January 2011 - kernelnewbies@kernelnewbies.org

Any tool under linux to parsing BPB/Bs/FAT table?
by loody March 3, 2011

March 3, 2011

Dear all: I recently trace FS/fat and I want to know is there any utility under linux that can help us to easily parse BPB/BS or FAT tables? appreciate your help, miloody

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Asking advice for graduate study
by cheng chen Feb. 2, 2011

Feb. 2, 2011

Hi, all! I am going to further my education in graduate school of Master of Science degree. I am interested in network, but I am not sure what direction I should choose and which professional books I should read. Therefore I ask for help and suggestion from you. In summary, I have both the fundamental knowledge about network programming as well as communication theory. Therefore I prefer an area which has the relationship with both the software and hardware (but with more attention on software.) By the way, I am especially interested in how the whole network system works, rather than how two single points communicate. If you have any suggestion about what I could do next (areas, books, whaever~), please be kind to tell me. Thank you very much. -- Cheng(誠) Fedora Project Contributor -- Ambassador https://fedoraproject.org/wiki/User:Freakrobot _______________________________________________ My Page: http://freakrobot.blogbus.com/

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ARM Cross Compilation Toolchain on x86 machine
by Madhavi Manchala Feb. 1, 2011

Feb. 1, 2011

Dear All, We are unable to build the ARM cross compilation tools for arm-elf-gcc-3.4.3 on my x86 machine on which we installed the Ubuntu 9.10 distribution OS with 2.6.35 kernel version. The gcc version on x86 machine is 4.3.3. We need to compile some sources on my x86 machine for our target machine which is based on ARM architecture. We have gone through following links to build the cross compilation tools for arm-elf-gcc 3.4.3 on my x86 machine. http://www.ailis.de/~k/archives/19-ARM-cross-compiling-howto.html http://www.kegel.com/crosstool/current/doc/crosstool-howto.html http://www.kegel.com/crosstool/ Unfortunately we end up with different types of errors. When we fix one error then we get another new error. We tried in different ways to build the tools on my x86 machine. There is no luck at all. We also gone through the http://www.gnuarm.com/ site and downloaded the binaries for gcc 3.4. toolchain. However, we did not find any README for how to use these binaries. Please let us know if there is any clean procedure/document/link for building/using the arm-elf-gcc 3.4.3 toolchain on my x86 machine. Any help would be greatly appreciated and help us a lot. Thanks and Regards, Madhavi M.

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what is spinlock depth
by Sri Ram Vemulpali Feb. 1, 2011

Feb. 1, 2011

Hi all, I am reading spinlock code and looking at struct raw_spinlock. I found struct lockdep_map as member. which is defined as struct lockdep_map { struct lock_class_key *key; struct lock_class *class_cache[NR_LOCKDEP_CACHING_CLASSES]; const char *name; #ifdef CONFIG_LOCK_STAT int cpu; unsigned long ip; #endif }; Can anyone help me explain, how this struct helps the spinlock. Why do we need lockdepth. Thanks for help in advance. -- Regards, Sri.

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storing the logs
by mohit verma Feb. 1, 2011

Feb. 1, 2011

hi , my module produces some data (very cititcal) and that i want to log that to some disk residing file like log files. So among several ways like using syslog (and family) ,audit daemon i am not finding the way to use the functionalities of any of these subsystems .i mean : practically i am still unable to do that. can someone point me to some practical implementations used by some other modules or some practically sound articles to achieve this? thanks a lot in advance. -- ........................ *MOHIT VERMA*

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process exception
by Sri Ram Vemulpali Feb. 1, 2011

Feb. 1, 2011

Hi all, This is regarding segment fault. Is there any feature that we can allow kernel to kill only the thread that generate seg fault rather than killing whole process in which it is running. Why is that we did not implement in such way. Is there any specific reason. Thanks in advance for explanation. -- Regards, Sri.

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typecheck code
by Sri Ram Vemulpali Jan. 31, 2011

Jan. 31, 2011

Hi all, /* * Check at compile time that something is of a particular type. * Always evaluates to 1 so you may use it easily in comparisons. */ #define typecheck(type,x) \ ({ type __dummy; \ typeof(x) __dummy2; \ (void)(&__dummy == &__dummy2); \ 1; \ }) #define typecheck_fn(type,function) \ ({ typeof(type) __tmp = function; \ (void)__tmp; \ }) Can anyone help me, explain the above code typecheck. How does (void)(&__dummy == &__dummy2) evaluates to 1 I appreciate any explain. -- Regards, Sri.

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Please correct this code
by Sri Ram Vemulpali Jan. 31, 2011

Jan. 31, 2011

Hi, I have following snippet of code. Code A __asm__ __volatile__( " lock ;\n" " addl %1,%0 ;\n" : "=m" (my_var) : "ir" (my_int), "m" (my_var) : /* no clobber-list */ ); Code B __asm__ __volatile__( "decl %0; sete %1" : "=m" (my_var), "=q" (cond) : "m" (my_var) : "memory" ); In Code A memory contents are getting updated. And in Code B memory contents and 'cond' var are getting updated. In Code B in cobbler column 'memory' is used to indicate that this code modifies memory contents. But where as in Code A it was not mentioned Is is not that Code A is wrong, for not mentioning cobbler list 'memory' to indicate memory contents are getting updated. Please rectify me, if I am wrong. Also, what does '+m' constraint mean, if I use in inline assembly. -- Regards, Sri.

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apparent workaround for i915 "black screen" issue
by Robert P. J. Day Jan. 31, 2011

Jan. 31, 2011

i'm fairly sure some folks here are at least aware of the recent intel intergrated graphics i915 issue that produced a totally black screen upon booting, even though the system quite clearly booted. after swapping numerous posts on the intel free desktop mailing list and getting piles of guidance from chris wilson, i isolated a workaround to applying this simple patch: diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c index 64fd644..28adc6d 100644 --- a/drivers/gpu/drm/i915/intel_opregion.c +++ b/drivers/gpu/drm/i915/intel_opregion.c @@ -495,6 +495,8 @@ int intel_opregion_setup(struct drm_device *dev) opregion->acpi = base + OPREGION_ACPI_OFFSET; } +return 0; // rday + if (mboxes & MBOX_SWSCI) { DRM_DEBUG_DRIVER("SWSCI supported\n"); opregion->swsci = base + OPREGION_SWSCI_OFFSET; i isolated the workaround to this file using "git bisect", then used chris' advice to return earlier than normal to see which of those conditional snippets was causing the problem. i won't pretend to know what's going on there, but if anyone else is seeing the i915-related black screen issue and wants to test the above, it would be nice to verify that this workaround works for someone else. rday -- ======================================================================== Robert P. J. Day Waterloo, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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Please correct this code
by Sri Ram Vemulpali Jan. 31, 2011

Jan. 31, 2011

I have following snippet of code. Code A __asm__ __volatile__( " lock ;\n" " addl %1,%0 ;\n" : "=m" (my_var) : "ir" (my_int), "m" (my_var) : /* no clobber-list */ ); Code B __asm__ __volatile__( "decl %0; sete %1" : "=m" (my_var), "=q" (cond) : "m" (my_var) : "memory" ); In Code A memory contents are getting updated. And in Code B memory contents and 'cond' var are getting updated. In Code B in cobbler column 'memory' is used to indicate that this code modifies memory contents. But where as in Code A it was not mentioned Is is not that Code A is wrong, for not mentioning cobbler list 'memory' to indicate memory contents are getting updated. Please rectify me, if I am wrong. -- Regards, Sri.

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