201 lines
4.4 KiB
C
201 lines
4.4 KiB
C
/*
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* character device wrapper for generic gpio layer
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA02111-1307USA
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*
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* Feedback, Bugs... blogic@openwrt.org
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*
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*/
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#include <linux/module.h>
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#include <linux/errno.h>
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#include <linux/init.h>
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#include <asm/uaccess.h>
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#include <asm/io.h>
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#include <asm/gpio.h>
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#include <asm/atomic.h>
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#include <linux/init.h>
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#include <linux/genhd.h>
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#include <linux/device.h>
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#include <linux/platform_device.h>
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#include <linux/gpio_dev.h>
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#define DRVNAME "gpiodev"
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#define DEVNAME "gpio"
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static int dev_major;
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static unsigned int gpio_access_mask;
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static struct class *gpiodev_class;
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/* Counter is 1, if the device is not opened and zero (or less) if opened. */
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static atomic_t gpio_open_cnt = ATOMIC_INIT(1);
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static int
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gpio_ioctl(struct inode * inode, struct file * file, unsigned int cmd, unsigned long arg)
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{
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int retval = 0;
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if (((1 << arg) & gpio_access_mask) != (1 << arg))
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{
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retval = -EINVAL;
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goto out;
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}
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switch (cmd)
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{
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case GPIO_GET:
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retval = gpio_get_value(arg);
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break;
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case GPIO_SET:
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gpio_set_value(arg, 1);
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break;
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case GPIO_CLEAR:
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gpio_set_value(arg, 0);
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break;
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case GPIO_DIR_IN:
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gpio_direction_input(arg);
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break;
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case GPIO_DIR_OUT:
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gpio_direction_output(arg, 0);
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break;
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default:
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retval = -EINVAL;
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break;
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}
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out:
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return retval;
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}
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static int
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gpio_open(struct inode *inode, struct file *file)
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{
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int result = 0;
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unsigned int dev_minor = MINOR(inode->i_rdev);
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if (dev_minor != 0)
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{
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printk(KERN_ERR DRVNAME ": trying to access unknown minor device -> %d\n", dev_minor);
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result = -ENODEV;
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goto out;
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}
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/* FIXME: We should really allow multiple applications to open the device
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* at the same time, as long as the apps access different IO pins.
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* The generic gpio-registration functions can be used for that.
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* Two new IOCTLs have to be introduced for that. Need to check userspace
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* compatibility first. --mb */
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if (!atomic_dec_and_test(&gpio_open_cnt)) {
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atomic_inc(&gpio_open_cnt);
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printk(KERN_ERR DRVNAME ": Device with minor ID %d already in use\n", dev_minor);
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result = -EBUSY;
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goto out;
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}
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out:
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return result;
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}
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static int
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gpio_close(struct inode * inode, struct file * file)
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{
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smp_mb__before_atomic_inc();
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atomic_inc(&gpio_open_cnt);
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return 0;
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}
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struct file_operations gpio_fops = {
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ioctl: gpio_ioctl,
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open: gpio_open,
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release: gpio_close
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};
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static int
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gpio_probe(struct platform_device *dev)
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{
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int result = 0;
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dev_major = register_chrdev(0, DEVNAME, &gpio_fops);
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if (!dev_major)
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{
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printk(KERN_ERR DRVNAME ": Error whilst opening %s \n", DEVNAME);
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result = -ENODEV;
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goto out;
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}
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gpiodev_class = class_create(THIS_MODULE, DRVNAME);
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device_create(gpiodev_class, NULL, MKDEV(dev_major, 0), dev, DEVNAME);
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printk(KERN_INFO DRVNAME ": gpio device registered with major %d\n", dev_major);
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if (dev->num_resources != 1)
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{
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printk(KERN_ERR DRVNAME ": device may only have 1 resource\n");
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result = -ENODEV;
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goto out;
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}
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gpio_access_mask = dev->resource[0].start;
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printk(KERN_INFO DRVNAME ": gpio platform device registered with access mask %08X\n", gpio_access_mask);
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out:
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return result;
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}
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static int
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gpio_remove(struct platform_device *dev)
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{
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unregister_chrdev(dev_major, DEVNAME);
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return 0;
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}
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static struct
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platform_driver gpio_driver = {
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.probe = gpio_probe,
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.remove = gpio_remove,
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.driver = {
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.name = "GPIODEV",
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.owner = THIS_MODULE,
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},
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};
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static int __init
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gpio_mod_init(void)
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{
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int ret = platform_driver_register(&gpio_driver);
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if (ret)
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printk(KERN_INFO DRVNAME ": Error registering platfom driver!");
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return ret;
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}
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static void __exit
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gpio_mod_exit(void)
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{
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platform_driver_unregister(&gpio_driver);
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}
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module_init (gpio_mod_init);
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module_exit (gpio_mod_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("John Crispin / OpenWrt");
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MODULE_DESCRIPTION("Character device for for generic gpio api");
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