ddi_copyout(9F)

NAME

     ddi_copyout - copy data from a driver

SYNOPSIS

     #include <sys/types.h>
     #include <sys/ddi.h>
     #include <sys/sunddi.h>

     int ddi_copyout(const void *driverbuf, void *buf, size_t cn,
     int flags);

INTERFACE LEVEL

     Solaris DDI specific (Solaris DDI).

PARAMETERS

     driverbuf
           Source address in the driver from which  the  data  is
           transferred.

     buf   Destination address to which the data is transferred.

     cn    Number of bytes to copy.

     flags Set of flag bits that provide address  space  informa-
           tion about buf.

DESCRIPTION

     This routine is designed for use in  driver  ioctl(9E)  rou-
     tines for drivers that support layered ioctls. ddi_copyout()
     copies data from a driver buffer to a  destination  address,
     buf.

     The flags argument determines the address space  information
     about  buf.  If the FKIOCTL flag is set, this indicates that
     buf is a kernel address,  and   ddi_copyout()  behaves  like
     bcopy(9F).  Otherwise,   buf is interpreted as a user buffer
     address, and ddi_copyout() behaves like copyout(9F).

     Addresses that are word-aligned are moved most  efficiently.
     However,  the  driver  developer  is  not  obliged to ensure
     alignment.  This function automatically finds the most effi-
     cient move algorithm according to address alignment.

RETURN VALUES

     Under normal conditions, 0 is returned to  indicate  a  suc-
     cessful  copy.  Otherwise, -1 is returned if one of the fol-
     lowing occurs:

        o  Paging fault; the driver tried to  access  a  page  of
           memory for which it did not have read or write access.

        o  Invalid user address, such as a  user  area  or  stack
           area.

        o  Invalid address that would have resulted in data being
           copied into the user block.

        o  Hardware fault; a hardware error prevented  access  to
           the  specified user memory. For example, an uncorrect-
           able parity or ECC error occurred.

     If -1 is returned to the caller, driver entry point routines
     should return EFAULT.

CONTEXT

     ddi_copyout() can be called  from  user  or  kernel  context
     only.

EXAMPLES

     Example 1: ddi_copyout() example

     A driver ioctl(9E) routine (line 12) can be used to  get  or
     set device attributes or registers. In the XX_GETREGS condi-
     tion (line 25), the driver copies the current device  regis-
     ter  values to another data area.  If the specified argument
     contains an invalid address, an error code is returned.

      1  struct device  {          /* layout of physical device registers  */
      2     int      control;      /* physical device control word  */
      3     int      status;       /* physical device status word   */
      4     short    recv_char;    /* receive character from device */
      5     short    xmit_char;    /* transmit character to device  */
      6  };

      7  struct device_state {
      8     volatile struct device *regsp;   /* pointer to device registers */
      9     kmutex_t reg_mutex;              /* protect device registers */
            . . .
     10  };

     11  static void *statep; /* for soft state routines */

     12  xxioctl(dev_t dev, int cmd, int arg, int mode,
     13      cred_t *cred_p, int *rval_p)
     14  {
     15      struct device_state *sp;
     16      volatile struct device *rp;
     17      struct device reg_buf;     /* temporary buffer for registers */
     18      int instance;

     19      instance = getminor(dev);
     20      sp = ddi_get_soft_state(statep, instance);
     21      if (sp == NULL)
     22          return (ENXIO);
     23      rp = sp->regsp;
             . . .
     24      switch (cmd)  {

     25      case XX_GETREGS:   /* copy registers to arg */
     26            mutex_enter(&sp->reg_mutex);
     27            /*
     28             * Copy data from device registers to
     29             * temporary device register buffer
     30             * e.g. reg_buf.control = rp->control;
     31             */
     32            mutex_exit(&sp->reg_mutex);
     33            if (ddi_copyout(&reg_buf, arg,
     34                sizeof (struct device), mode) != 0) {
     35                    return (EFAULT);
     36            }

     37            break;
     38      }
     39  }

SEE ALSO

     ioctl(9E),     bcopy(9F),      copyin(9F),      copyout(9F),
     ddi_copyin(9F), uiomove(9F)

     Writing Device Drivers

NOTES

     The value of the flags argument to ddi_copyout()  should  be
     passed  through  directly  from the mode argument of ioctl()
     untranslated.

     Driver defined locks should not be held across calls to this
     function.

     ddi_copyout() should not be used from a streams driver.  See
     M_COPYIN and M_COPYOUT in STREAMS Programming Guide.