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#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
}
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