Low level I/O ports accessed via CPU instructions
Hardware architecture specific I/O ports which are accessed via the inb() and outb() family of functions in <sys/io.h>.
Questions tagged [hardware-port]
19 questions
10
votes
2 answers
what does "outb" in AT&T asm mean?
I am reading some code of Linux.
The keyboard.S has something like
outb %al,$0x61
and
inb $0x61,%al
I think the pending 'b' means 'byte', but i still cannot find what these instructions mean.
onemach
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6
votes
3 answers
Low level I/O access using outb and inb
i'm having hard time trying to understand how interrupts work.
the code below initialize the Programmable Interrupt Controller
#define PIC0_CTRL 0x20 /* Master PIC control register address. */
#define PIC0_DATA 0x21 /* Master PIC data…
Amine Hajyoussef
- 4,381
- 3
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4
votes
4 answers
Finding device base address to communicate via inb() and outb()
I am trying to communicate with a disk drive using inb(), inw(), outb() and outw() commands so I can find specific information about the drive. However, to use these commands, I need the correct I/O ports for the device. When I have the correct…
Kevin S
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3
votes
1 answer
inline asm: operand type mismatch for 'out'
I don't know assembly in depth. Following code is for writing to hardware port.
Compiler gives operand type mismatch error in every line where inline asm is used.When I compile I get these errors:
port.cpp: Assembler messages:
port.cpp:27:…
welkin
- 43
- 5
2
votes
2 answers
What is outb() function call in Linux?
Can someone please explain the meaning of
outb(0x10,short_base+2);
I tried figuring out by googling it, but for no use.
Sagar Jain
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2
votes
0 answers
Not able to light up keyboard LED using outb() call
I am trying to light up the keyboard LED in Linux with the following program (found this on internet) but nothing seems to happen. Am I missing anything?
/* sample.c: very simple example of port I/O
*
* This code does nothing useful, just a port…
pkumarn
- 1,383
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2
votes
2 answers
How to access Parallel port in Linux
On my Linux machine (Debian Wheezy), I tried to access the parallel port by request_region() but it failed because the system had already loaded the kernel module parport...
So, I rmmod the modules lp, ppdev, parport_pc and parport. Then, I could…
Xiaobo Zhang
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1
vote
2 answers
Reading and writing on I/O ports
I am trying to understand the following code:
#include
#include
#include
#define baseport 0x378
int main()
{
int b;
if(ioperm(baseport,3,1))
{
perror("ioperm");
exit(1);
}
…
karan421
- 863
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- 43
1
vote
1 answer
PC hardware port access from Java on Linux
What is the Java-on-Linux equivalent to the C byte-sized PC-architecture hardware port input/output functions?
For output there is outb as in this:
tmp = inb(0x61);
if (tmp != (tmp | 0x01))
outb(0x61, tmp | 0x01);
For input there is inb as in…
H2ONaCl
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1
vote
0 answers
ReadFile reads from Hyperterminal window but not from external device
I have this program that uses winapi functions for reading from a serial port:
#include
#include
using std::cin;
using std::cout;
DCB blank_dcb = {0};
int main()
{
int ierr, jsu, jcs, jto, jrf, nt;
unsigned char…
TRPh
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- 1
- 9
1
vote
3 answers
Windows equivalent of inb(), outb(), low level i/o
I have some Linux code that monitors our hardware by collecting temperatures, voltages, and fan speeds, from the motherboard using inb(), outb(), inl(), etc. low level i/o functions.
My challenge is to port that code over to run under Windows as a…
Sebastian Dwornik
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- 2
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1
vote
1 answer
How can Java Write/Read hardware ports like C does? (outb, inb etc..)
I've a C application. This application writes and reads some I/O port addresses.
I think that Java can't access low level I/O address natively. Am I right?
Here is an example of C++ app:
#include
#include
#include…
The_Reaper
- 157
- 10
1
vote
2 answers
character device driver
The read() and write() callback functions in our ‘cmosram.c’ device-driver only transfer a single byte of data for each time called, so it takes 128 system-calls to read all of the RTC storage-locations!
Can you improve this driver’s efficiency, by…
sandra
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- 2
1
vote
1 answer
Driver accessing ports with inb() and outb()
I am making a device driver that turns on and off the keyboard leds by receiving any combination of three, two, one or none digit which should be 1, 2 or 3, if I make:
echo 12 > /dev/ledDevice
The program should turn on Num lock, Caps lock and…
Kaostias
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1
vote
2 answers
first kernel space driver in -- linux
I was able to control GPIO using mmap system call to control LED operation directly from the user space. Now I want to implement driver in kernel space.
I am trying to write my first kernel space device driver for 16*2 line of LCD in Linux for ARM…
Katoch
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