// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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)
 */

#include <linux/init.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/module.h>
#include <linux/mutex.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/compat.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);

static_assert(N_SPI_MINORS > 0 && N_SPI_MINORS <= 256);

/* 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_MODE_X_MASK | SPI_CS_HIGH \
                                | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
                                | SPI_NO_CS | SPI_READY | SPI_TX_DUAL \
                                | SPI_TX_QUAD | SPI_TX_OCTAL | SPI_RX_DUAL \
                                | SPI_RX_QUAD | SPI_RX_OCTAL \
                                | SPI_RX_CPHA_FLIP | SPI_3WIRE_HIZ \
                                | SPI_MOSI_IDLE_LOW)

struct spidev_data {
        dev_t                   devt;
        struct mutex            spi_lock;
        struct spi_device       *spi;
        struct list_head        device_entry;

        /* TX/RX buffers are NULL unless this device is open (users > 0) */
        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_unlocked(struct spi_device *spi, struct spi_message *message)
{
        ssize_t status;

        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_unlocked(spidev->spi, &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_unlocked(spidev->spi, &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 = -ESHUTDOWN;

        /* chipselect only toggles at start or end of operation */
        if (count > bufsiz)
                return -EMSGSIZE;

        spidev = filp->private_data;

        mutex_lock(&spidev->spi_lock);

        if (spidev->spi == NULL)
                goto err_spi_removed;

        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;
        }

err_spi_removed:
        mutex_unlock(&spidev->spi_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 = -ESHUTDOWN;
        unsigned long           missing;

        /* chipselect only toggles at start or end of operation */
        if (count > bufsiz)
                return -EMSGSIZE;

        spidev = filp->private_data;

        mutex_lock(&spidev->spi_lock);

        if (spidev->spi == NULL)
                goto err_spi_removed;

        missing = copy_from_user(spidev->tx_buffer, buf, count);
        if (missing == 0)
                status = spidev_sync_write(spidev, count);
        else
                status = -EFAULT;

err_spi_removed:
        mutex_unlock(&spidev->spi_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 = kzalloc_objs(*k_tmp, n_xfers);
        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++) {
                /* Ensure that also following allocations from rx_buf/tx_buf will meet
                 * DMA alignment requirements.
                 */
                unsigned int len_aligned = ALIGN(u_tmp->len, ARCH_DMA_MINALIGN);

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

                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.value = u_tmp->delay_usecs;
                k_tmp->delay.unit = SPI_DELAY_UNIT_USECS;
                k_tmp->speed_hz = u_tmp->speed_hz;
                k_tmp->word_delay.value = u_tmp->word_delay_usecs;
                k_tmp->word_delay.unit = SPI_DELAY_UNIT_USECS;
                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 %u usec %uHz\n",
                        k_tmp->len,
                        k_tmp->rx_buf ? "rx " : "",
                        k_tmp->tx_buf ? "tx " : "",
                        k_tmp->cs_change ? "cs " : "",
                        k_tmp->bits_per_word ? : spidev->spi->bits_per_word,
                        k_tmp->delay.value,
                        k_tmp->word_delay.value,
                        k_tmp->speed_hz ? : spidev->spi->max_speed_hz);
#endif
                spi_message_add_tail(k_tmp, &msg);
        }

        status = spidev_sync_unlocked(spidev->spi, &msg);
        if (status < 0)
                goto done;

        /* copy any rx data out of bounce buffer */
        for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
                        n;
                        n--, k_tmp++, u_tmp++) {
                if (u_tmp->rx_buf) {
                        if (copy_to_user((u8 __user *)
                                        (uintptr_t) u_tmp->rx_buf, k_tmp->rx_buf,
                                        u_tmp->len)) {
                                status = -EFAULT;
                                goto done;
                        }
                }
        }
        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;
        struct spi_controller   *ctlr;
        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;
        mutex_lock(&spidev->spi_lock);
        spi = spi_dev_get(spidev->spi);
        if (spi == NULL) {
                mutex_unlock(&spidev->spi_lock);
                return -ESHUTDOWN;
        }

        ctlr = spi->controller;

        switch (cmd) {
        /* read requests */
        case SPI_IOC_RD_MODE:
        case SPI_IOC_RD_MODE32:
                tmp = spi->mode & SPI_MODE_MASK;

                if (ctlr->use_gpio_descriptors && spi_get_csgpiod(spi, 0))
                        tmp &= ~SPI_CS_HIGH;

                if (cmd == SPI_IOC_RD_MODE)
                        retval = put_user(tmp, (__u8 __user *)arg);
                else
                        retval = put_user(tmp, (__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;
                        }

                        if (ctlr->use_gpio_descriptors && spi_get_csgpiod(spi, 0))
                                tmp |= SPI_CS_HIGH;

                        tmp |= spi->mode & ~SPI_MODE_MASK;
                        spi->mode = tmp & SPI_MODE_USER_MASK;
                        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: {
                u32 save;

                retval = get_user(tmp, (__u32 __user *)arg);
                if (retval)
                        break;
                if (tmp == 0) {
                        retval = -EINVAL;
                        break;
                }

                save = spi->max_speed_hz;

                spi->max_speed_hz = tmp;
                retval = spi_setup(spi);
                if (retval == 0) {
                        spidev->speed_hz = tmp;
                        dev_dbg(&spi->dev, "%d Hz (max)\n", spidev->speed_hz);
                }

                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;
        }

        spi_dev_put(spi);
        mutex_unlock(&spidev->spi_lock);
        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;
        mutex_lock(&spidev->spi_lock);
        spi = spi_dev_get(spidev->spi);
        if (spi == NULL) {
                mutex_unlock(&spidev->spi_lock);
                return -ESHUTDOWN;
        }

        /* 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:
        spi_dev_put(spi);
        mutex_unlock(&spidev->spi_lock);
        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 = NULL, *iter;
        int                     status = -ENXIO;

        mutex_lock(&device_list_lock);

        list_for_each_entry(iter, &device_list, device_entry) {
                if (iter->devt == inode->i_rdev) {
                        status = 0;
                        spidev = iter;
                        break;
                }
        }

        if (!spidev) {
                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) {
                        status = -ENOMEM;
                        goto err_find_dev;
                }
        }

        if (!spidev->rx_buffer) {
                spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
                if (!spidev->rx_buffer) {
                        status = -ENOMEM;
                        goto err_alloc_rx_buf;
                }
        }

        spidev->users++;
        filp->private_data = spidev;
        stream_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;
        int                     dofree;

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

        mutex_lock(&spidev->spi_lock);
        /* ... after we unbound from the underlying device? */
        dofree = (spidev->spi == NULL);
        mutex_unlock(&spidev->spi_lock);

        /* last close? */
        spidev->users--;
        if (!spidev->users) {

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

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

                if (dofree)
                        kfree(spidev);
                else
                        spidev->speed_hz = spidev->spi->max_speed_hz;
        }
#ifdef CONFIG_SPI_SLAVE
        if (!dofree)
                spi_target_abort(spidev->spi);
#endif
        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,
};

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

/* 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 const struct class spidev_class = {
        .name = "spidev",
};

/*
 * The spi device ids are expected to match the device names of the
 * spidev_dt_ids array below. Both arrays are kept in the same ordering.
 */
static const struct spi_device_id spidev_spi_ids[] = {
        { .name = /* abb */ "spi-sensor" },
        { .name = /* arduino */ "unoq-mcu" },
        { .name = /* cisco */ "spi-petra" },
        { .name = /* dh */ "dhcom-board" },
        { .name = /* elgin */ "jg10309-01" },
        { .name = /* gocontroll */ "moduline-module-slot"},
        { .name = /* lineartechnology */ "ltc2488" },
        { .name = /* lwn */ "bk4" },
        { .name = /* lwn */ "bk4-spi" },
        { .name = /* menlo */ "m53cpld" },
        { .name = /* micron */ "spi-authenta" },
        { .name = /* rohm */ "bh2228fv" },
        { .name = /* rohm */ "dh2228fv" },
        { .name = /* semtech */ "sx1301" },
        { .name = /* silabs */ "em3581" },
        { .name = /* silabs */ "si3210" },
        {},
};
MODULE_DEVICE_TABLE(spi, spidev_spi_ids);

/*
 * 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.
 */
static int spidev_of_check(struct device *dev)
{
        if (device_property_match_string(dev, "compatible", "spidev") < 0)
                return 0;

        dev_err(dev, "spidev listed directly in DT is not supported\n");
        return -EINVAL;
}

static const struct of_device_id spidev_dt_ids[] = {
        { .compatible = "abb,spi-sensor", .data = &spidev_of_check },
        { .compatible = "arduino,unoq-mcu", .data = &spidev_of_check },
        { .compatible = "cisco,spi-petra", .data = &spidev_of_check },
        { .compatible = "dh,dhcom-board", .data = &spidev_of_check },
        { .compatible = "elgin,jg10309-01", .data = &spidev_of_check },
        { .compatible = "gocontroll,moduline-module-slot", .data = &spidev_of_check},
        { .compatible = "lineartechnology,ltc2488", .data = &spidev_of_check },
        { .compatible = "lwn,bk4", .data = &spidev_of_check },
        { .compatible = "lwn,bk4-spi", .data = &spidev_of_check },
        { .compatible = "menlo,m53cpld", .data = &spidev_of_check },
        { .compatible = "micron,spi-authenta", .data = &spidev_of_check },
        { .compatible = "rohm,bh2228fv", .data = &spidev_of_check },
        { .compatible = "rohm,dh2228fv", .data = &spidev_of_check },
        { .compatible = "semtech,sx1301", .data = &spidev_of_check },
        { .compatible = "silabs,em3581", .data = &spidev_of_check },
        { .compatible = "silabs,si3210", .data = &spidev_of_check },
        {},
};
MODULE_DEVICE_TABLE(of, spidev_dt_ids);

/* Dummy SPI devices not to be used in production systems */
static int spidev_acpi_check(struct device *dev)
{
        dev_warn(dev, "do not use this driver in production systems!\n");
        return 0;
}

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", (kernel_ulong_t)&spidev_acpi_check },
        { "SPT0002", (kernel_ulong_t)&spidev_acpi_check },
        { "SPT0003", (kernel_ulong_t)&spidev_acpi_check },
        {},
};
MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);

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

static int spidev_probe(struct spi_device *spi)
{
        int (*match)(struct device *dev);
        struct spidev_data      *spidev;
        int                     status;
        unsigned long           minor;

        match = device_get_match_data(&spi->dev);
        if (match) {
                status = match(&spi->dev);
                if (status)
                        return status;
        }

        /* Allocate driver data */
        spidev = kzalloc_obj(*spidev);
        if (!spidev)
                return -ENOMEM;

        /* Initialize the driver data */
        spidev->spi = spi;
        mutex_init(&spidev->spi_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->controller->bus_num, spi_get_chipselect(spi, 0));
                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 void spidev_remove(struct spi_device *spi)
{
        struct spidev_data      *spidev = spi_get_drvdata(spi);

        /* prevent new opens */
        mutex_lock(&device_list_lock);
        /* make sure ops on existing fds can abort cleanly */
        mutex_lock(&spidev->spi_lock);
        spidev->spi = NULL;
        mutex_unlock(&spidev->spi_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);
}

static struct spi_driver spidev_spi_driver = {
        .driver = {
                .name =         "spidev",
                .of_match_table = spidev_dt_ids,
                .acpi_match_table = spidev_acpi_ids,
        },
        .probe =        spidev_probe,
        .remove =       spidev_remove,
        .id_table =     spidev_spi_ids,

        /* 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.
         */
        status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
        if (status < 0)
                return status;

        status = class_register(&spidev_class);
        if (status) {
                unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
                return status;
        }

        status = spi_register_driver(&spidev_spi_driver);
        if (status < 0) {
                class_unregister(&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_unregister(&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");