March 2012 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

static I/O device mapping of UART for early prints & console
by pcuser p March 11, 2012

March 11, 2012

I'm doing kernel porting to arm926 based FPGA board (similar to samsung-s3c6410 board). I'm trying to setup UART for early print and console. I gone through some reference boards(samsung-s3c6410) for setting up uart for early print & console. I can't trace the virtual mapping for UART registers in "adduart" macro in "debug-macro.S" file .macro addruart, rp, rv ldr \rp, = S3C_PA_UART ldr \rv, = S3C_VA_UART Basically,I want to know how to calculate this virtual address(S3C_VA_UART) from the physical address(S3C_PA_UART) Below are the details #define PLAT_PHYS_OFFSET 0x50000000 (with 256 MB SDRAM) #define CONFIG_PAGE_OFFSET 0xc0000000 #define S3C_ADDR_BASE 0xF6000000 (virtual address for device registers) #define S3C_VA_UART (S3C_ADDR_BASE + (0x01000000) ) #define S3C_PA_UART 0x7F005000 (UART - Physical address) #define S3C_VA_UART 0xF7000000 (UART virtual address = 0xF6000000 + 0x01000000) I tried to calculate the virtual address by using " __phys_to_virt(x)" macro. #define __phys_to_virt(x) ((x) - PHYS_OFFSET + PAGE_OFFSET) from the above macro, I expect __phys_to_virt(S3C_PA_UART) = S3C_VA_UART = 0xF7000000 but if i do calc, 0x7F005000 - 0x50000000 + 0xc0000000 = 0xef005000 which is not correct. I think, i'm not using the correct macro for getting the virtual address for UART. can someone suggest how to do this calculation for getting proper virtual address for UART for the above configuration. Thanks, pcuser

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Question about pullsing source of a specific version using git
by SADA SIVA REDDY S March 9, 2012

March 9, 2012

Hi All, Apologies if this question should not have been asked here. I am looking at pulling code using git (git clone git://some path). This path is same on www.kernel.org for any two close versions say 3.2.9 and 3.2.6 - git:// git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git How do I make my local copy same as the source code for 3.2.6 or 3.2.9 ? I have tried reading git tutorials not in full to find an answer and I am un successful so far. If it's a simple answer could you please let me know. Thanks, SADA

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slacks usage,..
by trisha yad March 9, 2012

March 9, 2012

Hi All, I am going through below topic http://patches.linaro.org/6833/. I could not got the meaning of slacks. Why I need this .. Is there some real example of need of slacks. Thanks

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crash in virt_to_pages
by revolver March 8, 2012

March 8, 2012

Hi, I am trying to solve crash on old patched 2.6.18 kernel where virt_to_page() used on stack variable address. function() { struct { u32 ... u32 ... ... } bla; ... = virt_to_page(&bla); } i386 it works fine but x86_64 kernl panics. When kernel panics, &bla is something like ffffffff80574d40, which is not valid for virt_to_pages, AFAIK. Any ideas? Why it is not save to use virt_to_pages on stack addresses? Thank you

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Need help: Generating patch using git
by amit mehta March 8, 2012

March 8, 2012

Hi, kernel janitors group seem like a good place to start learning linux kernel and after reading some of the information available on kernel newbies website, i tried to generate a dummy patch and need your help for moving in correct direction of learning and contributing to linux kernel. So these are the steps that i've followed to generate this dummy patch. 1: Download the latest linux kernel sources using git # mkdir linux-next # cd linux-next # git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git linux-2.6 2: Do some modifications. # pwd /root/linux-next/linux-2.6 # git diff diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c index 6e412a6..9858701 100644 --- a/net/ipv4/ipconfig.c +++ b/net/ipv4/ipconfig.c @@ -441,7 +441,7 @@ static int __init ic_defaults(void) &ic_myaddr); return -1; } - printk("IP-Config: Guessing netmask %pI4\n", &ic_netmask); + printk(KERN_INFO "IP-Config: Guessing netmask %pI4\n", &ic_netmask); } return 0; 3: Generate a patch # pwd /root/linux-next/linux-2.6 # mkdir ../patches # git diff >../patches/ipconfigPatch.txt 4: Test your patch 4a: Clear the local changes from the tree # git checkout -f 4b: Apply the patch # git apply ../patches/ipconfigPatch.txt The above step(4b) did not returned any git error so it seems to me that the steps to generate this patch was correct. 5: Check your mailer 5a: I just copied the contents of ../patches/ipconfigPatch.txt and pasted in the compose area and sent that mail to myself. After receiving this mail i copied and pasted the mail contents in a file under /root/linux-next/patches/dummyPatch.txt and tried to apply this patch using git but it gave me an error as below: # git apply ../patches/dummy.txt fatal: corrupt patch at line 11 Hence it seems i'm missing something here. Please note that this is just for my understanding purpose of generating and submitting patches. -Amit

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some question about time
by loody March 7, 2012

March 7, 2012

hi all: There are 2 time structs in kernel, timespec and ktime_t. Under what circumstances we will use timespec or ktime_t? under 32-bits system, they seem same because both them store second and nanosecond information, right? -- Regards,

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Re: linux camera drivers
by Mayank Agarwal March 7, 2012

March 7, 2012

On Fri, Mar 2, 2012 at 10:08 AM, Mayank Agarwal <mayank77fromindia(a)gmail.com > wrote: > 1.I think the device supports i2c or spi protocol.I want to know how the > i2c or spi is taking data > from image sensor and giving it to video buffers. > > 2.I want to understand the whole data flow from image sensor to the > display buffer and the role of linux kernel > camera drivers in that. > > 3.Currently i am looking at Sony IMX036,Aptima MT9P031. > > Thanks and Regards, > Mayank > > > On Thu, Mar 1, 2012 at 8:22 PM, Greg KH <greg(a)kroah.com> wrote: > >> On Thu, Mar 01, 2012 at 05:57:52PM +0530, Mayank Agarwal wrote: >> > Hi all, >> > >> > I have following questions regarding camera drivers in linux kernel. >> > >> > 1.which are the files/folder in kernel directory where camera drivers >> support >> > is provided in linux kernel. >> >> It depends, which type of protocol does your device support? >> >> > 2.Are they customisable according to different SOC requirements. >> >> It depends on what the requirements are. As it's software, it's always >> able to be changed :) >> >> > 3.Are there any tutorials/pdfs to understand camera drivers in linux >> kernel. >> >> What is wrong with the code itself? >> >> > 4.At present which sensor (i mean aptina/sony/omnivision) drivers are >> supported >> > in linux kernel. >> >> What sensor are you looking for exactly? >> >> What device do you need to support, and what protocol does your camera >> use to talk to the hardware? >> >> greg k-h >> > >

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Kernecel headers in kernel source
by rajaneesh acharya March 6, 2012

March 6, 2012

Hi, I recently compiled kernel from the GIT repo...Some of the application in the distro needs kernel header files...Which subdirectory of the source directory do I find the kernel header files in? Regards Rajaneesh

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suspicious RCU usage?
by Peter Senna Tschudin March 6, 2012

March 6, 2012

Dear list, I'm running custom Fedora 17 Kernel 3.3.0-0.rc5.git3.1.yfkm2.fc17.x86_64, and the warning was shown on dmesg: [ 858.634304] [ 858.634324] =============================== [ 858.634350] [ INFO: suspicious RCU usage. ] [ 858.634375] 3.3.0-0.rc5.git3.1.yfkm2.fc17.x86_64 #1 Not tainted [ 858.634409] ------------------------------- [ 858.634435] kernel/pid.c:425 find_task_by_pid_ns() needs rcu_read_lock() protection! [ 858.634478] [ 858.634479] other info that might help us debug this: [ 858.634480] [ 858.634528] [ 858.634529] rcu_scheduler_active = 1, debug_locks = 0 [ 858.634567] no locks held by monitor/10550. [ 858.634591] [ 858.634592] stack backtrace: [ 858.634620] Pid: 10550, comm: monitor Not tainted 3.3.0-0.rc5.git3.1.yfkm2.fc17.x86_64 #1 [ 858.634666] Call Trace: [ 858.634688] [<ffffffff810c8c55>] lockdep_rcu_suspicious+0xe5/0x100 [ 858.634727] [<ffffffff81086921>] find_task_by_pid_ns+0x81/0xa0 [ 858.634762] [<ffffffff81086962>] find_task_by_vpid+0x22/0x30 [ 858.634798] [<ffffffff8131ccd5>] yfkm2_is_pid_running+0x15/0x40 [ 858.634835] [<ffffffff8131ce54>] sys_yfkm2_monitor+0x14/0x80 [ 858.634870] [<ffffffff816a6ba9>] system_call_fastpath+0x16/0x1b monitor is user application that call sys_yfkm2_monitor syscall passing a pid to it. The custom code worked as expected but I'm curious with the warning message shown on dmesg. What am I doing wrong? The user application monitor.c: ... #define SYS_yfkm2_monitor __NR_yfkm2_monitor ... ret = syscall(SYS_yfkm2_monitor, pid); ... The Kernel code yfkm2.c: ... struct yfkm2 { pid_t monitor; /* PID to monitor */ pid_t notifyme; /* PID to notify */ struct list_head list; /* Linked List struct */ }; ... /* Define and initialize yfkm2_(linked)list */ LIST_HEAD(yfkm2_list); ... /* Define and initialize yfkm2_(read&write)lock */ DEFINE_RWLOCK(yfkm2_lock); ... /* * asmlinkage long sys_yfkm2_monitor(pid_t monitor) * * The system call that check if monitor correspond to a running pid and stores * monitor at yfkm2_list->monitor * * return 0 if pid is running * return 1 if pid is not running */ asmlinkage long sys_yfkm2_monitor(pid_t monitor) { struct yfkm2 *yfkm2_tmp; if (yfkm2_is_pid_running(monitor) == 0) { yfkm2_tmp = kmalloc(sizeof(*yfkm2_tmp), GFP_KERNEL); yfkm2_tmp->monitor = monitor; yfkm2_tmp->notifyme = 0; write_lock(&yfkm2_lock); list_add(&yfkm2_tmp->list, &yfkm2_list); write_unlock(&yfkm2_lock); return 0; } return 1; } ... /* * yfkm2_is_pid_running(pid_t pid) * * Check if pid is running * * return 0 if pid is running * return 1 if pid is not running */ int yfkm2_is_pid_running(pid_t pid) { struct task_struct *q; q = find_task_by_vpid(pid); if (q != NULL && q->pid == pid) return 0; return 1; } Thank you! Peter -- Peter Senna Tschudin peter.senna(a)gmail.com gpg id: 48274C36

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Re: Linux cdc-acm-driver
by Greg KH March 6, 2012

March 6, 2012

On Tue, Mar 06, 2012 at 11:30:33AM +0400, tamerlan311 wrote: > 2012/3/6 Greg KH <gregkh(a)linuxfoundation.org> > > On Mon, Mar 05, 2012 at 03:24:17PM +0400, tamerlan311 wrote: > > This kernel module was completely stable. > > But i think that i should do some clean up code before upstream it. > > There's no need to do that now, you can always send follow-on patches > doing that. > > Ok. > > > > > Was planned for future developments: > > implement write to device support. (I do not know why, but this feature > was > > implemented in original source) > > How can a barcode scanner be written to? > > Official service software can configure scanner via Bi-Directional port mode. > Instead of special barcode for config. > > > > > implement work in UNI-Directional mode (0c2e:0710) > > > > I am busy working, but I'll try to finish in few week. > > How about I take what you have now, that ensures we make the 3.4 kernel > release deadline, and then you send follow-on patches for the other > things as you work on them? That way people can use the driver now, > which is what they want to do :) > > > I do not mind, it's a great idea! > still need some kind of reaction from me at now? No, I can take the code as-is and create a patch and add it to the tree if you don't want to do that. I'll try to do it by the end of this week and I'll cc: you on the patch. thanks, greg k-h

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