Linux Device Drivers Development

The write method

The write() method is used to send data to the device; whenever a user app calls the write function on the device's file, the kernel implementation is called. Its prototype is as follows:

ssize_t(*write)(struct file *filp, const char __user *buf, size_t count, loff_t *pos); 

• The return value is the number of bytes (size) written
• *buf represents the data buffer coming from the user space
• count is the size of the requested transfer
• *pos indicates the start position from which data should be written in the file