February 2011 - kernelnewbies@kernelnewbies.org

Socket program in kernel
by prabhu Feb. 22, 2011

Feb. 22, 2011

Hi All, I wrote socket program in user level but i want to write the same program in kernel. Like the driver(socket server) should receive all the incoming TCP or UDP pocket(may be say raw socket) and write into the file. Please provide your valuable idea to do this program ... Also please point out pitfalls. Thanks, Prabhu

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new link list
by mohit verma Feb. 22, 2011

Feb. 22, 2011

hi all, i want to create a new link list of data structures( define by me) in kernel space. for that what are the essential steps to make this link list known to kernel?? thanks in advance :) -- ........................ *MOHIT VERMA*

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lm_device & platform_device
by Arun S Feb. 22, 2011

Feb. 22, 2011

Hi, What is the reason for 'linux/include/asm-arm/arch-integrator/lm.h' declaring lm_device & lm_driver while platform_device & platform_driver offers almost the same functionality? Thanks Arun

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Repetitive Mails and some errors with gmail
by Anuz Pratap Singh Tomar Feb. 22, 2011

Feb. 22, 2011

Hi Rik, There seem to be some trouble with new list and gmail. At times there are many repeats of some mails and as pointed out in previous conversation by Anish, there seem to be some issues in sending/receiving mails. Could you please look into this matter. Regards Anuz

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Ftracing in kernel
by Erlon Cruz Feb. 22, 2011

Feb. 22, 2011

Hi folks, I've configured my kernel(2.6.35) to support ftrace*. Everything seems to be ok. After I mounted the debugfs folder I can find all tracing stuffs there. The problem is not of all functions on my module seems to be listed in the funtions supported for tracing. In the file *available_filter_functions *that suppose to list all functions traced, only show 4 or 5 functions of my module. Does anyone knows why some functions are not listed? Regards, Erlon *CONFIG_FUNCTION_TRACER CONFIG_FUNCTION_GRAPH_TRACER CONFIG_STACK_TRACER CONFIG_DYNAMIC_FTRACE

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allocating memory at boot
by Philip Downer Feb. 22, 2011

Feb. 22, 2011

Hi folks, I'm currently trying to port a (currently for unreleased hardware and under nda) driver from x86 to arm and in doing so I've run into a problem with allocating memory using pci_alloc_consistent. Looking into it I can't allocate more than 1MB whereas I need to allocate at least 2MB of contiguous memory. Looking further into it, the conventional method to get around this at the moment seems to be to statically link the driver into the kernel and use alloc_bootmem or alloc_bootmem_low (mentioned in ldd3 and all over google). The problem I've run into however is that I get a warning at boot which is: WARNING: at mm/bootmem.c:672 alloc_arch_preferred_bootmem+0x34/0x64() Looking at that code in bootmem.c this is a warning which I think is there to tell me that SLAB is available and warn against trying to allocate at boot. However it reportedly allocates the memory but when the driver tries to use this memory later, then the system hangs. Is alloc_bootmem currently the correct way to get memory allocated at boot or is there a different call I should be using. Alternatively have I done something wrong by using alloc_bootmem as a drop-in replacement for pci_alloc_consistent? I've tried to grep the kernel sources for other drivers that use alloc_bootmem but there aren't many which appear in the listing and I find this strange for a technique which is referred to a lot. Thanks, Phil

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the use sin_zero in sockaddr_in
by prabhu Feb. 21, 2011

Feb. 21, 2011

Hi all, Could anyone please explain the use *sin_zero in *sockaddr_in? struct sockaddr_in{ short sin_family; /* AF_INET */ u_short sin_port; /* 16-bit port number */ /* network byte ordered */ struct in_addr sin_addr; /* 32-bit netid/hostid */ /* network byte ordered */ * char sin_zero[8]; /* unused */* } Thanks, Prabhu

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how to write modified inode back to disk?
by kashish bhatia Feb. 20, 2011

Feb. 20, 2011

hi all , here is my query : I made a module which access a disk inode using function named ext2_get_inode(). It returns structure pointer of disk block. I copied this structure pointer in a variable of same datatype as of disk inode which is present in my module. Then I changed some fields of this disk inode ( eg. block numbers ) in the variable. Now I want to write these changes back to disk. In other words , I want to write my module's variable back into disk inode in disk. Is there any method to do this? -- Regards, Kashish

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pci config space
by Asim Feb. 20, 2011

Feb. 20, 2011

Hi, While this may just be connecting the dots, I am not able to fully understand how pci_save_state works. I see that the pci_save_state and pci_restore_state are invoked at suspend and resume. This saves the PCI configuration registers during suspend. Are these the device registers or bridge registers? Consequently, is the pci_save_state and driver suspend routine saving the full device state/device state exposed to PCI or PCI state ? Thanks, Asim

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Page Table query
by anish singh Feb. 20, 2011

Feb. 20, 2011

As i understood whenver a user space program is run it is represented in kernel using VMA which is managed by struct mm_struct and whenever the program is trying to read/write to a memory location in user space it will be directed to physical address using PAGE TABLE translation done by struct mm_struct(done in kernel space).Am i right? Suppose a simple driver wants the user to directly access its device memory then we use mmap.This mmap associates a set of user space virtual address with device driver memory and it is done by creating kernel page tables for the user space virtual addresses.Is the page table translation done everytime whenever user space does read/write to the device memory?? In .nopage function call we return the page associated with the physical address which the user wants to associate with user space virtual address.Is the page address returned by the nopage function same as seen by the user or will it be converted to user space virtual address(range between 0-2 GB)? Thanks for reading.

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