/* * 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 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) 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, 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->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; 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. */ 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(&spidev->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 ? : 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 */ 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: kfree(k_xfers); return status; } static long spidev_ioctl(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; /* 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_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; } mutex_unlock(&spidev->buf_lock); 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 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, .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 __devinit 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, "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); list_add(&spidev->device_entry, &device_list); } mutex_unlock(&device_list_lock); if (status == 0) spi_set_drvdata(spi, spidev); else kfree(spidev); return status; } static int __devexit 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 = { .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.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");