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understanding GPIO registers
by OrazioPirataDelloSpazio (Lorenzo) Aug. 28, 2011

Aug. 28, 2011

Hi there, I have a motherbord (VIA EPIA LT) with a digital I/O port composed by 4 GPI and 4 GPO (chip: SMSC SCH3114). I want to provide voltage to GPO and read the input value of GPI with a software. Using the generic gpio kernel module, I tried to export pins without success : echo N > /sys/class/gpio/export write error : invalid argument I tried for several values of N (from 1 to 1000 !) then I gave up thinking I would have needed some information from the hardware producer. Now I have got this information that is the following offsets and addresses. How can I use these registers to fix the export problem or alternatively how to write a simple userspace C program to read and write these GPIO? I read gpio.txt but I'm still confused on how to pass from GPIO numbers to registers. Thanks Lorenzo #define sGPIOBaseAddr 0A00 #define GPI1_CTRL_REG 0x6E #define GPI2_CTRL_REG 0x6F #define GPI3_CTRL_REG 0x72 #define GPI4_CTRL_REG 0x73 #define GPO1_CTRL_REG 0x2C #define GPO2_CTRL_REG 0x2D #define GPO3_CTRL_REG 0x35 #define GPO4_CTRL_REG 0x36

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I need suggestions for a practical work related with Kernel Development
by Facundo Viale Aug. 27, 2011

Aug. 27, 2011

Hi! I'm new here and i what to introduce myself i'm teacher in a University in the course Operation Systems. During the course the students learn some Operatyng Systems concepts, specially everything relating to the Kernel. As a practice task, they also have to use C to make a program with some Kernel functionalities. This year this task consists on programming a File System (I chose FAT32 since I thought it was the easiest one to implement) using FUSE and simulating a Hard Disk and a RAID behavior. Since I'm not a Kernel expert I'm looking for some advice and ideas. The aim of the practice task I'm creating is to help the students make a program that simulates the behavior and functionalities of a Kernel (such as a File System, Memory Administrator, Planner, etc.), but at the same I would like those programs to really interact with the Kernel, being not only ideal simulation cases (like FUSE). But, as I said, I don't know that much to have a good idea of what can I use to make the most from the Kernel in the task. I could really use some ideas! Some of the things I have in mind: - Use netlinks - Build a kernel module - I'm also interested in the /dev/mem ¡Thanks a lot in advance!

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Need help with the Uncompressed kernel be overriden after decompress_kernel called?
by jiangtao.jit Aug. 27, 2011

Aug. 27, 2011

Hi all. In arch/x86/boot/compressed/head_32.S before the call of decompress_kernel() it load the address of z_extract_offset_negative(%ebx) as the output address and actually the output_len of the decompressed kernel is larger than extract_offset so the decompressed data will override the uncompressed data begin at input_data Is that the case? How does it worked as the the input buffer is covered by the output buffer while uncompressing? It confused me a lot. or I'd made some misunderstanding on the decompressing routine? Thanks. 2011-08-27 jiangtao.jit

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The core in which NAPI is using
by J.Hwan Kim Aug. 27, 2011

Aug. 27, 2011

Hi, everyone My ethernet card always interrupts at Core 0 . The driver of the device is using NAPI. When NAPI is appled, does the core in which NAPI is processing vary? Is the NAPI triggered by software interrupt, isn't it? My system monitor indicates the CPU loading varies randomly among 8 cores. Can you give an information if the core which NAPI is using varies? Thanks in advance. Best Regards, J.Hwan Kim

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(struct spi_transfer)->rx_buf == (struct spi_transfer)->tx_buf?
by Arvid Brodin Aug. 26, 2011

Aug. 26, 2011

I was tracing calls to dma_map_single() and noticed that spi drivers call this function repeatedly on the same buffer address (with no dma_unmap_single() between). Is this really OK? Looking into it I saw that the spi drivers' tx_buf and rx_buf were equal (same address), and these are "dma mapped" simultaneously in many spi drivers (tx_buf as DMA_TO_DEVICE; rx_buf as DMA_FROM_DEVICE). If this buffer (tx_buf === rx_buf) is both read from and written to using DMA, then shouldn't they use DMA_BIDIRECTIONAL? Also, DMA_TO_DEVICE mappings should be done before starting the transfer to the device, while DMA_FROM_DEVICE mappings should be done after the device has finished its transfer, if I understand dma_map_single() correctly (because this is just a cache synchronization thing, right?) This whole thing just seemed strange to me and I'm hoping someone can explain what's going on! BTW, the declaration of struct spi_transfer (http://lxr.linux.no/linux+*/include/linux/spi/spi.h#L430) has this comment: /* it's ok if tx_buf == rx_buf (right?) */ Since spi is always full duplex, I'm guessing that the idea with using only one buffer is that incoming bytes overwrites queued bytes? -- Arvid Brodin Enea Services Stockholm AB

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How to understand 'make oldconfig'?
by Parmenides Aug. 26, 2011

Aug. 26, 2011

Hi, I have tried to understand 'make oldconfig' command while configurating kernel. I do some experiments and get the following ideas: 1. When there is no a .config in /usr/src/linux, (1) If there is no a /boot/config-x.y.z, make will ask some questions and then produce a .config. (2) Otherwise, make will copy the /boot/config-x.y.z to /usr/src/linux/.config. My question: According to the messages generated by make, I get that both 'make defconfig' and 'make oldconfig' will gerenate .config based on 'i386_defconfig'. Why does 'make oldconfig' ask some questions, while 'make defconfig' does not? 2. When there is a .config in /usr/src/linux indeed, make do nothing but generate a copy of .config, namely .config.old. My question: According to Love, "After making changes to your configuration file, or when using an existing configuration file on a new kernel tree, you can validate and update the configuration: make oldconfig." But, whether I edit .config and make some changes or I copy an existing .config into /usr/src/linux, 'make oldconfig' seems do nothing. So, how can I understand 'make oldconfig' in this case?

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Soft interrupt in multi-core environment
by J.Hwan Kim Aug. 26, 2011

Aug. 26, 2011

Hi, everyone When network card interrupts occur in multi-core system, what core is used by soft irq for network interrupts? That is, for example, if the IRQ happens in core 0, does the soft irq run on the same core ? Is it possible for soft irq to use other core different from hard IRQ? Thanks in advance. Best Regards, J.Hwan Kim

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How to distribute IRQs to all cores
by J.Hwan Kim Aug. 26, 2011

Aug. 26, 2011

Hi, everyone The interrupts of my ixgbevf driver occurs only Core 0 although the user space "irqbalance" serivce is working. How can I distribute the interrupt of RX in ixgbevf to all cores? Is there any kernel compile option for it ? cat /proc/interrupts | grep "isv" 97: 8 0 0 0 0 0 0 0 PCI-MSI-edge isv0-rx-0 99: 7 0 0 0 0 0 0 0 PCI-MSI-edge isv0:lsc 103: 2059 0 0 0 0 0 0 0 PCI-MSI-edge isv2-rx-0 104: 14 0 0 0 0 0 0 0 PCI-MSI-edge isv2-tx-0 105: 1 0 0 0 0 0 0 0 PCI-MSI-edge isv2:mbx "isv" is netdevice name of my ixgbevf. Thanks in advance. Best Regards, J.Hwan Kim

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How to make the kernel support NTFS?
by Parmenides Aug. 25, 2011

Aug. 25, 2011

Hi, I have dumped a lfs 6.3 cdrom to a virutal hard disk in vmware, and it goes without any problem. The original kernel version of lfs 6.3 is 2.6.25. I have upgraded it to 2.6.34 and it seems work well. But, when trying to compile the kernnel 2.6.34 to include the NTFS support, the kernel can not boot and gives me the following messages: Root-NFS: No NFS server available, giving up. VFS: Unable to mount root fs via NFS, trying floppy. Kernel panic - not syncing: VFS Unable to mount root fs on unknown-block(2,0) When doing 'make menuconfig', I have selected these options: File systems -> FUSE(Filesystem in Userspace) support -> DOS/FAT/NT Filesystem -> NTFS file system support -> NTFS write support and all of them are compiled into the kernel, rather than kernel modules. The kermel parameter is also OK: default 0 timeout 30 title LFS root(hd0,0) kernel /boot/vmlinuz-2.6.34 root=/dev/hda1 Now that I just add NTFS support, what's the NFS matter? How can I make the kernel to support the NTFS file system?

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Error Building Fedora Kernel - problem in applying patch
by Vaibhav Jain Aug. 24, 2011

Aug. 24, 2011

Hi, I am trying to build fedora 15 kernel (2.6.39) on a fedora 15 machine (2.6.38.8.-25.fc15.i686.PAE). I am following the document : http://fedoraproject.org/wiki/Building_a_custom_kernel I made a few changes to the source code (only prink statements) and generated a patch as given in the doc by the name * linux-2.6-my-new-patch.patch*. I added the following lines to the spec file at the appropriate places: *Patch 20005: linux-2.6-my-new-patch.patch* * ApplyPatch linux-2.6-my-new-patch.patch* But as soon as I build the kernel I get the error : *ERROR: Patch linux-2.6-my-new-patch.patch not listed as a source patch in spec file* *error: Bad exit status from /var/tmp/rpm-tmp/t07KDk (%prep)* ** *RPM build error: * * Bad exit status from /var/tmp/rpm-tmp/t07KDk (%prep)* I am doing everything according to the doc. Please let me know what could have gone wrong. Thanks Vaibhav Jain

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