April 2013 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

How to get the inode - no path_lookup
by Rishi Agrawal Sept. 17, 2015

Sept. 17, 2015

Hi All, I had a module which used the path_lookup function to print the details of any file's inode. I now want to rewrite that module in order to show some juniors how to write some code in kernel. I am using 3.4.6 kernel, I tried finding out path_lookup but google showed that it has been removed. I tried the following code then which did not work . . . dentry = kern_path_create(AT_FDCWD, filename, &path, 1); if (IS_ERR(dentry)) { printk("Failed to obtain the dentry"); return; } its not returning dentry I again tried after seeing the implementation of vfs_stat function user_path_at(AT_FDCWD, filename, lookup_flags, &path); but this also fails. I am using a proc interface to pass the filename, and copying the filename into a kernel buffer. How can I get a copy of vfs inode for a file name. -- Regards, Rishi Agrawal

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How kernel handle interrupts
by Woody Wu Aug. 5, 2013

Aug. 5, 2013

Hi, List Where is the Kernel code that handles external interrupts? I want to have a look at it but haven't found out where it is. Actually, I have some basic questions about interrupt handling in Linux. 1. After Kernel's ISR received an interrupt, I believe it will invoke a handler defined in a device driver if any. But it should be the device driver's responsibility or kernel ISR's responsibility to clear (or acknowledge) the interrupt? 2. My device, an AX88796B network controller, asserting the interrupt line in a level-triggered manner. Now I met problem with the device that might caused by the CPU interrupt mode is not set as level-triggered by edge trigger. My CPU is Samsung S3C2410, an ARM920T powered one. Does anyone know usually where and how should I do this kind of setting? Thanks in advance. -- woody I can't go back to yesterday - because I was a different person then.

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linux segment
by Fan Yang June 20, 2013

June 20, 2013

Hi all: I print the cs ds and ss register in the user space, and it is same as the __USER_CS and __USER_DS which defined in kernel as 73 and 7b. In the kernel __KERNEL_CS and __KERNEL_DS defined as 60 and 68, but when I print this two value in my kernel module, I get 60 and 7b. Why ? It should be 60 and 68, shouldn't it?

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Documentation on device-mapper and friends
by Kumar Amit Mehta May 8, 2013

May 8, 2013

I'm looking for information on device-mapper, the kernel space utility for Logical Volume Management (LVM2). It seems that the relevant code resides under drivers/md and a lot of other information is under Documentation/device-mapper/ That's fine, but is there any other document that gives more finer details about the device-mapper. I've also recently subsribed to the device-mapper mailing list. -Amit

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Building multi-file modules
by Arlie Stephens May 8, 2013

May 8, 2013

Hi Folks, I've got a module, call it foo, presently built from a single source file, drivers/char/foo.c It's gotten enormous, so I want to split it. Ideally I'd keep the original name for one of the source files. So what I want is a module named foo, build from source files foo.c, bar.c and baz.c kbuild is being uncooperative. The following works: obj-$(CONFIG_FOO) += foo_renamed.o foo_renamed-objs := foo.o bar.o baz.o I'd just prefer not to rename either the module or the original source file. Is this supposed to be possible, and if so, how? I'm on RHEL 6.1, aka kernel 2.6.32, in case that matters. Also, in case that matters, I'm building the module into the kerenl ("y" not "m" in the config.) ----what I've tried---- The following gives me warnings from make: obj-$(CONFIG_FOO) += foo.o foo-objs := foo.o bar.o baz.o The following never compiles foo.c: obj-$(CONFIG_FOO) += foo.o foo-objs := bar.o baz.o Thanks for any insight, -- Arlie (Arlie Stephens arlie(a)worldash.org)

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hello and wiki edit
by Sven Dowideit May 1, 2013

May 1, 2013

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello there, I was browsing around and noticed that the wiki mentions the oftc #kernelnewbies group, which doesn't appear to be active at the moment. Assuming I'm correct, I'd like to update things like that - could I be added to the editor's list? Cheers Sven -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAlF/qFcACgkQPAwzu0QrW+mkUgCeLDzBUlsRd6RRzeLDe/6P/daO 1ysAn2c3GoNQwyh14k+zKzn7abfawgtq =qMQc -----END PGP SIGNATURE-----

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updated hands-on tutorial on how to load external firmware from your module
by Robert P. J. Day April 30, 2013

April 30, 2013

http://www.crashcourse.ca/wiki/index.php/Loading_external_firmware open to feedback/suggestions for improvement/etc. rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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[help] USB - kernel 3.8 : ULPI timeout
by Mylene Josserand April 30, 2013

April 30, 2013

Hi everyone, I have a USB problem. I have already posted it on USB mailing list where Fabio Estevam can reproduce it on mx27pdk and mx31pdk (see http://www.spinics.net/lists/linux-usb/msg84305.html) I thought that it is maybe a "newbie" question/error (because I am) so here I am :) My configuration is an IMX27 with an ISP1504 with a 3.8.2 kernel. I tested it with a SMSC USB3340 transceiver where the same error appears with ULPI (for a OTG and H2 port) : ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver ehci-mxc: Freescale On-Chip EHCI Host driver mxc-ehci mxc-ehci.2: initializing i.MX USB Controller timeout polling for ULPI device mxc-ehci mxc-ehci.2: unable to init transceiver, probably missing mxc-ehci mxc-ehci.0: initializing i.MX USB Controller timeout polling for ULPI device mxc-ehci mxc-ehci.0: unable to init transceiver, probably missing I have read the datasheet of the two USB transceiver. On the SMSC USB3340, we have some gpios on RESET_B and I put it in high in the init board code. With this, it should have been correctly initialiazed (right ?) but there is again this "timeout" of ULPI. Do you have already seen this "error" ? What is it due to ? A mistake in the init configuration ? Thank you in advance for any help to understand how ULPI is working and what I am certainly doing wrong. -- Mylène JOSSERAND Navocap

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[OT]kernel internship for women
by Anuz Pratap Singh Tomar April 30, 2013

April 30, 2013

Hi all, Not sure if you have seen this one already but this was posted on Linux foundation website and I am sure there may be some aspiring female kernel hackers who might benefit from this internship. Rest of the details are already in the link https://www.linux.com/news/featured-blogs/167-amanda-mcpherson/716409-annou… -- Thank you Warm Regards Anuz

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Do we use ARM's system mode in linux kernel
by Dhiraj Kumar April 29, 2013

April 29, 2013

Hi All, ARM is running in Supervisor(SVC) Mode in kernel. ARM also has another mode called System(SYS) Mode. I just needed info if linux kernel uses system mode of ARM processor. Please share information if anyone knows. Thanks in advance !!!!! -- Dhiraj

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