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Software Installation
rev 2.0
SFPCI -VME SERIES User’s Guide and Installation Manual
38
5.7.2 PVME Control Registers
The PVME nexus driver exports another device file for direct access to the nexus’s
control registers:
/dev/pvme/nexctl-Used to access the PVME control registers.
This file is present for diagnostic purposes, such as to examine the current control
register settings of the PVME. It is not ordinarily something that the user has a need to
use. Since it permits direct access to the PVME device registers, it is possible to change
PVME control register settings with this mechanism. The user is advised to exercise
great caution if he desires to try this, since an incorrect value inserted into one of the
PVME control registers has the potential to put the PVME into a mode that could result
in a system panic.
5.7.3 VME Device File Example
The VME device files give a user the ability to access any of the VME address spaces
directly.
To illustrate, VME A32 space may be accessed by a user program by opening the
/dev/
pvme/vme32d32
device file and then using
mmap
(2) or
lseek
(2) and
read
(2) or
write
(2) to access the desired address in VME A32 space.
Example 4, “User mapping of a VME address space,” on page 35 illustrate show this
might be done.