fmh_gpib.c

// SPDX-License-Identifier: GPL-2.0

/***************************************************************************
 * GPIB Driver for fmh_gpib_core, see
 * https://github.com/fmhess/fmh_gpib_core
 *
 * More specifically, it is a driver for the hardware arrangement described by
 *  src/examples/fmh_gpib_top.vhd in the fmh_gpib_core repository.
 *
 * Author: Frank Mori Hess <[email protected]>
 * Copyright: (C) 2006, 2010, 2015 Fluke Corporation
 *	(C) 2017 Frank Mori Hess
 ***************************************************************************/

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

#include "fmh_gpib.h"

#include "gpibP.h"
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("GPIB Driver for fmh_gpib_core");
MODULE_AUTHOR("Frank Mori Hess <[email protected]>");

static irqreturn_t fmh_gpib_interrupt(int irq, void *arg);
static int fmh_gpib_attach_holdoff_all(struct gpib_board *board,
				       const struct gpib_board_config *config);
static int fmh_gpib_attach_holdoff_end(struct gpib_board *board,
				       const struct gpib_board_config *config);
static void fmh_gpib_detach(struct gpib_board *board);
static int fmh_gpib_pci_attach_holdoff_all(struct gpib_board *board,
					   const struct gpib_board_config *config);
static int fmh_gpib_pci_attach_holdoff_end(struct gpib_board *board,
					   const struct gpib_board_config *config);
static void fmh_gpib_pci_detach(struct gpib_board *board);
static int fmh_gpib_config_dma(struct gpib_board *board, int output);
static irqreturn_t fmh_gpib_internal_interrupt(struct gpib_board *board);
static struct platform_driver fmh_gpib_platform_driver;
static struct pci_driver fmh_gpib_pci_driver;

// wrappers for interface functions
static int fmh_gpib_read(struct gpib_board *board, u8 *buffer, size_t length,
			 int *end, size_t *bytes_read)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_read(board, &priv->nec7210_priv, buffer, length, end, bytes_read);
}

static int fmh_gpib_write(struct gpib_board *board, u8 *buffer, size_t length,
			  int send_eoi, size_t *bytes_written)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_write(board, &priv->nec7210_priv, buffer, length, send_eoi, bytes_written);
}

static int fmh_gpib_command(struct gpib_board *board, u8 *buffer, size_t length,
			    size_t *bytes_written)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_command(board, &priv->nec7210_priv, buffer, length, bytes_written);
}

static int fmh_gpib_take_control(struct gpib_board *board, int synchronous)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_take_control(board, &priv->nec7210_priv, synchronous);
}

static int fmh_gpib_go_to_standby(struct gpib_board *board)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_go_to_standby(board, &priv->nec7210_priv);
}

static int fmh_gpib_request_system_control(struct gpib_board *board, int request_control)
{
	struct fmh_priv *priv = board->private_data;
	struct nec7210_priv *nec_priv = &priv->nec7210_priv;

	return nec7210_request_system_control(board, nec_priv, request_control);
}

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

	nec7210_interface_clear(board, &priv->nec7210_priv, assert);
}

static void fmh_gpib_remote_enable(struct gpib_board *board, int enable)
{
	struct fmh_priv *priv = board->private_data;

	nec7210_remote_enable(board, &priv->nec7210_priv, enable);
}

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

	return nec7210_enable_eos(board, &priv->nec7210_priv, eos_byte, compare_8_bits);
}

static void fmh_gpib_disable_eos(struct gpib_board *board)
{
	struct fmh_priv *priv = board->private_data;

	nec7210_disable_eos(board, &priv->nec7210_priv);
}

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

	return nec7210_update_status(board, &priv->nec7210_priv, clear_mask);
}

static int fmh_gpib_primary_address(struct gpib_board *board, unsigned int address)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_primary_address(board, &priv->nec7210_priv, address);
}

static int fmh_gpib_secondary_address(struct gpib_board *board, unsigned int address, int enable)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_secondary_address(board, &priv->nec7210_priv, address, enable);
}

static int fmh_gpib_parallel_poll(struct gpib_board *board, u8 *result)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_parallel_poll(board, &priv->nec7210_priv, result);
}

static void fmh_gpib_parallel_poll_configure(struct gpib_board *board, u8 configuration)
{
	struct fmh_priv *priv = board->private_data;

	nec7210_parallel_poll_configure(board, &priv->nec7210_priv, configuration);
}

static void fmh_gpib_parallel_poll_response(struct gpib_board *board, int ist)
{
	struct fmh_priv *priv = board->private_data;

	nec7210_parallel_poll_response(board, &priv->nec7210_priv, ist);
}

static void fmh_gpib_local_parallel_poll_mode(struct gpib_board *board, int local)
{
	struct fmh_priv *priv = board->private_data;

	if (local) {
		write_byte(&priv->nec7210_priv, AUX_I_REG | LOCAL_PPOLL_MODE_BIT, AUXMR);
	} else	{
		/*
		 * For fmh_gpib_core, remote parallel poll config mode is unaffected by the
		 * state of the disable bit of the parallel poll register (unlike the tnt4882).
		 * So, we don't need to worry about that.
		 */
		write_byte(&priv->nec7210_priv, AUX_I_REG | 0x0, AUXMR);
	}
}

static void fmh_gpib_serial_poll_response2(struct gpib_board *board, u8 status,
					   int new_reason_for_service)
{
	struct fmh_priv *priv = board->private_data;
	unsigned long flags;
	const int MSS = status & request_service_bit;
	const int reqt = MSS && new_reason_for_service;
	const int reqf = MSS == 0;

	spin_lock_irqsave(&board->spinlock, flags);
	if (reqt) {
		priv->nec7210_priv.srq_pending = 1;
		clear_bit(SPOLL_NUM, &board->status);
	} else if (reqf) {
		priv->nec7210_priv.srq_pending = 0;
	}

	if (reqt) {
		/*
		 * It may seem like a race to issue reqt before updating
		 * the status byte, but it is not.  The chip does not
		 * issue the reqt until the SPMR is written to at
		 * a later time.
		 */
		write_byte(&priv->nec7210_priv, AUX_REQT, AUXMR);
	} else if (reqf) {
		write_byte(&priv->nec7210_priv, AUX_REQF, AUXMR);
	}
	/*
	 * We need to always zero bit 6 of the status byte before writing it to
	 * the SPMR to insure we are using
	 * serial poll mode SP1, and not accidentally triggering mode SP3.
	 */
	write_byte(&priv->nec7210_priv, status & ~request_service_bit, SPMR);
	spin_unlock_irqrestore(&board->spinlock, flags);
}

static u8 fmh_gpib_serial_poll_status(struct gpib_board *board)
{
	struct fmh_priv *priv = board->private_data;

	return nec7210_serial_poll_status(board, &priv->nec7210_priv);
}

static void fmh_gpib_return_to_local(struct gpib_board *board)
{
	struct fmh_priv *priv = board->private_data;
	struct nec7210_priv *nec_priv = &priv->nec7210_priv;

	write_byte(nec_priv, AUX_RTL2, AUXMR);
	udelay(1);
	write_byte(nec_priv, AUX_RTL, AUXMR);
}

static int fmh_gpib_line_status(const struct gpib_board *board)
{
	int status = VALID_ALL;
	int bsr_bits;
	struct fmh_priv *e_priv;
	struct nec7210_priv *nec_priv;

	e_priv = board->private_data;
	nec_priv = &e_priv->nec7210_priv;

	bsr_bits = read_byte(nec_priv, BUS_STATUS_REG);

	if ((bsr_bits & BSR_REN_BIT) == 0)
		status |= BUS_REN;
	if ((bsr_bits & BSR_IFC_BIT) == 0)
		status |= BUS_IFC;
	if ((bsr_bits & BSR_SRQ_BIT) == 0)
		status |= BUS_SRQ;
	if ((bsr_bits & BSR_EOI_BIT) == 0)
		status |= BUS_EOI;
	if ((bsr_bits & BSR_NRFD_BIT) == 0)
		status |= BUS_NRFD;
	if ((bsr_bits & BSR_NDAC_BIT) == 0)
		status |= BUS_NDAC;
	if ((bsr_bits & BSR_DAV_BIT) == 0)
		status |= BUS_DAV;
	if ((bsr_bits & BSR_ATN_BIT) == 0)
		status |= BUS_ATN;

	return status;
}

static int fmh_gpib_t1_delay(struct gpib_board *board, unsigned int nano_sec)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	unsigned int retval;

	retval = nec7210_t1_delay(board, nec_priv, nano_sec);

	if (nano_sec <= 350) {
		write_byte(nec_priv, AUX_HI_SPEED, AUXMR);
		retval = 350;
	} else {
		write_byte(nec_priv, AUX_LO_SPEED, AUXMR);
	}
	return retval;
}

static int lacs_or_read_ready(struct gpib_board *board)
{
	const struct fmh_priv *e_priv = board->private_data;
	const struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	int retval = 0;
	unsigned long flags;

	spin_lock_irqsave(&board->spinlock, flags);
	retval = test_bit(LACS_NUM, &board->status) ||
		test_bit(READ_READY_BN, &nec_priv->state);
	spin_unlock_irqrestore(&board->spinlock, flags);

	return retval;
}

static int wait_for_read(struct gpib_board *board)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	int retval = 0;

	if (wait_event_interruptible(board->wait,
				     lacs_or_read_ready(board) ||
				     test_bit(DEV_CLEAR_BN, &nec_priv->state) ||
				     test_bit(TIMO_NUM, &board->status)))
		retval = -ERESTARTSYS;

	if (test_bit(TIMO_NUM, &board->status))
		retval = -ETIMEDOUT;
	if (test_and_clear_bit(DEV_CLEAR_BN, &nec_priv->state))
		retval = -EINTR;
	return retval;
}

static int wait_for_rx_fifo_half_full_or_end(struct gpib_board *board)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	int retval = 0;

	if (wait_event_interruptible(board->wait,
				     (fifos_read(e_priv, FIFO_CONTROL_STATUS_REG) &
				      RX_FIFO_HALF_FULL) ||
				     test_bit(RECEIVED_END_BN, &nec_priv->state) ||
				     test_bit(DEV_CLEAR_BN, &nec_priv->state) ||
				     test_bit(TIMO_NUM, &board->status)))
		retval = -ERESTARTSYS;

	if (test_bit(TIMO_NUM, &board->status))
		retval = -ETIMEDOUT;
	if (test_and_clear_bit(DEV_CLEAR_BN, &nec_priv->state))
		retval = -EINTR;
	return retval;
}

/*
 * Wait until the gpib chip is ready to accept a data out byte.
 */
static int wait_for_data_out_ready(struct gpib_board *board)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	int retval = 0;

	if (wait_event_interruptible(board->wait,
				     (test_bit(TACS_NUM, &board->status) &&
				      (read_byte(nec_priv, EXT_STATUS_1_REG) &
				       DATA_OUT_STATUS_BIT)) ||
				     test_bit(DEV_CLEAR_BN, &nec_priv->state) ||
				     test_bit(TIMO_NUM, &board->status)))
		retval = -ERESTARTSYS;

	if (test_bit(TIMO_NUM, &board->status))
		retval = -ETIMEDOUT;
	if (test_and_clear_bit(DEV_CLEAR_BN, &nec_priv->state))
		retval = -EINTR;

	return retval;
}

static void fmh_gpib_dma_callback(void *arg)
{
	struct gpib_board *board = arg;
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	unsigned long flags;

	spin_lock_irqsave(&board->spinlock, flags);

	nec7210_set_reg_bits(nec_priv, IMR1, HR_DOIE | HR_DIIE, HR_DOIE | HR_DIIE);
	wake_up_interruptible(&board->wait);

	fmh_gpib_internal_interrupt(board);

	clear_bit(DMA_WRITE_IN_PROGRESS_BN, &nec_priv->state);
	clear_bit(DMA_READ_IN_PROGRESS_BN, &nec_priv->state);

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

/*
 * returns true when all the bytes of a write have been transferred to
 * the chip and successfully transferred out over the gpib bus.
 */
static int fmh_gpib_all_bytes_are_sent(struct fmh_priv *e_priv)
{
	if (fifos_read(e_priv, FIFO_XFER_COUNTER_REG) & fifo_xfer_counter_mask)
		return 0;

	if ((read_byte(&e_priv->nec7210_priv, EXT_STATUS_1_REG) & DATA_OUT_STATUS_BIT) == 0)
		return 0;

	return 1;
}

static int fmh_gpib_dma_write(struct gpib_board *board, u8 *buffer, size_t length,
			      size_t *bytes_written)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	unsigned long flags;
	int retval = 0;
	dma_addr_t address;
	struct dma_async_tx_descriptor *tx_desc;

	*bytes_written = 0;
	if (WARN_ON_ONCE(length > e_priv->dma_buffer_size))
		return -EFAULT;
	dmaengine_terminate_all(e_priv->dma_channel);
	memcpy(e_priv->dma_buffer, buffer, length);
	address = dma_map_single(board->dev, e_priv->dma_buffer, length, DMA_TO_DEVICE);
	if (dma_mapping_error(board->dev,  address))
		dev_err(board->gpib_dev, "dma mapping error in dma write!\n");
	/* program dma controller */
	retval = fmh_gpib_config_dma(board, 1);
	if (retval)
		goto cleanup;

	tx_desc = dmaengine_prep_slave_single(e_priv->dma_channel, address, length, DMA_MEM_TO_DEV,
					      DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
	if (!tx_desc) {
		dev_err(board->gpib_dev, "failed to allocate dma transmit descriptor\n");
		retval = -ENOMEM;
		goto cleanup;
	}
	tx_desc->callback = fmh_gpib_dma_callback;
	tx_desc->callback_param = board;

	spin_lock_irqsave(&board->spinlock, flags);
	fifos_write(e_priv, length & fifo_xfer_counter_mask, FIFO_XFER_COUNTER_REG);
	fifos_write(e_priv, TX_FIFO_DMA_REQUEST_ENABLE | TX_FIFO_CLEAR, FIFO_CONTROL_STATUS_REG);
	nec7210_set_reg_bits(nec_priv, IMR1, HR_DOIE, 0);
	nec7210_set_reg_bits(nec_priv, IMR2, HR_DMAO, HR_DMAO);

	dmaengine_submit(tx_desc);
	dma_async_issue_pending(e_priv->dma_channel);
	clear_bit(WRITE_READY_BN, &nec_priv->state);
	set_bit(DMA_WRITE_IN_PROGRESS_BN, &nec_priv->state);

	spin_unlock_irqrestore(&board->spinlock, flags);

	// suspend until message is sent
	if (wait_event_interruptible(board->wait,
				     fmh_gpib_all_bytes_are_sent(e_priv) ||
				     test_bit(BUS_ERROR_BN, &nec_priv->state) ||
				     test_bit(DEV_CLEAR_BN, &nec_priv->state) ||
				     test_bit(TIMO_NUM, &board->status)))
		retval = -ERESTARTSYS;

	if (test_bit(TIMO_NUM, &board->status))
		retval = -ETIMEDOUT;
	if (test_and_clear_bit(DEV_CLEAR_BN, &nec_priv->state))
		retval = -EINTR;
	if (test_and_clear_bit(BUS_ERROR_BN, &nec_priv->state))
		retval = -EIO;
	// disable board's dma
	nec7210_set_reg_bits(nec_priv, IMR2, HR_DMAO, 0);
	fifos_write(e_priv, 0, FIFO_CONTROL_STATUS_REG);

	dmaengine_terminate_all(e_priv->dma_channel);
	// make sure fmh_gpib_dma_callback got called
	if (test_bit(DMA_WRITE_IN_PROGRESS_BN, &nec_priv->state))
		fmh_gpib_dma_callback(board);

	*bytes_written = length - (fifos_read(e_priv, FIFO_XFER_COUNTER_REG) &
				   fifo_xfer_counter_mask);
	if (WARN_ON_ONCE(*bytes_written > length))
		return -EFAULT;
cleanup:
	dma_unmap_single(board->dev, address, length, DMA_TO_DEVICE);
	return retval;
}

static int fmh_gpib_accel_write(struct gpib_board *board, u8 *buffer,
				size_t length, int send_eoi, size_t *bytes_written)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	size_t remainder = length;
	size_t transfer_size;
	ssize_t retval = 0;
	size_t dma_remainder = remainder;

	if (!e_priv->dma_channel) {
		dev_err(board->gpib_dev, "No dma channel available, cannot do accel write.");
		return -ENXIO;
	}

	*bytes_written = 0;
	if (length < 1)
		return 0;

	smp_mb__before_atomic();
	clear_bit(DEV_CLEAR_BN, &nec_priv->state); // XXX FIXME
	smp_mb__after_atomic();

	if (send_eoi)
		--dma_remainder;

	while (dma_remainder > 0) {
		size_t num_bytes;

		retval = wait_for_data_out_ready(board);
		if (retval < 0)
			break;

		transfer_size = (e_priv->dma_buffer_size < dma_remainder) ?
			e_priv->dma_buffer_size : dma_remainder;
		retval = fmh_gpib_dma_write(board, buffer, transfer_size, &num_bytes);
		*bytes_written += num_bytes;
		if (retval < 0)
			break;
		dma_remainder -= num_bytes;
		remainder -= num_bytes;
		buffer += num_bytes;
		if (need_resched())
			schedule();
	}
	if (retval < 0)
		return retval;
	// handle sending of last byte with eoi
	if (send_eoi) {
		size_t num_bytes;

		if (WARN_ON_ONCE(remainder != 1))
			return -EFAULT;

		/*
		 * wait until we are sure we will be able to write the data byte
		 * into the chip before we send AUX_SEOI.  This prevents a timeout
		 * scenario where we send AUX_SEOI but then timeout without getting
		 * any bytes into the gpib chip.  This will result in the first byte
		 * of the next write having a spurious EOI set on the first byte.
		 */
		retval = wait_for_data_out_ready(board);
		if (retval < 0)
			return retval;

		write_byte(nec_priv, AUX_SEOI, AUXMR);
		retval = fmh_gpib_dma_write(board, buffer, remainder, &num_bytes);
		*bytes_written += num_bytes;
		if (retval < 0)
			return retval;
		remainder -= num_bytes;
	}
	return 0;
}

static int fmh_gpib_get_dma_residue(struct dma_chan *chan, dma_cookie_t cookie)
{
	struct dma_tx_state state;
	int result;

	result = dmaengine_pause(chan);
	if (result < 0)	{
		pr_err("dma pause failed?\n");
		return result;
	}
	dmaengine_tx_status(chan, cookie, &state);
	/*
	 * dma330 hardware doesn't support resume, so dont call this
	 * method unless the dma transfer is done.
	 */
	return state.residue;
}

static int wait_for_tx_fifo_half_empty(struct gpib_board *board)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	int retval = 0;

	if (wait_event_interruptible(board->wait,
				     (test_bit(TACS_NUM, &board->status) &&
				      (fifos_read(e_priv, FIFO_CONTROL_STATUS_REG) &
				       TX_FIFO_HALF_EMPTY)) ||
				     test_bit(DEV_CLEAR_BN, &nec_priv->state) ||
				     test_bit(TIMO_NUM, &board->status)))
		retval = -ERESTARTSYS;

	if (test_bit(TIMO_NUM, &board->status))
		retval = -ETIMEDOUT;
	if (test_and_clear_bit(DEV_CLEAR_BN, &nec_priv->state))
		retval = -EINTR;

	return retval;
}

/*
 * supports writing a chunk of data whose length must fit into the hardware'd xfer counter,
 * called in a loop by fmh_gpib_fifo_write()
 */
static int fmh_gpib_fifo_write_countable(struct gpib_board *board, u8 *buffer,
					 size_t length, int send_eoi, size_t *bytes_written)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	int retval = 0;
	unsigned int remainder;

	*bytes_written = 0;
	if (WARN_ON_ONCE(length > fifo_xfer_counter_mask))
		return -EFAULT;

	fifos_write(e_priv, length & fifo_xfer_counter_mask, FIFO_XFER_COUNTER_REG);
	fifos_write(e_priv, TX_FIFO_CLEAR, FIFO_CONTROL_STATUS_REG);
	nec7210_set_reg_bits(nec_priv, IMR1, HR_DOIE, 0);
	nec7210_set_reg_bits(nec_priv, IMR2, HR_DMAO, HR_DMAO);

	remainder = length;
	while (remainder > 0) {
		int i;

		fifos_write(e_priv, TX_FIFO_HALF_EMPTY_INTERRUPT_ENABLE, FIFO_CONTROL_STATUS_REG);
		retval = wait_for_tx_fifo_half_empty(board);
		if (retval < 0)
			goto cleanup;

		for (i = 0; i < fmh_gpib_half_fifo_size(e_priv) && remainder > 0; ++i) {
			unsigned int data_value = *buffer;

			if (send_eoi && remainder == 1)
				data_value |= FIFO_DATA_EOI_FLAG;
			fifos_write(e_priv, data_value, FIFO_DATA_REG);
			++buffer;
			--remainder;
		}
	}

	// suspend until last byte is sent
	nec7210_set_reg_bits(nec_priv, IMR1, HR_DOIE, HR_DOIE);
	if (wait_event_interruptible(board->wait,
				     fmh_gpib_all_bytes_are_sent(e_priv) ||
				     test_bit(BUS_ERROR_BN, &nec_priv->state) ||
				     test_bit(DEV_CLEAR_BN, &nec_priv->state) ||
				     test_bit(TIMO_NUM, &board->status)))
		retval = -ERESTARTSYS;

	if (test_bit(TIMO_NUM, &board->status))
		retval = -ETIMEDOUT;
	if (test_and_clear_bit(DEV_CLEAR_BN, &nec_priv->state))
		retval = -EINTR;
	if (test_and_clear_bit(BUS_ERROR_BN, &nec_priv->state))
		retval = -EIO;

cleanup:
	nec7210_set_reg_bits(nec_priv, IMR1, HR_DOIE, 0);
	nec7210_set_reg_bits(nec_priv, IMR2, HR_DMAO, 0);
	fifos_write(e_priv, 0, FIFO_CONTROL_STATUS_REG);

	*bytes_written = length - (fifos_read(e_priv, FIFO_XFER_COUNTER_REG) &
				   fifo_xfer_counter_mask);
	if (WARN_ON_ONCE(*bytes_written > length))
		return -EFAULT;

	return retval;
}

static int fmh_gpib_fifo_write(struct gpib_board *board, u8 *buffer, size_t length,
			       int send_eoi, size_t *bytes_written)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	size_t remainder = length;
	size_t transfer_size;
	ssize_t retval = 0;

	*bytes_written = 0;
	if (length < 1)
		return 0;

	clear_bit(DEV_CLEAR_BN, &nec_priv->state); // XXX FIXME

	while (remainder > 0) {
		size_t num_bytes;
		int last_pass;

		retval = wait_for_data_out_ready(board);
		if (retval < 0)
			break;

		if (fifo_xfer_counter_mask < remainder)	{
			// round transfer size to a multiple of half fifo size
			transfer_size = (fifo_xfer_counter_mask /
					 fmh_gpib_half_fifo_size(e_priv)) *
				fmh_gpib_half_fifo_size(e_priv);
			last_pass = 0;
		} else {
			transfer_size = remainder;
			last_pass = 1;
		}
		retval = fmh_gpib_fifo_write_countable(board, buffer, transfer_size,
						       last_pass && send_eoi, &num_bytes);
		*bytes_written += num_bytes;
		if (retval < 0)
			break;
		remainder -= num_bytes;
		buffer += num_bytes;
		if (need_resched())
			schedule();
	}

	return retval;
}

static int fmh_gpib_dma_read(struct gpib_board *board, u8 *buffer,
			     size_t length, int *end, size_t *bytes_read)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	int retval = 0;
	unsigned long flags;
	int residue;
	int wait_retval;
	dma_addr_t bus_address;
	struct dma_async_tx_descriptor *tx_desc;
	dma_cookie_t dma_cookie;

	*bytes_read = 0;
	*end = 0;
	if (length == 0)
		return 0;

	bus_address = dma_map_single(board->dev, e_priv->dma_buffer,
				     length, DMA_FROM_DEVICE);
	if (dma_mapping_error(board->dev, bus_address))
		dev_err(board->gpib_dev, "dma mapping error in dma read!");

	/* program dma controller */
	retval = fmh_gpib_config_dma(board, 0);
	if (retval) {
		dma_unmap_single(board->dev, bus_address, length, DMA_FROM_DEVICE);
		return retval;
	}
	tx_desc = dmaengine_prep_slave_single(e_priv->dma_channel, bus_address,
					      length, DMA_DEV_TO_MEM,
					      DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
	if (!tx_desc)  {
		dev_err(board->gpib_dev, "failed to allocate dma transmit descriptor\n");
		dma_unmap_single(board->dev, bus_address, length, DMA_FROM_DEVICE);
		return -EIO;
	}
	tx_desc->callback = fmh_gpib_dma_callback;
	tx_desc->callback_param = board;

	spin_lock_irqsave(&board->spinlock, flags);
	// enable nec7210 dma
	fifos_write(e_priv, length & fifo_xfer_counter_mask, FIFO_XFER_COUNTER_REG);
	fifos_write(e_priv, RX_FIFO_DMA_REQUEST_ENABLE | RX_FIFO_CLEAR, FIFO_CONTROL_STATUS_REG);
	nec7210_set_reg_bits(nec_priv, IMR1, HR_DIIE, 0);
	nec7210_set_reg_bits(nec_priv, IMR2, HR_DMAI, HR_DMAI);

	dma_cookie = dmaengine_submit(tx_desc);
	dma_async_issue_pending(e_priv->dma_channel);

	set_bit(DMA_READ_IN_PROGRESS_BN, &nec_priv->state);

	spin_unlock_irqrestore(&board->spinlock, flags);

	// wait for data to transfer
	wait_retval = wait_event_interruptible(board->wait,
					       test_bit(DMA_READ_IN_PROGRESS_BN, &nec_priv->state)
					       == 0 ||
					       test_bit(RECEIVED_END_BN, &nec_priv->state) ||
					       test_bit(DEV_CLEAR_BN, &nec_priv->state) ||
					       test_bit(TIMO_NUM, &board->status));
	if (wait_retval)
		retval = -ERESTARTSYS;

	if (test_bit(TIMO_NUM, &board->status))
		retval = -ETIMEDOUT;
	if (test_bit(DEV_CLEAR_BN, &nec_priv->state))
		retval = -EINTR;
	// stop the dma transfer
	nec7210_set_reg_bits(nec_priv, IMR2, HR_DMAI, 0);
	fifos_write(e_priv, 0, FIFO_CONTROL_STATUS_REG);
	/*
	 * give time for pl330 to transfer any in-flight data, since
	 * pl330 will throw it away when dmaengine_pause is called.
	 */
	usleep_range(10, 15);
	residue = fmh_gpib_get_dma_residue(e_priv->dma_channel, dma_cookie);
	if (WARN_ON_ONCE(residue > length || residue < 0))
		return -EFAULT;
	*bytes_read += length - residue;
	dmaengine_terminate_all(e_priv->dma_channel);
	// make sure fmh_gpib_dma_callback got called
	if (test_bit(DMA_READ_IN_PROGRESS_BN, &nec_priv->state))
		fmh_gpib_dma_callback(board);

	dma_unmap_single(board->dev, bus_address, length, DMA_FROM_DEVICE);
	memcpy(buffer, e_priv->dma_buffer, *bytes_read);

	/* Manually read any dregs out of fifo. */
	while ((fifos_read(e_priv, FIFO_CONTROL_STATUS_REG) & RX_FIFO_EMPTY) == 0) {
		if ((*bytes_read) >= length) {
			dev_err(board->dev, "unexpected extra bytes in rx fifo, discarding!  bytes_read=%d length=%d residue=%d\n",
				(int)(*bytes_read), (int)length, (int)residue);
			break;
		}
		buffer[(*bytes_read)++] = fifos_read(e_priv, FIFO_DATA_REG) & fifo_data_mask;
	}

	/*
	 * If we got an end interrupt, figure out if it was
	 * associated with the last byte we dma'd or with a
	 * byte still sitting on the cb7210.
	 */
	spin_lock_irqsave(&board->spinlock, flags);
	if (*bytes_read > 0 && test_bit(READ_READY_BN, &nec_priv->state) == 0) {
		/*
		 * If there is no byte sitting on the cb7210 and we
		 * saw an end, we need to deal with it now
		 */
		if (test_and_clear_bit(RECEIVED_END_BN, &nec_priv->state))
			*end = 1;
	}
	spin_unlock_irqrestore(&board->spinlock, flags);

	return retval;
}

static void fmh_gpib_release_rfd_holdoff(struct gpib_board *board, struct fmh_priv *e_priv)
{
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	unsigned int ext_status_1;
	unsigned long flags;

	spin_lock_irqsave(&board->spinlock, flags);

	ext_status_1 = read_byte(nec_priv, EXT_STATUS_1_REG);

	/*
	 * if there is an end byte sitting on the chip, don't release
	 * holdoff.  We want it left set after we read out the end
	 * byte.
	 */
	if ((ext_status_1 & (DATA_IN_STATUS_BIT | END_STATUS_BIT)) !=
	    (DATA_IN_STATUS_BIT | END_STATUS_BIT))	{
		if (ext_status_1 & RFD_HOLDOFF_STATUS_BIT)
			write_byte(nec_priv, AUX_FH, AUXMR);

		/*
		 * Check if an end byte raced in before we executed the AUX_FH command.
		 * If it did, we want to make sure the rfd holdoff is in effect.  The end
		 * byte can arrive since
		 * AUX_RFD_HOLDOFF_ASAP doesn't immediately force the acceptor handshake
		 * to leave ACRS.
		 */
		if ((read_byte(nec_priv, EXT_STATUS_1_REG) &
		     (RFD_HOLDOFF_STATUS_BIT | DATA_IN_STATUS_BIT | END_STATUS_BIT)) ==
		    (DATA_IN_STATUS_BIT | END_STATUS_BIT)) {
			write_byte(nec_priv, AUX_RFD_HOLDOFF_ASAP, AUXMR);
			set_bit(RFD_HOLDOFF_BN, &nec_priv->state);
		} else {
			clear_bit(RFD_HOLDOFF_BN, &nec_priv->state);
		}
	}
	spin_unlock_irqrestore(&board->spinlock, flags);
}

static int fmh_gpib_accel_read(struct gpib_board *board, u8 *buffer, size_t length,
			       int *end, size_t *bytes_read)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	size_t remain = length;
	size_t transfer_size;
	int retval = 0;
	size_t dma_nbytes;
	unsigned long flags;

	smp_mb__before_atomic();
	clear_bit(DEV_CLEAR_BN, &nec_priv->state); // XXX FIXME
	smp_mb__after_atomic();
	*end = 0;
	*bytes_read = 0;

	retval = wait_for_read(board);
	if (retval < 0)
		return retval;

	fmh_gpib_release_rfd_holdoff(board, e_priv);
	while (remain > 0) {
		transfer_size = (e_priv->dma_buffer_size < remain) ?
			e_priv->dma_buffer_size : remain;
		retval = fmh_gpib_dma_read(board, buffer, transfer_size, end, &dma_nbytes);
		remain -= dma_nbytes;
		buffer += dma_nbytes;
		*bytes_read += dma_nbytes;
		if (*end)
			break;
		if (retval < 0)
			break;
		if (need_resched())
			schedule();
	}

	spin_lock_irqsave(&board->spinlock, flags);
	if (test_bit(RFD_HOLDOFF_BN, &nec_priv->state) == 0) {
		write_byte(nec_priv, AUX_RFD_HOLDOFF_ASAP, AUXMR);
		set_bit(RFD_HOLDOFF_BN, &nec_priv->state);
	}
	spin_unlock_irqrestore(&board->spinlock, flags);

	return retval;
}

/*
 * Read a chunk of data whose length is within the limits of the hardware's
 * xfer counter.  Called in a loop from fmh_gpib_fifo_read().
 */
static int fmh_gpib_fifo_read_countable(struct gpib_board *board, u8 *buffer,
					size_t length, int *end, size_t *bytes_read)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	int retval = 0;

	*bytes_read = 0;
	*end = 0;
	if (length == 0)
		return 0;

	fifos_write(e_priv, length & fifo_xfer_counter_mask, FIFO_XFER_COUNTER_REG);
	fifos_write(e_priv, RX_FIFO_CLEAR, FIFO_CONTROL_STATUS_REG);
	nec7210_set_reg_bits(nec_priv, IMR1, HR_DIIE, 0);
	nec7210_set_reg_bits(nec_priv, IMR2, HR_DMAI, HR_DMAI);

	while (*bytes_read < length && *end == 0) {
		int i;

		fifos_write(e_priv, RX_FIFO_HALF_FULL_INTERRUPT_ENABLE, FIFO_CONTROL_STATUS_REG);
		retval = wait_for_rx_fifo_half_full_or_end(board);
		if (retval < 0)
			goto cleanup;

		for (i = 0; i < fmh_gpib_half_fifo_size(e_priv) && *end == 0; ++i) {
			unsigned int data_value;

			data_value = fifos_read(e_priv, FIFO_DATA_REG);
			buffer[(*bytes_read)++] = data_value & fifo_data_mask;
			if (data_value & FIFO_DATA_EOI_FLAG)
				*end = 1;
		}
	}

cleanup:
	// stop the transfer
	nec7210_set_reg_bits(nec_priv, IMR2, HR_DMAI, 0);
	fifos_write(e_priv, 0, FIFO_CONTROL_STATUS_REG);

	/* Manually read any dregs out of fifo. */
	while ((fifos_read(e_priv, FIFO_CONTROL_STATUS_REG) & RX_FIFO_EMPTY) == 0) {
		unsigned int data_value;

		if ((*bytes_read) >= length) {
			dev_err(board->dev, "unexpected extra bytes in rx fifo, discarding!  bytes_read=%d length=%d\n",
				(int)(*bytes_read), (int)length);
			break;
		}
		data_value = fifos_read(e_priv, FIFO_DATA_REG);
		buffer[(*bytes_read)++] = data_value & fifo_data_mask;
		if (data_value & FIFO_DATA_EOI_FLAG)
			*end = 1;
	}

	return retval;
}

static int fmh_gpib_fifo_read(struct gpib_board *board, u8 *buffer, size_t length,
			      int *end, size_t *bytes_read)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	size_t remain = length;
	size_t transfer_size;
	int retval = 0;
	size_t nbytes;
	unsigned long flags;

	clear_bit(DEV_CLEAR_BN, &nec_priv->state); // XXX FIXME
	*end = 0;
	*bytes_read = 0;

	/*
	 * Do a little prep with data in interrupt so that following wait_for_read()
	 * will wake up if a data byte is received.
	 */
	nec7210_set_reg_bits(nec_priv, IMR1, HR_DIIE, HR_DIIE);
	fmh_gpib_interrupt(0, board);

	retval = wait_for_read(board);
	if (retval < 0)
		return retval;

	fmh_gpib_release_rfd_holdoff(board, e_priv);
	while (remain > 0) {
		if (fifo_xfer_counter_mask < remain) {
			// round transfer size to a multiple of half fifo size
			transfer_size = (fifo_xfer_counter_mask /
					 fmh_gpib_half_fifo_size(e_priv)) *
				fmh_gpib_half_fifo_size(e_priv);
		} else {
			transfer_size = remain;
		}
		retval = fmh_gpib_fifo_read_countable(board, buffer, transfer_size, end, &nbytes);
		remain -= nbytes;
		buffer += nbytes;
		*bytes_read += nbytes;
		if (*end)
			break;
		if (retval < 0)
			break;
		if (need_resched())
			schedule();
	}

	if (*end == 0)	{
		spin_lock_irqsave(&board->spinlock, flags);
		write_byte(nec_priv, AUX_RFD_HOLDOFF_ASAP, AUXMR);
		set_bit(RFD_HOLDOFF_BN, &nec_priv->state);
		spin_unlock_irqrestore(&board->spinlock, flags);
	}

	return retval;
}

static struct gpib_interface fmh_gpib_unaccel_interface = {
	.name = "fmh_gpib_unaccel",
	.attach = fmh_gpib_attach_holdoff_all,
	.detach = fmh_gpib_detach,
	.read = fmh_gpib_read,
	.write = fmh_gpib_write,
	.command = fmh_gpib_command,
	.take_control = fmh_gpib_take_control,
	.go_to_standby = fmh_gpib_go_to_standby,
	.request_system_control = fmh_gpib_request_system_control,
	.interface_clear = fmh_gpib_interface_clear,
	.remote_enable = fmh_gpib_remote_enable,
	.enable_eos = fmh_gpib_enable_eos,
	.disable_eos = fmh_gpib_disable_eos,
	.parallel_poll = fmh_gpib_parallel_poll,
	.parallel_poll_configure = fmh_gpib_parallel_poll_configure,
	.parallel_poll_response = fmh_gpib_parallel_poll_response,
	.local_parallel_poll_mode = fmh_gpib_local_parallel_poll_mode,
	.line_status = fmh_gpib_line_status,
	.update_status = fmh_gpib_update_status,
	.primary_address = fmh_gpib_primary_address,
	.secondary_address = fmh_gpib_secondary_address,
	.serial_poll_response2 = fmh_gpib_serial_poll_response2,
	.serial_poll_status = fmh_gpib_serial_poll_status,
	.t1_delay = fmh_gpib_t1_delay,
	.return_to_local = fmh_gpib_return_to_local,
};

static struct gpib_interface fmh_gpib_interface = {
	.name = "fmh_gpib",
	.attach = fmh_gpib_attach_holdoff_end,
	.detach = fmh_gpib_detach,
	.read = fmh_gpib_accel_read,
	.write = fmh_gpib_accel_write,
	.command = fmh_gpib_command,
	.take_control = fmh_gpib_take_control,
	.go_to_standby = fmh_gpib_go_to_standby,
	.request_system_control = fmh_gpib_request_system_control,
	.interface_clear = fmh_gpib_interface_clear,
	.remote_enable = fmh_gpib_remote_enable,
	.enable_eos = fmh_gpib_enable_eos,
	.disable_eos = fmh_gpib_disable_eos,
	.parallel_poll = fmh_gpib_parallel_poll,
	.parallel_poll_configure = fmh_gpib_parallel_poll_configure,
	.parallel_poll_response = fmh_gpib_parallel_poll_response,
	.local_parallel_poll_mode = fmh_gpib_local_parallel_poll_mode,
	.line_status = fmh_gpib_line_status,
	.update_status = fmh_gpib_update_status,
	.primary_address = fmh_gpib_primary_address,
	.secondary_address = fmh_gpib_secondary_address,
	.serial_poll_response2 = fmh_gpib_serial_poll_response2,
	.serial_poll_status = fmh_gpib_serial_poll_status,
	.t1_delay = fmh_gpib_t1_delay,
	.return_to_local = fmh_gpib_return_to_local,
};

static struct gpib_interface fmh_gpib_pci_interface = {
	.name = "fmh_gpib_pci",
	.attach = fmh_gpib_pci_attach_holdoff_end,
	.detach = fmh_gpib_pci_detach,
	.read = fmh_gpib_fifo_read,
	.write = fmh_gpib_fifo_write,
	.command = fmh_gpib_command,
	.take_control = fmh_gpib_take_control,
	.go_to_standby = fmh_gpib_go_to_standby,
	.request_system_control = fmh_gpib_request_system_control,
	.interface_clear = fmh_gpib_interface_clear,
	.remote_enable = fmh_gpib_remote_enable,
	.enable_eos = fmh_gpib_enable_eos,
	.disable_eos = fmh_gpib_disable_eos,
	.parallel_poll = fmh_gpib_parallel_poll,
	.parallel_poll_configure = fmh_gpib_parallel_poll_configure,
	.parallel_poll_response = fmh_gpib_parallel_poll_response,
	.local_parallel_poll_mode = fmh_gpib_local_parallel_poll_mode,
	.line_status = fmh_gpib_line_status,
	.update_status = fmh_gpib_update_status,
	.primary_address = fmh_gpib_primary_address,
	.secondary_address = fmh_gpib_secondary_address,
	.serial_poll_response2 = fmh_gpib_serial_poll_response2,
	.serial_poll_status = fmh_gpib_serial_poll_status,
	.t1_delay = fmh_gpib_t1_delay,
	.return_to_local = fmh_gpib_return_to_local,
};

static struct gpib_interface fmh_gpib_pci_unaccel_interface = {
	.name = "fmh_gpib_pci_unaccel",
	.attach = fmh_gpib_pci_attach_holdoff_all,
	.detach = fmh_gpib_pci_detach,
	.read = fmh_gpib_read,
	.write = fmh_gpib_write,
	.command = fmh_gpib_command,
	.take_control = fmh_gpib_take_control,
	.go_to_standby = fmh_gpib_go_to_standby,
	.request_system_control = fmh_gpib_request_system_control,
	.interface_clear = fmh_gpib_interface_clear,
	.remote_enable = fmh_gpib_remote_enable,
	.enable_eos = fmh_gpib_enable_eos,
	.disable_eos = fmh_gpib_disable_eos,
	.parallel_poll = fmh_gpib_parallel_poll,
	.parallel_poll_configure = fmh_gpib_parallel_poll_configure,
	.parallel_poll_response = fmh_gpib_parallel_poll_response,
	.local_parallel_poll_mode = fmh_gpib_local_parallel_poll_mode,
	.line_status = fmh_gpib_line_status,
	.update_status = fmh_gpib_update_status,
	.primary_address = fmh_gpib_primary_address,
	.secondary_address = fmh_gpib_secondary_address,
	.serial_poll_response2 = fmh_gpib_serial_poll_response2,
	.serial_poll_status = fmh_gpib_serial_poll_status,
	.t1_delay = fmh_gpib_t1_delay,
	.return_to_local = fmh_gpib_return_to_local,
};

irqreturn_t fmh_gpib_internal_interrupt(struct gpib_board *board)
{
	unsigned int status0, status1, status2, ext_status_1, fifo_status;
	struct fmh_priv *priv = board->private_data;
	struct nec7210_priv *nec_priv = &priv->nec7210_priv;
	int retval = IRQ_NONE;

	status0 = read_byte(nec_priv, ISR0_IMR0_REG);
	status1 = read_byte(nec_priv, ISR1);
	status2 = read_byte(nec_priv, ISR2);
	fifo_status = fifos_read(priv, FIFO_CONTROL_STATUS_REG);

	if (status0 & IFC_INTERRUPT_BIT) {
		push_gpib_event(board, EVENT_IFC);
		retval = IRQ_HANDLED;
	}

	if (nec7210_interrupt_have_status(board, nec_priv, status1, status2) == IRQ_HANDLED)
		retval = IRQ_HANDLED;

	ext_status_1 = read_byte(nec_priv, EXT_STATUS_1_REG);

	if (ext_status_1 & DATA_IN_STATUS_BIT)
		set_bit(READ_READY_BN, &nec_priv->state);
	else
		clear_bit(READ_READY_BN, &nec_priv->state);

	if (ext_status_1 & DATA_OUT_STATUS_BIT)
		set_bit(WRITE_READY_BN, &nec_priv->state);
	else
		clear_bit(WRITE_READY_BN, &nec_priv->state);

	if (ext_status_1 & COMMAND_OUT_STATUS_BIT)
		set_bit(COMMAND_READY_BN, &nec_priv->state);
	else
		clear_bit(COMMAND_READY_BN, &nec_priv->state);

	if (ext_status_1 & RFD_HOLDOFF_STATUS_BIT)
		set_bit(RFD_HOLDOFF_BN, &nec_priv->state);
	else
		clear_bit(RFD_HOLDOFF_BN, &nec_priv->state);

	if (ext_status_1 & END_STATUS_BIT) {
		/*
		 * only set RECEIVED_END while there is still a data
		 * byte sitting in the chip, to avoid spuriously
		 * setting it multiple times after it has been cleared
		 * during a read.
		 */
		if (ext_status_1 & DATA_IN_STATUS_BIT)
			set_bit(RECEIVED_END_BN, &nec_priv->state);
	} else {
		clear_bit(RECEIVED_END_BN, &nec_priv->state);
	}

	if ((fifo_status & TX_FIFO_HALF_EMPTY_INTERRUPT_IS_ENABLED) &&
	    (fifo_status & TX_FIFO_HALF_EMPTY)) {
		/*
		 * We really only want to clear the
		 * TX_FIFO_HALF_EMPTY_INTERRUPT_ENABLE bit in the
		 * FIFO_CONTROL_STATUS_REG.  Since we are not being
		 * careful, this also has a side effect of disabling
		 * DMA requests and the RX fifo interrupt.  That is
		 * fine though, since they should never be in use at
		 * the same time as the TX fifo interrupt.
		 */
		fifos_write(priv, 0x0, FIFO_CONTROL_STATUS_REG);
		retval = IRQ_HANDLED;
	}

	if ((fifo_status & RX_FIFO_HALF_FULL_INTERRUPT_IS_ENABLED) &&
	    (fifo_status & RX_FIFO_HALF_FULL)) {
		/*
		 * We really only want to clear the
		 * RX_FIFO_HALF_FULL_INTERRUPT_ENABLE bit in the
		 * FIFO_CONTROL_STATUS_REG.  Since we are not being
		 * careful, this also has a side effect of disabling
		 * DMA requests and the TX fifo interrupt.  That is
		 * fine though, since they should never be in use at
		 * the same time as the RX fifo interrupt.
		 */
		fifos_write(priv, 0x0, FIFO_CONTROL_STATUS_REG);
		retval = IRQ_HANDLED;
	}

	if (retval == IRQ_HANDLED)
		wake_up_interruptible(&board->wait);

	return retval;
}

irqreturn_t fmh_gpib_interrupt(int irq, void *arg)
{
	struct gpib_board *board = arg;
	unsigned long flags;
	irqreturn_t retval;

	spin_lock_irqsave(&board->spinlock, flags);
	retval = fmh_gpib_internal_interrupt(board);
	spin_unlock_irqrestore(&board->spinlock, flags);
	return retval;
}

static int fmh_gpib_allocate_private(struct gpib_board *board)
{
	struct fmh_priv *priv;

	board->private_data = kmalloc(sizeof(struct fmh_priv), GFP_KERNEL);
	if (!board->private_data)
		return -ENOMEM;
	priv = board->private_data;
	memset(priv, 0, sizeof(struct fmh_priv));
	init_nec7210_private(&priv->nec7210_priv);
	priv->dma_buffer_size = 0x800;
	priv->dma_buffer = kmalloc(priv->dma_buffer_size, GFP_KERNEL);
	if (!priv->dma_buffer)
		return -ENOMEM;
	return 0;
}

static void fmh_gpib_generic_detach(struct gpib_board *board)
{
	if (board->private_data) {
		struct fmh_priv *e_priv = board->private_data;

		kfree(e_priv->dma_buffer);
		kfree(board->private_data);
		board->private_data = NULL;
	}
	if (board->dev)
		dev_set_drvdata(board->dev, NULL);
}

// generic part of attach functions
static int fmh_gpib_generic_attach(struct gpib_board *board)
{
	struct fmh_priv *e_priv;
	struct nec7210_priv *nec_priv;
	int retval;

	board->status = 0;

	retval = fmh_gpib_allocate_private(board);
	if (retval < 0)
		return retval;
	e_priv = board->private_data;
	nec_priv = &e_priv->nec7210_priv;
	nec_priv->read_byte = gpib_cs_read_byte;
	nec_priv->write_byte = gpib_cs_write_byte;
	nec_priv->offset = 1;
	nec_priv->type = CB7210;
	return 0;
}

static int fmh_gpib_config_dma(struct gpib_board *board, int output)
{
	struct fmh_priv *e_priv = board->private_data;
	struct dma_slave_config config;

	config.device_fc = true;

	if (e_priv->dma_burst_length < 1) {
		config.src_maxburst = 1;
		config.dst_maxburst = 1;
	} else {
		config.src_maxburst = e_priv->dma_burst_length;
		config.dst_maxburst = e_priv->dma_burst_length;
	}

	config.src_addr_width = 1;
	config.dst_addr_width = 1;

	if (output) {
		config.direction = DMA_MEM_TO_DEV;
		config.src_addr = 0;
		config.dst_addr = e_priv->dma_port_res->start + FIFO_DATA_REG * fifo_reg_offset;
	} else {
		config.direction = DMA_DEV_TO_MEM;
		config.src_addr = e_priv->dma_port_res->start + FIFO_DATA_REG * fifo_reg_offset;
		config.dst_addr = 0;
	}
	return dmaengine_slave_config(e_priv->dma_channel, &config);
}

static int fmh_gpib_init(struct fmh_priv *e_priv, struct gpib_board *board, int handshake_mode)
{
	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
	unsigned long flags;
	unsigned int fifo_status_bits;

	fifos_write(e_priv, RX_FIFO_CLEAR | TX_FIFO_CLEAR, FIFO_CONTROL_STATUS_REG);

	nec7210_board_reset(nec_priv, board);
	write_byte(nec_priv, AUX_LO_SPEED, AUXMR);
	nec7210_set_handshake_mode(board, nec_priv, handshake_mode);

	/* Hueristically check if hardware supports fifo half full/empty interrupts */
	fifo_status_bits = fifos_read(e_priv, FIFO_CONTROL_STATUS_REG);
	e_priv->supports_fifo_interrupts = (fifo_status_bits & TX_FIFO_EMPTY) &&
		(fifo_status_bits & TX_FIFO_HALF_EMPTY);

	nec7210_board_online(nec_priv, board);

	write_byte(nec_priv, IFC_INTERRUPT_ENABLE_BIT | ATN_INTERRUPT_ENABLE_BIT, ISR0_IMR0_REG);

	spin_lock_irqsave(&board->spinlock, flags);
	write_byte(nec_priv, AUX_RFD_HOLDOFF_ASAP, AUXMR);
	set_bit(RFD_HOLDOFF_BN, &nec_priv->state);
	spin_unlock_irqrestore(&board->spinlock, flags);
	return 0;
}

/* Match callback for driver_find_device */
static int fmh_gpib_device_match(struct device *dev, const void *data)
{
	const struct gpib_board_config *config = data;

	if (dev_get_drvdata(dev))
		return 0;

	if (gpib_match_device_path(dev, config->device_path) == 0)
		return 0;

	// driver doesn't support selection by serial number
	if (config->serial_number)
		return 0;

	dev_dbg(dev, "matched: %s\n", of_node_full_name(dev_of_node((dev))));
	return 1;
}

static int fmh_gpib_attach_impl(struct gpib_board *board, const struct gpib_board_config *config,
				unsigned int handshake_mode, int acquire_dma)
{
	struct fmh_priv *e_priv;
	struct nec7210_priv *nec_priv;
	int retval;
	int irq;
	struct resource *res;
	struct platform_device *pdev;

	board->dev = driver_find_device(&fmh_gpib_platform_driver.driver,
					NULL, (const void *)config, &fmh_gpib_device_match);
	if (!board->dev)	{
		dev_err(board->gpib_dev, "No matching fmh_gpib_core device was found, attach failed.");
		return -ENODEV;
	}
	// currently only used to mark the device as already attached
	dev_set_drvdata(board->dev, board);
	pdev = to_platform_device(board->dev);

	retval = fmh_gpib_generic_attach(board);
	if (retval)
		return retval;

	e_priv = board->private_data;
	nec_priv = &e_priv->nec7210_priv;

	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "gpib_control_status");
	if (!res) {
		dev_err(board->dev, "Unable to locate mmio resource\n");
		return -ENODEV;
	}

	if (request_mem_region(res->start,
			       resource_size(res),
			       pdev->name) == NULL) {
		dev_err(board->dev, "cannot claim registers\n");
		return -ENXIO;
	}
	e_priv->gpib_iomem_res = res;

	nec_priv->mmiobase = ioremap(e_priv->gpib_iomem_res->start,
				     resource_size(e_priv->gpib_iomem_res));
	if (!nec_priv->mmiobase) {
		dev_err(board->dev, "Could not map I/O memory\n");
		return -ENOMEM;
	}
	dev_dbg(board->dev, "iobase %pr remapped to %p\n",
		e_priv->gpib_iomem_res, nec_priv->mmiobase);

	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "dma_fifos");
	if (!res) {
		dev_err(board->dev, "Unable to locate mmio resource for gpib dma port\n");
		return -ENODEV;
	}
	if (request_mem_region(res->start,
			       resource_size(res),
			       pdev->name) == NULL) {
		dev_err(board->dev, "cannot claim registers\n");
		return -ENXIO;
	}
	e_priv->dma_port_res = res;
	e_priv->fifo_base = ioremap(e_priv->dma_port_res->start,
				    resource_size(e_priv->dma_port_res));
	if (!e_priv->fifo_base) {
		dev_err(board->dev, "Could not map I/O memory for fifos\n");
		return -ENOMEM;
	}
	dev_dbg(board->dev, "dma fifos 0x%lx remapped to %p, length=%ld\n",
		(unsigned long)e_priv->dma_port_res->start, e_priv->fifo_base,
		(unsigned long)resource_size(e_priv->dma_port_res));

	irq = platform_get_irq(pdev, 0);
	if (irq < 0)
		return -EBUSY;
	retval = request_irq(irq, fmh_gpib_interrupt, IRQF_SHARED, pdev->name, board);
	if (retval) {
		dev_err(board->dev,
			"cannot register interrupt handler err=%d\n",
			retval);
		return retval;
	}
	e_priv->irq = irq;

	if (acquire_dma) {
		e_priv->dma_channel = dma_request_slave_channel(board->dev, "rxtx");
		if (!e_priv->dma_channel) {
			dev_err(board->dev, "failed to acquire dma channel \"rxtx\".\n");
			return -EIO;
		}
	}
	/*
	 * in the future we might want to know the half-fifo size
	 * (dma_burst_length) even when not using dma, so go ahead an
	 * initialize it unconditionally.
	 */
	e_priv->dma_burst_length = fifos_read(e_priv, FIFO_MAX_BURST_LENGTH_REG) &
		fifo_max_burst_length_mask;

	return fmh_gpib_init(e_priv, board, handshake_mode);
}

int fmh_gpib_attach_holdoff_all(struct gpib_board *board, const struct gpib_board_config *config)
{
	return fmh_gpib_attach_impl(board, config, HR_HLDA, 0);
}

int fmh_gpib_attach_holdoff_end(struct gpib_board *board, const struct gpib_board_config *config)
{
	return fmh_gpib_attach_impl(board, config, HR_HLDE, 1);
}

void fmh_gpib_detach(struct gpib_board *board)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv;

	if (e_priv) {
		if (e_priv->dma_channel)
			dma_release_channel(e_priv->dma_channel);
		nec_priv = &e_priv->nec7210_priv;

		if (e_priv->irq)
			free_irq(e_priv->irq, board);
		if (e_priv->fifo_base)
			fifos_write(e_priv, 0, FIFO_CONTROL_STATUS_REG);
		if (nec_priv->mmiobase) {
			write_byte(nec_priv, 0, ISR0_IMR0_REG);
			nec7210_board_reset(nec_priv, board);
		}
		if (e_priv->fifo_base)
			iounmap(e_priv->fifo_base);
		if (nec_priv->mmiobase)
			iounmap(nec_priv->mmiobase);
		if (e_priv->dma_port_res) {
			release_mem_region(e_priv->dma_port_res->start,
					   resource_size(e_priv->dma_port_res));
		}
		if (e_priv->gpib_iomem_res)
			release_mem_region(e_priv->gpib_iomem_res->start,
					   resource_size(e_priv->gpib_iomem_res));
	}
	fmh_gpib_generic_detach(board);

	if (board->dev) {
		put_device(board->dev);
		board->dev = NULL;
	}
}

static int fmh_gpib_pci_attach_impl(struct gpib_board *board,
				    const struct gpib_board_config *config,
				    unsigned int handshake_mode)
{
	struct fmh_priv *e_priv;
	struct nec7210_priv *nec_priv;
	int retval;
	struct pci_dev *pci_device;

	retval = fmh_gpib_generic_attach(board);
	if (retval)
		return retval;

	e_priv = board->private_data;
	nec_priv = &e_priv->nec7210_priv;

	// find board
	pci_device = gpib_pci_get_device(config, BOGUS_PCI_VENDOR_ID_FLUKE,
					 BOGUS_PCI_DEVICE_ID_FLUKE_BLADERUNNER, NULL);
	if (!pci_device)	{
		dev_err(board->gpib_dev, "No matching fmh_gpib_core pci device was found, attach failed.");
		return -ENODEV;
	}
	board->dev = &pci_device->dev;

	// bladerunner prototype has offset of 4 between gpib control/status registers
	nec_priv->offset = 4;

	if (pci_enable_device(pci_device)) {
		dev_err(board->dev, "error enabling pci device\n");
		return -EIO;
	}
	if (pci_request_regions(pci_device, KBUILD_MODNAME)) {
		dev_err(board->dev, "pci_request_regions failed\n");
		return -EIO;
	}
	e_priv->gpib_iomem_res = &pci_device->resource[gpib_control_status_pci_resource_index];
	e_priv->dma_port_res =	&pci_device->resource[gpib_fifo_pci_resource_index];

	nec_priv->mmiobase = ioremap(pci_resource_start(pci_device,
							gpib_control_status_pci_resource_index),
				     pci_resource_len(pci_device,
						      gpib_control_status_pci_resource_index));
	dev_dbg(board->dev, "base address for gpib control/status registers remapped to 0x%p\n",
		nec_priv->mmiobase);

	if (e_priv->dma_port_res->flags & IORESOURCE_MEM) {
		e_priv->fifo_base = ioremap(pci_resource_start(pci_device,
							       gpib_fifo_pci_resource_index),
					    pci_resource_len(pci_device,
							     gpib_fifo_pci_resource_index));
		dev_dbg(board->dev, "base address for gpib fifo registers remapped to 0x%p\n",
			e_priv->fifo_base);
	} else {
		e_priv->fifo_base = NULL;
		dev_dbg(board->dev, "hardware has no gpib fifo registers.\n");
	}

	if (pci_device->irq) {
		retval = request_irq(pci_device->irq, fmh_gpib_interrupt, IRQF_SHARED,
				     KBUILD_MODNAME, board);
		if (retval) {
			dev_err(board->dev, "cannot register interrupt handler err=%d\n", retval);
			return retval;
		}
	}
	e_priv->irq = pci_device->irq;

	e_priv->dma_burst_length = fifos_read(e_priv, FIFO_MAX_BURST_LENGTH_REG) &
		fifo_max_burst_length_mask;

	return fmh_gpib_init(e_priv, board, handshake_mode);
}

int fmh_gpib_pci_attach_holdoff_all(struct gpib_board *board,
				    const struct gpib_board_config *config)
{
	return fmh_gpib_pci_attach_impl(board, config, HR_HLDA);
}

int fmh_gpib_pci_attach_holdoff_end(struct gpib_board *board,
				    const struct gpib_board_config *config)
{
	int retval;
	struct fmh_priv *e_priv;

	retval = fmh_gpib_pci_attach_impl(board, config, HR_HLDE);
	e_priv = board->private_data;
	if (retval == 0 && e_priv && e_priv->supports_fifo_interrupts == 0) {
		dev_err(board->gpib_dev, "your fmh_gpib_core does not appear to support fifo interrupts.  Try the fmh_gpib_pci_unaccel board type instead.");
		return -EIO;
	}
	return retval;
}

void fmh_gpib_pci_detach(struct gpib_board *board)
{
	struct fmh_priv *e_priv = board->private_data;
	struct nec7210_priv *nec_priv;

	if (e_priv)	{
		nec_priv = &e_priv->nec7210_priv;

		if (e_priv->irq)
			free_irq(e_priv->irq, board);
		if (e_priv->fifo_base)
			fifos_write(e_priv, 0, FIFO_CONTROL_STATUS_REG);
		if (nec_priv->mmiobase) {
			write_byte(nec_priv, 0, ISR0_IMR0_REG);
			nec7210_board_reset(nec_priv, board);
		}
		if (e_priv->fifo_base)
			iounmap(e_priv->fifo_base);
		if (nec_priv->mmiobase)
			iounmap(nec_priv->mmiobase);
		if (e_priv->dma_port_res || e_priv->gpib_iomem_res)
			pci_release_regions(to_pci_dev(board->dev));
		if (board->dev)
			pci_dev_put(to_pci_dev(board->dev));
	}
	fmh_gpib_generic_detach(board);
}

static int fmh_gpib_platform_probe(struct platform_device *pdev)
{
	return 0;
}

static const struct of_device_id fmh_gpib_of_match[] = {
	{ .compatible = "fmhess,fmh_gpib_core"},
	{ {0} }
};
MODULE_DEVICE_TABLE(of, fmh_gpib_of_match);

static struct platform_driver fmh_gpib_platform_driver = {
	.driver = {
		.name = DRV_NAME,
		.of_match_table = fmh_gpib_of_match,
	},
	.probe = &fmh_gpib_platform_probe
};

static int fmh_gpib_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
{
	return 0;
}

static const struct pci_device_id fmh_gpib_pci_match[] = {
	{ BOGUS_PCI_VENDOR_ID_FLUKE, BOGUS_PCI_DEVICE_ID_FLUKE_BLADERUNNER, 0, 0, 0 },
	{ 0 }
};
MODULE_DEVICE_TABLE(pci, fmh_gpib_pci_match);

static struct pci_driver fmh_gpib_pci_driver = {
	.name = DRV_NAME,
	.id_table = fmh_gpib_pci_match,
	.probe = &fmh_gpib_pci_probe
};

static int __init fmh_gpib_init_module(void)
{
	int result;

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

	result = pci_register_driver(&fmh_gpib_pci_driver);
	if (result) {
		pr_err("pci_register_driver failed: error = %d\n", result);
		goto err_pci_driver;
	}

	result = gpib_register_driver(&fmh_gpib_unaccel_interface, THIS_MODULE);
	if (result) {
		pr_err("gpib_register_driver failed: error = %d\n", result);
		goto err_unaccel;
	}

	result = gpib_register_driver(&fmh_gpib_interface, THIS_MODULE);
	if (result) {
		pr_err("gpib_register_driver failed: error = %d\n", result);
		goto err_interface;
	}

	result = gpib_register_driver(&fmh_gpib_pci_unaccel_interface, THIS_MODULE);
	if (result) {
		pr_err("gpib_register_driver failed: error = %d\n", result);
		goto err_pci_unaccel;
	}

	result = gpib_register_driver(&fmh_gpib_pci_interface, THIS_MODULE);
	if (result) {
		pr_err("gpib_register_driver failed: error = %d\n", result);
		goto err_pci;
	}

	return 0;

err_pci:
	gpib_unregister_driver(&fmh_gpib_pci_unaccel_interface);
err_pci_unaccel:
	gpib_unregister_driver(&fmh_gpib_interface);
err_interface:
	gpib_unregister_driver(&fmh_gpib_unaccel_interface);
err_unaccel:
	pci_unregister_driver(&fmh_gpib_pci_driver);
err_pci_driver:
	platform_driver_unregister(&fmh_gpib_platform_driver);

	return result;
}

static void __exit fmh_gpib_exit_module(void)
{
	gpib_unregister_driver(&fmh_gpib_pci_interface);
	gpib_unregister_driver(&fmh_gpib_pci_unaccel_interface);
	gpib_unregister_driver(&fmh_gpib_unaccel_interface);
	gpib_unregister_driver(&fmh_gpib_interface);

	pci_unregister_driver(&fmh_gpib_pci_driver);
	platform_driver_unregister(&fmh_gpib_platform_driver);
}

module_init(fmh_gpib_init_module);
module_exit(fmh_gpib_exit_module);