Question

For my assignment I need to read some strings coming from a serial port.
This has to be done in a kernel module, so I can’t use stdio library.
I’m trying in this way:

#include <linux/module.h>
#include <linux/unistd.h>
#include <asm/io.h>
#include <asm/fcntl.h>
#define SERIAL_PORT "/dev/ttyACM0"

void myfun(void){
  int fd = open(SERIAL_PORT,O_RDONLY | O_NOCTTY);
  ..reading...

}

but it gives me “implicit declaration of function open”

Answer 1

You want to use the filp_open() function, it is pretty much a helper to open a file in kernelspace. You can find the man on it here

The file pointer from filp_open() is of type struct file and don’t forget to close it with filp_close() when you’re done:

#include <linux/fs.h>
//other includes...

//other code...    

struct file *filp = filp_open("/dev/ttyS0");
//do serial stuff...
filp_close(filp);