smb4freebsd

Usage

Overview

The smb character device driver provides generic I/O to any smbus(4) instance. To control SMB devices, use /dev/smb? with the ioctls described below. Any of these ioctl commands takes a pointer to struct smbcmd as its argument.

#include <sys/types.h>
struct smbcmd {
	u_char cmd;
	u_char reserved;
	u_short op;
	union {
		char    byte;
		char    buf[2];
		short   word;
	} wdata;
	union {
		char    byte;
		char    buf[2];
		short   word;
	} rdata;
	int  slave;
	char *wbuf;     /* use wdata if NULL */
	int  wcount;
	char *rbuf;     /* use rdata if NULL */
	int  rcount;
};

The slave field is always used, and provides the address of the SMBus slave device. The slave address is specified in the seven most significant bits (i.e., “left-justified”). The least significant bit of the slave address must be zero.

The read(2) and write(2) system calls are not implemented by this driver.

Errors

The ioctl(2) commands can cause the following driver-specific errors:

[ENXIO]

Device did not respond to selection.

[EBUSY]

Device still in use.

[ENODEV]

Operation not supported by device (not supposed to happen).

[EINVAL]

General argument error.

[EWOULDBLOCK]

SMBus transaction timed out.