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

issue with ASUS Fan maximal mode
by Sergey Ivanov June 14, 2020

June 14, 2020

Hi there. I have a headache with linux bug https://bugzilla.kernel.org/show_bug.cgi?id=153281 and i'm one from many others that still suffered from the described issue. Personally i was able to move forward a bit. In particular, 1) with a great soft that manipulates with fan speed ranges https://github.com/dominiksalvet/asus-fan-control/issues/43 i was able to understand how maximal mode is activated at very low level in the so-called embedded controller in addresses 0x0521 and 0x0522. 2) It seems i understand that there is another driver/hardware mode that activates maximal mode eternally. 3) I disassembled my dsdt tables and found no more destructive code that could change maximal mode back https://github.com/icegood/my_dsdts ================ So, i'm interest in people here who could help me cruising in kernel sources to understand who else can communicate with an embedded controller. For now, I'm interested how driver asus-nb-wmi registers it's controlling chipset to hwmon so /sys/devices/platform/asus-nb-wmi/hwmon/hwmon5 node is created. >From sensors i see that it is a asus-isa-0000 Adapter: ISA adapter cpu_fan: 1900 RPM temp1: +53.0°C and i wonder how it registered. -- Kind regards, Sergey Ivanov

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replacing if-then-else strcmp ladders with switch cases
by jim.cromie＠gmail.com June 13, 2020

June 13, 2020

considering lib/dynamic_debug.c we have ... } else if (!strcmp(words[i], "module")) { rc = check_set(&query->module, words[i+1], "module"); } else if (!strcmp(words[i], "format")) { ... are there any built-in hash functions which would allow this ? switch (keyword) { case Hash("module"): ..... break; case Hash("format"): .... break; default: return -EINVAL }

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sticky bits in /proc etc
by jim.cromie＠gmail.com June 11, 2020

June 11, 2020

Id like to ask about a possible new use for file and directory sticky bits, or setuid bits, to address the root-only use of /proc (etc) files this needs root echo module kvm +p > /proc/dynamic_debug/control how about this ? cat root-owned-readonly-file > /proc/dynamic_debug/control the root-owned-file can define a fixed set of dprintk enablements, and since its ro, its contents are controlled. is there some combination of special-bits on the source (ro root owned) and destination (root owned) that could safely allow joe-user to cat that file into control ? If it could fit here, it might then be a general workaround to root-shell access for /proc /sys manipulations

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Current Instruction Pointer Along Memory Access for A specific Process
by Irfan Ullah (울라 이르판) June 11, 2020

June 11, 2020

Hi everyone, I am trying to generate the log of instruction pointers (IPs) along with corresponding memory accesses (including the page faults) in a sequence for a specific application. I have generated the log of page faults along with corresponding memory addresses by modifying the Linux Kernel code for a specific application, but I didn't find the location of the current instruction pointers along with corresponding memory addresses; being analyzing Linux kernel code for more than a week. I think what I need is available in the code related to the CPU control unit because it handles the fetch-execute cycle; I looked for it but couldn't find the code responsible for the fetch-execute cycle in the kernel code. Could anyone suggest to me where could I find the current value of IP along with the memory address in the Kernel code? There are some tools available to generate the log of instruction pointers with memory accesses but I can't use them because I need a log of memory accesses and page faults in exact sequence and order along with corresponding IPs. Thank you. -- *Best Regards,* *Mr. Irfan Ullah* PhD Candidate Data and Knowledge Engineering(DKE) Lab Department of Computer Science and Engineering Kyung Hee University, South Korea. +82-010-591-51651 <+82%2010-3877-8867> sahibzada.iu(a)gmail.com *Skype*: sahibzada_irfanullah

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Generic way for verifying GPIO wakeup capability
by Pintu Agarwal June 10, 2020

June 10, 2020

Hi All, I am looking for ways to wakeup any devices (from sleep) using any arbitrary gpio wakeup method in a generic way (either from user space or kernel space) that should work on any kernel version (starting from 4.14 onwards). What are the options available right now ? I wanted to experiment with all of them and decide which is best for us. Is /sys/class/gpio/ method still valid with the latest kernel ? Or is there any other method to do it from user space ? One option I know is to use enable/disable_irq_wake() API from kernel driver suspend/resume path. Just like this: https://lwn.net/Articles/569027/ But this requires an additional kernel driver and device-tree changes for each gpio wakeup, which the end-user needs to implement on their own. Is there any other existing generic mechanism? Thanks, Pintu

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Re: [staging-testing] drivers/staging/wfx/hif_tx.c
by Jérôme Pouiller June 10, 2020

June 10, 2020

On Wednesday 10 June 2020 08:53:13 CEST Mohamed Dawod wrote: > Hello, > > I read this point in staging/wfx/TODO file > > - In wfx_cmd_send(), "async" allow to send command without waiting the reply. > It may help in some situation, but it is not yet used. In add, it may cause > some trouble: > https://lore.kernel.org/driverdev-devel/alpine.DEB.2.21.1910041317381.2992@… > So, fix it (by replacing the mutex with a semaphore) or drop it. > > I think that this issue has already been fixed in hif_shutdown() function, hasn't it ? Indeed, when I wrote the TODO file, the function hif_shutdown() didn't exist yet. > I have another question. How can (replacing the mutex with a semaphore) solve the problem? My understanding is that a mutex aims to be acquired and released from the same context. In some specific usages (RT-mutex? lock proving?), acquire mutex from a context and release it from another can produce some errors. In contrary a boolean semaphore does not have this restriction. (can anyone confirm that?) -- Jérôme Pouiller

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[staging-testing] drivers/staging/wfx/hif_tx.c
by Mohamed Dawod June 10, 2020

June 10, 2020

Hello, I read this point in staging/wfx/TODO file - In wfx_cmd_send(), "async" allow to send command without waiting the > reply. > It may help in some situation, but it is not yet used. In add, it may > cause > some trouble: > > https://lore.kernel.org/driverdev-devel/alpine.DEB.2.21.1910041317381.2992@… > So, fix it (by replacing the mutex with a semaphore) or drop it. > I think that this issue has already been fixed in *hif_shutdown*() function, hasn't it ? I have another question. How can (replacing the mutex with a semaphore) solve the problem? Thank You. -- Mohamed Dawod Computer Engineer

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IPX support
by Dmitry Podgorny June 3, 2020

June 3, 2020

Hello, Recently I've created repositories with IPX for kernel 4.18+. If anyone needs it, feel free to use and improve the code. I have personal interest in IPX, because I'm working on tunneling software and retro gaming over IPX is one of examples how to use it. With time, I'll add few utilities (ping, diag, performance measurement) and maybe add new features to the kernel module. Unless I see any other usecase, the main goal will be to keep things working for games running under wine. Kernel module: https://github.com/pasis/ipx Userspace utilities: https://github.com/pasis/ipx-utils Best regards, Dmitry

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