Device driver question (generic device driver)

Device driver question (generic device driver)

Post by Herbert Wenga » Sat, 27 Jul 1996 04:00:00

Hi, I post this for a colleague, who is unable to post here, so please

Now his questions:

I'm currently involved in writing a generic device driver, that
implements some common functions for other real drivers. My problem is:
How can I make sure that the generic driver is loaded first (before the
real driver modules)? Is there any order besides the order in the
How does the OS loads it's own generic driver-modules?
Is it on demand ?
If yes, how is the "demanding" encoded, and where (Is there a defaults
file for this ? Is it hardcoded or can it be configured?) ?

Any help appreciated!
Thanks in advance for your replies!




"Now's the time to impress not suppress your intellect, hold a gun to
 your head, if your mind's dead, blow away the cobweb" TEST DEPT; "bang
 on it" (Metal Edit) CD LEGACY (1990-1993), freud cd 047, efa 75230-2


1. Device driver calling another device driver.


I am having a problem writing a "meta-driver", ie one that is sandwiched
between the kernel and a real device driver. The platform I am using
consists of a Sun IPC, running SunOS 4.1.1.

My problem is that in attempting to use the OPEN(2V) system call from within
the "xxopen" routine of my metadriver (to open another device-driver (which
then opens the device)); OPEN(2V) "fails".

It appears that calling OPEN(2V) from within the kernel requires a different
calling sequence and argument list. Viz-a-viz: instead of a file descriptor
being returned by OPEN(2V), it seems a pointer is returned (which itself is
a pointer to something else).

Is this true? Is the OPEN(2V) syscall different for a process executing in
user address space, compared to the OPEN call executed by a process running
in kernel mode/address space?

If this is true for OPEN, what about CLOSE, READ, WRITE, etc? Unfortunately,
I don't have (easy) access to any Unix (source) code, to verify this.

Thanks in advance for help/advice.

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