copyin(D3)

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

SYNOPSIS
     #include <sys/types.h>
     #include <sys/ddi.h>
     int copyin(caddr_t userbuf, caddr_t driverbuf, size_t count);

   Arguments
     userbuf   User source address from which copy is made.

     driverbuf Driver destination address to which copy is made.

     count     Number of bytes to copy.

DESCRIPTION
     copyin copies count bytes of data from the user virtual address specified
     by userbuf to the kernel virtual address specified by driverbuf.

   Return Values
     If the copy is successful, 0 is returned.  Otherwise, -1 is returned to
     indicate that the specified user address range is not valid.

USAGE
     The driver must ensure that adequate space is allocated for the
     destination address.

     copyin 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, multithreaded
     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.

   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_SETREGS (line
     9), the driver copies user data to the device registers (line 11).  If
     the user address is invalid, an error code is returned.

      1  struct  device {     /* device registers layout */
          ...
      2   int command;   /* device command 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_SETREGS:    /* copy user program data to device registers */
     10        dp = &xx_dev[getminor(dev)];
     11        if (copyin(arg, (caddr_t)dp, sizeof(struct device)))
     12             return (EFAULT);
     13        break;

REFERENCES
     bcopy(D3), copyout(D3), uiomove(D3), ureadc(D3), uwritec(D3)