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Questions tagged [userspace]

109 questions
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Toggling multiple GPIOS using from linux userspace

I am writing application over linux embedded. I have two leds that I can turn on and off using two different GPIO's pins. I would like to sync them, by setting both GPIO pins at the same time. This is doable since the GPIO HW has one register for…
Arnon Charas
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Why the size of operating systems (clean install) is increasing?

Ok, this is just a simple question, but I really like to have some answers from people that create distributions (linux) or if there are also people involved on OsX or Windows. The size after installation seems to be increasing, Windows 10 requires…
Antonio Caruso
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share memory between kernel and user space using sys v

i see that is so easy to share memory segment between user space process using sys v api (shmget(), shmat(), shmdt() ), is there any solution to use the same api to share memory from kernel to user space.
Mondher123
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Questions about memory management of a process

I have few question of operating system. I Google a lot but not able to find out any answer. Can anyone please help me. Q1. How much memory is made available to a user program by the kernel, is there any limit to it? Q2. What is the range of…
Geek
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Data cannot be written to device file from userspace program

I am developing a kernel module for custom device that, in fact, a 4*8-bit i-o ports attached to ISA bus with addresses 0x0120 - 0x0123. This driver is based on "scull" by Alessandro Rubini and Jonathan Corbet. My OS is Ubuntu 10.04, kernel is…
AV_Master
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Linux userspace DMA access (for memory-memory copy)

My embedded ARM device has a 800x480 16 bit Linux framebuffer LCD which needs to be double-buffered manually. At the moment I'm just using memcpy() to write the double buffer to the framebuffer which is awfully slow. A while(1){memcpy(lfb,dbuf)}…
thecoder
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How to access SurfaceFlinger from userspace program?

I would like to write a userspace program to talk to SurfaceFlinger and call its dump function. How can I access SurfaceFlinger and make such a call from my C++ program? I know that SurfaceFlinger is instantiated in main_surfaceflinger.cpp and is…
Matt
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How to send Notification from Kernel to user space application using SYSFS

I'm working in an USB ACM driver, "where i need to send notification from kernel space to user space application for invoking a call back function". I'm not much aware of using kernel to user interfaces in code. how well can sysfs help for this…
Mukesh Bharath Ramalingam
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In reference to fibers, what is user space?

When people explain the difference between threads and fibers, they often refer to the fact that fibers are in "user space". What does "user space" mean?
Jacob Zimmerman
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Can I pass an integer to `access_ok()` as it's second argument?

In LDD3's example, access_ok() is placed at the beginning of ioctl method of a kernel module to check whether a pointer passed from userspace is valid. It is correct when userspace application calls ioctl() system call, and passes it an address of a…
Douglas Su
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How does this FOPS read method work?

I (and fellow classmates) cannot figure out the following question: "Consider the following FOPS read() method: ssize_t my_chrdrv_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) { char readBuf[] = "ABCD"; …
Mathias Siig Nørregaard
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Linux NFQUEUE handling issue

I am trying to write a userspace application that binds to an NFQUEUE socket to which a kernel module will forward incoming packets (by tagging them NF_QUEUE). This is accomplised by using an iptables rule like: iptables -­A INPUT -j NFQUEUE…
user1231049
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U-Boot: Loop Variable through to user space

during the execution of th MLO I create a variable, whose value I want to make accessible to user space applications in Android. How can this be achieved? One way would be to write the contents of the variable to external memory and let it read by…
user1192748
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How to test from userspace if the kernel supports IPv6?

I am seeking for a simple way to test if the kernel supports IPv6 on Linux in C/C++. Is it enough to check if the socket() call fails and that errno is set to EINVAL ?
evelina
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Linux kernel syscall return not given pointer

I am trying to implement a new syscall as an experiment, but I always get a segfault. I think the problem is that I try to return a pointer to a char array that is not in the user space. I tried to allocate the memory in the user space by using the…
Thorben
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