spi: fix refcount-related spidev oops-on-rmmod

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / spi / spidev.c

/*
 * spidev.c -- 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

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

#include <asm/uaccess.h>


/*
 * This supports acccess 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 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 unsigned long    minors[N_SPI_MINORS / BITS_PER_LONG];


/* Bit masks for spi_device.mode management.  Note that incorrect
 * settings for CS_HIGH and 3WIRE can cause *lots* of trouble for other
 * devices on a shared bus:  CS_HIGH, because this device will be
 * active when it shouldn't be;  3WIRE, because when active it won't
 * behave as it should.
 *
 * REVISIT should changing those two modes be privileged?
 */
#define SPI_MODE_MASK           (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
                                | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP)

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

        /* buffer is NULL unless this device is open (users > 0) */
        struct mutex            buf_lock;
        unsigned                users;
        u8                      *buffer;
};

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");

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

/*
 * We can't use the standard synchronous wrappers for file I/O; we
 * need to protect against async removal of the underlying spi_device.
 */
static void spidev_complete(void *arg)
{
        complete(arg);
}

static ssize_t
spidev_sync(struct spidev_data *spidev, struct spi_message *message)
{
        DECLARE_COMPLETION_ONSTACK(done);
        int status;

        message->complete = spidev_complete;
        message->context = &done;

        spin_lock_irq(&spidev->spi_lock);
        if (spidev->spi == NULL)
                status = -ESHUTDOWN;
        else
                status = spi_async(spidev->spi, message);
        spin_unlock_irq(&spidev->spi_lock);

        if (status == 0) {
                wait_for_completion(&done);
                status = message->status;
                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->buffer,
                        .len            = len,
                };
        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->buffer,
                        .len            = len,
                };
        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->buffer, count);
                if (count && missing == count)
                        status = -EFAULT;
                else
                        status = count - 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->buffer, buf, count);
        if (missing == 0) {
                status = spidev_sync_write(spidev, count);
                if (status == 0)
                        status = 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;
        u8                      *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.
         */
        mutex_lock(&spidev->buf_lock);
        buf = spidev->buffer;
        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;
                if (total > bufsiz) {
                        status = -EMSGSIZE;
                        goto done;
                }

                if (u_tmp->rx_buf) {
                        k_tmp->rx_buf = buf;
                        if (!access_ok(VERIFY_WRITE, (u8 __user *)
                                                (uintptr_t) u_tmp->rx_buf,
                                                u_tmp->len))
                                goto done;
                }
                if (u_tmp->tx_buf) {
                        k_tmp->tx_buf = buf;
                        if (copy_from_user(buf, (const u8 __user *)
                                                (uintptr_t) u_tmp->tx_buf,
                                        u_tmp->len))
                                goto done;
                }
                buf += k_tmp->len;

                k_tmp->cs_change = !!u_tmp->cs_change;
                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;
#ifdef VERBOSE
                dev_dbg(&spi->dev,
                        "  xfer len %zd %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 ? : spi->bits_per_word,
                        u_tmp->delay_usecs,
                        u_tmp->speed_hz ? : 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 */
        buf = spidev->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, buf,
                                        u_tmp->len)) {
                                status = -EFAULT;
                                goto done;
                        }
                }
                buf += u_tmp->len;
        }
        status = total;

done:
        mutex_unlock(&spidev->buf_lock);
        kfree(k_xfers);
        return status;
}

static int
spidev_ioctl(struct inode *inode, struct file *filp,
                unsigned int cmd, unsigned long arg)
{
        int                     err = 0;
        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;

        /* Check access direction once here; don't repeat below.
         * IOC_DIR is from the user perspective, while access_ok is
         * from the kernel perspective; so they look reversed.
         */
        if (_IOC_DIR(cmd) & _IOC_READ)
                err = !access_ok(VERIFY_WRITE,
                                (void __user *)arg, _IOC_SIZE(cmd));
        if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
                err = !access_ok(VERIFY_READ,
                                (void __user *)arg, _IOC_SIZE(cmd));
        if (err)
                return -EFAULT;

        /* 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;

        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_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(spi->max_speed_hz, (__u32 __user *)arg);
                break;

        /* write requests */
        case SPI_IOC_WR_MODE:
                retval = __get_user(tmp, (u8 __user *)arg);
                if (retval == 0) {
                        u8      save = spi->mode;

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

                        tmp |= spi->mode & ~SPI_MODE_MASK;
                        spi->mode = (u8)tmp;
                        retval = spi_setup(spi);
                        if (retval < 0)
                                spi->mode = save;
                        else
                                dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
                }
                break;
        case SPI_IOC_WR_LSB_FIRST:
                retval = __get_user(tmp, (__u8 __user *)arg);
                if (retval == 0) {
                        u8      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)
                                spi->max_speed_hz = save;
                        else
                                dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
                }
                break;

        default:
                /* segmented and/or full-duplex I/O request */
                if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
                                || _IOC_DIR(cmd) != _IOC_WRITE) {
                        retval = -ENOTTY;
                        break;
                }

                tmp = _IOC_SIZE(cmd);
                if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
                        retval = -EINVAL;
                        break;
                }
                n_ioc = tmp / sizeof(struct spi_ioc_transfer);
                if (n_ioc == 0)
                        break;

                /* copy into scratch area */
                ioc = kmalloc(tmp, GFP_KERNEL);
                if (!ioc) {
                        retval = -ENOMEM;
                        break;
                }
                if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
                        kfree(ioc);
                        retval = -EFAULT;
                        break;
                }

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

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 == 0) {
                if (!spidev->buffer) {
                        spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
                        if (!spidev->buffer) {
                                dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
                                status = -ENOMEM;
                        }
                }
                if (status == 0) {
                        spidev->users++;
                        filp->private_data = spidev;
                        nonseekable_open(inode, filp);
                }
        } else
                pr_debug("spidev: nothing for minor %d\n", iminor(inode));

        mutex_unlock(&device_list_lock);
        return status;
}

static int spidev_release(struct inode *inode, struct file *filp)
{
        struct spidev_data      *spidev;
        int                     status = 0;

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

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

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

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

                if (dofree)
                        kfree(spidev);
        }
        mutex_unlock(&device_list_lock);

        return status;
}

static 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,
        .ioctl =        spidev_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 struct class *spidev_class;

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

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

        /* 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%d.%d",
                                spi->master->bus_num, spi->chip_select);
                status = IS_ERR(dev) ? PTR_ERR(dev) : 0;
        } else {
                dev_dbg(&spi->dev, "no minor number available!\n");
                status = -ENODEV;
        }
        if (status == 0) {
                set_bit(minor, minors);
                spi_set_drvdata(spi, spidev);
                list_add(&spidev->device_entry, &device_list);
        }
        mutex_unlock(&device_list_lock);

        if (status != 0)
                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;
        spi_set_drvdata(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 = {
                .name =         "spidev",
                .owner =        THIS_MODULE,
        },
        .probe =        spidev_probe,
        .remove =       __devexit_p(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.name);
                return PTR_ERR(spidev_class);
        }

        status = spi_register_driver(&spidev_spi);
        if (status < 0) {
                class_destroy(spidev_class);
                unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
        }
        return status;
}
module_init(spidev_init);

static void __exit spidev_exit(void)
{
        spi_unregister_driver(&spidev_spi);
        class_destroy(spidev_class);
        unregister_chrdev(SPIDEV_MAJOR, spidev_spi.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");