DDI_COPYOUT(9F) Kernel Functions for Drivers DDI_COPYOUT(9F)

ddi_copyout - copy data from a driver

#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);

illumos DDI specific (illumos DDI).

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 information about buf.

This routine is designed for use in driver ioctl(9E) routines 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 efficient move algorithm according to address alignment.

Under normal conditions, 0 is returned to indicate a successful copy. Otherwise, −1 is returned if one of the following occurs:

Paging fault; the driver tried to access a page of memory for which it did not have read or write access.
Invalid user address, such as a user area or stack area.
Invalid address that would have resulted in data being copied into the user block.
Hardware fault; a hardware error prevented access to the specified user memory. For example, an uncorrectable parity or ECC error occurred.

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

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

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 condition (line 25), the driver copies the current device register 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  }

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

Writing Device Drivers

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.

April 19, 2000 OmniOS