read.c File Reference

Macros
#define	pr_fmt(fmt)   KBUILD_MODNAME ": " fmt

Functions
ssize_t	can_read (struct file *file, char __user *buffer, size_t count, loff_t *loff)
	ssize_t read(int fd, void *buf, size_t count); the read system call More...

Detailed Description

Author

Heinz-Jürgen Oertel

Module Description see Doxygen Doc for all possibilities

Function Documentation

ssize_t can_read	(	struct file *	file,
		char __user *	buffer,
		size_t	count,
		loff_t *	loff
	)

ssize_t read(int fd, void *buf, size_t count); the read system call

Parameters

fd	The descriptor to read from.
buf	The destination data buffer (array of CAN canmsg_t).
count	The number of bytes to read.

read() attempts to read up to count CAN messages (not bytes! ) from file descriptor fd into the buffer starting at buf. buf must be large enough to hold count times the size of one CAN message structure canmsg_t.

int got;
canmsg_t rx[80];                        // receive buffer for read()

    got = read(can_fd, rx , 80 );
    if( got > 0) {
      ...
    } else {
        // read returned with error
        fprintf(stderr, "- Received got = %d\n", got);
        fflush(stderr);
    }

* 

ERRORS

the following errors can occur

• EINVAL buf points not to an large enough area,

Returns

On success, the number of CAN messages read is returned (zero indicates end of file). It is not an error if this number is smaller than the number of messages requested; this may happen for example because fewer messages are actually available right now, or because read() was interrupted by a signal. On error, -1 is returned, and errno is set appropriately.