priv->talker_state != talker_idle) {
		dev_err(board->gpib_dev, "listener/talker state machine conflict\n");
	}
	if (atn_asserted) {
		if (priv->listener_state == listener_active)
			priv->listener_state = listener_addressed;
		if (priv->talker_state == talker_active)
			priv->talker_state = talker_addressed;
		SET_DIR_WRITE(priv);  // need to be able to read bus NRFD/NDAC
	} else {
		if (priv->listener_state == listener_addressed) {
			priv->listener_state = listener_active;
			SET_DIR_READ(priv); // make sure holdoff is active when we unassert ATN
		}
		if (priv->talker_state == talker_addressed)
			priv->talker_state = talker_active;
	}
	gpiod_direction_output(_ATN, !atn_asserted);
}

static int bb_take_control(struct gpib_board *board, int synchronous)
{
	dbg_printk(2, "%d\n", synchronous);
	set_atn(board, 1);
	return 0;
}

static int bb_go_to_standby(struct gpib_board *board)
{
	dbg_printk(2, "\n");
	set_atn(board, 0);
	return 0;
}

static int bb_request_system_control(struct gpib_board *board, int request_control)
{
	struct bb_priv *priv = board->private_data;

	dbg_printk(2, "%d\n", request_control);
	if (!request_control)
		return -EINVAL;

	gpiod_direction_output(REN, 1); /* user space must enable REN if needed */
	gpiod_direction_output(IFC, 1); /* user space must toggle IFC if needed */
	if (sn7516x)
		gpiod_direction_output(DC, 0); /* enable ATN as output on SN75161/2 */

	gpiod_direction_input(SRQ);

	ENABLE_IRQ(priv->irq_SRQ, IRQ_TYPE_EDGE_FALLING);

	return 0;
}

static void bb_interface_clear(struct gpib_board *board, int assert)
{
	struct bb_priv *priv = board->private_data;

	dbg_printk(2, "%d\n", assert);
	if (assert) {
		gpiod_direction_output(IFC, 0);
		priv->talker_state = talker_idle;
		priv->listener_state = listener_idle;
		set_bit(CIC_NUM, &board->status);
	} else {
		gpiod_direction_output(IFC, 1);
	}
}

static void bb_remote_enable(struct gpib_board *board, int enable)
{
	dbg_printk(2, "%d\n", enable);
	if (enable) {
		set_bit(REM_NUM, &board->status);
		gpiod_direction_output(REN, 0);
	} else {
		clear_bit(REM_NUM, &board->status);
		gpiod_direction_output(REN, 1);
	}
}

static int bb_enable_eos(struct gpib_board *board, u8 eos_byte, int compare_8_bits)
{
	struct bb_priv *priv = board->private_data;

	dbg_printk(2, "%s\n", "EOS_en");
	priv->eos = eos_byte;
	priv->eos_flags = REOS;
	if (compare_8_bits)
		priv->eos_flags |= BIN;

	return 0;
}

static void bb_disable_eos(struct gpib_board *board)
{
	struct bb_priv *priv = board->private_data;

	dbg_printk(2, "\n");
	priv->eos_flags &= ~REOS;
}

static unsigned int bb_update_status(struct gpib_board *board, unsigned int clear_mask)
{
	struct bb_priv *priv = board->private_data;

	board->status &= ~clear_mask;

	if (gpiod_get_value(SRQ))	       /* SRQ asserted low */
		clear_bit(SRQI_NUM, &board->status);
	else
		set_bit(SRQI_NUM, &board->status);
	if (gpiod_get_value(_ATN))			/* ATN asserted low */
		clear_bit(ATN_NUM, &board->status);
	else
		set_bit(ATN_NUM, &board->status);
	if (priv->talker_state == talker_active ||
	    priv->talker_state == talker_addressed)
		set_bit(TACS_NUM, &board->status);
	else
		clear_bit(TACS_NUM, &board->status);

	if (priv->listener_state == listener_active ||
	    priv->listener_state == listener_addressed)
		set_bit(LACS_NUM, &board->status);
	else
		clear_bit(LACS_NUM, &board->status);

	dbg_printk(2, "0x%lx mask 0x%x\n", board->status, clear_mask);

	return board->status;
}

static int bb_primary_address(struct gpib_board *board, unsigned int address)
{
	dbg_printk(2, "%d\n", address);
	board->pad = address;
	return 0;
}

static int bb_secondary_address(struct gpib_board *board, unsigned int address, int enable)
{
	dbg_printk(2, "%d %d\n", address, enable);
	if (enable)
		board->sad = address;
	return 0;
}

static int bb_parallel_poll(struct gpib_board *board, u8 *result)
{
	return -ENOENT;
}

static void bb_parallel_poll_configure(struct gpib_board *board, u8 config)
{
}

static void bb_parallel_poll_response(struct gpib_board *board, int ist)
{
}

static void bb_serial_poll_response(struct gpib_board *board, u8 status)
{
}

static u8 bb_serial_poll_status(struct gpib_board *board)
{
	return 0; // -ENOENT;
}

static int bb_t1_delay(struct gpib_board *board,  unsigned int nano_sec)
{
	struct bb_priv *priv = board->private_data;

	if (nano_sec <= 350)
		priv->t1_delay = 350;
	else if (nano_sec <= 1100)
		priv->t1_delay = 1100;
	else
		priv->t1_delay = 2000;

	dbg_printk(2, "t1 delay set to %d nanosec\n", priv->t1_delay);

	return priv->t1_delay;
}

static void bb_return_to_local(struct gpib_board *board)
{
}

static int bb_line_status(const struct gpib_board *board)
{
	int line_status = VALID_ALL;

	if (gpiod_get_value(REN) == 0)
		line_status |= BUS_REN;
	if (gpiod_get_value(IFC) == 0)
		line_status |= BUS_IFC;
	if (gpiod_get_value(NDAC) == 0)
		line_status |= BUS_NDAC;
	if (gpiod_get_value(NRFD) == 0)
		line_status |= BUS_NRFD;
	if (gpiod_get_value(DAV) == 0)
		line_status |= BUS_DAV;
	if (gpiod_get_value(EOI) == 0)
		line_status |= BUS_EOI;
	if (gpiod_get_value(_ATN) == 0)
		line_status |= BUS_ATN;
	if (gpiod_get_value(SRQ) == 0)
		line_status |= BUS_SRQ;

	dbg_printk(2, "status lines: %4x\n", line_status);

	return line_status;
}

/***************************************************************************
 *									   *
 * Module Management							   *
 *									   *
 ***************************************************************************/

static int allocate_private(struct gpib_board *board)
{
	board->private_data = kzalloc(sizeof(struct bb_priv), GFP_KERNEL);
	if (!board->private_data)
		return -1;
	return 0;
}

static void free_private(struct gpib_board *board)
{
	kfree(board->private_data);
	board->private_data = NULL;
}

static int bb_get_irq(struct gpib_board *board, char *name,
		      struct gpio_desc *gpio, int *irq,
		      irq_handler_t handler, irq_handler_t thread_fn, unsigned long flags)
{
	if (!gpio)
		return -1;
	gpiod_direction_input(gpio);
	*irq = gpiod_to_irq(gpio);
	dbg_printk(2, "IRQ %s: %d\n", name, *irq);
	if (*irq < 0) {
		dev_err(board->gpib_dev, "can't get IRQ for %s\n", name);
		return -1;
	}
	if (request_threaded_irq(*irq, handler, thread_fn, flags, name, board)) {
		dev_err(board->gpib_dev, "can't request IRQ for %s %d\n", name, *irq);
		*irq = 0;
		return -1;
	}
	DISABLE_IRQ(*irq);
	return 0;
}

static void bb_free_irq(struct gpib_board *board, int *irq, char *name)
{
	if (*irq) {
		free_irq(*irq, board);
		dbg_printk(2, "IRQ %d(%s) freed\n", *irq, name);
		*irq = 0;
	}
}

static void release_gpios(void)
{
	int j;

	for (j = 0 ; j < NUM_PINS ; j++) {
		if (all_descriptors[j]) {
			gpiod_put(all_descriptors[j]);
			all_descriptors[j] = NULL;
		}
	}
}

static int allocate_gpios(struct gpib_board *board)
{
	int j;
	int table_index = 0;
	char name[256];
	struct gpio_desc *desc;
	struct gpiod_lookup_table *lookup_table;

	if (!board->gpib_dev) {
		pr_err("NULL gpib dev for board\n");
		return -ENOENT;
	}

	lookup_table = lookup_tables[table_index];
	lookup_table->dev_id = dev_name(board->gpib_dev);
	gpiod_add_lookup_table(lookup_table);
	dbg_printk(1, "Allocating gpios using table index %d\n", table_index);

	for (j = 0 ; j < NUM_PINS ; j++) {
		if (gpios_vector[j] < 0)
			continue;
		/* name not really used in gpiod_get_index() */
		sprintf(name, "GPIO%d", gpios_vector[j]);
try_again:
		dbg_printk(1, "Allocating gpio %s pin no %d\n", name, gpios_vector[j]);
		desc = gpiod_get_index(board->gpib_dev, name, gpios_vector[j], GPIOD_IN);

		if (IS_ERR(desc)) {
			gpiod_remove_lookup_table(lookup_table);
			table_index++;
			lookup_table = lookup_tables[table_index];
			if (!lookup_table) {
				dev_err(board->gpib_dev, "Unable to obtain gpio descriptor for pin %d error %ld\n",
					gpios_vector[j], PTR_ERR(desc));
				goto alloc_gpios_fail;
			}
			dbg_printk(1, "Allocation failed, now using table_index %d\n", table_index);
			lookup_table->dev_id = dev_name(board->gpib_dev);
			gpiod_add_lookup_table(lookup_table);
			goto try_again;
		}
		all_descriptors[j] = desc;
	}

	gpiod_remove_lookup_table(lookup_table);

	return 0;

alloc_gpios_fail:
	release_gpios();
	return -1;
}

static void bb_detach(struct gpib_board *board)
{
	struct bb_priv *priv = board->private_data;

	dbg_printk(2, "Enter with data %p\n", board->private_data);
	if (!board->private_data)
		return;

	bb_free_irq(board, &priv->irq_DAV, NAME "_DAV");
	bb_free_irq(board, &priv->irq_NRFD, NAME "_NRFD");
	bb_free_irq(board, &priv->irq_NDAC, NAME "_NDAC");
	bb_free_irq(board, &priv->irq_SRQ, NAME "_SRQ");

	if (strcmp(PINMAP_2, pin_map) == 0) { /* YOGA */
		gpiod_set_value(YOGA_ENABLE, 0);
	}

	release_gpios();

	dbg_printk(2, "detached board: %d\n", board->minor);
	dbg_printk(0, "NRFD: idle %d, seq %d,  NDAC: idle %d, seq %d  DAV: idle %d  seq: %d  all: %ld",
		   priv->nrfd_idle, priv->nrfd_seq,
		   priv->ndac_idle, priv->ndac_seq,
		   priv->dav_idle, priv->dav_seq, priv->all_irqs);

	free_private(board);
}

static int bb_attach(struct gpib_board *board, const struct gpib_board_config *config)
{
	struct bb_priv *priv;
	int retval = 0;

	dbg_printk(2, "%s\n", "Enter ...");

	board->status = 0;

	if (allocate_private(board))
		return -ENOMEM;
	priv = board->private_data;
	priv->direction = -1;
	priv->t1_delay = 2000;
	priv->listener_state = listener_idle;
	priv->talker_state = talker_idle;

	sn7516x = sn7516x_used;
	if (strcmp(PINMAP_0, pin_map) == 0) {
		if (!sn7516x) {
			gpios_vector[&(PE) - &all_descriptors[0]] = -1;
			gpios_vector[&(DC) - &all_descriptors[0]] = -1;
			gpios_vector[&(TE) - &all_descriptors[0]] = -1;
		}
	} else if (strcmp(PINMAP_1, pin_map) == 0) {
		if (!sn7516x) {
			gpios_vector[&(PE) - &all_descriptors[0]] = -1;
			gpios_vector[&(DC) - &all_descriptors[0]] = -1;
			gpios_vector[&(TE) - &all_descriptors[0]] = -1;
		}
		gpios_vector[&(REN) - &all_descriptors[0]] = 0; /* 27 -> 0 REN on GPIB pin 0 */
	} else if (strcmp(PINMAP_2, pin_map) == 0) { /* YOGA */
		sn7516x = 0;
		gpios_vector[&(D03) - &all_descriptors[0]] = YOGA_D03_pin_nr;
		gpios_vector[&(D04) - &all_descriptors[0]] = YOGA_D04_pin_nr;
		gpios_vector[&(D05) - &all_descriptors[0]] = YOGA_D05_pin_nr;
		gpios_vector[&(D06) - &all_descriptors[0]] = YOGA_D06_pin_nr;
		gpios_vector[&(PE)  - &all_descriptors[0]] = -1;
		gpios_vector[&(DC)  - &all_descriptors[0]] = -1;
	} else {
		dev_err(board->gpib_dev, "Unrecognized pin map %s\n", pin_map);
		goto bb_attach_fail;
	}
	dbg_printk(0, "Using pin map \"%s\" %s\n", pin_map, (sn7516x) ?
		   " with SN7516x driver support" : "");

	if (allocate_gpios(board))
		goto bb_attach_fail;

/*
 * Configure SN7516X control lines.
 * drive ATN, IFC and REN as outputs only when master
 * i.e. system controller. In this mode can only be the CIC
 * When not master then enable device mode ATN, IFC & REN as inputs
 */
	if (sn7516x) {
		gpiod_direction_output(DC, 0);
		gpiod_direction_output(TE, 1);
		gpiod_direction_output(PE, 1);
	}
/* Set main control lines to a known state */
	gpiod_direction_output(IFC, 1);
	gpiod_direction_output(REN, 1);
	gpiod_direction_output(_ATN, 1);

	if (strcmp(PINMAP_2, pin_map) == 0) { /* YOGA: enable level shifters */
		gpiod_direction_output(YOGA_ENABLE, 1);
	}

	spin_lock_init(&priv->rw_lock);

	/* request DAV interrupt for read */
	if (bb_get_irq(board, NAME "_DAV", DAV, &priv->irq_DAV, bb_DAV_interrupt, NULL,
		       IRQF_TRIGGER_NONE))
		goto bb_attach_fail_r;

	/* request NRFD interrupt for write */
	if (bb_get_irq(board, NAME "_NRFD", NRFD, &priv->irq_NRFD, bb_NRFD_interrupt, NULL,
		       IRQF_TRIGGER_NONE))
		goto bb_attach_fail_r;

	/* request NDAC interrupt for write */
	if (bb_get_irq(board, NAME "_NDAC", NDAC, &priv->irq_NDAC, bb_NDAC_interrupt, NULL,
		       IRQF_TRIGGER_NONE))
		goto bb_attach_fail_r;

	/* request SRQ interrupt for Service Request */
	if (bb_get_irq(board, NAME "_SRQ", SRQ, &priv->irq_SRQ, bb_SRQ_interrupt, NULL,
		       IRQF_TRIGGER_NONE))
		goto bb_attach_fail_r;

	dbg_printk(0, "attached board %d\n", board->minor);
	goto bb_attach_out;

bb_attach_fail_r:
	release_gpios();
bb_attach_fail:
	retval = -1;
bb_attach_out:
	return retval;
}

static struct gpib_interface bb_interface = {
	.name =	NAME,
	.attach = bb_attach,
	.detach = bb_detach,
	.read = bb_read,
	.write = bb_write,
	.command = bb_command,
	.take_control = bb_take_control,
	.go_to_standby = bb_go_to_standby,
	.request_system_control = bb_request_system_control,
	.interface_clear = bb_interface_clear,
	.remote_enable = bb_remote_enable,
	.enable_eos = bb_enable_eos,
	.disable_eos = bb_disable_eos,
	.parallel_poll = bb_parallel_poll,
	.parallel_poll_configure = bb_parallel_poll_configure,
	.parallel_poll_response = bb_parallel_poll_response,
	.line_status = bb_line_status,
	.update_status = bb_update_status,
	.primary_address = bb_primary_address,
	.secondary_address = bb_secondary_address,
	.serial_poll_response = bb_serial_poll_response,
	.serial_poll_status = bb_serial_poll_status,
	.t1_delay = bb_t1_delay,
	.return_to_local = bb_return_to_local,
};

static int __init bb_init_module(void)
{
	int result = gpib_register_driver(&bb_interface, THIS_MODULE);

	if (result) {
		pr_err("gpib_register_driver failed: error = %d\n", result);
		return result;
	}

	return 0;
}

static void __exit bb_exit_module(void)
{
	gpib_unregister_driver(&bb_interface);
}

module_init(bb_init_module);
module_exit(bb_exit_module);

/***************************************************************************
 *									   *
 * UTILITY Functions							   *
 *									   *
 ***************************************************************************/
inline long usec_diff(struct timespec64 *a, struct timespec64 *b)
{
	return ((a->tv_sec - b->tv_sec) * 1000000 +
		(a->tv_nsec - b->tv_nsec) / 1000);
}

static inline int check_for_eos(struct bb_priv *priv, u8 byte)
{
	if (priv->eos_check)
		return 0;

	if (priv->eos_check_8) {
		if (priv->eos == byte)
			return 1;
	} else {
		if (priv->eos_mask_7 == (byte & 0x7f))
			return 1;
	}
	return 0;
}

static void set_data_lines_output(void)
{
	gpiod_direction_output(D01, 1);
	gpiod_direction_output(D02, 1);
	gpiod_direction_output(D03, 1);
	gpiod_direction_output(D04, 1);
	gpiod_direction_output(D05, 1);
	gpiod_direction_output(D06, 1);
	gpiod_direction_output(D07, 1);
	gpiod_direction_output(D08, 1);
}

static void set_data_lines(u8 byte)
{
	gpiod_set_value(D01, !(byte & 0x01));
	gpiod_set_value(D02, !(byte & 0x02));
	gpiod_set_value(D03, !(byte & 0x04));
	gpiod_set_value(D04, !(byte & 0x08));
	gpiod_set_value(D05, !(byte & 0x10));
	gpiod_set_value(D06, !(byte & 0x20));
	gpiod_set_value(D07, !(byte & 0x40));
	gpiod_set_value(D08, !(byte & 0x80));
}

static u8 get_data_lines(void)
{
	u8 ret;

	ret = gpiod_get_value(D01);
	ret |= gpiod_get_value(D02) << 1;
	ret |= gpiod_get_value(D03) << 2;
	ret |= gpiod_get_value(D04) << 3;
	ret |= gpiod_get_value(D05) << 4;
	ret |= gpiod_get_value(D06) << 5;
	ret |= gpiod_get_value(D07) << 6;
	ret |= gpiod_get_value(D08) << 7;
	return ~ret;
}

static void set_data_lines_input(void)
{
	gpiod_direction_input(D01);
	gpiod_direction_input(D02);
	gpiod_direction_input(D03);
	gpiod_direction_input(D04);
	gpiod_direction_input(D05);
	gpiod_direction_input(D06);
	gpiod_direction_input(D07);
	gpiod_direction_input(D08);
}

static inline void SET_DIR_WRITE(struct bb_priv *priv)
{
	if (priv->direction == DIR_WRITE)
		return;

	gpiod_direction_input(NRFD);
	gpiod_direction_input(NDAC);
	set_data_lines_output();
	gpiod_direction_output(DAV, 1);
	gpiod_direction_output(EOI, 1);

	if (sn7516x) {
		gpiod_set_value(PE, 1);	 /* set data lines to transmit on sn75160b */
		gpiod_set_value(TE, 1);	 /* set NDAC and NRFD to receive and DAV to transmit */
	}

	priv->direction = DIR_WRITE;
}

static inline void SET_DIR_READ(struct bb_priv *priv)
{
	if (priv->direction == DIR_READ)
		return;

	gpiod_direction_input(DAV);
	gpiod_direction_input(EOI);

	set_data_lines_input();

	if (sn7516x) {
		gpiod_set_value(PE, 0);	 /* set data lines to receive on sn75160b */
		gpiod_set_value(TE, 0);	 /* set NDAC and NRFD to transmit and DAV to receive */
	}

	gpiod_direction_output(NRFD, 0);  // hold off the talker
	gpiod_direction_output(NDAC, 0);  // data not accepted

	priv->direction = DIR_READ;
}