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

NAME

copyout - copy data from a driver to a user program

SYNOPSIS

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


int copyout(const void *driverbuf, void *userbuf, size_t cn);

INTERFACE LEVEL

This interface is obsolete.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

PARAMETERS

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


userbuf
Destination address in the user program to which the data
is transferred.


cn
Number of bytes moved.

DESCRIPTION

copyout() copies data from driver buffers to user data space.


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 algorithm according to
address alignment.

RETURN VALUES

Under normal conditions, a 0 is returned to indicate a successful copy.
Otherwise, a -1 is returned if one of the following 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 uncorrectable parity
or ECC error occurred.


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

CONTEXT

copyout() can be called from user context only.

EXAMPLES

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 };
7
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) {
16
17 case XX_GETREGS: /* copy device regs. to user program */
18 if (copyout(rp, arg, sizeof(struct device)))
19 return(EFAULT);
20 break;
21 ...
22 }
23 ...
24 }

ATTRIBUTES

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


+----------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+----------------+-----------------+
|Stability Level | Obsolete |
+----------------+-----------------+

SEE ALSO

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


Writing Device Drivers

NOTES

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


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


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

September 27, 2002 COPYOUT(9F)