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.  The slave element consists of a 7-bit  address  and  a  read/write  bit  (i.e.,  7-bit
                    address  <<  1  |  r/w).  If the read/write bit is set a read operation is initiated, if the
                    read/write bit is cleared a write operation is initiated.  All other elements are ignored.

       I2CRPTSTART  (struct iiccmd) Sends the repeated start condition to  the  slave  specified  by  the  slave
                    element  to  the  bus.   The  slave  address  should be specified as in I2CSTART.  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 with the read/write bit  for  the  transfer.   The
                    read/write  bit  will  be  handled  by  the  iicbus  stack  based  on the specified transfer
                    operation.  The len element is the number of (struct iic_msg) messages  encoded  on  (struct
                    iic_rdwr_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 length */
                     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.

Debian                                            June 24, 2014                                           IIC(4)