ioctl (Input Output ConTroL) is a system call for device-specific I/O operations and other operations which cannot be expressed by regular system calls and it provides an interface through which an application can communicate directly with a device driver(or any other global kernel space variables). Applications can use the standard control codes or device-specific control codes to perform direct input and output operations.
Questions tagged [ioctl]
691 questions
15
votes
3 answers
unlocked_ioctl vs normal ioctl
In my driver's file_operations structure, I have:
struct file_operations Fops = {
read: device_read,
write: device_write,
unlocked_ioctl: device_ioctl,
...
};
I.e. there is no ioctl field used. Is this sufficient to avoid Big Kernel…
anon
14
votes
4 answers
Reading / writing from using I2C on Linux
I'm trying to read/write to a FM24CL64-GTR FRAM chip that is connected over a I2C bus on address 0b 1010 011.
When I'm trying to write 3 bytes (data address 2 bytes, + data one byte), I get a kernel message ([12406.360000] i2c-adapter i2c-0:…
TheSeeker
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14
votes
3 answers
How to set errno in Linux device driver?
I am designing a Linux character device driver. I want to set errno when error occurs in ioctl() system call.
long my_own_ioctl(struct file *file, unsigned int req, unsigned long arg)
{
long ret = 0;
BOOL isErr = FALSE;
// some…
Andrew Chang
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13
votes
2 answers
ioctl is not called if cmd = 2
I am developing a kernel module that uses unlocked_ioctl. I tested it with kernel version 2.6.24-23-generic and it works perfectly. Now I tried it with kernel version 3.3.1-1-ARCH and something weird happens: the ioctl function is not executed when…
Javier J. Salmeron Garcia
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12
votes
2 answers
Get IPv6 addresses in linux using ioctl
I trying to get IPv6 addresses in my linux OS like following:
sd = Socket_m(AF_INET6_m, SOCK_DGRAM_m, 0);
ifc.ifc_buf = buffer_p;
ifc.ifc_len = buffSize;
Ioctl_m(sd, SIOCGIFCONF, &ifc);
It works succesfully if any IPv4 address are configured for…
Yury Bushev
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11
votes
3 answers
Maximum buffer length for sendto?
How do you get the maximum number of bytes that can be passed to a sendto(..) call for a socket opened as a UDP port?
epatel
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11
votes
1 answer
Where are ioctl parameters (such as 0x1268 / BLKSSZGET) actually specified?
I am looking for a definitive specification describing the expected arguments and behavior of ioctl 0x1268 (BLKSSZGET).
This number is declared in many places (none of which contain a definitive reference source), such as linux/fs.h, but I can find…
Jason C
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10
votes
2 answers
Set IP address using SIOCSIFADDR ioctl
I am trying to get and set the IP address using the IOCTL interface on Linux.
I am successfully able to get and set it. When I set the ip address,
ifconfig eth0 shows a proper IP address, but then the system gets disconnected.
i.e. System is not…
PrashantB
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10
votes
3 answers
How to check if interface is up
Title pretty much says it all. If I run ifconfig, I get this:
eth0: flags=4163 mtu 1500
inet -snip- netmask 255.255.255.0 broadcast -snip-
...
Using this, I can know if it's up or not (
MiJyn
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10
votes
3 answers
How to properly convert a C ioctl call to a python fcntl.ioctl call?
Following an example on resetting a serial port in Linux I wanted to translate the following snippet
fd = open(filename, O_WRONLY);
ioctl(fd, USBDEVFS_RESET, 0);
close(fd);
into valid python code. Here is what I have tried so far
file_handler =…
Alex
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9
votes
2 answers
Send IOCTL to Windows device driver - CreateFile fails
I want to send an IOCTL command to a PC/SC reader connected to my computer (win7 64 bit).
In order to send an IOCTL command I need a HANDLE to the device, which I'm unable to create.
The device is listed as "OMNIKEY 1021" in the device manager, the…
bmotmans
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9
votes
3 answers
Is it possible to call a user-space callback function from kernel space in Linux (ioctl)?
Is it possible to expand the ioctl interface in Linux so that the user-space application can send a pointer to a function to the kernel space driver?
I'm in particular thinking of ways to handle the stream in user-controllable way but doing it in…
Makis
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9
votes
4 answers
How Linux knows which ioctl function to call?
Here is the ioctl call in user space:
int ioctl(int fd, int cmd, ...);
As far as I know, when we want to perfrom IO operations, we define our own ioctl function with a set of requests (commands), assign our ioctl to a file_operations structure like…
Amumu
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9
votes
3 answers
Using RNDADDENTROPY to add entropy to /dev/random
I have a device which generates some noise that I want to add to the entropy pool for the /dev/random device in an embedded Linux system.
I'm reading the man page on /dev/random and I don't really understand the structure that you pass into the…
Benjamin Leinweber
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8
votes
4 answers
C/C++ Linux MAC Address of all interfaces
I am using the following code to retrieve all MAC addresses for current computer:
ifreq ifr;
ifconf ifc;
char buf[1024];
int sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
if (sock == -1) { ... };
ifc.ifc_len = sizeof(buf);
ifc.ifc_buf = buf;
if…
user1173626
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