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来自「linux下的MPEG1」· 代码 · 共 39 行

dhahelper is small driver to provide some kernel function into userspace.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The main reason you need to use dhahelper is for busmastering.
(Btw, lacking of possibility to implement conversion of
virtual addresses into physical in userspace caused
implementing of so-called DRM drivers for Linux from
XFree86 side).
Second goal (still is unfinished) - provide possibility
to control port and physical memory access through
groups and access rights of this driver. (Unix way).

Installation:
~~~~~~~~~~~~~
just type in this directory:
make all install

The device node /dev/dhahelper will be created.  The initial
permissions of this node are restrictive.  See below for information
on how to make it available to non-root users.

Porting:
~~~~~~~~
This driver was developed only for Linux.
So if someone will port that on other unices
then any patches are gladly accepted.

WARNING:
~~~~~~~~

This driver violates some kernel security rules.  To keep this driver
from anonymous access I suggest you create a new group (e.g. dha) for
/dev/dhahelper and set the permissions to 660 (or ug+rw,o-rw).  Then
do one of the following:

- add trusted users to group dha.
- make trusted applications SGID to dha.

Good luck!