fix echo input + cat output

1 files changed, 23 insertions, 2 deletions

diff --git a/1/fopdrv.c b/1/fopdrv.c
index d048f15..18a1d35 100644
--- a/1/fopdrv.c
+++ b/1/fopdrv.c
@@ -3,17 +3,37 @@
 #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);
-	return 0;
+
+	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 < 1) return count;
+	if (count > 2) return count;
 
 	// copy buffer for reading (see [kernel-labs-chrdev] in ../readme.md)
 	char input_buf[10];
@@ -39,6 +59,7 @@ ssize_t fop_write(struct file *file, const char __user *buf, size_t count, loff_
 
 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