copyout(D3)copyout(D3)NAMEcopyout - copy data from a driver buffer to a user buffer
SYNOPSIS
#include <sys/types.h>
#include <sys/ddi.h>
int copyout(caddr_t driverbuf, caddr_t userbuf, size_t count);
Arguments
driverbuf Driver source address from which copy is made.
userbuf User destination address to which copy is made.
count Number of bytes to copy.
DESCRIPTIONcopyout copies count bytes of data from the kernel virtual address
specified by driverbuf to the user virtual address specified by userbuf.
Return Values
On success, copyout returns 0. On failure, it returns -1 to indicate
that the specified user address range is not valid.
USAGEcopyout chooses the best algorithm based on address alignment and number
of bytes to copy. Although the source and destination addresses are not
required to be word aligned, word aligned addresses may result in a more
efficient copy.
Drivers usually convert a return value of -1 into an EFAULT error.
Level
Base only.
Synchronization Constraints
Can sleep.
Driver-defined basic locks and read/write locks may not be held across
calls to this function.
Driver-defined sleep locks may be held across calls to this function.
Warnings
The driver source buffer must be completely within the kernel address
space, or the system can panic.
When holding sleep locks across calls to this function, drivers must be
careful to avoid creating a deadlock. During the data transfer, page
fault resolution might result in another I/O to the same device. For
example, this could occur if the driver controls the disk drive used as
the swap device.
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copyout(D3)copyout(D3)
Examples
A driver ioctl(D2) routine (line 5) can be used to get or set device
attributes or registers. If the specified command is XX_GETREGS (line
9), the driver copies the current device register values to a user data
area (line 11). If the user address is invalid, an error code is
returned.
1 struct device { /* device registers layout */
...
2 int status; /* device status word */
3 };
4 extern struct device xx_dev[]; /* physical device registers */
...
5 xxioctl(dev_t dev, int cmd, void *arg, int mode, cred_t *crp, int *rvp)
6 {
7 struct device *dp;
8 switch (cmd) {
9 case XX_GETREGS: /* copy device registers to user program */
10 dp = &xx_dev[getminor(dev)];
11 if (copyout((caddr_t)dp, arg, sizeof(struct device)))
12 return (EFAULT);
13 break;
REFERENCESbcopy(D3), copyin(D3), uiomove(D3), ureadc(D3), uwritec(D3)
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