October 2016 - kernelnewbies@kernelnewbies.org

Web Forum Registration Failure
by nick＠nnbits.org Oct. 3, 2016

Oct. 3, 2016

Hello everyone, I tried to register on Kernelnewbies Web Forum, but got this message: You did not provide the correct code for the spam prevention check. Please try again. Would you please help me understand what I was doing wrong? There was no field for spam check and no captcha, only username, email, password, password repeat. I tried two different browsers. I would appreciate any help or support. Thank you. Nick.

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MODULE_DEVICE_TABLE type=of means?
by Muni Sekhar Oct. 3, 2016

Oct. 3, 2016

Hi All, I see that following dma engine driver uses MODULE_DEVICE_TABLE with ‘type=of’. What does ‘type=of’ means? How to trigger this driver’s probe and remove to be called? http://lxr.linux.no/linux+v4.8/drivers/dma/xilinx/zynqmp_dma.c static const struct of_device_id zynqmp_dma_of_match[] = { { .compatible = "xlnx,zynqmp-dma-1.0", }, {} }; MODULE_DEVICE_TABLE(of, zynqmp_dma_of_match); static struct platform_driver zynqmp_dma_driver = { .driver = { .name = "xilinx-zynqmp-dma", .of_match_table = zynqmp_dma_of_match, }, .probe = zynqmp_dma_probe, .remove = zynqmp_dma_remove, }; module_platform_driver(zynqmp_dma_driver); MODULE_AUTHOR("Xilinx, Inc."); MODULE_DESCRIPTION("Xilinx ZynqMP DMA driver"); -- Thanks, Sekhar

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Virtual Address Space
by Madhu K Oct. 3, 2016

Oct. 3, 2016

Hi All, This is to understand the Virtual address space.Basically who generates the virtual addresses CPU or GNU compiler? Thanks Madhu

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Booting of Linux kernel
by Er Krishna Oct. 2, 2016

Oct. 2, 2016

Hi all I have a basic question for understanding : If we want to boot the Linux kernel without bootloader what needs to be done? In other words what all the core subsystem like memory and all needs initialisation by bootloader and if bootloader is not there then how to do it ? Thanks Krishna

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Re: Options for adding I2C devices and how-to
by vibnwis Oct. 1, 2016

Oct. 1, 2016

> > > https://events.linuxfoundation.org/sites/events/files/slides/petazzoni- > device-tree-dummies.pdf > check page 29/45 > >> >> > This is awesome. Very helpful. I would recommend to get your hands dirty. Start playing with userspace i2c > tools > to get an idea and also there are many raspberry project out there to get > you started with. > Agreed and thanks for the advice.

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Re: Options for adding I2C devices and how-to
by vibnwis Oct. 1, 2016

Oct. 1, 2016

Many thanks Anish for answering my doubts. > You need to find out the device address of your device. > find out which device is not connected and connect your device on that bus > and change the device tree to replace the device address. > Would you elaborate on device tree, please? > You can certainly use i2c_detect and i2c_get user space tools to work with > your device. However is there is a existing kernel space i2c device on that > bus then it will certain lead to bus hogging problems. > > Besides i2c_detect and i2c_get user space tools. I think one can also change two existing GPIOs for SDA and SCLK respectively and using software logics to drive them as I2C bus. I presume the entire GPIOs are able to be mapped for user space, is it not? > Feel free to add any comments or suggestions. > Please add information about your device and kernel version which you are > trying to use. May be there is already a driver for it in open source. > > I am doing some sort research at the moment. I like to know the whole picture before putting my hand on. Hence, at the moment it is pure on papers. However, the kernel version should be 2.6.38 and above. Nevertheless, since I have Pandaboard rev B , and Raspberry 3, I will definitely things that available for these two. Does it make sense? Thanks in advance.

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Does a kernel developer need a hardware to do kernel development?
by Amit Kumar Oct. 1, 2016

Oct. 1, 2016

Hi, (1) I want to work on staging drivers. But I've two questions, Does a kernel developer need a hardware (e.g. board) to do kernel development? (2) I'm able to send patch using sendmail and git. I'm able to apply patch using git-am. But unable to setup mutt to download patch from this emailid. How to setup mutt to download patches? -- Regards, Amit Kumar Twitter: @freeark1 Only Numbers Can Command.

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Options for adding I2C devices and how-to
by vibnwis Oct. 1, 2016

Oct. 1, 2016

Hi there, My questions are about the options available for adding I2C devices onto existing single board computers, such as Panda Board or Raspberry Pi. Later then I would ask how to get it done. By far, I have found out the following options. Correct me if I am wrong as my understanding s still hazy. 1. BitBanging method. That is by connecting it to existing unused GPIOs. Need to create a Bitbanging client driver for the device with the two GPIOs for SDA, SCLK respectively 2. Use existing allocated I2C Pins. Assuming the kernel driver for the device is already available, then simply run make menuconfig to configure to use the right I2c device. However, if the driver is not available. One needs to create a new client driver. if up to now I am still not wrong, then I have a few questions. a) what address is it and how to specify one for the new device? would like wise to use the existing allocated addresses which are not being used due to non-existence of those I2C devices on the system? b) if somehow, the new I2C device has somewhat similar architecture with the existing supporter I2C devices, would it wise to use it instead of developing a new client driver? I am trying to say that would it wise to trial and error some of the existing supporting driver if they are compatible. Only after testing then decide if new driver development is needed. Is it the right thing to do? 3. Writing/using user mode I2c driver. Feel free to add any comments or suggestions. Thank you in advance. Best regards, Lim

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