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How to use .dts file for Kernel Image Compilation
by sanchayan maity Jan. 28, 2014

Jan. 28, 2014

Hello Everyone, I am compiling kernel image for a Toradex Colibri module which uses the NVidia Tegra2 processor. The device tree support and files are supplied, which i can see on the below link. http://lxr.free-electrons.com/source/arch/arm/boot/dts/?a=arm The file name is tegra20-iris-512.dts which then includes tegra20-colibri-512.dtsi. I want to know how can i link this while doing "make" for kernel image compilation. This is required as board config file is not present and the device tree has to be used. Based on my current findings, if the file name is for example exynos4.dts, this will be specified in the config file with CONFIG_MACH_EXYNOS4_DT=y. I want to know if this is the correct way of specifying a device tree file for which .dtb has been generated? The kernel version for which i am trying to do this is 3.12.6. Thanks & Regards, Sanchayan

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Where is the version.h?
by parmenides Jan. 28, 2014

Jan. 28, 2014

Hi, According to LDD3, the linux/module.h automatically includes the linux/version, which define some macros to help test the kernel version. But I search the source tree, and can not find version.h in include/linux. Where can I find it? Thanks!

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How to identify a 'fresh' page from read_cache_page?
by Zameer Manji Jan. 28, 2014

Jan. 28, 2014

Hey, My colleague Will and I are working on improving eCryptfs, an encrypted file system that ships with linux. We are trying to add a new cipher mode and we have run into a problem [1]. When the user calls `ftruncate` on a file and increases the file size, eCryptfs attempts fetch new pages for the file by calling `read_mapping_page` and which calls `read_cache_page`. This calls eCryptfs' `readpage` implementation. We believe `read_cache_page` calls `readpage` with a page that we have not written to before (since the user is increasing the file size via `ftruncate`). What function can we use to identify when we are given a page to our `readpage` implementation that is a page we have never written to before? We need to do this so we know if should check the integrity of the data in the page (if we wrote to it before) or just ignore the contents (because it is a fresh pagewith garbage data). For more information our ecryptfs_readpage implementation is available on github [2]. Please note that I am not subscribed to kernelnewbies so please include me directly in any replies. [1]: http://marc.info/?l=ecryptfs-users&m=139007357027191&w=2 [2]: https://github.com/zmanji/ecryptfs/blob/next-patch/fs/ecryptfs/mmap.c#L193 -- Zameer Manji

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editing and building ./drivers/pci/iov.c
by Kelly Zytaruk Jan. 28, 2014

Jan. 28, 2014

I am trying to trace a bug I have with some hardware and I am putting printk() statements in iov.c Every time I make a change to the source file, I am building the entire linux kernel, ie 'make' from top directory. While it is not complex, it is time consuming, it takes several minutes to go through all of the dependencies and link all of the modules together. I spend a lot of time waiting. Am I doing this correctly or is there a short cut to do either of the following; 1) Compile only iov.c to find coding syntax errors a. I tried running 'make' in the ./drivers/pci directory but it told me that there were no targets. 2) Do the final build. a. Do I have to build the entire linux kernel or can I somehow insert/replace the pci driver into an existing image. Thanks, Kelly

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How to use memcpy in kernel driver
by m silverstri Jan. 27, 2014

Jan. 27, 2014

Hi, How can I use memcoyp in memcpy? I try #include stdio.h and string.h, but .h fails to include during compilation. Can you please help me? Thank you.

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make kernel driver closed
by phani kumar Jan. 27, 2014

Jan. 27, 2014

Hi all, Is there any way to make kernel driver closed(not open source)? Description: I have driver, I want make it non-open source. how can I do it? Thanks, Phanindrakumar.Y

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Questions on Call single data (CSD)
by Vignesh Radhakrishnan Jan. 27, 2014

Jan. 27, 2014

Hi, I have couple of questions on Call single data (CSD) . I am going through kernel/smp.c - From what i understand CSD struct is used to run a particular function on a another core (Not sure if i am right ) ? (csd -> func) ( in function smp_call_function_many) - What do these csd_lock_wait and csd_lock do. As per the code this its used to serialize access and it says there is a per CPU CSD resources. I am not getting what is meant here.If its per CPU , then why serialize access ? - The list inside csd . Is this by any chance circular ? Thanks and regards, Vignesh -- http://vigneshradhakrishnan.blogspot.com/

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insmod and capabilty
by Kevin Wilson Jan. 25, 2014

Jan. 25, 2014

Hi, Does "insmod" needs some capability ? Is there a capability which when not set, you cannot run perform insmod of a kernel module ? I don't see such capability in man 7 capabilities. regards, Kevin

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How about using dma_buf_kmap
by m silverstri Jan. 24, 2014

Jan. 24, 2014

Hi, I need help in using dma_buf_kmap. https://www.kernel.org/doc/htmldocs/device-drivers/API-dma-buf-kmap.html I create a dma buffer in user side, size is 307200 and I want to map that to kernel so that my driver can access it. I have a dma_buf pointer, so I think I need to use dma_buf_kmap. My question is what should I pass to the 2nd parameter of (page in PAGE_SIZE units to map) dma_buf_kmap? I want the whole dma_buf to be accessible. Thank you for your help.

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What's the meaning of CONFIG_BROKEN_ON_SMP?
by parmenides Jan. 24, 2014

Jan. 24, 2014

Hi, I compiled a driver, ang get the following message: CONFIG_BROKEN_ON_SMP: should be set in the kernel configuration, but isn't. Somebody suggested to disable the kernel's SMP feature. I did, and the problem got solved. Then, I googled the meaning of CONFIG_BROKEN_ON_SMP, but did not get definitive explanation, such as http://cateee.net/lkddb/web-lkddb/BROKEN_ON_SMP.html I wonder what the meaning of the configuration is. How does it work? Thx!

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