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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.

     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 #include <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.