Hardware I/O Port

[Dinosaur]

Hi All

I have converted a fairly large project from XPe to Linux, but before I tell the customer that I can do this
there is no way for me to test my hardware I/O ports.(because I dont have an ISA bus or I/O board)

For example:
ISA Bus
Plug in I/O board at &H1B0 address
First I/O bit would be turned on in

Dos
Out &H1b0,1

In XPe
InitializeWinIo (a library)
Out &H1b0,1

However what would be the equivalent in Linux ?

Regards

[D.J.Peters]

https://www.howtoforge.com/tutorial/acc ... -on-linux/
http://as6edriver.sourceforge.net/Paral ... ssing.html
http://tldp.org/HOWTO/IO-Port-Programming.html

[Dinosaur]

Hi All

D.J Peters thanks for the response.
I had already spent a lot of time browsing but came to an obstacle.

Print ioperm(&H1B0, 16, 1) will return -1 if not at Root and 0 when the program is executed as Root.

However my problem is how to get in & out of root before and after the IOPerm statement.
Hopefully without "Shell". It is written that once you have issued the IOPerm statement you can revert back to user level.

Is there a way to use SetUID from within my application, and what are the declare statements.
Most of the browsing shows that a certain ".h" file has to be included, but that that doesn't work in FB of course.

Regards

Edit: I guess another way is to start the Program as Root, then once the IOPerm calls are done, call SetUid to cancel Root.
Edit2: The other question that I cant find an answer to is: Does the calling program have to stay in privileged mode to allow the IO ?

[D.J.Peters]

directly access (as none driver) hardware is a security hole so it must be done with root rights !

I thing (but i'm not sure) a normal user can use /dev/parport0 /dev/lpt0 ... to access the lpt ports as file


1 On the Linux host system, use the ls command to determine the owner and group for the device.

For example: ls –la /dev/parport0

The third and fourth columns of the output show the owner and group, respectively. In most cases, the owner of the device is root and the associated group is lp.

2 To add the user to the device group, become root and open the /etc/group file in a text editor.

3 On the line that defines the lp group, add the Workstation username.

For example: lp::7:daemon,lp,username

Joshy

[Dinosaur]

Hi All

However the hardware is not a LPT port, it is a digital I/O board.
Would that work by simply changing the address as if it was an LPT port.
Like instead of &h378 let it be &H1b0

REgards

[D.J.Peters]

sorry I was meant IO port = LPT

my fault :-(

why not ask the manufacturer to solve your problem ?

Joshy

[Dinosaur]

Hi All

Joshy
I am the manufacturer of the equipment, and write the software to control it.

Regards

[D.J.Peters]

then write a linux driver that can use any user without root rights
what are the problem there are many examples in the kernel tree ?

Joshy

[D.J.Peters]

http://www.xml.com/ldd/chapter/book/ch08.html

[D.J.Peters]

Linux Device Drivers Training 01, Simple Loadable Kernel Module
https://www.youtube.com/watch?v=Zn8mEZX ... freload=10

Linux Device Drivers Training 02, module_init() and module_exit()
https://www.youtube.com/watch?v=IiHrZcZ ... freload=10

Linux Device Drivers Training 03, Modules from Multiple C Files, MODULE_LICENSE(), __init
https://www.youtube.com/watch?v=78YkQ4K ... freload=10

Linux Device Drivers Training 04, Exporting Symbols
Linux Device Drivers Training 05, Module Parameters
...

[Dinosaur]

Hi All

Thank you Joshy, some reading to do.

REgards

[caseih]

I'm not convinced that a linux kernel driver is necessary nor desired.

In CNC applications it's common to interface with controllers via a parallel-port, and this can be accomplished without root, provided the /dev/lp# entry has read and write perms for normal users. I believe you can read and write to signals in a manner similar to how you describe in Windows.

Another possible solution is to use a USB to general-purpose i/o adapter and use libusb to communicate with it, requiring no drivers whatsoever. How many digital logic signals do you need to work with and do you require special, strict timing on those signals? Do you need interrupt routines to fire on a signal changing or can you poll for the signal change from your application?

[Dinosaur]

Hi All

caseih thanks for your reply.
So far I have concluded that if I start my program as Root, then using "IOPerm(&H1B0,16,1)" the ports seem to be accessible.
By using "Shell su newuser" I can cancel the Root user, which according to the docs will then still allow the port IO.
However that is not the cleanest solution.

Basically I am fixed with hardware, the system already exists and the purpose of the exercise is to evaluate if I can
convert from XPe to Linux. The cpu boards used are becoming obsolete, and there is a need to replace them and thus the need to go to Linux.
There are in fact 5 x 48 bit I/O boards with Timer/counters in this particular installation. WinXPe demands new licenses for the new cpu boards, plus the
fact that new compact flash images have to be created.

REgards

[TJF]

So far I have concluded that if I start my program as Root, then using "IOPerm(&H1B0,16,1)" the ports seem to be accessible.
By using "Shell su newuser" I can cancel the Root user, which according to the docs will then still allow the port IO.
However that is not the cleanest solution.

I think setuid() is what you're looking for.

Regards

[Dinosaur]

Hi All

After lots of trials, the following works in Terms of the Code.
But I have not actually confirmed it working on a system with an addressable I/O board.

In a Root Terminal give the program RawIO capabilities:

Code: Select all

setcap cap_sys_rawio=ep MyExecutable

setcap means set capabilities.
e Meaning Effective User
p Meaning Permission
To confirm the capabilities:

getcap MyExecutable 'will print the following
MyExecutable = cap_sys_rawio+ep

Now in my code:

Code: Select all

Declare Function ioperm Cdecl Alias "ioperm" (Byval Portbase As Integer,Byval nPorts As Integer,Byval value As Integer) As Integer
Print	ioperm(&H140, 16, 1)

If it prints 0 (zero) then success, -1 = Failure.

Would dearly love someone with the hardware to prove this for me.
Even just an LPT port.

Regards