NAME¶
iic —
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 specified 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 arbitrary number of devices on the bus. A read transfer is
specified if
IIC_M_RD is set in
flags. Otherwise the transfer 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 referenced
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 handshake 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 ALSO¶
ioctl(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.
