physiock(D3)

NAME
     physiock - validate and issue a raw I/O request

SYNOPSIS
     #include <sys/types.h>
     #include <sys/buf.h>
     #include <sys/uio.h>
     #include <sys/ddi.h>
     int physiock(void (*strat)(), buf_t *bp, dev_t dev, int rwflag,
          daddr_t nblocks, uio_t *uiop);

   Arguments
     strat     Address of the driver strategy(D2) routine, or similar
               function.
     bp        Pointer to the buf(D4) structure describing the I/O request.
     dev       External device number.
     rwflag    Flag indicating whether the access is a read or a write.
     nblocks   Number of blocks that the logical device dev can support.
     uiop      Pointer to the uio(D4) structure that defines the user space of
               the I/O request.

DESCRIPTION
     physiock is called by the character interface ioctl(D2), read(D2), and
     write(D2) routines of block drivers to help perform unbuffered I/O while
     maintaining the buffer header as the interface structure.

   Return Values
     physiock returns 0 if the result is successful, or the appropriate error
     number on failure.  If a partial transfer occurs, the uio structure is
     updated to indicate the amount not transferred and an error is returned.
     If a read is performed at the end of the device, 0 is returned.

     ENOSPC
          An attempt is made to read beyond the end of the device.

     ENOSPC
          An attempt is made to write at or beyond the end of the device.

     EFAULT
          The user memory is not valid.

     EAGAIN
          physiock could not lock all of the pages.

     EINVAL
          The offset is not a multiple of NBPSCTR.

     EBUSY
          There is not enough kernel memory available to map the user pages to
          kernel virtual memory.
USAGE
     physiock performs the following functions:

          verifies the requested transfer is valid by checking if the offset
          is at or past the end of the device (this check is bypassed if the
          size parameter argument nblocks is zero) and that the offset is a
          multiple of NBPSCTR

          sets up a buffer header describing the transfer

          faults pages in and locks the pages impacted by the I/O transfer so
          they can't be swapped out

          calls the driver strategy routine passed to it (strat)

          sleeps until the transfer is complete and is awakened by a call to
          biodone(D3) from the driver's I/O completion handler

          performs the necessary cleanup and updates, then returns to the
          driver routine

     A transfer using physiock is considered valid if the specified data
     location exists on the device, and the user has specified a storage area
     large enough that exists in user memory space.

     If bp is set to NULL, a buffer is allocated temporarily and freed after
     the transfer completes.

     If rwflag is set to B_READ, the direction of the data transfer will be
     from the kernel to the user's buffer.  If rwflag is set to B_WRITE, the
     direction of the data transfer will be from the user's buffer to the
     kernel.

     One block is equal to NBPSCTR bytes.  NBPSCTR is defined in sys/param.h.

   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.

REFERENCES
     buf(D4), ioctl(D2), read(D2), strategy(D2), uio(D4), write(D2),
     uiophysio(D3X)