January 2011 - kernelnewbies@kernelnewbies.org

Need advice/help with my driver debug
by Vic lix Jan. 18, 2011

Jan. 18, 2011

I am trying out a scheme where in I want to emulate a disk storage in the app space. With this in mind, I created a chain of "BlkDrv <-> CharDrv <-> DiskApp" Disk_app has the real storage (done in memory); BlkDrv is to have block driver interface to this disk for the rest of the system; While CharDrv is use for communicating between BlkDrv and DiskApp. (Order of loading is insmod chardrv; create a link node; run DiskApp.out ; insmod blkDrv) BlkDrv is mostly something I picked up from the web (RamDisk). And use to work fine with a local vmalloc-ed RAM. But once I added my logic; I see that once I do fdisk and try to mkfs on the disk it hangs my system. Can you please advice something which I might be doing wrong. Thanks, -Vic

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Query regarding size-16384 cache in kernel
by Sowmya Sridharan Jan. 18, 2011

Jan. 18, 2011

Hi, We see an continuous increase in slab size of 1GB for slab cache named "size-16384" in a system. The system is stable and sending/receiving bulk amounts of packets. "/proc/slabinfo" Initial Value: size-16384(DMA) 0 0 16384 1 4 : tunables 8 4 0 : slabdata 0 0 0 size-16384 9247 9247 16384 1 4 : tunables 8 4 0 : slabdata 9247 9247 0 "/proc/slabinfo" Final Value: size-16384(DMA) 0 0 16384 1 4 : tunables 8 4 0 : slabdata 0 0 0 size-16384 75023 75023 16384 1 4 : tunables 8 4 0 : slabdata 75023 75023 0 Can anyone please tell us what kind of functions in kernel need to allocate an object for "size-16384"? In what possible scenarios are these slab objects allocated? Thanks, Sowmya =====-----=====-----===== Notice: The information contained in this e-mail message and/or attachments to it may contain confidential or privileged information. If you are not the intended recipient, any dissemination, use, review, distribution, printing or copying of the information contained in this e-mail message and/or attachments to it are strictly prohibited. If you have received this communication in error, please notify us by reply e-mail or telephone and immediately and permanently delete the message and any attachments. Thank you

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Implement custom network protocol for local processes
by Kfir Lavi Jan. 18, 2011

Jan. 18, 2011

Hi, How can one implement custom header network protocol. I mean header that wraps regular network packets like ethernet, udp, tcp, etc... The sending of this custom packets is done between processes running locally. ie. I get a Ethernet packet, inspect it, then add my custom header and forward it to another process that listens to a socket, and expect to get data wrapped with this custom header. What is a good way to go about and implement this thing? Thanks, Kfir

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accessing the contents of video memory
by Elvis Y. Tamayo Moyares Jan. 18, 2011

Jan. 18, 2011

Hello list. How I can access the video memory directly from user space? I tried to map the framebuffer (/dev/fb0) using mmap() and ioctl(), but I have not been successful. Really I want to make a copy of the contents of video memory and save it as an image. have any suggestions? ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.

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NULL pointer dereference....
by Murali N Jan. 18, 2011

Jan. 18, 2011

Hi, I am seeing a kernel panic while i keep on reset my device (ARM based) . In one of the reset sequence ( not every immediate reset, after a random resets) i am seeing my platform device structure becoming NULL. The device pointer is one of the member in the my local driver structure. Interestingly it is a first variable in that structure. When the kernel panic happens when i check the other structure variables all are fine except the first 2 variables. ( device pointer is the first variable in that structure). In kernel is there any way that i can put a watch on the memory locations/variable updates? If it is possible please know me the procedure to do that. I appreciate your help. -- Regards, Murali N

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Trouble running Custom kernel
by shivanth m p Jan. 18, 2011

Jan. 18, 2011

I compiled a custom kernel on a virtual box and wen i try to boot the kernel , It says "udev:Wating for device /dev/sda1"and then after 10 seconds it drops to ramfs shell . I think this is a configuration mistake . I tried to make the kernel with the distro specific .config file from /proc/config.gz , But it still doesn't respond . Anybody had this problem before ? May be you guys could help me out .

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RAM disk
by Ugu Barr jr. Jan. 17, 2011

Jan. 17, 2011

Hi there, I would like to study the code of the Linux RAM Disk. Could someone, please point me where to start. Thanks, Ugu

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Messaging
by Sri Ram Vemulpali Jan. 17, 2011

Jan. 17, 2011

Hi, Can anyone help me explain how messaging works in linux kernel. I am very confused with mqueue_inode_info struct. Thanks in advance. -- Regards, Sri.

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anyone know of a resolution for the intel i915 "black screen" issue?
by Robert P. J. Day Jan. 15, 2011

Jan. 15, 2011

i haven't been following closely enough -- has there been a solution checked in for the (common) problem of recent git trees producing a totally black screen shortly after boot with onboard intel i915 graphics? i'd really like to start building kernels again for my ubuntu system but everything lately still gives me a black screen. 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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how CAN-bus Linux driver MCP251x.c works
by cheng chen Jan. 15, 2011

Jan. 15, 2011

I am studying CAN-bus chip Linux driver, MCP251x.c in the kernel source. However, I find a little confused about how this driver works, it registers itself as a SPI slave device using the structure struct spi_driver mcp2510_can_driver = { .driver = {...} .probe= ... } In probe function, it registers itself as a "net_device" with "mcp251x_netdev_ops". So I am not sure how this system works. I know that the userspace must see it as a network driver. But can userspace really see this driver? Or what it can see is the module "can.ko" -- the protocol stack ? Does the network stack talks to SPI and SPI talks to mcp2510 chip and transmit messages can-bus? Or something else? Thanks -- Cheng(誠) My Page: http://freakrobot.blogbus.com/

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