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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.

     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.