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

copyin - copy data from a user program to a driver buffer

#include <sys/types.h>
#include <sys/ddi.h>
int copyin(const void *userbuf, void *driverbuf, size_t cn);

This interface is obsolete. ddi_copyin(9F) should be used instead.

User program source address from which data is transferred.


Driver destination address to which data is transferred.


Number of bytes transferred.

copyin() copies data from a user program source address to a driver buffer. The driver developer must ensure that adequate space is allocated for the destination address.

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

Under normal conditions, a 0 is returned indicating a successful copy. Otherwise, a −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 a −1 is returned to the caller, driver entry point routines should return EFAULT.

copyin() can be called from user context only.

Example 1 An ioctl() Routine

A driver ioctl(9E) routine (line 10) can be used to get or set device attributes or registers. In the XX_GETREGS condition (line 17), the driver copies the current device register values to a user data area (line 18). 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  };
 8  extern struct device xx_addr[];   /* phys. device regs. location */
 9    ...
10  xx_ioctl(dev_t dev, int cmd, int arg, int mode,
11      cred_t *cred_p, int *rval_p)
12               ...
13  {
14      register struct device *rp = &xx_addr[getminor(dev) >> 4];
15      switch (cmd) {
17      case XX_GETREGS: /* copy device regs. to user program */
18            if (copyin(arg, rp, sizeof(struct device)))
19                return(EFAULT);
20            break;
21               ...
22      }
23               ...
24  }

See attributes(7) for a description of the following attributes:

Stability Level Obsolete

attributes(7), ioctl(9E), bcopy(9F), copyout(9F), ddi_copyin(9F), ddi_copyout(9F), uiomove(9F)

Writing Device Drivers

Driver writers who intend to support layered ioctls in their ioctl(9E) routines should use ddi_copyin(9F) instead.

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

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

September 27, 2002 OmniOS