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IIC(4)                 FreeBSD Kernel Interfaces Manual                 IIC(4)

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
                      (that is, a 7-bit address << 1 | r/w).  A read operation
                      is initiated when the read/write bit is set, or a write
                      operation when it is cleared.  All other elements are
                      ignored.  If successful, the file descriptor receives
                      exclusive ownership of the underlying iicbus instance.

     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.  I2CSTART must have
                      previously been issued on the same file descriptor.

     I2CSTOP          No argument is passed.  Sends the stop condition to the
                      bus.  If I2CSTART was previously issued on the file
                      descriptor, the current transaction is terminated and
                      exclusive ownership of the underlying iicbus instance is
                      released.  Otherwise, no action is performed.

     I2CRSTCARD       (struct iiccmd) Resets the bus.  The argument is
                      completely ignored.  This command does not require
                      I2CSTART to have been previously issued on the file
                      descriptor.  If it was previously issued, exclusive
                      ownership of the underlying iicbus instance is released.

     I2CWRITE         (struct iiccmd) Writes data to the iicbus(4).  The bus
                      must already be started by a previous I2CSTART on the
                      file descriptor.  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
                      must already be started by a previous I2CSTART on the
                      file descriptor.  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.  Any previous
                      transaction started by I2CSTART must be terminated by
                      I2CSTOP or I2CRSTCARD before I2CRDWR can be issued on
                      the same file descriptor.  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.

     I2CSADDR         (uint8_t) Associate the specified address with the file
                      descriptor for use by subsequent read(2) or write(2)
                      calls.  The argument is an 8-bit address (that is, a
                      7-bit address << 1).  The read/write bit in the least-
                      significant position is ignored.  Any subsequent read or
                      write operation will set or clear that bit as needed.

     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_WR        0       /* Fake flag for write */
           #define IIC_M_RD        0x0001  /* read vs write */
           #define IIC_M_NOSTOP    0x0002  /* do not send a I2C stop after message */
           #define IIC_M_NOSTART   0x0004  /* do not send a I2C start before message */
                   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(2) or write(2), in which case the I2C
     start/stop handshake is managed by iicbus(4).  The address used for the
     read/write operation is the one passed to the most recent I2CSTART
     ioctl(2) or I2CSADDR ioctl(2) on the open /dev/iic? file descriptor.
     Closing the file descriptor clears any addressing state established by a
     previous I2CSTART or I2CSADDR, stops any transaction established by a
     not-yet-terminated I2CSTART, and releases iicbus ownership.  Because
     addressing state is stored on a per-file-descriptor basis, it is
     permissible for multiple file descriptors to be simultaneously open on
     the same /dev/iic? device.  Concurrent transactions on those descriptors
     are synchronized by the exclusive-ownership requests issued to the
     underlying iicbus instance.

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.

FreeBSD 11.1-RELEASE-p4          May 15, 2015          FreeBSD 11.1-RELEASE-p4
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