May 2014 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Re: Writing kernel in C
by Abu Rasheda May 26, 2014

May 26, 2014

> > > 1. It called TempOS. It is a kernel for educational purpose too. http://tempos-project.org The project is listed in OSDev Wiki too http://wiki.osdev.org/Projects 2. Here's another nice one: https://fosdem.org/2014/schedule/event/04_uk_escape 3. take a look at that [0], it's a small unix clone designed for learning purpose. It also comes with a pdf guide which documents the implementation. [0] http://pdos.csail.mit.edu/6.828/2012/xv6.html 4. http://www.oxkernel.com

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Unexpected driver interrupt behavior during init
by Alvin Abitria May 26, 2014

May 26, 2014

I am currently developing a PCI block driver and can use only MSI interrupt. During interrupt initialization, I called the pci_enable_msi and request_irq with following sample irq initialization function - static int mydev_init_irq(struct mydevice *dev_ptr) { int error; struct pci_dev *pdev = dev_ptr->pdev; const char *mydev_irq = "mydev_irq"; error = pci_enable_msi(pdev); if (error) { printk(KERN_WARNING "Failed to enable MSI."); return error; } error = request_irq(pdev->irq, mydev_irq_handler, IRQF_SHARED, mydev_irq, dev_ptr); return error; } After the request_irq executes, I always see from my debug trace that my driver is interrupted i.e. mydev_irq_handler got called. I don't think it's proper behavior, because I'm sure at this point of the initialization the device is not fully initialized as well and hasn't sent me an interrupt yet (didn't see this behavior in our Windows driver). At this point in initialization, since the device is not yet fully initialized and can't provide other info to the spurious interrupt I received, the IRQ handler will skip most of the handler function body and go straight to return IRQ_HANDLED, but I'm concerned with this bug. What could be causing that, and did I miss anything during interrupt initialization that caused it? Right now it's harmless, but I'm worried that it may cause problems in the future, like if I ported it to another Linux distro, and so I want to be able to prevent this. Sent from Samsung Mobile

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pgd table entry pointing null after process switching
by Chan Kim May 26, 2014

May 26, 2014

hi, linux folks, I'm seeing an 'unable to handle kernel paging request' after loading busybox elf loading. The context table is now pointing a new pgd table and the releavant pgd table entry is pointing null. What could be the cause? the address to access is frame buffer that I had linux allocate from consistent memory region. (I'm borrowing arm dma_alloc_writecombine conde in arch/arm/mm/dma-mappping.c for sparc.) Something is wrong duing the process address space allocation. (I'm reading a book section while doing this..) Any hint will be greatly appreciated. Thanks! Chan

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How does device tree support for two different LCD panel in the same kernel image ?
by Rahul Garg May 26, 2014

May 26, 2014

I am having confusion with device tree concept. As device tree is used, so that same kernel image can be flashed on the different device (which are compatible). Now suppose I want to use two different LCD panel for same project, For that I will have 2 separate dtsi file which will be having panel settings for respective lcd panel. What I want to know is, how can I put conditions in my driver code or in main dts file, so that If I flash the same kernel image on device A (with Panel A) or on device B ( with Panel B), it works fine. is there any way to do this or not? Regards Rahul

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Re: How to enable zramfs in android...
by sandeep kumar May 26, 2014

May 26, 2014

Dear All Thanks for your help. I could activate zram0, after doing the mkswap on the device. These all steps i followed, echo 50M > /sys/block/zram0/disksize mkswap /dev/block/zram0 swapon -p 100 /dev/block/zram0 after that, i saw my swap partition is being used. From the stats i saw 44MB RAM data is compressed into 14MB. But i have a doubt, When i reserve 50M RAM for swap partition, is it like a carve out memory? i mean Kernel cant use this anymore? On Sat, May 24, 2014 at 12:31 PM, Chen, Yiqun <feedingfranzy(a)gmail.com>wrote: > Um, well that sounds pretty weird. > Have you checked that you've loaded that module? If so, I guess there's > something wrong with modprobe stuff that it didn't mknod for zram, so > try mknod for zram manually. > Check your /dev/block/ directory for the device numbers. On my box it > was 254:0 254:1 which were mapped to my zram0 and zram1 respectively. > Then: > mknod /dev/zram0 b 254 0 > It should create a suitable /dev/zram* for you. Then try mkswap-swapon > procedure as others suggest. Please notice that -p argument for swapon is > somehow > necessary since on my gentoo box the priority of swap devices is set minus > by default. So your system may not use the zram swap at all even if > you've successfully create the zram device for it. > Please let my know if it still doesn't work :-) > On Fri, May 23, 2014 at 02:51:39PM +0530, sandeep kumar wrote: > > >>In my system /dev/zram0 is not present but sys/block/zram0 is present. > > thats why i m having this doubt > > just now i found that we have zram0 in /dev/block/zram0 > > i tried the command you told, > > > > *root@kleoslte:/ # swapon -p 100 /dev/block/zram0* > > *swapon -p 100 /dev/block/zram0* > > *swapon failed for /dev/block/zram0* > > > > is there anything else that i can try? > > > > > > > > On Fri, May 23, 2014 at 2:18 PM, sandeep kumar < > coolsandyforyou(a)gmail.com>wrote: > > > > > Dear Anders > > > > > > >Yes, zram is activated, otherwise you wouldn't have had zram0 created. > > > > > > >Though you might not be using it... > > > >If you want to use it for swap, you'll have to run `swapon -p 100 > > > /dev/zram0`. > > > >Well, '-p 100' isn't necessary, it's just to set the swap priority. > > > > > > In my system /dev/zram0 is not present but sys/block/zram0 is present. > > > thats why i m having this doubt > > > > > > thanks > > > sandeep > > > > > > > > > On Thu, May 22, 2014 at 4:56 PM, Anders Darander < > > > anders.darander(a)gmail.com> wrote: > > > > > >> On 22 May 2014 12:58, sandeep kumar <coolsandyforyou(a)gmail.com> > wrote: > > >> > Dear All, > > >> > > > >> > we are trying to make use of zramfs. In our android based board, > > >> > we are seeing this output, > > >> > > > >> > root@sandeep:/sys/block/zram0 # ls > > >> > > >> > > > >> > Does this mean zram is activated ? > > >> > > >> Yes, zram is activated, otherwise you wouldn't have had zram0 created. > > >> > > >> Though you might not be using it... > > >> If you want to use it for swap, you'll have to run `swapon -p 100 > > >> /dev/zram0`. > > >> Well, '-p 100' isn't necessary, it's just to set the swap priority. > > >> > > >> > we are trying to do the operation to set disk size, > > >> > echo $((50*1024*1024)) > /sys/block/zram0/disksize > > >> > > >> This should have set the size of zram0. > > >> > > >> Cheers, > > >> Anders > > >> > > >> -- > > >> Anders Darander > > >> EPO guidelines 1978: "If the contribution to the known art resides > > >> solely in a computer program then the subject matter is not > > >> patentable in whatever manner it may be presented in the claims." > > >> > > > > > > > > > > > > -- > > > With regards, > > > Sandeep Kumar Anantapalli, > > > > > > > > > > > -- > > With regards, > > Sandeep Kumar Anantapalli, > > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies(a)kernelnewbies.org > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > -- > Best regards > Chen, Yiqun > -- With regards, Sandeep Kumar Anantapalli,

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mmap(): enodev
by Pietro Paolini May 25, 2014

May 25, 2014

Hello everyone, in order to try to use mmap() to perform IPC I am writing a test program like this : int main(char **argv, int argn) { char *addr; int fd; if ((fd = open(FILENAME, O_RDWR) == -1)) { perror("open:"); exit(1); } addr = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if (addr == MAP_FAILED) { printf("mmap() : %p %s", addr, strerror(errno)); exit(1); } close(fd); .... I am running under Linux crunchbang 3.2.0-4-amd64 #1 SMP Debian 3.2.54-2 x86_64 GNU/Linux My problem is that everytime I have got an "No such device" error which I don't fully get, could a problem of my platoform or am I simply doing something wrong ? Thanks all, Pietro

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RE: gadgetfs : hangs during repeated communication with PC
by Ranjith T. C. May 24, 2014

May 24, 2014

Hi all, I am using gadgetfs driver with linux 2.6.22.18 kernel for my device. After some repeated communication with PC,gadgetfs hangs. I can see that i am receiving the hardware interrupts in the ISR for the incoming USB packets. But gadgetfs is still in a hang state. Has anyone come across this issue? Any help in this regard is very much appreciated. Please copy me in the further communications. Regards, Ranjith ________________________________ Confidentiality Statement/Disclaimer : This message and any attachments is intended for the sole use of the intended recipient. It may contain confidential information. Any unauthorized use, dissemination or modification is strictly prohibited. If you are not the intended recipient, please notify the sender immediately then delete it from all your systems, and do not copy, use or print. Internet communications are not secure and it is the responsibility of the recipient to make sure that it is virus/malicious code exempt. The company/sender cannot be responsible for any unauthorized alterations or modifications made to the contents. If you require any form of confirmation of the contents, please contact the company/sender. The company/sender is not liable for any errors or omissions in the content of this message. ________________________________

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Question about task 5 of the Eudyptula Challenge
by Peter Tosh May 24, 2014

May 24, 2014

Hey guys, I have written a module for task 5 that I believe should work, but it isn't. I have hard coded the values of Vendor ID and Product ID (for the call to the USB_DEVICE macro) to match the USB keyboard I'm testing with, but the Logitech driver seems to be getting selected first. My google-foo is apparently crap, as I haven't found a solution to this yet. I have read chapter 14 as the task suggests, but couldn't find a solution in there. If someone could point in the right direction I would appreciate it a lot. Cheers!

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How to enable zramfs in android...
by sandeep kumar May 24, 2014

May 24, 2014

Dear All, we are trying to make use of zramfs. In our android based board, we are seeing this output, *root@sandeep:/sys/block/zram0 # ls* *ls* *alignment_offset* *bdi* *capability* *compr_data_size* *dev* *discard_alignment* *disksize* *ext_range* *holders* *inflight* *initstate* *invalid_io* *mem_used_total* *notify_free* *num_reads* *num_writes* *orig_data_size* *power* *queue* *range* *removable* *reset* *ro* *size* *slaves* *stat* *subsystem* *uevent* *zero_pages* *Does this mean zram is activated ?* we are trying to do the operation to set disk size, *echo $((50*1024*1024)) > /sys/block/zram0/disksize* but still num_reads, num_writes is still zero. Can you pls let us know how to enable zramfs? -- With regards, Sandeep Kumar Anantapalli,

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Eudyptula Challenge
by Greg Donald May 23, 2014

May 23, 2014

Anyone know what's happening with the Eudyptula Challenge? I sent in my Task 03 solution a few days ago and have got no response. I resent it, and still nothing. Apologies in advance if this is the wrong place to ask about it. Thanks. -- Greg Donald

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