June 2014 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Why the page tables are needed for lowmem?
by sandeep kumar June 19, 2014

June 19, 2014

Hi All i was going through mm initialization code, and saw paging_init() implementation. it has a function map_lowmem(). I was wondering why do we need page table entries for lowmem ?? because all the pages in lowmem can be addressed by kernel logical address and differ only an offset from the physical address. Why cant we simply add that offset to the virtual(logical) address and get the job done. Why waste some memory for creating PTEs for them? can any one clarify? -- With regards, Sandeep Kumar Anantapalli,

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Eudyptula Challenge Task 01
by me storage June 19, 2014

June 19, 2014

Hi i every one i am new to linux kernel programming .I am participating in Eudyptula Challenge .Recently i submitted my solutions to Task 01 but i gives me reply like the below "Please read the requirements for the Makefile and allow the module to be built against any kernel source tree on the filesystem, not just those kernels that happened to be installed in /lib/ at some point in time." And my make file is like this ifneq ($(KERNELRELEASE),) obj-m += helloworld.o else default: make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules clean: make -C /lib/modules/$(shell uname -r)/bulid M=$(PWD) clean end So can any please tell me how to allow the module to be built against any kernel source tree on the filesystem? or can any one pleae tell me what does it mean? Thank you

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out-of-tree configuration
by John Bougs June 18, 2014

June 18, 2014

I am working with a kernel module that has a few kconfig options associated with it. The makefile for the module as it is does not support out-of-tree builds. I am trying to change the the makefile to do out-of-tree builds. Most of this is pretty straight forward, however I can't seem to find any recomendations on to do local configurations for just the out of tree build. right now I use the code below, but I don't realy think it is a good solution because of the possible confilict between the local .config file and the kernel .config file. Any suggestions on how I should handle this? ifneq ($(KERNELRELEASE),) # kbuild part of makefile # Optionally, include config file to allow out of tree kernel modules build -include $(src)/.config # Core module obj-$(CONFIG_XXX) += xxx.o xxx-y += xxx-core.o xxx-sysfs.o # drivers obj-$(CONFIG_XXX_1) += xxx1.o obj-$(CONFIG_XXX_2) += xxx2.o else # normal makefile KDIR ?= /lib/modules/`uname -r`/build default: .config $(MAKE) -C $(KDIR) M=$$PWD modules .config: @echo need local .config exit 1 modules_install: $(MAKE) -C $(KDIR) M=$$PWD modules_install clean: rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions \ modules.order Module.symvers endif

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Re: Unsuccessful transactions during usb enumeration
by Greg KH June 18, 2014

June 18, 2014

On Wed, Jun 18, 2014 at 06:26:23AM +0000, Ranjith T. C. wrote: > Thanks for the reply. > > > What exactly do you mean by this? > > What I meant is whether it could be could be an of the USB controller driver or the hardware? It could be both. Or a bad cable, or bad connection. Try putting some debugging code in the Linux device side and see what that is telling you is happening. Try plugging the device into different operating systems with different types of host controller hardware to see if it is a timing issue. Good luck, greg k-h

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Unsuccessful transactions during usb enumeration
by Ranjith T. C. June 18, 2014

June 18, 2014

Hi, I am using a device with Marvel USB controller in device mode with Linux 2.6.22 running on it. During the enumeration, I am getting so many unsuccessful transactions in my USB packet sniffer. Can anyone please tell me the possible reason for this? Any help in this regard is much appreciated. Please copy me in the further communications. Regards, Ranjith ________________________________ Confidentiality Statement / Disclaimer : This message and any attachments is intended for the sole use of the intended recipient. It may contain confidential information. Any unauthorized use, dissemination or modification is strictly prohibited. If you are not the intended recipient, please notify the sender immediately then delete it from all your systems, and do not copy, use or print. Internet communications are not secure and it is the responsibility of the recipient to make sure that it is virus/malicious code exempt. The company/sender cannot be responsible for any unauthorized alterations or modifications made to the contents. If you require any form of confirmation of the contents, please contact the company/sender. The company/sender is not liable for any errors or omissions in the content of this message. ________________________________

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Adding new board support
by Varka Bhadram June 18, 2014

June 18, 2014

Hi, I am having a board which is customized for our requirement and it is based on cortex-a8 arm architecture. I want to add the board support for this in linux kernel. From where can i start to get it work...? Any tutorial for this to be done...? Thanks and Regards, Varka Bhadram ------------------------------------------------------------------------------------------------------------------------------- [ C-DAC is on Social-Media too. Kindly follow us at: Facebook: https://www.facebook.com/CDACINDIA & Twitter: @cdacindia ] This e-mail is for the sole use of the intended recipient(s) and may contain confidential and privileged information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies and the original message. Any unauthorized review, use, disclosure, dissemination, forwarding, printing or copying of this email is strictly prohibited and appropriate legal action will be taken. -------------------------------------------------------------------------------------------------------------------------------

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SOC: Zedboard: Driver question
by amit mehta June 18, 2014

June 18, 2014

We are working on a school project in which we are trying to develop a audio mixer on Zedboard (Development board from Digilent). We have developed the IP and have integrated it with the overall hardware using Programmable logic. This board has ARM core. We have a Digilent pre-configured Linux source which we cross-compiled for ARM board, device tree blob and bootloader for Zync(BOOT.BIN). The system boots fine with Linux, but now to expose the recently added hardware implementation of audio mixer, we are trying to develop the driver using the platform driver API. Currently, In our reconfigurable hardware, we have 2 channels and a mixer and we want to access those individually as some file nodes under /proc FS. The sample code is shown below: <snip from myiir.c> /* device match table to match with device node in device tree * These are the list of devices that we want to expose as platform device */ static const struct of_device_id myiir_of_match[] __devinitconst = { {.compatible = "dglnt,myiir-audio-ch0"}, {.compatible = "dglnt,myiir-audio-ch1"}, {.compatible = "dglnt,myiir-audio-mix0"}, {}, }; MODULE_DEVICE_TABLE(of, myiir_of_match); /* platform driver structure for myiir driver */ static struct platform_driver myiir_driver = { .driver = { .name = DRIVER_NAME, .owner = THIS_MODULE, .of_match_table = myiir_of_match}, .probe = myiir_probe, .remove = __devexit_p(myiir_remove), .shutdown = __devexit_p(myiir_shutdown) }; /* Register myiir platform driver */ module_platform_driver(myiir_driver); <myiir.c> Now, inside the probe routine (myiir_probe), can we create proc entries by calling create_proc for each of these nodes and setting the appropriate read and write methods(file_operations) ? <snip from the myiir_probe> struct proc_dir_entry *myiir_proc_entry[3]; myiir_proc_entry[0] = proc_create("myiir-audio-ch0", 0, NULL, &proc_myiir_ch0_operations); myiir_proc_entry[1] = proc_create("myiir-audio-ch1", 0, NULL, &proc_myiir_ch1_operations); myiir_proc_entry[2] = proc_create("myiir-audio-mix0", 0, NULL, &proc_myiir_mix0_operations); <snip from the myiir_probe> While browsing the Internet, we found some sample driver code, which we are also using as a template. I've attached the driver that is based on the same template. <snip from device tree file> myiir-aud-ch0 { compatible = "dglnt,myiir-audio-ch0"; reg = <0x74200000 0x10000>; }; myiir-aud-ch1 { compatible = "dglnt,myiir-audio-ch1"; reg = <0x74220000 0x10000>; }; myiir-aud-mix0 { compatible = "dglnt,myiir-audio-mix0"; reg = <0x68600000 0x10000>; }; <snip from device tree file> The driver is far from complete, but as of now the compilation woks fine. <snip> user@fpga4v:~/tutorial/IIRdriver$ make ARCH=arm CROSS_COMPILE=arm-xilinx-linux-gnueabi- make -C ../linux-digilent-3.6-digilent-13.01/ M=/home/user/tutorial/IIRdriver modules make[1]: Entering directory `/home/user/tutorial/linux-digilent-3.6-digilent-13.01' CC [M] /home/user/tutorial/IIRdriver/myiir.o Building modules, stage 2. MODPOST 1 modules CC /home/user/tutorial/IIRdriver/myiir.mod.o LD [M] /home/user/tutorial/IIRdriver/myiir.ko make[1]: Leaving directory `/home/user/tutorial/linux-digilent-3.6-digilent-13.01' <snip> Thanks, Kumar

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Kernel Kconfig doubt..
by siva sangeetha June 17, 2014

June 17, 2014

Hi, I am facing one config issue in kernel building. I have added new define in my board def config, i added the config in Kconfig also but it is not taking and my expected part of define based code not building. Can anyone tel me what i am missing.

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Unsuccessful transactions during usb enumeration
by Ranjith T. C. June 17, 2014

June 17, 2014

Hi, I am using a device with Marvel USB controller in device mode. During the enumeration, I am getting so many unsuccessful transactions in my USB packet sniffer. A screenshot of the issue is attached herewith. Can anyone please tell me the possible reason for this? Any help in this regard is much appreciated. Please copy me in the further communications. Regards, Ranjith ________________________________ Confidentiality Statement / Disclaimer : This message and any attachments is intended for the sole use of the intended recipient. It may contain confidential information. Any unauthorized use, dissemination or modification is strictly prohibited. If you are not the intended recipient, please notify the sender immediately then delete it from all your systems, and do not copy, use or print. Internet communications are not secure and it is the responsibility of the recipient to make sure that it is virus/malicious code exempt. The company/sender cannot be responsible for any unauthorized alterations or modifications made to the contents. If you require any form of confirmation of the contents, please contact the company/sender. The company/sender is not liable for any errors or omissions in the content of this message. ________________________________

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How to capture channel 2 's frames when wireless interface was set to channel 1
by jiangtao.jit June 17, 2014

June 17, 2014

Hi ALL: How to capture channel 2 's frames when wireless interface was set to channel 1. Wireless card is in mode 11g. Bandwidth is 20MHz, between channel 1 and 2 is 5MHz, 20MHz include channel 2. So it's can capture channel 2's frames when wireless card is set in channel 1. Is that right? Thank you. -------------- Tao Jiang (姜涛) jiangtao.jit(a)gmail.com 2014-06-16

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