IIC(4) BSD Kernel Interfaces Manual IIC(4)NAMEiic — I2C generic I/O device driver
SYNOPSIS
device iic
#include <dev/iicbus/iic.h>
DESCRIPTION
The iic device driver provides generic I/O to any iicbus(4) instance. In
order to control I2C devices, use /dev/iic? with the following ioctls:
I2CSTART (struct iiccmd) Sends the start condition to the slave spec‐
ified by the slave element to the bus. All other elements
are ignored.
I2CRPTSTART (struct iiccmd) Sends the repeated start condition to the
slave specified by the slave element to the bus. All other
elements are ignored.
I2CSTOP No argument is passed. Sends the stop condition to the bus.
This terminates the current transaction.
I2CRSTCARD (struct iiccmd) Resets the bus. The argument is completely
ignored.
I2CWRITE (struct iiccmd) Writes data to the iicbus(4). The bus
should already be started. The slave element is ignored.
The count element is the number of bytes to write. The last
element is a boolean flag. It is non-zero when additional
write commands will follow. The buf element is a pointer to
the data to write to the bus.
I2CREAD (struct iiccmd) Reads data from the iicbus(4). The bus
should already be started. The slave element is ignored.
The count element is the number of bytes to write. The last
element is a boolean flag. It is non-zero when additional
write commands will follow. The buf element is a pointer to
where to store the data read from the bus. Short reads on
the bus produce undefined results.
I2CRDWR (struct iic_rdwr_data) Generic read/write interface. Allows
for an arbitrary number of commands to be sent to an arbi‐
trary number of devices on the bus. A read transfer is
specified if IIC_M_RD is set in flags. Otherwise the trans‐
fer is a write transfer. The slave element specifies the
7-bit address for the transfer. The len element is the
length of the data. The buf element is a buffer for that
data. This ioctl is intended to be Linux compatible.
The following data structures are defined in <dev/iicbus/iic.h> and ref‐
erenced above:
struct iiccmd {
u_char slave;
int count;
int last;
char *buf;
};
/* Designed to be compatible with linux's struct i2c_msg */
struct iic_msg
{
uint16_t slave;
uint16_t flags;
#define IIC_M_RD 0x0001 /* read vs write */
uint16_t len; /* msg legnth */
uint8_t * buf;
};
struct iic_rdwr_data {
struct iic_msg *msgs;
uint32_t nmsgs;
};
It is also possible to use read/write routines, then I2C start/stop hand‐
shake is managed by the iicbus(4) system. However, the address used for
the read/write routines is the one passed to last I2CSTART ioctl(2) to
this device.
SEE ALSOioctl(2), read(2), write(2), iicbus(4)HISTORY
The iic manual page first appeared in FreeBSD 3.0.
AUTHORS
This manual page was written by Nicolas Souchu and M. Warner Losh.
BUGS
Only the I2CRDWR ioctl(2) is thread safe. All other interfaces suffer
from some kind of race.
BSD September 6, 2006 BSD