Programming :: Signal From Kernel Space To User Space?
Jul 21, 2011
I have the following requirement in my module. The driver gets some data from the external device. After getting 1MB of data it has to send it to the user space application. What is the best thing to implement for this in driver.? Is it ok to implement like, after getting data, the driver will send a signal to the user space application. Then the user space application sends an ioctl to read the data. Is there any alternate, that the driver directly sends the data without the user space application asks for it.?
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Dec 13, 2010
I am developing a I2C CDROM client driver. The CDROM firmware supports TOC information read through a I2C command. It sends the TOC information in burst ( Interrupts a GPIO pin when it is ready ) and my CPU does a I2C read to read the TOC. When the CDROM firmware finishes sending the last data burst , it informs my CPU that it is done with the TOC, by a flag in the last data burst. I would like to know, which is the most efficinet way I can send these TOC information to userspace?
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Jul 7, 2009
I wanna write a file in kernel space but from my searching I can to know that instead of writeing file in kernel space ,I can write data to user space by copy_to_user space.
But link is missing ...I dont know how will my user space will access kernel space means my function in kernel space which will do copy_to_user /....How my user space function will call my kernel level function ..
Can any one of you provide me with some example file which are doing this .I know every char driver is using it ...but i could not trace back how user level function is accessing it ...i m confused between user space and kernel space.
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Jul 14, 2009
How to use execv from kernel space to call a user space program writtenfor socket prog.
I tried to write code for socket in kernel but its not working.
Socket code in kernel is also needed.
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Jan 4, 2010
Logical Memory Space of 4GB is divided in to 3GB User Space and 1GB Kernel Space. Always. Correct?
1. How can we change it? (just changing value of PAGE_OFFSET is okay?)
2. If system have only 256MB of memory (embedded system) and suppose Kernel Modules eat away all the memory during boot. User space will be left will no memory. Is this case possible?
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Sep 22, 2009
I am writing device driver in which i have to call callback function from kernel space, which are saving my data. But the callback functions are in userspace. While accessing them i am getting segmentation fault.
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Dec 10, 2008
I am writing a program which i dont want the kernel scheduler to preempt before certain time duration. I am using the system call sched_get_priority_max to set the maximum priority. However it is not producing results.
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Nov 28, 2010
measure kernel space time and user space time?
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Jun 21, 2010
In a 32-bit system, max memory addressable is 4GB. Now Linux kernel does memory mapping division of 1GB for kernel address space and 3GB for user address space. That means 4GB of virtual address space is divided between kernel (1GB) and user (3GB).
Q1. All virtual mapping utilizes the available physical RAM without any division? I mean to say that if RAM is 512MB then a page in kernel space can lie any where RAM (leave aside old PCI dma accesses)? (How this fits to fact that kernel memory is non-pageble)
Q2. If a process is created in user space, it has visibility 4GB address space or 3GB address space?
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Oct 25, 2010
I'm pretty new to this whole (micro)kernel architecture story.
Im wondering if a kernel module is running in kernel or in user space?
Is a driver running as kernel module slower than a driver build into kernel?
If so, are there some current articles, benchmarks?
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Feb 22, 2010
If the calling process passes me the virtual address of an its array for example, how can I access it without using copy_from_user?
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Jul 12, 2010
what difference between user and kernel space.
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May 3, 2010
I need a shared buffer between user and kernel space. I read that one way is to allocated buffer in kernel and then call mmap from the user space. I searched for an example but couldn't find something useful. If you know, could you please send me any links or sample code that does this..
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Jul 14, 2011
I have written a device driver and I would like to disable an interrupt. In kernel space there is a function called "disable_irq(int irq)", but, is it possible to do it from user space?
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Sep 17, 2010
I am looking for a way to issue ioctls to a usb driver from user space. Upon googling, I found that usbfs provides a way to do that, anyhow I can't find sample code to try that out.
Note:
I have written a sample usb driver on the lines of 'Linux device drivers' book. Now I need to try ioctls with usb drivers.
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Jun 10, 2009
I'm using vmsplice & splice to send memory buffers through a TCP socket. I have two issues using these methods:
1) According to the documentation, when using vmsplice with the flag SPLICE_F_GIFT, you cannot modify the buffer you've "given" the kernel. Currently, each time I want to send a buffer, I have to allocate a page-aligned buffer (fill it with data) and send it using vmsplice- splice. When can I deallocate this buffer? Is it possible to modify this buffer after the buffer is sent through the socket?
2) The buffer should be page-aligned both in memory and in length, but most of the time the sent messages (to the TCP socket) - are smaller than a page size - is it possible to "clear" the pipe from the remaining buffer?
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Jan 29, 2010
Driven by my needs , i need to toggle only the flow control (RTS, CTS) bits and have nothing to do with the rest of the functionality (e.g. normaltx , rx operation). I am presuming that there exists a line discipline from user space for toggling RTS as ioctl (*file, cmd, *unsigned long ) can be used easily to toggle RTS. However, the use of IOCTL in kernel space for the same purpose brings about no change on RTS (oscilloscope shows no change). google led me to this [URL] and according to that i should make changes directly in the driver.
Code:
int x=0;
int actual_module()
{ int k;
mm_segment_t oldfs;
[code]....
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Jul 28, 2010
I want to simulate a serial protocol in user space program to test reception algorithm. The protocol is similar to UART protocol but frame format is different. The duration of 1 bit is 114,46 us. In my main function I'm creating two threads. Tx for simulating transmitting data and Rx for reception data. For measure time I use create_timer() function and signals. Each thread has its own timer and signal handler. Tx timer uses SIGUSR1 and Rx timer uses SIGUSR2. Tx thread sets the global variable and Rx reads it.
The timers are set to sample with 114,46 us period. When they reach this value signal handler should set the flag. Flag is check in thread and some operation are made. When I set the timers period for longer time (100 ms) everything works fine but when I change it to default value (114,46 us) the Rx thread doesn't receive the proper data. I am wondering if the 114,46 timer period is possible to simulate in user space? Whether the time will give me the proper resolution ? Theoretically it should provide 1 ns resolution.
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Mar 6, 2010
I have linux and windowsxp on one machine. I have only 3gigs free on the windowxp machine and 20gigs free on the linux machine. I want to transfer space from the linux box to the windows machine.Is this possible and what steps would I need to follow to do this?
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Mar 20, 2010
my home partition is an extended one, and when i want to create an unallocated space the space will stay in that extended partition. but there is also an 7 gb unallocated space which i want to merge with the other unallocated space. I also cannot extend that partition over that 7 gb. how can i overcome that problem?
i m also uploading a screenshot of gparted.[URL]..
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Jan 31, 2010
Today I was installing a lot of software since I'm just setting up my Slackware system again after a fresh install, and I realized that my root partition has very little space left.
Here is the output of df -h:
Code:
As you can see, I have a 20G (19G here for some reason) root partition, 8G /var, and 86G of /home. I thought this would be plenty since many recent recommendations for / are 10-15G. Now, though, 17G are used up for some reason! How is this possible? I thought a full slackware install only had about 4G of software! I don't have any music or movies or any crazy huge files that I know of, and those would be in my /home directory anyway. Is there any way I can see which files are taking up all this space?
If it's necessary to allocate more space to my / partition, is it still possible to boot up a GParted live Cd, shrink /home a bit, move some partitions to the right, and expand my root partition? I would REALLY prefer I don't have to reinstall since I just spent a ton of time setting up my system again, but if worst comes to worst ... :'-(
In case you're curious, here's my /etc/fstab:
Code:
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Jun 7, 2010
I was trying to install Fedora 13, on to my laptop. I have 30 GB of unallocated space in extended partition. When trying to install Fedora 13, I got stuck, as the installer says that there is no free space for installation.can convert the unallocated space into free space.
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May 25, 2010
i used gddrescure to clone an 80gb harddrive and this is the result ROFL.i guess you can only do this making sure the target drive is the same size, you see i didnt know lol so..i now have THIS problem.can anyone tell me how to turn my unallocated space into a usable 'free' space? i could play with gparted right now but i dont wanna do anything wrong, so if theres anyone who can tell me how to do this.
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Aug 25, 2009
OS: RHEL AS 5 64-bit
HDD:300 GB Hardware mirror (HP blade bl460c)
While installing OS, in partition window after OS file system structure I've left 277 GB. But after installation it shows Size - 255GB and available disk space is 242 GB.
Isn't it weired? How can I use the total amount of space in Linux? I need the whole 277GB exactly. What should be my workaround?
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Oct 14, 2009
I have a list of files in a directory which starts with - or have space.
I need to copy them back without the space or -?
linux1[sim]% ls linux1[sim]% cp ./-* ./*
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Dec 30, 2010
I have red hat linux server and it has mysql installed whenever i write on terminal command mysql -u root it shows error "ERROR 2002 (HY000): can't connect to local MYSQL server through '/var/lib/mysql/mysql.sock (111) "
And another problem is that it is showing 0 byte free space istaed of freeing the space. it may seems that both problems are dependent on each other.
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Jun 16, 2011
Do you think there is a way of accessing different user data from another account which I have set up.
Ie. user 1 = account has messed up
user 2 = account works fine
access user account 1 home directory from user 2 work space?
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Jul 22, 2010
i made space by shrinking my window partition and so i have unallocated and would like to add to sda2 to have more space. Check out this pic. How can i do this?
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Apr 23, 2011
I installed Ubuntu 10.10 with wubi and i have been enjoying my Ubuntu experience a lot. I installed quite a bit of programs and spent a couple hours customizing my machine. The problem is im running out of disc space. Any ideas on how i can add more space. I have gparted but i dont know where to move the free space to because wubi installed it.
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Jul 5, 2011
My system is dual boot with win7 and ubuntu. I have free space of around 10 gb. I want to add this free space to my ubuntu drive. How can i do that?
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