June 2020 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

How to make /dev/ttyACM0 (and friends) exclusive?
by Jeffrey Walton Oct. 11, 2020

Oct. 11, 2020

Hi Everyone, I'm trying to trackdown a problem using my dialup modem. I have a program that opens the modem and watches caller id's. It flashes the hook when a telemarketer calls. It works well until... When another program opens the modem then my program starts reading intermittent responses intended for the other program. I cannot seem to open the device in exclusive mode. The current open is (I also tried with O_EXCL): int modem = open(device_path, O_RDWR | O_NOCTTY | O_SYNC); I'm not sure if it because udev configures the device incorrectly or the kernel driver is configured incorrectly. Or maybe it is impossible to do. Does anyone know how I can make the device exclusive? Thanks in advance.

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Git pull and untracked files
by Gautam Bhat July 5, 2020

July 5, 2020

Hi, When I do a git pull to get the latest changes (from v5.2) , git status shows the following files as untracked: scripts/conmakehash scripts/pnmtologo scripts/sortextable I don't see the files in .gitignore too but in the earlier version i.e. v5.2 it is present. These files are binaries, should I go ahead and delete them? -Gautam.

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Is there some method or software that could purposely generate a lot of physical memory fragmentations on linux?
by 孙世龙 sunshilong July 3, 2020

July 3, 2020

Hi, list Is there some method or software that could purposely generate a lot of physical memory fragmentations on Linux? I need to do some tests under such circumstances. Thank you for your attention to this matter.

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Where to place my driver
by jaap aarts July 1, 2020

July 1, 2020

Hello kernel newbies, I am currently writing a driver for asetek 6th gen CPU coolers. Communication to these coolers goes via USB, but 3/4 (but not all!!) metrics are hwmon metrics. There is a case for either USB or hwmon but I don't know where I am supposed to put my driver. There is also the 1/4, RGB controls, these obviously don't fit in hwmon, but I don't know where to put these kinds of controls in the filesystem. If anyone could help me with these 2 choices I can start submitting my first code (I already have fan control working). Thanks, Jaap Aarts

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Advice about the linux kernel development process
by Oscar Carter June 27, 2020

June 27, 2020

Hi, I've been working in the KSPP task number 20: "Enable -Wcast-function-type globally" [1] but now I have some questions about the development process. I sent a v3 patch for the firewire subsystem [2] and a v5 patch series for the acpi/irqchip subsystems [3]. During the process I've received comments and suggestions about my work but now these two threads have no responses in three weeks. When I've send patches to the staging area if they have no responses, in a few days I received a mail from Greg to tell me that the specific patch had been applied to one of the branches of his git tree. Now, what it's the correct workflow out of the staging area? Are these patches in a process of been applied or have they been forgotten? Do I need to insist? And how? [1] https://github.com/KSPP/linux/issues/20 [2] https://lore.kernel.org/kernel-hardening/20200530090839.7895-1-oscar.carter… [3] https://lore.kernel.org/kernel-hardening/20200530143430.5203-1-oscar.carter… Thanks in advance Oscar Carter

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Are there some potential problems that I should be aware of if I allocate the memory which doesn't have any relation to peripheral hardwares(i.e. DMA, PCI, serial port and etc) by vmalloc() instead of kmalloc()?
by 孙世龙 sunshilong June 27, 2020

June 27, 2020

Hi, list Besides kmalloc() is more efficient, are there some potential problems that I should be aware of if I allocate the memory which doesn't have any relation to peripheral hardwares(i.e. DMA,PCI,serial port and etc) by vmalloc() instead of kmalloc() to avoid the page allocation failure(caused by kmalloc() while there are too much memory fragment)? Thank you for your attention to this matter.

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Besides kmalloc() is more efficient, are there some potential problems that I should be aware of if I allocate the memory which doesn't have any relation to peripheral hardwares(i.e. DMA,PCI,serial port and etc) by vmalloc() instead of kmalloc() to avoid the page allocation failure?
by 孙世龙 sunshilong June 26, 2020

June 26, 2020

Hi, list Besides kmalloc() is more efficient, are there some potential problems that I should be aware of if I allocate the memory which doesn't have any relation to peripheral hardwares(i.e. DMA,PCI,serial port and etc) by vmalloc() instead of kmalloc() to avoid the page allocation failure(caused by kmalloc() while there are too much memory fragment)? Thank you for your attention to this matter.

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Are there still some methods that could be used by the Linux kernel to reduce memory fragmentation while both CONFIG-MIGRATION and CONFIG-COMPACTION are disabled?
by 孙世龙 sunshilong June 23, 2020

June 23, 2020

Are there still some methods that could be used by the Linux kernel to reduce memory fragmentation while both CONFIG-MIGRATION and CONFIG-COMPACTION are disabled? Are there some system settings that could make for this goal?

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What are the potential problems if the option CONFIG_MIGRATION is disabled?
by 孙世龙 sunshilong June 22, 2020

June 22, 2020

As the subject, I find it has some relation with the error: "page allocation failure: order:9".This error occurs frequently if this option is disabled. Could memory fragmentation still be reduced by other methods if this option is disabled?

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Crash recovery kernel error
by Harsh chopra June 22, 2020

June 22, 2020

I cloned the kernel from "git clone git:// git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git". I selected the branch 5.7.y for building the kernel, I used the command "make menuconfig" to select specific modules and to avoid other options that come up while making the .config file. I was able to successfully install the kernel but when I started the kernel version 5.8.3+ , the system freezes with the message "see systemctl status kdump.service". When I looked in the logs I found this message "Failed to start Crash recovery kernel arming" My operating system is Centos 7.8.2003 kernel 3.10. Any help will be appreciated.

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