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

New kernel for Chipbox
by Sertac TULLUK June 10, 2012

June 10, 2012

Dear All; I have a digital satellite receiver (named Chipbox), which uses linux kernel 2.6.12.5. Main chipset name is Celestial CSM1203 ( It is ARM926EJ-S core). The original kernel source (and all other sources) can be downloaded here: http://www.merihvideo.com.tr/chipbox-source.php I would like to add some functionality (Such as CIFS, USB WIFI...) to my STB. In order to do that, I need to cross compile new kernel. However, the chipset provider ( Celestial) does not provide a new kernel to do this. They just compiled 2.6.12.5 for about 5-6 years ago, and they didn't do a new kernel from that time. So, I need your helps: 1) Celestial has done a lot of modifications on the original 2.6.12.5 source ( drivers, headers, definitions...) All these changes can be seen by using MELD tool. 2) In order to have a new kernel ( Such as 2.6.35.13) which can be running on my chipbox, what are the steps should be done one by one? Can you please explain for a newbie please? Best Regards Sertac

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kernel_sendpage query.
by Pranay Kumar Srivastava June 10, 2012

June 10, 2012

Hi, I've been trying to understand kernel_sendpage but I've not been able to figure it out completely and hopefully someone else knows better so please help me out on this. I'm using kernel_sendpage for a TCP connection and it works well when there are lesser number of kernel threads trying to send data using it. Now the page I hand over to kernel_sendpage is reused again for reading data from the socket and then processing it and then again resending the processed data in the same page again. It's at maximum 2KB data and never lesser than 120 bytes. As I see it in the code, the page isn't copied in the skb frags array it's just assigned and get_page is called to increment the page reference count. (I don't free it anyway until the thread is stopped and it never is unless it gets a signal). Now I don't know wether kernel_sendpage will wait for the page to be sent or it won't. I've tried with MSG_DONTWAIT and passing 0 for flags but after every now and then the problem occurs at client which I'm describing below with the best explanation I could think of... When too many kernel threads are trying to send data using kernel_sendpage, with NO MSG_DONTWAIT flag, then also it seems that this call succeeds? However since I'm reusing the page the data can get overridden by the next sock_recvmsg and when the network stack is ready to send my page it gets garbage data at client? The same issue I observed with MSG_DONTWAIT set even in that case the client sometimes get garbage data. So my query is, To use kernel_sendpage what I need to do in order to be sure that network stack indeed has sent my page and that I can reuse it for sock_recvmsg again. Thanks a lot for reading! Regards, Pranay Kr. Srivastava pranay.shrivastava(a)hcl.com Software Engineer ERS,HCL Technologies A-5, Sector 24, Noida 201301, U.P. (India) ::DISCLAIMER:: ---------------------------------------------------------------------------------------------------------------------------------------------------- The contents of this e-mail and any attachment(s) are confidential and intended for the named recipient(s) only. E-mail transmission is not guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or may contain viruses in transmission. The e mail and its contents (with or without referred errors) shall therefore not attach any liability on the originator or HCL or its affiliates. Views or opinions, if any, presented in this email are solely those of the author and may not necessarily reflect the views or opinions of HCL or its affiliates. Any form of reproduction, dissemination, copying, disclosure, modification, distribution and / or publication of this message without the prior written consent of authorized representative of HCL is strictly prohibited. If you have received this email in error please delete it and notify the sender immediately. Before opening any email and/or attachments, please check them for viruses and other defects. ----------------------------------------------------------------------------------------------------------------------------------------------------

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Setting up development environment using QEMU.
by Aft nix June 9, 2012

June 9, 2012

---------- Forwarded message ---------- From: Aft nix <aftnix(a)gmail.com> Date: Fri, Jun 8, 2012 at 6:07 PM Subject: Setting up development environment using QEMU. To: kernelnewbies(a)kernelnwebies.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi all, I'm trying to set up a development environment for Kernel development. What have done is follows: 1. setarch linux32 make defconfig. 2.make oldconfig O=/mnt/build/linux 3.make menuconfig O=/mnt/build/linux 4.make. After that i'm trying to boot the the new kernel in QEMU with GDB stub as following: $qemu -s -S /dev/zero -kernel /mnt/build/linux/arch/x86/boot/bzImage Then i get the tcp port which qemu listens for an incoming gdb client : $netstat -tap | grep qemu Then i use gdb /mnt/build/linux/vmlinux to load the image. And set the target to the remote port. But when i get a connection, Qemu Starts to boot. But it complains that the kernel needs a 64 bit Cpu. But as i have configured it to be x86 it should not be the case. Where i'm doing something wrong? Cheers - -- - -aft -----BEGIN PGP SIGNATURE----- Version: OpenPGP.js v0.1 Comment: http://openpgpjs.org wsBcBAEBAgAQBQJP0ernCRCJVJ6A/SK8awAAKFIH/islnSkDpngVvblI8saV g5eBZC1rwtaHTgdpNEi6PmlwdIid8jXerKASpeW3KGtW0KGjIR0KBnFbpbW5 O2A/XJUdmwakx6hFxs2eqGUOysCCCY/c6wyEWmnsLeThkS0KId2sQR7jf4HH 9Paa3Qzl6c1cXM96P+VZeDPcY08iQaBbFkqIZtW5RxTA8dmyUoHAzAepjpTS TeI/Lypsd4G4vpbYJ3ecNfiei0zowc0DRcaPmCY7goNVxU7M7rsVUchasQOo IQ+Djc9CRMVWxXc040mQroZMOzvdoG4zgeNRrbYQVWkcxHPXaOPNsUXy2OBV wPql8fe5CMI3FgvcRusTsBI= =5ORx -----END PGP SIGNATURE----- -- -aft

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Question: kdb and USB?!
by Jan-Simon Moeller June 9, 2012

June 9, 2012

Hi! I wonder what's the status of this as I found no traces of this in latest upstream kernels. I mean direct USB keyboard support. I already tried kdb over USB debug port, but that seems either not available (on the outside ports) or not stable. Is there direct USB keyboard support available? Best, JS

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hello
by yungho breezy June 9, 2012

June 9, 2012

hello,I want to be added to this mailing list.

2 1

Module vs Kernel main performacne
by Abu Rasheda June 9, 2012

June 9, 2012

Hi, I am working on x8_64 arch. Profiled (oprofile) Linux kernel module and notice that whole lot of cycles are spent in copy_from_user call. I compared same flow from kernel proper and noticed that for more data through put cycles spent in copy_from_user are much less. Kernel proper has 1/8 cycles compared to module. (There is a user process which keeps sending data, like iperf) Used perf tool to gather some statistics and found that call from kernel proper 185,719,857,837 cpu-cycles # 3.318 GHz [90.01%] 99,886,030,243 instructions # 0.54 insns per cycle [95.00%] 1,696,072,702 cache-references # 30.297 M/sec [94.99%] 786,929,244 cache-misses # 46.397 % of all cache refs [95.00%] 16,867,747,688 branch-instructions # 301.307 M/sec [95.03%] 86,752,646 branch-misses # 0.51% of all branches [95.00%] 5,482,768,332 bus-cycles # 97.938 M/sec [20.08%] 55967.269801 cpu-clock 55981.842225 task-clock # 0.933 CPUs utilized and call from kernel module 9,388,787,678 cpu-cycles # 1.527 GHz [89.77%] 1,706,203,221 instructions # 0.18 insns per cycle [94.59%] 551,010,961 cache-references # 89.588 M/sec [94.73%] 369,632,492 cache-misses # 67.083 % of all cache refs [95.18%] 291,358,658 branch-instructions # 47.372 M/sec [94.68%] 10,291,678 branch-misses # 3.53% of all branches [95.01%] 582,651,999 bus-cycles # 94.733 M/sec [20.55%] 6112.471585 cpu-clock 6150.490210 task-clock # 0.102 CPUs utilized 367 page-faults # 0.000 M/sec 367 minor-faults # 0.000 M/sec 0 major-faults # 0.000 M/sec 25,770 context-switches # 0.004 M/sec 23 cpu-migrations # 0.000 M/sec So obviously, CPU is stalling when it is copying data and there are more cache misses. My question is, is there a difference calling copy_from_user from kernel proper compared to calling from LKM ?

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Booting MX28-EVK without bootloader support
by Subodh Nijsure June 8, 2012

June 8, 2012

I am using git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc.git for-next branch to get familiar with device tree. I am following procedure described in following thread -- http://lists.ozlabs.org/pipermail/devicetree-discuss/2012-April/014600.html Turn on CONFIG_ARM_APPENDED_DTB, CONFIG_ARM_ARAG_DTB, then appending imx28-evk.dtb and constructing zImage_dtb However this image never initializes network interfaces, I can't mount nfs as rootfs. Is the appended DTB supposed to work from above referenced git repo & branch? Is there a device-tree newbies mailing list by any chance? -Subodh

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Re: How can I disable all USB devices?
by 夏业添 June 8, 2012

June 8, 2012

Sorry for reply so late. I'm an intern and I cannot test your suggestion in the past two days. I didn't fully understand this udev stuff and your reply, and here is my questions: a. about ":=" The man page says that the ":=" means that "Assign a value to a key finally; disallow any later changes, which may be used to prevent changes by any later rules." So I think a rule like this: SUBSYSTEMS=="usb", ACTION=="add", RUN:="/test.sh usb" will prevent adding more programs to RUN, and finally stop calling any "modprobe" in /lib/udev/rules.d/80-drivers.rules so that drivers are not loaded. But the usb devices are still working. b. The function of steps 2 My environment is a costumed Linux, I cannot find /lib/modules/$(uname -r) directory... c. how to identify the device is a usb device. Just seeing the examples on http://www.reactivated.net/writing_udev_rules.html, I'm more confused. Each usb device has a particular match keys. I just want to know whether this device is connecting to usb ports, and manage it. If anybody has some hints, please tell me. Thanks! 2012/6/5 <Ashish_Bunkar(a)dell.com>: > If this is the case here are the steps you can use : > 1. You can tweak udev rules for USB storagedevices. > 2. You can explicitely can make your kernel to not load usb storage driver as below > > $ ls /lib/modules/$(uname -r)/kernel/drivers/usb/storage/usb-storage.ko > $ mv /lib/modules/$(uname -r)/kernel/drivers/usb/storage/usb-storage.ko /root > > Thanks > ASHU > > -----Original Message----- > From: kernelnewbies-bounces(a)kernelnewbies.org [mailto:kernelnewbies-bounces@kernelnewbies.org] On Behalf Of ??? > Sent: Tuesday, June 05, 2012 12:33 PM > To: kernelnewbies > Subject: Fwd: How can I disable all USB devices? > > Thanks for reply! But it seems not suitable for my job. > > Sorry for that I didn't talk about my situation clearly. I was asked to only enable usb Network Interface Card, and disable all other usb devices(like keyboard, mouse, stick, etc.). > > I need a way to distinguish different usb devices and disable/enable them. If anyone has some idea, please tell me. > > 2012/6/5 <Ashish_Bunkar(a)dell.com>: >> Hi >> >> You can just disable the USB support for your kernel by editing kernel parameters. >> Just add "nousb" to you kernel parameters In "/etc/grub.conf" and your kernel should not support USB device thereafter. >> Also when you would like to enable them again just remove "nousb" from kernel command line and all should work fine with that. >> >> Please let me know if that helped you. >> >> Ashish Bunkar >> Linux Engineering >> Dell | BDC >> office +91-80-28078131, mobile +91-7259183696 Ashish_Bunkar(a)dell.com >> >> >> >> -----Original Message----- >> From: kernelnewbies-bounces(a)kernelnewbies.org [mailto:kernelnewbies-bounces@kernelnewbies.org] On Behalf Of ??? >> Sent: Tuesday, June 05, 2012 8:48 AM >> To: kernelnewbies >> Subject: How can I disable all USB devices? >> >> Hi there, >> >> I want to disable all my USB devices (mouse, keyboard,... ) now, but hope to enable some certain device in the future. And I don't want to recompile kernel or disable usb module. >> >> I've searched on the Internet, and it seems that udev manage devices connecting to my computer. Can I use udev to disable all USB devices? >> >> Thanks! >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

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Compile the pwm driver
by jeshwanth Kumar N K June 8, 2012

June 8, 2012

Hello all Accidenteally my sys interface for pwm got deleted in beaglebone. Now I have got the source code, it contains kconfig, make file and source code. Please help me to compile and install I am new to kconfig such things. Thank you. Sent from my HTC

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How to understand super.c/descriptor_loc for ext2/ext3/ext4?
by Ryan Wang June 7, 2012

June 7, 2012

Hi, I'm reading the source code for ext2/ext3/ext4, and cannot figure out how descriptor_loc() runs: 1600static ext3_fsblk_t descriptor_loc(struct super_block *sb, 1601 ext3_fsblk_t logic_sb_block, 1602 int nr) 1603{ 1604 struct ext3_sb_info *sbi = EXT3_SB(sb); 1605 unsigned long bg, first_meta_bg; 1606 int has_super = 0; 1607 1608 first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg); 1) Who can setup the field ->s_first_meta_bg, mke2fs? And what does it mean? What's a meta block group? 1609 1610 if (!EXT3_HAS_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_META_BG) || 1611 nr < first_meta_bg) 2) In which case, we can have "nr < first_meta_bg"? And how does EXT3_FEATURE_INCOMPAT_META_BG affect the physical disk layout? 1612 return (logic_sb_block + nr + 1); 1613 bg = sbi->s_desc_per_block * nr; 1614 if (ext3_bg_has_super(sb, bg)) 1615 has_super = 1; 1616 return (has_super + ext3_group_first_block_no(sb, bg)); 3) It always return the first block no of the specific bg, right? Then its caller ext3_fill_super will read in the disk block. It seems that ext3_fill_super just read many copies of one same block (1st block), right? I'm sure I'm wrong with it, but cannot find out the right way. 1617} Any explanation are welcome. thanks,

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