linux/drivers/spi/spidev.c
Anton Vorontsov 6f166e3833 spidev supports more communications modes
The spidev driver doesn't currently expose all SPI communications modes to
userspace.  This passes them all through to the driver.

Two of them are potentially troublesome, in the sense that they could cause
hardware conflicts on shared busses.  It might be appropriate to add some
privilege checks for for those modes.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-31 15:39:40 -07:00

595 lines
15 KiB
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/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 {
struct device dev;
struct spi_device *spi;
struct list_head device_entry;
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");
/*-------------------------------------------------------------------------*/
/* 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;
struct spi_device *spi;
ssize_t status = 0;
/* chipselect only toggles at start or end of operation */
if (count > bufsiz)
return -EMSGSIZE;
spidev = filp->private_data;
spi = spidev->spi;
mutex_lock(&spidev->buf_lock);
status = spi_read(spi, spidev->buffer, 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;
struct spi_device *spi;
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;
spi = spidev->spi;
mutex_lock(&spidev->buf_lock);
missing = copy_from_user(spidev->buffer, buf, count);
if (missing == 0) {
status = spi_write(spi, spidev->buffer, 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;
struct spi_device *spi = spidev->spi;
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, 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 *)
(ptrdiff_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 = spi_sync(spi, &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 *)
(ptrdiff_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;
spidev = filp->private_data;
spi = spidev->spi;
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)
return -ENOTTY;
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;
}
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->dev.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;
spidev->users--;
if (!spidev->users) {
kfree(spidev->buffer);
spidev->buffer = NULL;
}
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 void spidev_classdev_release(struct device *dev)
{
struct spidev_data *spidev;
spidev = container_of(dev, struct spidev_data, dev);
kfree(spidev);
}
static struct class spidev_class = {
.name = "spidev",
.owner = THIS_MODULE,
.dev_release = spidev_classdev_release,
};
/*-------------------------------------------------------------------------*/
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;
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) {
spidev->dev.parent = &spi->dev;
spidev->dev.class = &spidev_class;
spidev->dev.devt = MKDEV(SPIDEV_MAJOR, minor);
snprintf(spidev->dev.bus_id, sizeof spidev->dev.bus_id,
"spidev%d.%d",
spi->master->bus_num, spi->chip_select);
status = device_register(&spidev->dev);
} else {
dev_dbg(&spi->dev, "no minor number available!\n");
status = -ENODEV;
}
if (status == 0) {
set_bit(minor, minors);
dev_set_drvdata(&spi->dev, 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 = dev_get_drvdata(&spi->dev);
mutex_lock(&device_list_lock);
list_del(&spidev->device_entry);
dev_set_drvdata(&spi->dev, NULL);
clear_bit(MINOR(spidev->dev.devt), minors);
device_unregister(&spidev->dev);
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;
status = class_register(&spidev_class);
if (status < 0) {
unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
return status;
}
status = spi_register_driver(&spidev_spi);
if (status < 0) {
class_unregister(&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_unregister(&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");