From: David Hawkins <dwh@ovro•caltech.edu>
To: Ming Liu <eemingliu@hotmail•com>
Cc: linuxppc-embedded@ozlabs•org
Subject: Re: how an application program utilizes the driver.
Date: Wed, 20 Sep 2006 09:14:46 -0700 [thread overview]
Message-ID: <451168F6.3030701@ovro.caltech.edu> (raw)
In-Reply-To: <BAY110-F240E99BA0EDF765EC09402B2230@phx.gbl>
Hi Ming,
> My situation is: I want to write a driver for my custom device.(In the
> driver there are some functions defined to read or write my device.) Then
> in my application program, I use these defined functions to operate my
> hardware device. I think this is a normal process to operate the hardware
> with driver+app, right?
Right, but you've missed a few critical points.
For your custom device, you'll create a driver that implements
*kernel space* functions my_driver_open(), read(), write(), close()
etc. You'll install that module and create an appropriate
device node, eg. /dev/my_driver.
In your *user-space* application code, you'll open that device
int main(argc, argv) ...
int fd = open("/dev/my_driver" ...)
and then write to your device ...
int write(fd, buffer, len);
or read from your device ...
int read(fd, buffer, len);
The user-space calls open, read, write eventually call down into
your driver space code. The driver and application are not
linked, they communicate via the /dev interface.
You really should read through Linux Device Drivers by Rubini,
or check out a tutorial such as
http://www.ovro.caltech.edu/~dwh/correlator/pdf/LNX-723-Hawkins.pdf
http://www.ovro.caltech.edu/~dwh/correlator/software/driver_design.tar.gz
http://www.ovro.caltech.edu/~dwh/correlator/index.html
Regards,
Dave
next prev parent reply other threads:[~2006-09-20 16:15 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-20 13:48 how an application program utilizes the driver Ming Liu
2006-09-20 16:14 ` David Hawkins [this message]
2006-09-20 16:30 ` Josh Boyer
2006-09-21 8:13 ` Ming Liu
2006-09-21 17:06 ` Eric Nuckols
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