What is ioctl in Linux kernel?
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What is ioctl in Linux kernel?
In computing, ioctl (an abbreviation of input/output control) is a system call for device-specific input/output operations and other operations which cannot be expressed by regular system calls. It takes a parameter specifying a request code; the effect of a call depends completely on the request code.
How is ioctl implemented in Linux?
ioctl() is typically implemented as part of the corresponding driver, and then an appropriate function pointer is initialised with it, exactly as in other system calls like open() , read() , etc. For example, in character drivers, it is the ioctl or unlocked_ioctl (since kernel 2.6.
Where is ioctl defined?
An ioctl() request has encoded in it whether the argument is an in parameter or out parameter, and the size of the argument argp in bytes. Macros and defines used in specifying an ioctl() request are located in the file .
How do you communicate from user space to kernel space?
There are couple of well known methods to communicate from user space to kernel space.
- Virtual file system like /proc , /sys , /configfs , /debugfs Standard.
- system call like read() , write() , open() , close() , fork()
- ioctl for char drivers.
- netlink socket – mostly used by network subsystem.
How do I find my I2C device address?
Connect the device you want to probe to the Arduino (preferably without connecting other I2C devices at the same time), and run the sketch. The scanner will cycle through all possible I2C addresses, and once it receives a response from the device, it will inform you of the address that worked.
What is the difference between kernel space and user space?
Kernel space is strictly reserved for running a privileged operating system kernel, kernel extensions, and most device drivers. In contrast, user space is the memory area where application software and some drivers execute.
How is kernel space and user space interface?
3.2 Kernel and user space The kernel provides certain services, and user space, that is, everything outside the kernel, both libraries and application programs, uses these. Programs in user space contain system calls that ask the kernel to do something, and the kernel does so, or returns an error code.
