Linux Device Drivers Development

The read method

The prototype of the read() method is given as follows:

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

The return value is the size read. The rest of the method's elements are described here:

• *buf is the buffer we receive from the user space
• count is the size of the requested transfer (size of the user buffer)
• *pos indicates the start position from which data should be read in the file