drivers/spi/spidev.c

// 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/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_TX_OCTAL | SPI_RX_DUAL | SPI_RX_QUAD | SPI_RX_OCTAL)

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;

    /* 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;
    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++) {
        /* Ensure that also following allocations from rx_buf/tx_buf will meet
         * DMA alignment requirements.
         */
        unsigned int len_aligned = ALIGN(u_tmp->len, ARCH_KMALLOC_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(spidev, &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;
    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) {
                struct spi_controller *ctlr = spi->controller;
                u32 save = spi->mode;

                if (tmp & ~SPI_MODE_MASK) {
                    retval = -EINVAL;
                    break;
                }

                if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods && ctlr->cs_gpiods[spi->chip_select]) {
                    tmp |= SPI_CS_HIGH;
                }

                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;
                    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;
    }

    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;
    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;

    spin_lock_irq(&spidev->spi_lock);
    /* ... after we unbound from the underlying device? */
    dofree = (spidev->spi == NULL);
    spin_unlock_irq(&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_slave_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,
    .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"},
    {.compatible = "lwn,bk4"},
    {.compatible = "dh,dhcom-board"},
    {.compatible = "menlo,m53cpld"},
    {.compatible = "rockchip,spidev"},
    {},
};
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.
     */
    WARN(spi->dev.of_node && of_device_is_compatible(spi->dev.of_node, "spidev"),
         "%pOF: buggy DT: spidev listed directly in DT\n", spi->dev.of_node);

    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);

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

    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");