1. 根目录:
2. drivers
3. char
4. nsc_gpio.c

/* linux/drivers/char/nsc_gpio.c

   National Semiconductor common GPIO device-file/VFS methods.
   Allows a user space process to control the GPIO pins.

   Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>
   Copyright (c) 2005      Jim Cromie <jim.cromie@gmail.com>
*/

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/nsc_gpio.h>
#include <linux/platform_device.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#define NAME "nsc_gpio"

void nsc_gpio_dump(struct nsc_gpio_ops *amp, unsigned index)
{
	/* retrieve current config w/o changing it */
	u32 config = amp->gpio_config(index, ~0, 0);

	/* user requested via 'v' command, so its INFO */
	dev_info(amp->dev, "io%02u: 0x%04x %s %s %s %s %s %s %s\tio:%d/%d\n",
		 index, config,
		 (config & 1) ? "OE" : "TS",      /* output-enabled/tristate */
		 (config & 2) ? "PP" : "OD",      /* push pull / open drain */
		 (config & 4) ? "PUE" : "PUD",    /* pull up enabled/disabled */
		 (config & 8) ? "LOCKED" : "",    /* locked / unlocked */
		 (config & 16) ? "LEVEL" : "EDGE",/* level/edge input */
		 (config & 32) ? "HI" : "LO",     /* trigger on rise/fall edge */
		 (config & 64) ? "DEBOUNCE" : "", /* debounce */

		 amp->gpio_get(index), amp->gpio_current(index));
}

ssize_t nsc_gpio_write(struct file *file, const char __user *data,
		       size_t len, loff_t *ppos)
{
	unsigned m = iminor(file_inode(file));
	struct nsc_gpio_ops *amp = file->private_data;
	struct device *dev = amp->dev;
	size_t i;
	int err = 0;

	for (i = 0; i < len; ++i) {
		char c;
		if (get_user(c, data + i))
			return -EFAULT;
		switch (c) {
		case '0':
			amp->gpio_set(m, 0);
			break;
		case '1':
			amp->gpio_set(m, 1);
			break;
		case 'O':
			dev_dbg(dev, "GPIO%d output enabled\n", m);
			amp->gpio_config(m, ~1, 1);
			break;
		case 'o':
			dev_dbg(dev, "GPIO%d output disabled\n", m);
			amp->gpio_config(m, ~1, 0);
			break;
		case 'T':
			dev_dbg(dev, "GPIO%d output is push pull\n", m);
			amp->gpio_config(m, ~2, 2);
			break;
		case 't':
			dev_dbg(dev, "GPIO%d output is open drain\n", m);
			amp->gpio_config(m, ~2, 0);
			break;
		case 'P':
			dev_dbg(dev, "GPIO%d pull up enabled\n", m);
			amp->gpio_config(m, ~4, 4);
			break;
		case 'p':
			dev_dbg(dev, "GPIO%d pull up disabled\n", m);
			amp->gpio_config(m, ~4, 0);
			break;
		case 'v':
			/* View Current pin settings */
			amp->gpio_dump(amp, m);
			break;
		case '\n':
			/* end of settings string, do nothing */
			break;
		default:
			dev_err(dev, "io%2d bad setting: chr<0x%2x>\n",
				m, (int)c);
			err++;
		}
	}
	if (err)
		return -EINVAL;	/* full string handled, report error */

	return len;
}

ssize_t nsc_gpio_read(struct file *file, char __user * buf,
		      size_t len, loff_t * ppos)
{
	unsigned m = iminor(file_inode(file));
	int value;
	struct nsc_gpio_ops *amp = file->private_data;

	value = amp->gpio_get(m);
	if (put_user(value ? '1' : '0', buf))
		return -EFAULT;

	return 1;
}

/* common file-ops routines for both scx200_gpio and pc87360_gpio */
EXPORT_SYMBOL(nsc_gpio_write);
EXPORT_SYMBOL(nsc_gpio_read);
EXPORT_SYMBOL(nsc_gpio_dump);

static int __init nsc_gpio_init(void)
{
	printk(KERN_DEBUG NAME " initializing\n");
	return 0;
}

static void __exit nsc_gpio_cleanup(void)
{
	printk(KERN_DEBUG NAME " cleanup\n");
}

module_init(nsc_gpio_init);
module_exit(nsc_gpio_cleanup);

MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
MODULE_DESCRIPTION("NatSemi GPIO Common Methods");
MODULE_LICENSE("GPL");