/*

   * Simple synchronous userspace interface to SPI devices

   *
   * Copyright (C) 2006 SWAPP
   *	Andrea Paterniani <a.paterniani@swapp-eng.it>
   * Copyright (C) 2007 David Brownell (simplification, cleanup)
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.

   */
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/ioctl.h>
  #include <linux/fs.h>
  #include <linux/device.h>

  #include <linux/err.h>

  #include <linux/list.h>
  #include <linux/errno.h>
  #include <linux/mutex.h>
  #include <linux/slab.h>

  #include <linux/compat.h>

  #include <linux/of.h>
  #include <linux/of_device.h>

  #include <linux/acpi.h>

  
  #include <linux/spi/spi.h>
  #include <linux/spi/spidev.h>

  #include <linux/uaccess.h>

  
  
  /*

   * This supports access to SPI devices using normal userspace I/O calls.

   * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
   * and often mask message boundaries, full SPI support requires full duplex

   * transfers.  There are several kinds of internal message boundaries to

   * handle chipselect management and other protocol options.
   *
   * SPI has a character major number assigned.  We allocate minor numbers
   * dynamically using a bitmask.  You must use hotplug tools, such as udev
   * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
   * nodes, since there is no fixed association of minor numbers with any
   * particular SPI bus or device.
   */
  #define SPIDEV_MAJOR			153	/* assigned */
  #define N_SPI_MINORS			32	/* ... up to 256 */

  static DECLARE_BITMAP(minors, N_SPI_MINORS);

  /* Bit masks for spi_device.mode management.  Note that incorrect

   * settings for some settings can cause *lots* of trouble for other
   * devices on a shared bus:

   *

   *  - CS_HIGH ... this device will be active when it shouldn't be
   *  - 3WIRE ... when active, it won't behave as it should
   *  - NO_CS ... there will be no explicit message boundaries; this
   *	is completely incompatible with the shared bus model
   *  - READY ... transfers may proceed when they shouldn't.
   *
   * REVISIT should changing those flags be privileged?

   */
  #define SPI_MODE_MASK		(SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \

  				| SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \

  				| SPI_NO_CS | SPI_READY | SPI_TX_DUAL \
  				| SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)

  
  struct spidev_data {

  	dev_t			devt;

  	spinlock_t		spi_lock;

  	struct spi_device	*spi;
  	struct list_head	device_entry;

  	/* TX/RX buffers are NULL unless this device is open (users > 0) */

  	struct mutex		buf_lock;
  	unsigned		users;

  	u8			*tx_buffer;
  	u8			*rx_buffer;

  	u32			speed_hz;

  };
  
  static LIST_HEAD(device_list);
  static DEFINE_MUTEX(device_list_lock);
  
  static unsigned bufsiz = 4096;
  module_param(bufsiz, uint, S_IRUGO);
  MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  
  /*-------------------------------------------------------------------------*/

  static ssize_t
  spidev_sync(struct spidev_data *spidev, struct spi_message *message)
  {

  	int status;

  	struct spi_device *spi;

  
  	spin_lock_irq(&spidev->spi_lock);

  	spi = spidev->spi;
  	spin_unlock_irq(&spidev->spi_lock);
  
  	if (spi == NULL)

  		status = -ESHUTDOWN;
  	else

  		status = spi_sync(spi, message);
  
  	if (status == 0)
  		status = message->actual_length;

  	return status;
  }
  
  static inline ssize_t
  spidev_sync_write(struct spidev_data *spidev, size_t len)
  {
  	struct spi_transfer	t = {

  			.tx_buf		= spidev->tx_buffer,

  			.len		= len,

  			.speed_hz	= spidev->speed_hz,

  		};
  	struct spi_message	m;
  
  	spi_message_init(&m);
  	spi_message_add_tail(&t, &m);
  	return spidev_sync(spidev, &m);
  }
  
  static inline ssize_t
  spidev_sync_read(struct spidev_data *spidev, size_t len)
  {
  	struct spi_transfer	t = {

  			.rx_buf		= spidev->rx_buffer,

  			.len		= len,

  			.speed_hz	= spidev->speed_hz,

  		};
  	struct spi_message	m;
  
  	spi_message_init(&m);
  	spi_message_add_tail(&t, &m);
  	return spidev_sync(spidev, &m);
  }
  
  /*-------------------------------------------------------------------------*/

  /* Read-only message with current device setup */
  static ssize_t
  spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
  {
  	struct spidev_data	*spidev;

  	ssize_t			status = 0;
  
  	/* chipselect only toggles at start or end of operation */
  	if (count > bufsiz)
  		return -EMSGSIZE;
  
  	spidev = filp->private_data;

  
  	mutex_lock(&spidev->buf_lock);

  	status = spidev_sync_read(spidev, count);

  	if (status > 0) {

  		unsigned long	missing;

  		missing = copy_to_user(buf, spidev->rx_buffer, status);

  		if (missing == status)

  			status = -EFAULT;
  		else

  			status = status - missing;

  	}
  	mutex_unlock(&spidev->buf_lock);
  
  	return status;
  }
  
  /* Write-only message with current device setup */
  static ssize_t
  spidev_write(struct file *filp, const char __user *buf,
  		size_t count, loff_t *f_pos)
  {
  	struct spidev_data	*spidev;

  	ssize_t			status = 0;
  	unsigned long		missing;
  
  	/* chipselect only toggles at start or end of operation */
  	if (count > bufsiz)
  		return -EMSGSIZE;
  
  	spidev = filp->private_data;

  
  	mutex_lock(&spidev->buf_lock);

  	missing = copy_from_user(spidev->tx_buffer, buf, count);

  	if (missing == 0)

  		status = spidev_sync_write(spidev, count);

  	else

  		status = -EFAULT;
  	mutex_unlock(&spidev->buf_lock);
  
  	return status;
  }
  
  static int spidev_message(struct spidev_data *spidev,
  		struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
  {
  	struct spi_message	msg;
  	struct spi_transfer	*k_xfers;
  	struct spi_transfer	*k_tmp;
  	struct spi_ioc_transfer *u_tmp;

  	unsigned		n, total, tx_total, rx_total;

  	u8			*tx_buf, *rx_buf;

  	int			status = -EFAULT;
  
  	spi_message_init(&msg);
  	k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
  	if (k_xfers == NULL)
  		return -ENOMEM;
  
  	/* Construct spi_message, copying any tx data to bounce buffer.
  	 * We walk the array of user-provided transfers, using each one
  	 * to initialize a kernel version of the same transfer.
  	 */

  	tx_buf = spidev->tx_buffer;
  	rx_buf = spidev->rx_buffer;

  	total = 0;

  	tx_total = 0;
  	rx_total = 0;

  	for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
  			n;
  			n--, k_tmp++, u_tmp++) {
  		k_tmp->len = u_tmp->len;

  		total += k_tmp->len;

  		/* Since the function returns the total length of transfers
  		 * on success, restrict the total to positive int values to

  		 * avoid the return value looking like an error.  Also check
  		 * each transfer length to avoid arithmetic overflow.

  		 */

  		if (total > INT_MAX || k_tmp->len > INT_MAX) {

  			status = -EMSGSIZE;
  			goto done;
  		}

  		if (u_tmp->rx_buf) {

  			/* this transfer needs space in RX bounce buffer */
  			rx_total += k_tmp->len;
  			if (rx_total > bufsiz) {
  				status = -EMSGSIZE;
  				goto done;
  			}

  			k_tmp->rx_buf = rx_buf;

  			rx_buf += k_tmp->len;

  		}
  		if (u_tmp->tx_buf) {

  			/* this transfer needs space in TX bounce buffer */
  			tx_total += k_tmp->len;
  			if (tx_total > bufsiz) {
  				status = -EMSGSIZE;
  				goto done;
  			}

  			k_tmp->tx_buf = tx_buf;
  			if (copy_from_user(tx_buf, (const u8 __user *)

  						(uintptr_t) u_tmp->tx_buf,

  					u_tmp->len))
  				goto done;

  			tx_buf += k_tmp->len;

  		}

  
  		k_tmp->cs_change = !!u_tmp->cs_change;

  		k_tmp->tx_nbits = u_tmp->tx_nbits;
  		k_tmp->rx_nbits = u_tmp->rx_nbits;

  		k_tmp->bits_per_word = u_tmp->bits_per_word;
  		k_tmp->delay_usecs = u_tmp->delay_usecs;
  		k_tmp->speed_hz = u_tmp->speed_hz;

  		if (!k_tmp->speed_hz)
  			k_tmp->speed_hz = spidev->speed_hz;

  #ifdef VERBOSE

  		dev_dbg(&spidev->spi->dev,

  			"  xfer len %u %s%s%s%dbits %u usec %uHz
  ",

  			u_tmp->len,
  			u_tmp->rx_buf ? "rx " : "",
  			u_tmp->tx_buf ? "tx " : "",
  			u_tmp->cs_change ? "cs " : "",

  			u_tmp->bits_per_word ? : spidev->spi->bits_per_word,

  			u_tmp->delay_usecs,

  			u_tmp->speed_hz ? : spidev->spi->max_speed_hz);

  #endif
  		spi_message_add_tail(k_tmp, &msg);
  	}

  	status = spidev_sync(spidev, &msg);

  	if (status < 0)
  		goto done;
  
  	/* copy any rx data out of bounce buffer */

  	rx_buf = spidev->rx_buffer;

  	for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
  		if (u_tmp->rx_buf) {

  			if (copy_to_user((u8 __user *)

  					(uintptr_t) u_tmp->rx_buf, rx_buf,

  					u_tmp->len)) {
  				status = -EFAULT;
  				goto done;
  			}

  			rx_buf += u_tmp->len;

  		}

  	}
  	status = total;
  
  done:

  	kfree(k_xfers);
  	return status;
  }

  static struct spi_ioc_transfer *
  spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
  		unsigned *n_ioc)
  {

  	u32	tmp;
  
  	/* Check type, command number and direction */
  	if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
  			|| _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
  			|| _IOC_DIR(cmd) != _IOC_WRITE)
  		return ERR_PTR(-ENOTTY);
  
  	tmp = _IOC_SIZE(cmd);
  	if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
  		return ERR_PTR(-EINVAL);
  	*n_ioc = tmp / sizeof(struct spi_ioc_transfer);
  	if (*n_ioc == 0)
  		return NULL;
  
  	/* copy into scratch area */

  	return memdup_user(u_ioc, tmp);

  }

  static long
  spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)

  {

  	int			retval = 0;
  	struct spidev_data	*spidev;
  	struct spi_device	*spi;
  	u32			tmp;
  	unsigned		n_ioc;
  	struct spi_ioc_transfer	*ioc;
  
  	/* Check type and command number */
  	if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
  		return -ENOTTY;

  	/* guard against device removal before, or while,
  	 * we issue this ioctl.
  	 */

  	spidev = filp->private_data;

  	spin_lock_irq(&spidev->spi_lock);
  	spi = spi_dev_get(spidev->spi);
  	spin_unlock_irq(&spidev->spi_lock);
  
  	if (spi == NULL)
  		return -ESHUTDOWN;

  	/* use the buffer lock here for triple duty:
  	 *  - prevent I/O (from us) so calling spi_setup() is safe;
  	 *  - prevent concurrent SPI_IOC_WR_* from morphing
  	 *    data fields while SPI_IOC_RD_* reads them;
  	 *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
  	 */
  	mutex_lock(&spidev->buf_lock);

  	switch (cmd) {
  	/* read requests */
  	case SPI_IOC_RD_MODE:

  		retval = put_user(spi->mode & SPI_MODE_MASK,

  					(__u8 __user *)arg);
  		break;

  	case SPI_IOC_RD_MODE32:

  		retval = put_user(spi->mode & SPI_MODE_MASK,

  					(__u32 __user *)arg);
  		break;

  	case SPI_IOC_RD_LSB_FIRST:

  		retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,

  					(__u8 __user *)arg);
  		break;
  	case SPI_IOC_RD_BITS_PER_WORD:

  		retval = put_user(spi->bits_per_word, (__u8 __user *)arg);

  		break;
  	case SPI_IOC_RD_MAX_SPEED_HZ:

  		retval = put_user(spidev->speed_hz, (__u32 __user *)arg);

  		break;
  
  	/* write requests */
  	case SPI_IOC_WR_MODE:

  	case SPI_IOC_WR_MODE32:
  		if (cmd == SPI_IOC_WR_MODE)

  			retval = get_user(tmp, (u8 __user *)arg);

  		else

  			retval = get_user(tmp, (u32 __user *)arg);

  		if (retval == 0) {

  			u32	save = spi->mode;

  
  			if (tmp & ~SPI_MODE_MASK) {
  				retval = -EINVAL;
  				break;
  			}
  
  			tmp |= spi->mode & ~SPI_MODE_MASK;

  			spi->mode = (u16)tmp;

  			retval = spi_setup(spi);
  			if (retval < 0)
  				spi->mode = save;
  			else

  				dev_dbg(&spi->dev, "spi mode %x
  ", tmp);

  		}
  		break;
  	case SPI_IOC_WR_LSB_FIRST:

  		retval = get_user(tmp, (__u8 __user *)arg);

  		if (retval == 0) {

  			u32	save = spi->mode;

  
  			if (tmp)
  				spi->mode |= SPI_LSB_FIRST;
  			else
  				spi->mode &= ~SPI_LSB_FIRST;
  			retval = spi_setup(spi);
  			if (retval < 0)
  				spi->mode = save;
  			else
  				dev_dbg(&spi->dev, "%csb first
  ",
  						tmp ? 'l' : 'm');
  		}
  		break;
  	case SPI_IOC_WR_BITS_PER_WORD:

  		retval = get_user(tmp, (__u8 __user *)arg);

  		if (retval == 0) {
  			u8	save = spi->bits_per_word;
  
  			spi->bits_per_word = tmp;
  			retval = spi_setup(spi);
  			if (retval < 0)
  				spi->bits_per_word = save;
  			else
  				dev_dbg(&spi->dev, "%d bits per word
  ", tmp);
  		}
  		break;
  	case SPI_IOC_WR_MAX_SPEED_HZ:

  		retval = get_user(tmp, (__u32 __user *)arg);

  		if (retval == 0) {
  			u32	save = spi->max_speed_hz;
  
  			spi->max_speed_hz = tmp;
  			retval = spi_setup(spi);

  			if (retval >= 0)
  				spidev->speed_hz = tmp;

  			else
  				dev_dbg(&spi->dev, "%d Hz (max)
  ", tmp);

  			spi->max_speed_hz = save;

  		}
  		break;
  
  	default:
  		/* segmented and/or full-duplex I/O request */

  		/* Check message and copy into scratch area */
  		ioc = spidev_get_ioc_message(cmd,
  				(struct spi_ioc_transfer __user *)arg, &n_ioc);
  		if (IS_ERR(ioc)) {
  			retval = PTR_ERR(ioc);

  			break;
  		}

  		if (!ioc)
  			break;	/* n_ioc is also 0 */

  
  		/* translate to spi_message, execute */
  		retval = spidev_message(spidev, ioc, n_ioc);
  		kfree(ioc);
  		break;
  	}

  
  	mutex_unlock(&spidev->buf_lock);

  	spi_dev_put(spi);

  	return retval;
  }

  #ifdef CONFIG_COMPAT
  static long

  spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
  		unsigned long arg)
  {
  	struct spi_ioc_transfer __user	*u_ioc;
  	int				retval = 0;
  	struct spidev_data		*spidev;
  	struct spi_device		*spi;
  	unsigned			n_ioc, n;
  	struct spi_ioc_transfer		*ioc;
  
  	u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);

  
  	/* guard against device removal before, or while,
  	 * we issue this ioctl.
  	 */
  	spidev = filp->private_data;
  	spin_lock_irq(&spidev->spi_lock);
  	spi = spi_dev_get(spidev->spi);
  	spin_unlock_irq(&spidev->spi_lock);
  
  	if (spi == NULL)
  		return -ESHUTDOWN;
  
  	/* SPI_IOC_MESSAGE needs the buffer locked "normally" */
  	mutex_lock(&spidev->buf_lock);
  
  	/* Check message and copy into scratch area */
  	ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
  	if (IS_ERR(ioc)) {
  		retval = PTR_ERR(ioc);
  		goto done;
  	}
  	if (!ioc)
  		goto done;	/* n_ioc is also 0 */
  
  	/* Convert buffer pointers */
  	for (n = 0; n < n_ioc; n++) {
  		ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
  		ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
  	}
  
  	/* translate to spi_message, execute */
  	retval = spidev_message(spidev, ioc, n_ioc);
  	kfree(ioc);
  
  done:
  	mutex_unlock(&spidev->buf_lock);
  	spi_dev_put(spi);
  	return retval;
  }
  
  static long

  spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
  {

  	if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
  			&& _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
  			&& _IOC_DIR(cmd) == _IOC_WRITE)
  		return spidev_compat_ioc_message(filp, cmd, arg);

  	return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
  }
  #else
  #define spidev_compat_ioctl NULL
  #endif /* CONFIG_COMPAT */

  static int spidev_open(struct inode *inode, struct file *filp)
  {
  	struct spidev_data	*spidev;
  	int			status = -ENXIO;
  
  	mutex_lock(&device_list_lock);
  
  	list_for_each_entry(spidev, &device_list, device_entry) {

  		if (spidev->devt == inode->i_rdev) {

  			status = 0;
  			break;
  		}
  	}

  
  	if (status) {
  		pr_debug("spidev: nothing for minor %d
  ", iminor(inode));
  		goto err_find_dev;
  	}
  
  	if (!spidev->tx_buffer) {
  		spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
  		if (!spidev->tx_buffer) {

  			dev_dbg(&spidev->spi->dev, "open/ENOMEM
  ");
  			status = -ENOMEM;

  			goto err_find_dev;

  		}

  	}

  
  	if (!spidev->rx_buffer) {
  		spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
  		if (!spidev->rx_buffer) {
  			dev_dbg(&spidev->spi->dev, "open/ENOMEM
  ");
  			status = -ENOMEM;
  			goto err_alloc_rx_buf;

  		}

  	}
  
  	spidev->users++;
  	filp->private_data = spidev;
  	nonseekable_open(inode, filp);

  
  	mutex_unlock(&device_list_lock);

  	return 0;
  
  err_alloc_rx_buf:
  	kfree(spidev->tx_buffer);
  	spidev->tx_buffer = NULL;
  err_find_dev:
  	mutex_unlock(&device_list_lock);

  	return status;
  }
  
  static int spidev_release(struct inode *inode, struct file *filp)
  {
  	struct spidev_data	*spidev;

  
  	mutex_lock(&device_list_lock);
  	spidev = filp->private_data;
  	filp->private_data = NULL;

  
  	/* last close? */

  	spidev->users--;
  	if (!spidev->users) {

  		int		dofree;

  		kfree(spidev->tx_buffer);
  		spidev->tx_buffer = NULL;
  
  		kfree(spidev->rx_buffer);
  		spidev->rx_buffer = NULL;

  		spin_lock_irq(&spidev->spi_lock);

  		if (spidev->spi)
  			spidev->speed_hz = spidev->spi->max_speed_hz;

  		/* ... after we unbound from the underlying device? */

  		dofree = (spidev->spi == NULL);
  		spin_unlock_irq(&spidev->spi_lock);
  
  		if (dofree)
  			kfree(spidev);

  	}
  	mutex_unlock(&device_list_lock);

  	return 0;

  }

  static const struct file_operations spidev_fops = {

  	.owner =	THIS_MODULE,
  	/* REVISIT switch to aio primitives, so that userspace
  	 * gets more complete API coverage.  It'll simplify things
  	 * too, except for the locking.
  	 */
  	.write =	spidev_write,
  	.read =		spidev_read,

  	.unlocked_ioctl = spidev_ioctl,

  	.compat_ioctl = spidev_compat_ioctl,

  	.open =		spidev_open,
  	.release =	spidev_release,

  	.llseek =	no_llseek,

  };
  
  /*-------------------------------------------------------------------------*/
  
  /* The main reason to have this class is to make mdev/udev create the
   * /dev/spidevB.C character device nodes exposing our userspace API.
   * It also simplifies memory management.
   */

  static struct class *spidev_class;

  #ifdef CONFIG_OF
  static const struct of_device_id spidev_dt_ids[] = {
  	{ .compatible = "rohm,dh2228fv" },

  	{ .compatible = "lineartechnology,ltc2488" },

  	{ .compatible = "ge,achc" },

  	{ .compatible = "semtech,sx1301" },

  	{},
  };
  MODULE_DEVICE_TABLE(of, spidev_dt_ids);
  #endif

  #ifdef CONFIG_ACPI
  
  /* Dummy SPI devices not to be used in production systems */
  #define SPIDEV_ACPI_DUMMY	1
  
  static const struct acpi_device_id spidev_acpi_ids[] = {
  	/*
  	 * The ACPI SPT000* devices are only meant for development and
  	 * testing. Systems used in production should have a proper ACPI
  	 * description of the connected peripheral and they should also use
  	 * a proper driver instead of poking directly to the SPI bus.
  	 */
  	{ "SPT0001", SPIDEV_ACPI_DUMMY },
  	{ "SPT0002", SPIDEV_ACPI_DUMMY },
  	{ "SPT0003", SPIDEV_ACPI_DUMMY },
  	{},
  };
  MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);
  
  static void spidev_probe_acpi(struct spi_device *spi)
  {
  	const struct acpi_device_id *id;
  
  	if (!has_acpi_companion(&spi->dev))
  		return;
  
  	id = acpi_match_device(spidev_acpi_ids, &spi->dev);
  	if (WARN_ON(!id))
  		return;
  
  	if (id->driver_data == SPIDEV_ACPI_DUMMY)
  		dev_warn(&spi->dev, "do not use this driver in production systems!
  ");
  }
  #else
  static inline void spidev_probe_acpi(struct spi_device *spi) {}
  #endif

  /*-------------------------------------------------------------------------*/

  static int spidev_probe(struct spi_device *spi)

  {
  	struct spidev_data	*spidev;
  	int			status;
  	unsigned long		minor;

  	/*
  	 * spidev should never be referenced in DT without a specific

  	 * compatible string, it is a Linux implementation thing

  	 * rather than a description of the hardware.
  	 */
  	if (spi->dev.of_node && !of_match_device(spidev_dt_ids, &spi->dev)) {
  		dev_err(&spi->dev, "buggy DT: spidev listed directly in DT
  ");
  		WARN_ON(spi->dev.of_node &&
  			!of_match_device(spidev_dt_ids, &spi->dev));
  	}

  	spidev_probe_acpi(spi);

  	/* Allocate driver data */
  	spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
  	if (!spidev)
  		return -ENOMEM;
  
  	/* Initialize the driver data */
  	spidev->spi = spi;

  	spin_lock_init(&spidev->spi_lock);

  	mutex_init(&spidev->buf_lock);
  
  	INIT_LIST_HEAD(&spidev->device_entry);
  
  	/* If we can allocate a minor number, hook up this device.
  	 * Reusing minors is fine so long as udev or mdev is working.
  	 */
  	mutex_lock(&device_list_lock);

  	minor = find_first_zero_bit(minors, N_SPI_MINORS);

  	if (minor < N_SPI_MINORS) {

  		struct device *dev;
  
  		spidev->devt = MKDEV(SPIDEV_MAJOR, minor);

  		dev = device_create(spidev_class, &spi->dev, spidev->devt,
  				    spidev, "spidev%d.%d",
  				    spi->master->bus_num, spi->chip_select);

  		status = PTR_ERR_OR_ZERO(dev);

  	} else {
  		dev_dbg(&spi->dev, "no minor number available!
  ");
  		status = -ENODEV;
  	}
  	if (status == 0) {
  		set_bit(minor, minors);

  		list_add(&spidev->device_entry, &device_list);
  	}
  	mutex_unlock(&device_list_lock);

  	spidev->speed_hz = spi->max_speed_hz;

  	if (status == 0)
  		spi_set_drvdata(spi, spidev);
  	else

  		kfree(spidev);
  
  	return status;
  }

  static int spidev_remove(struct spi_device *spi)

  {

  	struct spidev_data	*spidev = spi_get_drvdata(spi);

  	/* make sure ops on existing fds can abort cleanly */
  	spin_lock_irq(&spidev->spi_lock);
  	spidev->spi = NULL;
  	spin_unlock_irq(&spidev->spi_lock);

  	/* prevent new opens */
  	mutex_lock(&device_list_lock);

  	list_del(&spidev->device_entry);

  	device_destroy(spidev_class, spidev->devt);
  	clear_bit(MINOR(spidev->devt), minors);
  	if (spidev->users == 0)
  		kfree(spidev);

  	mutex_unlock(&device_list_lock);
  
  	return 0;
  }

  static struct spi_driver spidev_spi_driver = {

  	.driver = {
  		.name =		"spidev",

  		.of_match_table = of_match_ptr(spidev_dt_ids),

  		.acpi_match_table = ACPI_PTR(spidev_acpi_ids),

  	},
  	.probe =	spidev_probe,

  	.remove =	spidev_remove,

  
  	/* NOTE:  suspend/resume methods are not necessary here.
  	 * We don't do anything except pass the requests to/from
  	 * the underlying controller.  The refrigerator handles
  	 * most issues; the controller driver handles the rest.
  	 */
  };
  
  /*-------------------------------------------------------------------------*/
  
  static int __init spidev_init(void)
  {
  	int status;
  
  	/* Claim our 256 reserved device numbers.  Then register a class
  	 * that will key udev/mdev to add/remove /dev nodes.  Last, register
  	 * the driver which manages those device numbers.
  	 */
  	BUILD_BUG_ON(N_SPI_MINORS > 256);
  	status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
  	if (status < 0)
  		return status;

  	spidev_class = class_create(THIS_MODULE, "spidev");
  	if (IS_ERR(spidev_class)) {

  		unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);

  		return PTR_ERR(spidev_class);

  	}

  	status = spi_register_driver(&spidev_spi_driver);

  	if (status < 0) {

  		class_destroy(spidev_class);

  		unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);

  	}
  	return status;
  }
  module_init(spidev_init);
  
  static void __exit spidev_exit(void)
  {

  	spi_unregister_driver(&spidev_spi_driver);

  	class_destroy(spidev_class);

  	unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);

  }
  module_exit(spidev_exit);
  
  MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
  MODULE_DESCRIPTION("User mode SPI device interface");
  MODULE_LICENSE("GPL");

  MODULE_ALIAS("spi:spidev");