Specifications

Operating System Routines
IOC$MOVFRUSER, IOC$MOVFRUSER2
IOC$MOVFRUSER, IOC$MOVFRUSER2
Move data from a user buffer to a device.
Module
BUFFERCTL
Input
Location Contents
R0 Address of byte to be moved (IOC$MOVFRUSER2
only)
R1 Address of driver’s buffer
R2 Number of bytes to move
R5 Address of UCB
DPT$B_FLAGS Bit DPT$V_SVP set (causing a system page-table
entry (SPTE) to be allocated to the driver)
UCB$L_SVAPTE System virtual address of PTE that maps the first
page of the buffer
UCB$L_SVPN System virtual page number of SPTE allocated to
driver
UCB$W_BOFF Byte offset to start of transfer in page
Output
R0 Next address of user’s buffer
Synchronization
The caller of IOC$MOVFRUSER or IOC$MOVFRUSER2 may be executing at
fork IPL or above and must hold the corresponding fork lock in a multiprocessing
environment. Either routine returns control to its caller at the caller’s IPL. The
caller retains any spinlocks it held at the time of the call.
Description
A driver calls IOC$MOVFRUSER and IOC$MOVFRUSER2 to move data from a
user buffer to a device that cannot itself map the user buffer to system virtual
addresses (for instance, a non-DMA device).
In order to accomplish the move, IOC$MOVFRUSER and IOC$MOVFRUSER2
first map the user buffer using the system page-table entry (SPTE) the driver
allocated in a DPTAB macro invocation. If an SPTE has not been allocated to
the driver, these routines cause an access violation when they attempt to refer
to the location addressed by the contents of the field UCB$L_SVAPTE. (See the
description of the DPTAB macro in Chapter 2 for information on how to allocate
this SPTE.)
3–108