IIC(9) | Kernel Developer's Manual | IIC(9) |
iic_acquire_bus
,
iic_release_bus
, iic_exec
,
iic_smbus_write_byte
,
iic_smbus_read_byte
,
iic_smbus_receive_byte
—
#include <dev/i2c/i2cvar.h>
int
iic_acquire_bus
(i2c_tag_t ic,
int flags);
void
iic_release_bus
(i2c_tag_t ic,
int flags);
int
iic_exec
(i2c_tag_t ic,
i2c_op_t op, i2c_addr_t addr,
const void *cmdbuf, size_t
cmdlen, void *buf, size_t
buflen, int flags);
int
iic_smbus_write_byte
(i2c_tag_t
ic, i2c_addr_t addr, uint8_t
cmd, uint8_t data, int
flags);
int
iic_smbus_read_byte
(i2c_tag_t
ic, i2c_addr_t addr, uint8_t
cmd, uint8_t *datap, int
flags);
int
iic_smbus_receive_byte
(i2c_tag_t
ic, i2c_addr_t addr, uint8_t
*datap, int flags);
iic
interface
provides a means of communicating with I2C-connected devices. The System
Management Bus, or SMBus, is a variant of the I2C bus with a simplified
command protocol and some electrical differences.
struct i2c_attach_args { i2c_tag_t ia_tag; /* controller */ i2c_addr_t ia_addr; /* address of device */ int ia_size; /* size (for EEPROMs) */ };
iic_acquire_bus
(ic,
flags)I2C_F_POLL
flag
indicates to iic_acquire_bus
() that sleeping is
not permitted.iic_release_bus
(ic,
flags)I2C_F_POLL
flag was passed to
iic_acquire_bus
(), it must also be passed to
iic_release_bus
().iic_exec
(ic,
op, addr,
cmdbuf, cmdlen,
buf, buflen,
flags)iic_exec
() initiates the operation by sending a
START condition on the I2C bus and then transmitting the address of the
target device along with the transaction type. If
cmdlen is non-zero, the command pointed to by
cmdbuf is then sent to the device. If
buflen is non-zero,
iic_exec
() will then transmit or receive the data,
as indicated by op. If op
indicates a read operation, iic_exec
() will send a
REPEATED START before transferring the data. If op
so indicates, a STOP condition will be sent on the I2C bus at the
conclusion of the operation. Passing the
I2C_F_POLL
flag indicates to
iic_exec
() that sleeping is not permitted.iic_smbus_write_byte
(ic,
addr, cmd,
data, flags)iic_smbus_read_byte
(ic,
addr, cmd,
datap, flags)iic_smbus_receive_byte
(ic,
addr, datap,
flags)struct i2c_controller { void *ic_cookie; /* controller private */ int (*ic_acquire_bus)(void *, int); void (*ic_release_bus)(void *, int); int (*ic_exec)(void *, i2c_op_t, i2c_addr_t, const void *, size_t, void *, size_t, int); int (*ic_send_start)(void *, int); int (*ic_send_stop)(void *, int); int (*ic_initiate_xfer)(void *, i2c_addr_t, int); int (*ic_read_byte)(void *, uint8_t *, int); int (*ic_write_byte)(void *, uint8_t, int); };
The (*ic_acquire_bus)
() and
(*ic_release_bus)
() functions must always be
provided.
The controller driver may elect to provide an
(*ic_exec)
() function. This function is intended for
use by automated controllers that do not provide manual control over I2C bus
conditions such as START and STOP.
If the (*ic_exec)
() function is not
provided, the following 5 functions will be used by
iic_exec
() in order to execute the I2C bus
operation:
(*ic_send_start)
(cookie,
flags)I2C_F_POLL
flag indicates that sleeping is not
permitted.(*ic_send_stop)
(cookie,
flags)I2C_F_POLL
flag indicates that sleeping is not
permitted.(*ic_initiate_xfer)
(cookie,
addr, flags)I2C_F_READ
flag indicates a read transfer; the
lack of this flag indicates a write transfer. The
I2C_F_POLL
flag indicates that sleeping is not
permitted. The error code ETIMEDOUT
should be
returned if a timeout that would indicate that the device is not present
occurs.(*ic_read_byte)
(cookie,
datap, flags)I2C_F_LAST
flag
indicates that this is the final byte of the transfer, and that a NACK
condition should be sent on the I2C bus following the transfer of the
byte. The I2C_F_STOP
flag indicates that a STOP
condition should be sent on the I2C bus following the transfer of the
byte. The I2C_F_POLL
flag indicates that sleeping
is not permitted.(*ic_write_byte)
(cookie,
data, flags)I2C_F_STOP
flag indicates that a STOP condition
should be sent on the I2C bus following the transfer of the byte. The
I2C_F_POLL
flag indicates that sleeping is not
permitted.NXP Semiconductors, I2C-bus Specification and User Manual, Revision 03, http://www.ics.nxp.com/support/documents/i2c/pdf/i2c.bus.specification.pdf, June 19, 2007.
Duracell Inc. et. al., System Management Bus (SMBus) Specification, Version 2.0, http://smbus.org/specs/smbus20.pdf, August 3, 2000.
iic
API first appeared in NetBSD
2.0. OpenBSD support was added in
OpenBSD 3.6.
iic
API was written by Steve C. Woodford and Jason
R. Thorpe for NetBSD and then ported to
OpenBSD by Alexander Yurchenko
<grange@openbsd.org>.
October 15, 2011 | NetBSD 9.2 |