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32 results

intel_idle.c

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  • spidev.c 21.66 KiB
    /*
     * 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)
    {
    	DECLARE_COMPLETION_ONSTACK(done);
    	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\n",
    			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)
    {
    	struct spi_ioc_transfer	*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 */
    	ioc = kmalloc(tmp, GFP_KERNEL);
    	if (!ioc)
    		return ERR_PTR(-ENOMEM);
    	if (__copy_from_user(ioc, u_ioc, tmp)) {
    		kfree(ioc);
    		return ERR_PTR(-EFAULT);
    	}
    	return ioc;
    }
    
    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\n", 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\n",
    						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\n", 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)\n", 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\n", 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\n");
    			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\n");
    			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!\n");
    }
    #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\n");
    		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!\n");
    		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");