Unix Programming - Need sample C code for access I/O ports

Author

Need sample C code for access I/O ports

Steven Woody

2005-08-23, 5:56 pm

i got a mutipl-port serial board and need to write a simple C program to set
its base addresses in a Linux box. according to the user manual of the board,
the job can be accomplish be write/read some bytes to some specify IO ports.

i got no more experiences in accessing IO ports in Linux, so i think i'd better
find some simple code rather than coding from scratch.

any help will be highly appreciated.

--
steven woody (id: narke)

Ben Sanderson: Are you desirable? Are you irresistible? Maybe if you
drank bourbon with me, it would help. Maybe if you kissed me and I
could taste the sting in your mouth it would help. If you drank
bourbon with me naked. If you smelled of bourbon as you XXXXed me, it
would help. It would increase my esteem for you. If you poured bourbon
onto your naked body and said to me "drink this". If you spread your
legs and you had bourbon dripping from your breasts and your pussy and
said "drink here" then I could fall in love with you. Because then I
would have a purpose. To clean you up and that, that would prove that
I'm worth something. I'd lick you clean so that you could go away and
XXXX someone else.

- Leaving Las Vegas (1995)

Henrik Carlqvist

2005-08-23, 5:56 pm

Steven Woody <anti-spam.narkewoody@gmail.com.dont-post-to> wrote:
> i got a mutipl-port serial board and need to write a simple C program to
> set its base addresses in a Linux box. according to the user manual of
> the board, the job can be accomplish be write/read some bytes to some
> specify IO ports.

It sounds as if you are going to write a driver for that card? There are a
lot of "sample code" in /usr/src/linux. Check in
/usr/src/linux/driver/char for files like moxa.c and serial.c.

regards Henrik
--
The address in the header is only to prevent spam. My real address is:
hc7(at)uthyres.com Examples of addresses which go to spammers:
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Steven Woody

2005-08-24, 6:11 pm

Fletcher Glenn

2005-08-24, 6:11 pm

Steven Woody wrote:
> Henrik Carlqvist <Henrik.Carlqvist@deadspam.com> writes:
>
>
>
>
> no, i am _not_ going to write any driver program. what i want to write is a
> program running on user space and change the boards's base address by writting
> specific bytes to some specific ports.
>
>

Unfortunately, user space programs do not have access to the raw memory
interface. If you have a driver for this card that allows you to
interact with the card directly, then fine. Otherwise, you must
write a driver that executes from kernel space.

--

Fletcher Glenn

David Schwartz

2005-08-24, 6:11 pm

"Steven Woody" <anti-spam.narkewoody@gmail.com.dont-post-to> wrote in
message news:87u0hgnakp.fsf@narke.yellow.line...

> i got a mutipl-port serial board and need to write a simple C program to
> set
> its base addresses in a Linux box. according to the user manual of the
> board,
> the job can be accomplish be write/read some bytes to some specify IO
> ports.
>
> i got no more experiences in accessing IO ports in Linux, so i think i'd
> better
> find some simple code rather than coding from scratch.
>
> any help will be highly appreciated.

Read the man page for "iopl". But you are doing this the wrong way, you
should write a driver.

DS

Steven Woody

2005-08-25, 6:04 pm

Henrik Carlqvist <Henrik.Carlqvist@deadspam.com> writes:

> Steven Woody <anti-spam.narkewoody@gmail.com.dont-post-to> wrote:
>
> It sounds as if you are going to write a driver for that card? There are a
> lot of "sample code" in /usr/src/linux. Check in
> /usr/src/linux/driver/char for files like moxa.c and serial.c.
>
> regards Henrik
> --
> The address in the header is only to prevent spam. My real address is:
> hc7(at)uthyres.com Examples of addresses which go to spammers:
> info@k-soft.se info@k-software.biz info@webrider.ru root@localhost
>

no! i am not about to write any driver. i just want to do some setting things
on a multiport serial board. the board got some eeprom and use it to store io
addresses and irq numbers for each serial port build on it. according to the
manual, if i want to get/change those data stored in the eeprom, i have to do
it via read/write some specific io ports which is dedicated for configuration.

today, i skimmed the Linux's IO Port programming HOWTO, i think i should use
inb/outb to do the job, is that right?

thanks.

--
steven woody (id: narke)

How Far You Fall Doesn't Matter, It's How You Land

- Haine, La (1995)

Henrik Carlqvist

2005-08-25, 6:04 pm

Steven Woody <anti-spam.narkewoody@gmail.com.dont-post-to> wrote:
> no! i am not about to write any driver. i just want to do some setting things
> on a multiport serial board. the board got some eeprom and use it to store io
> addresses and irq numbers for each serial port build on it. according to the
> manual, if i want to get/change those data stored in the eeprom, i have to do
> it via read/write some specific io ports which is dedicated for configuration.
>
> today, i skimmed the Linux's IO Port programming HOWTO, i think i should use
> inb/outb to do the job, is that right?

Yes, you can probably write a program using ioperm and outb to change
those settings. But then what? If you from user space change the IRQ
and/or address of a serial port the kernel is going to be confused if it
before thought that the port should have other values. Maybe you could fix
this with the program setserial.

regards Henrik
--
The address in the header is only to prevent spam. My real address is:
hc7(at)uthyres.com Examples of addresses which go to spammers:
info@k-soft.se info@k-software.biz info@webrider.ru root@localhost

Floyd L. Davidson

2005-08-25, 8:52 pm

Henrik Carlqvist <Henrik.Carlqvist@deadspam.com> wrote:
>Steven Woody <anti-spam.narkewoody@gmail.com.dont-post-to> wrote:

Yes, that should do just fine for writing a board configuration
program. This isn't something that will be used except for the
one time you install and configure the board.
[vbcol=seagreen]
>Yes, you can probably write a program using ioperm and outb to change
>those settings. But then what? If you from user space change the IRQ
>and/or address of a serial port the kernel is going to be confused if it
>before thought that the port should have other values. Maybe you could fix
>this with the program setserial.

That is exactly the same as if the board had hardware jumpers to
set the port addresses and IRQ's. In either case the kernel
(driver) doesn't really know what they are, and if it isn't the
default it has to be set. I'm not sure what the approved way to
do that is today, but /setserial/ should work.

However, I would expect that the best way would be to load the
driver with the appropriate command line options, assuming the
driver for that board does in fact have such facilities. In any
case, reading the docs on the driver being used would be
essential.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

Steven Woody

2005-08-28, 2:48 am

"David Schwartz" <davids@webmaster.com> writes:

> "Steven Woody" <anti-spam.narkewoody@gmail.com.dont-post-to> wrote in
> message news:87u0hgnakp.fsf@narke.yellow.line...
>
>
> Read the man page for "iopl". But you are doing this the wrong way, you
> should write a driver.
>
> DS
>
>

i believe there is some misunderstands here, a user space program rather than a
driver should do the job. allow me to describe the problem in a more clear way,

i have a multiple-port-serial-board. the board comes w/o any jumpers, it gets
io/irq values for each port it provided by reading those values from its
on-board EEPROM as soon as power up. so, if one would like to change the
io/irq settings in linux, he has to

1, write new io/irq values into the board's eeprose.
2, power down the board.
3, 'setserial' to the new io/irq's, so the software setting will agree with
hardward facts.

so, the program i about to write need to do only the 1st step. writing values
to EEPROM needs not be any driver program, doesn't it?

--
steven woody (id: narke)

Charles: Let me ask you one thing. Do you think - after we've dried
off, after we've spent lots more time together - you might agree *not*
to marry me? And do you think not being married to me might maybe be
something you could consider doing for the rest of your life?
Carrie: I do.

- Four Weddings and a Funeral (1994)

Eef Hartman

2005-08-30, 8:14 am

In alt.os.linux.slackware Steven Woody <anti-spam.narkewoody@gmail.com.dont-post-to> wrote:
> 1, write new io/irq values into the board's eeprose.
> 2, power down the board.
> 3, 'setserial' to the new io/irq's, so the software setting will agree with
> hardward facts.
>
>
> so, the program i about to write need to do only the 1st step. writing values
> to EEPROM needs not be any driver program, doesn't it?

Yeah, but I don't believe a user-mode program CAN write to eeprom, all I/O
addresses are under kernel control (which means you have to be able to call
the driver TO get those addresses allocated to "your program", which means
the kernel MUST already have a driver for that board).
--
****************************************
****************************
** Eef Hartman, Delft university of Technology, dept. EWI/TW **
** e-mail: E.J.M.Hartman@math.tudelft.nl, fax: +31-15-278 7295 **
** snail-mail: P.O. Box 5031, 2600 GA Delft, The Netherlands **
****************************************
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Nils O. Selåsdal

2005-08-30, 6:00 pm

Eef Hartman wrote:
> In alt.os.linux.slackware Steven Woody <anti-spam.narkewoody@gmail.com.dont-post-to> wrote:
>
>
>
> Yeah, but I don't believe a user-mode program CAN write to eeprom, all I/O
> addresses are under kernel control (which means you have to be able to call
> the driver TO get those addresses allocated to "your program", which means
> the kernel MUST already have a driver for that board).
There are exceptions.
e.g. linux on x86 can give user applications the privilege to execute
in/out instructions directly.