October 2011 - kernelnewbies@kernelnewbies.org

some question about request queue in blok device
by loody Oct. 24, 2011

Oct. 24, 2011

Dear all: I found there is a member of request_queue, bounce_pfn and it will be set up by calling blk_queue_bounce_limit. it seems someone will use that when calling blk_queue_bounce, but what and when it will be called? -- Appreciate your help,

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How to avoid volatiles
by Prabhakar Lad Oct. 24, 2011

Oct. 24, 2011

Hi everyone, I had question in want eradicate volatile from here: for example: #define 0x01c40800 if ((volatile void *)pllbase == (volatile void *)DAVINCI_PLL_CNTRL0_BASE) /**HERE**/ return 8; else return pll_div(pllbase, PLLC_PREDIV); Thanks. Regards --Prabhakar

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I am hoping to develop the linux kernel, which version should I modify
by Jimmy Pan Oct. 24, 2011

Oct. 24, 2011

There is a 3.0 in my hard disk, which I downloaded around Aug 10. There is 3.0.4 and 3.1-rc4 code. Which version should I use. Since I am a newbie, I think I don't need to use the newest version. Can I use my 3.0 version, or should I download a new one? Maybe I can read the kernel source on the web, is there a way to use the source on web to make patches? Thanks in advance.

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Re: mmap local APIC address
by Vaibhav Jain Oct. 21, 2011

Oct. 21, 2011

On Wed, Oct 19, 2011 at 10:57 AM, bob <ilikepie420(a)live.com> wrote: > It would be nice to share your solution in case someone else comes into the > same problem. > Hi, It was stupid mistake. I forgot to initialize the file descriptor which was passed to mmap and therefore it was throwing "Bad file descriptor" error.i realized it after looking the errors in "man mmap". Thanks Vaibhav Jain

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Problem with a UDP server implements
by jiangtao.jit Oct. 21, 2011

Oct. 21, 2011

Hi: I'm writing a UDP server and meet a problem the UDP server program is run on a box with single card but has multi ip: like eth0 10.0.0.1 eth0:1 10.0.0.2 eth0:2 11.0.0.1 I bind the server socket with INADDR_ANY when a client send a packet to 10.0.0.2(the eth0:1 's ip) the server can recieve the packet and reply, but the client can't recieve the server's response I use wireshark to capture the response packet and found that the server use 10.0.0.1(the eth0 's ip) as saddr in the response packet I expected it to be 10.0.0.2 but it's not my question : is there any way to let the UDP server relpy just use the ip it receieved the request ? It's : when a client send a request to 10.0.0.1(eth0); the server use 10.0.0.1 to response and another client send a request to 10.0.0.2(eth0:1); the server use 10.0.0.2 to response Thanks. 2011-10-15 jiangtao.jit

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Re: Getting physical address of memory allocated by vmalloc()
by Dave Hylands Oct. 21, 2011

Oct. 21, 2011

Hi Jacky, On Oct 20, 2011 6:32 PM, "Jacky Lam" <lamshuyin(a)gmail.com> wrote: > > Hi, > > Is there any generic way to get the physical address of memory > (first page) allocated by vmalloc()? PFN_PHYS( vmalloc_to_pfn( address )) -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com

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Getting physical address of memory allocated by vmalloc()
by Jacky Lam Oct. 21, 2011

Oct. 21, 2011

Hi, Is there any generic way to get the physical address of memory (first page) allocated by vmalloc()? Thanks a lot. Jacky

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How can I test if a physical address is already mapped or not.
by StephanT Oct. 20, 2011

Oct. 20, 2011

Hi all, In a kernel module is there a way to test if an address range has been already mapped by the kernel or not. Ex: (on a PC with the latest kernel) - an access to physical 0xC0000000 will return the value at this address - an access to physical 0x00100000 will have the kernel kill the module/application using the module. Dmesg: BUG: unable to handle kernel paging request at 00100000. How can I test this condition before dereferencing the address. Thanks, Stephan.

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Getting 'bad file number' error writing to device driver
by Philip Anil-QBW348 Oct. 20, 2011

Oct. 20, 2011

I am trying to write to mydriver but get a 'Bad file number' error. int fd = open("/dev/mydriver",O_RDWR); this opens successfully as fd is not -1. ssize_t bytesToWrite = strlen(buf); value is: bytesToWrite 28 ssize_t bytesWritten = write(fd,buf,bytesToWrite); value is: bytesWritten -1 __android_log_print(ANDROID_LOG_INFO,__FILE__,"ANIL strerror(errno) %s", strerror(errno)); value is: strerror(errno) Bad file number Any help appreciated. Anil

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mmap local APIC address
by Vaibhav Jain Oct. 19, 2011

Oct. 19, 2011

Hi, I am trying to map local APIC on an intel system (physical address 0xfee00000) in a user level program using mmap but my mmap is failing saying "Bad file descriptor". I am not sure if this problem is related to apic or mmap. I am running the program as root. Please help me figure this out. Thanks Vaibhav Jain

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