April 2011 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

/lib/modules/2.6.38.4/kernel/drivers/gpu/drm: no such file or directory
by Aravind Vijayan April 27, 2011

April 27, 2011

I am trying to build a kernel ( *2.6.38.4) *on fedora 12 in a virtual machine according to the data found at :http://kernelnewbies.org/KernelBuild i have successfully completed until: "Make all" but when i tried to run: su -c "make modules_install install" i got an error : "find :/lib/modules/2.6.38.4/kernel/drivers/gpu/drm: no such file or directory May i know how can i overcome this?

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VMA of processes and CPU registers
by limp April 27, 2011

April 27, 2011

Hi all, I know that each user processes has a number of virtual memory areas (VMA) which consist its (virtual memory) address space. For example cat /proc/1426/maps will return the (virtual memory) address space of the process 1426. What I don't know for sure is if the actual CPU registers contain the virtual address of a running process or the "translated" by MMU physical address. I think that every access to a VA must be resolved to a corresponding PA so I guess the CPU registers will deal with the physical addresses rather than the virtual ones but I wanted to be sure about it. Thank you all for your help. John K.

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thinking of updating the canonical online udev document
by Robert P. J. Day April 27, 2011

April 27, 2011

[not sure if this is the right forum for this, but i suspect others on this list might be interested so ... there you go.] as part of a device driver course i may very well be teaching in the near future (still waiting to hear), i'm thinking of adding a sizable section on how udev works (after i figure all that out, of course.) currently, the canonical udev document is this one: http://reactivated.net/writing_udev_rules.html but as good as that doc is, it's obvious that it's getting a bit dated. for example, it refers to separate udev-related utilities such as udevinfo, udevtrigger and so on when, these days, there's just "udevadm" with the appropriate subcommand, so that's something that could be tidied up. other picky things to be updated include claiming that the default udev rules file is /etc/udev/rules.d/50-udev.rules when -- at least on my ubuntu system -- it's /lib/udev/rules.d/50-udev-default.rules. again, not serious, just something that could be corrected. (mind you, i don't know if the udev file and directory structure differs drastically on other distros, something i'll look into.) and sometimes the documentation is not clear on some issues. for instance, are the only two possible entries for the udev.conf file udev_root udev_log the man page for "udev" suggests that, i just wasn't sure whether there were any other possibilities. finally, i was checking the default udev rules file on my ubuntu system and, right at the top, i read: SUBSYSTEM=="block", SYMLINK{unique}+="block/%M:%m" SUBSYSTEM!="block", SYMLINK{unique}+="char/%M:%m" AFAICT, there is nothing in the udev man page that explains the "SYMLINK{unique}" notation. it's easy enough to see how it creates that set of symlinks based on major and minor numbers, but what's with the "unique"? oh, and for this udev tutorial, i want to come up with some real, hands-on examples, so that people can see what's happening with events when they do stuff like insert USB keys and so on. anyway, this will undoubtedly take more than a few days but feel free to use this as a thread to go through the current document, check it against your system, post differences or updates, and i'll collect them all and eventually write up an updated version and post it somewhere. 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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What is the adventage of macros against function
by İsmail Baydan April 27, 2011

April 27, 2011

Currently I am trying to learn linux kernel while looking around I saw that a lot of function likes macros are defined.What is the adventage of macros over functions. Thanks -- İsmail Baydan

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block request execution failing on RHEL6.0 (2.6.32-71.el6.x86_64)
by ajit jain April 26, 2011

April 26, 2011

Hi All, I have written a func to send a CDB on a scsi device from the kernel. For that I am getting a request and queueing for execution. But blk_execute_rq() func is setting errors field of request to 65536 and sense length is set but all the fields in sense header is 0. I dont know what I am missing, any suggestion would be great help. snippet of the code =========================== rq = blk_get_request(q, rw, __GFP_WAIT); if(!rq){ goto out; } if (buflen && blk_rq_map_kern(q, rq, buf, buflen, __GFP_WAIT)){ goto out; } rq->cmd_len = cmdlen; memcpy(rq->cmd, cmd, cmdlen); memset(sense, 0, sizeof(sense)); rq->sense_len = 0; rq->sense = sense; rq->cmd_type |= REQ_TYPE_BLOCK_PC; rq->cmd_type |= REQ_NOMERGE; rq->timeout = WRITE_SCSI_TIMEOUT; //WRITE_SCSI_TIMEOUT is set to 60 sec blk_execute_rq(q, bd_disk, rq, 0); error = rq->errors; if( error ){ dbg("error in blk_execute_rq error %d",error); } if(rq->sense_len){ process_sense_info(rq->sense); } else { info("no sense available"); } ========================================== thanks, ajit PS:We can not use sg_ioctl interface because code expects user space application only to invoke sg_ioctl that the reason it does a copyin.

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Linux kernel patches - websites
by Anand Moon April 26, 2011

April 26, 2011

Hi All, Are their any website's which will give us information regarding Linux kernel patch's, before these patch's get merge in kernel main tree. with regards Anand Moon

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VFAT: flush mount option
by luca ellero April 26, 2011

April 26, 2011

Hi all, I've read somewhere that the suggested mount option for USB key with FAT filesystem is "-o flush" instead of "-o sync" (if you want to remove the key safely, without executing umount or sync). sync option is quite dangerous (and slow) for flash file-systems since it does an aggressive flushing on the FAT, which can damage the flash. Anyway with flush option (kernel 2.6.32), I experienced the following: - if I create or modify a file on the key, the fs is sync'ed immediately so I can pull out the key immediately with no side effects - but if I only create a directory and anything else, the "flush" is not executed immediately, so if I pull out the key, the directory just created disappear (which is not what I would expect). Can someone please tell me if this is the right behaviour or am I missing something. Thanks Best regards Luca Ellero

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LTS kernel?
by Greg Freemyer April 25, 2011

April 25, 2011

All, I just read http://article.gmane.org/gmane.linux.kernel.stable/9103 It talks about the new "longterm" 2.6.34 kernel release. Does anyone know if longterm in this case just means its a post initial release update? Or does it mean 2.6.34 now has some special longterm designation? Greg

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2.6.38 Nvidia Problems : NVRM: The system BIOS may have misconfigured your GPU.
by Venkatram Tummala April 25, 2011

April 25, 2011

Hi, I am trying to run 2.6.38(x86_64) with nvidia 7200GS video card with 4GB of RAM. Although the kernel boots up, i just get a blank screen. I can ssh into the system. dmesg shows the following output : [ 11.535703] NVRM: This PCI I/O region assigned to your NVIDIA device is invalid: [ 11.535704] NVRM: BAR1 is 0M @ 0x0 (PCI:0000:01:00.0) [ 11.535706] NVRM: The system BIOS may have misconfigured your GPU. [ 11.535710] nvidia: probe of 0000:01:00.0 failed with error -1 [ 11.535728] NVRM: The NVIDIA probe routine failed for 1 device(s). [ 11.535730] NVRM: None of the NVIDIA graphics adapters were initialized! [ 11.706755] vesafb: cannot reserve video memory at 0xa0000000 [ 11.706761] vesafb: abort, cannot ioremap video memory 0x500000 @ 0xa0000000 [ 11.706764] Trying to free nonexistent resource <00000000a0000000-00000000a04fffff> [ 11.706768] vesafb: probe of vesafb.0 failed with error -5 It seems lots of people had the same issues with some older kernels ( 2.6.27) and this apparently happens only with 4GB of RAM with nvidia. Anything less than 4GB of RAM is not a problem. Has anyone figured this out yet.

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work_struct not getting scheduled
by Pankaj B April 23, 2011

April 23, 2011

Hi, At my end I was using tasklets to do some handling. But while doing the handling the handler had to sleep, so I had to switch to workqueues. I am scheduling a work as follows: INIT_WORK(&event->work, do_handling_work); schedule_work(&event->work); flush_scheduled_work(); But the work never gets scheduled. I have put some printks in the do_handling_work() function. Creating workqueue and queueing the work to that workqueue doen't work either. I find this a very strange problem. Does anybody knows about this? FYI: my system has heavy IO load when I schedule the work. Thanks

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