#include <linux/io.h>

#include "fopdrv.h"
#include "config.h"

bool printed = false;

// driver/char/mem.c read_null (/dev/null)
ssize_t fop_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) {
	printk("%s(<file>, <buf>, %u, <ppos>)\n", __PRETTY_FUNCTION__, count);

	if (count < 2) return 0;
	if (printed) return 0;

	ti_am335x_word_t* gpio1 = ioremap(TI_AM335X_GPIO1_ADDR, GPIO_REG_SIZE);
	barrier();

	ti_am335x_word_t gpio = ioread32(gpio1 + GPIO_DATAIN); rmb();
	bool on = (gpio & (1<<PIN)) > 0;

	char output[10];
	snprintf(output, 10, "%d\n", on);

	if (copy_to_user(buf, output + *ppos, 2))
		return -EFAULT;
	*ppos += 2;
	printed = true;
	return 2;
}

ssize_t fop_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) {
	printk("%s(<file>, <buf>, %u, <ppos>)\n", __PRETTY_FUNCTION__, count);

	// only allow single character as input
	if (count < 1) return count;
	if (count > 2) return count;

	// copy buffer for reading (see [kernel-labs-chrdev] in ../readme.md)
	char input_buf[10];
	if (copy_from_user(input_buf + *ppos, buf, count))
		return -EFAULT;

	ti_am335x_word_t* gpio1 = ioremap(TI_AM335X_GPIO1_ADDR, GPIO_REG_SIZE);
	barrier();

	if (input_buf[0] == '0') {
		printk("TODO: TURN OFF OUTPUT\n");
		iowrite32((1<<PIN), gpio1 + GPIO_CLEARDATAOUT); wmb();
	}
	if (input_buf[0] == '1') {
		printk("TODO: TURN ON OUTPUT\n");
		iowrite32((1<<PIN), gpio1 + GPIO_SETDATAOUT); wmb();
	}

	iounmap(gpio1);

	return count;
}

int fop_open(struct inode * inode, struct file * file) {
	printk("%s(<inode>, <file>)\n", __PRETTY_FUNCTION__);
	printed = false;
	return 0;
	// 0 seems to be a safe return value as it's used in driver/char/mem.c. The
	// manual page for open(2) says that the system call returns a nonnegative
	// integer representing the file descriptor on success, but it does not
	// appears to be required.
}

int fop_release(struct inode * inode, struct file * file) {
	printk("%s(<inode>, <file>)\n", __PRETTY_FUNCTION__);
	return 0;
	// same as above, but found in driver/char/lp.c
}