October 2018 - kernelnewbies@kernelnewbies.org

Add IIO example to the kernelnewbies wiki
by Gaston Gonzalez Feb. 21, 2019

Feb. 21, 2019

Hi, I'm testing an AD7746 eval board using a Diolan DLN-2 adapter. I wrote some basic notes about the installation an instanciation process for my own use. But then I thought it could be useful for someone else. So maybe I could put this in the kernel newbies page under the IIO section? If you think is worth it, I would be glad to add it to the wiki page. Best regards, Gaston Notes: The setup ========= AD7746-EVAL BOARD --> Diolan DLN-2 Adapter --> Thinkpad T430 The connection between the AD7746 eval board and adapter is as detailed in [2] I2C Interface Configuration Options, External connection (pag 4). The connection between Diolan DLN-2 and the T430 is USB straighforward. Drivers ======= Both in mainline kernel: - Diolan DLN-2 driver: I2C_DLN2 (prompt Diolan DLN-2 USB I2C adapter) Loc: drivers/i2c/busses/ - AD7746: AD7746 Loc: drivers/staging/iio/cdc/ Bus of interest =============== $ sudo i2cdetect -l We get something like: ... i2c-10 i2c dln2-i2c-1-1.2:1.0-0 I2C adapter ... So our bus is the number 10. Getting the address =================== $ sudo i2cdetect -y -r 10 We get something like: 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- 48 -- -- -- -- -- -- -- 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- -- 3. Device instantiation: # echo add7746 0x48 > /sys/bus/i2c/devices/i2c-10/new_device We must see something like: $ cd /sys/bus/i2c/devices/i2c-10/10-0048/ $ ls driver iio:device0 modalias name power subsystem uevent $ cd iio:device0 $ ls dev in_capacitance-capacitance_calibbias in_capacitance0_calibbias_calibration in_capacitance-capacitance_sampling_frequency in_capacitance0_calibscale in_capacitance-capacitance_scale in_capacitance0_calibscale_calibration in_capacitance_sampling_frequency in_capacitance0-capacitance2_calibscale in_capacitance_sampling_frequency_available in_capacitance0-capacitance2_offset in_capacitance_scale in_capacitance0-capacitance2_raw in_temp0_input in_capacitance0_offset in_temp1_input in_capacitance0_raw in_voltage0_calibscale_calibration in_capacitance1_calibbias_calibration in_voltage0_raw in_capacitance1_calibscale in_voltage1_supply_raw in_capacitance1_calibscale_calibration in_voltage_sampling_frequency in_capacitance1-capacitance3_calibscale in_voltage_sampling_frequency_available in_capacitance1-capacitance3_offset in_voltage_scale in_capacitance1-capacitance3_raw name in_capacitance1_offset power in_capacitance1_raw subsystem in_capacitance_calibbias uevent Checking the permits: $ ll -r--r--r-- 1 root root 4096 mar 31 09:57 dev --w------- 1 root root 4096 mar 31 09:57 in_capacitance0_calibbias_calibration -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance0_calibscale --w------- 1 root root 4096 mar 31 09:57 in_capacitance0_calibscale_calibration -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance0-capacitance2_calibscale -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance0-capacitance2_offset -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance0-capacitance2_raw -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance0_offset -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance0_raw --w------- 1 root root 4096 mar 31 09:57 in_capacitance1_calibbias_calibration -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance1_calibscale --w------- 1 root root 4096 mar 31 09:57 in_capacitance1_calibscale_calibration -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance1-capacitance3_calibscale -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance1-capacitance3_offset -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance1-capacitance3_raw -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance1_offset -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance1_raw -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance_calibbias -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance-capacitance_calibbias -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance-capacitance_sampling_frequency -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance-capacitance_scale -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance_sampling_frequency -r--r--r-- 1 root root 4096 mar 31 09:57 in_capacitance_sampling_frequency_available -rw-r--r-- 1 root root 4096 mar 31 09:57 in_capacitance_scale -rw-r--r-- 1 root root 4096 mar 31 09:57 in_temp0_input -rw-r--r-- 1 root root 4096 mar 31 09:57 in_temp1_input --w------- 1 root root 4096 mar 31 09:57 in_voltage0_calibscale_calibration -rw-r--r-- 1 root root 4096 mar 31 09:57 in_voltage0_raw -rw-r--r-- 1 root root 4096 mar 31 09:57 in_voltage1_supply_raw -rw-r--r-- 1 root root 4096 mar 31 09:57 in_voltage_sampling_frequency -r--r--r-- 1 root root 4096 mar 31 09:57 in_voltage_sampling_frequency_available -rw-r--r-- 1 root root 4096 mar 31 09:57 in_voltage_scale -r--r--r-- 1 root root 4096 mar 31 09:57 name drwxr-xr-x 2 root root 0 mar 31 09:57 power lrwxrwxrwx 1 root root 0 mar 31 09:57 subsystem -> ../../../../../../../../../../../bus/iio -rw-r--r-- 1 root root 4096 mar 31 09:57 uevent 4. Capacitance According to [2], the capacitive length sensor is connected to CIN2+ and CIN2-. In the driver, the values are mapped to capacitance0. Raw values vs sensor length: Note: (+) values means the sensor was moved to the left, (-) values means the sensor was moved to the right. I.e. +1 cm means the rule was moved 1 to the left, while -1 means the rule was moved 1 cm to the right. Note2: note the raw value for -10 is 8224733, while +10 is -8224726, the difference is because when the rule is moved 10 cm to the left, the is still 2 o 3 cm of dielectric between the plates. The design is obviously thought to move the rule to the right. Length (cm) | Raw Value Cap0 ------------------------------ -10 -8224733 -9 -8224730 -8 -8224728 -7 -8224725 -6 -8224724 -5 -8224722 -4 -8224720 -3 -8224718 -2 -8224716 -1 -8224714 +0 -8224711 +1 -8224711 +2 -8224711 +3 -8224711 +4 -8224713 +5 -8224715 +6 -8224717 +7 -8224719 +8 -8224721 +9 -8224723 +10 -8224726 References ========== [1] http://www.analog.com/media/en/technical-documentation/data-sheets/AD7745_7… [2] http://www.analog.com/media/en/technical-documentation/evaluation-documenta… [3] https://i2c.wiki.kernel.org/index.php/Main_Page [4] https://kernelsense.wordpress.com/2016/01/22/achievement-unlocked-first-iio…

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deferred pages
by Damian Tometzki Nov. 20, 2018

Nov. 20, 2018

Hello together, can anyone me short explain what is deferred page(s) ? Many thanks Best regards Damian

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error: /boot/vmlinuz-4.18.16-1-default has invalid signature
by Manuel Quintero Fonseca Nov. 6, 2018

Nov. 6, 2018

I Compiled the stable kernel obtained from kernel.org, when starting the grub the error came out: Loadin Linux 4.18.16-1-default .. error: /boot/vmlinuz-4.18.16-1-default has invalid signature. loading initial ramdisk ... error: the kernel must be loaded first The steps for the process were: $ git clone git: // git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git cd linux-stable $ git checkout -b stable v4.18.16 $ cp / boot / config-`uname -r` * .config $ make #make modules_install install #reboot with that it is supposed to be compiled and installed in the system and I configure the grub the source: https://kernelnewbies.org/KernelBuild openSUSE TW NOTE: I tested it on a virtual machine in the same way, and did not frame the error regards

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Quick interview with any community members
by Alex Frederiksen Oct. 31, 2018

Oct. 31, 2018

Hey guys. I decided to do a college paper on the Linux discourse community, particularly on how a person navigates between groups and gains "authority" within the community. If ya guys could answer some of my questions, that would be real swell and I'd appreciate it. (: 1. Would you consider yourself closer to a "novice" or an "expert" in the community? 2. How do "novices" and "experts" interact? 3. What would you say is the primary way(s) of communication? 4. Are there ways to attain authority (as a maintainer or leader of sorts)? If so, how? 5. What are some of the common goals of the community? Regards, Alex

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Backporting stacked security patch
by Lev Olshvang Oct. 31, 2018

Oct. 31, 2018

Hi All, I week ago I asked the list about kernel 4.2 stacked security patch location , but Greg strongly advised me against, without going into details. I highly appreciate Greg advice, and I know he is a very busy person. Unfortunately I do not have a choice to upgrade kernel, and I am asking again : - what are major challenges of a such backport ? Does kernel security changed so much between 3.18 and 4.2 ? The link is https://kernelnewbies.org/Linux_4.2#Stacking_of_security_modules Regards, Lev

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[me: Does Rockchip RK808 driver unload work as intended?]
by Matti Vaittinen Oct. 30, 2018

Oct. 30, 2018

Hello Peeps! Few months ago I sent question below to clk mailing list. I got zero replies so I took that as a hint that I am mistaken =) Hence I resend same question to this list - perhaps this is a better place to search for answer to (simple) question like this. ----- Forwarded message from Matti Vaittinen <matti.vaittinen(a)fi.rohmeurope.com> ----- > Date: Fri, 7 Sep 2018 13:19:40 +0300 > From: Matti Vaittinen <matti.vaittinen(a)fi.rohmeurope.com> > To: zyw(a)rock-chips.com, mturquette(a)baylibre.com, sboyd(a)kernel.org, w.egorov(a)phytec.de > Cc: linux-clk(a)vger.kernel.org, linux-kernel(a)vger.kernel.org > Subject: Does Rockchip RK808 driver unload work as intended? > User-Agent: Mutt/1.9.2 (2017-12-15) > > Hi dee Ho peeps, > > I was browsing through the clk drivers as I tried to do some cleaning. > Few days ago I submitted a patch which would add devm variants for > clkdev lookup registration. I also added devm of_provider registration > for cases where it is actually the parent device which contains clock > definitions in DT. This seems to be quite typical for MFDs. > > While doing this I hit to Rockchip RK808 driver which seems to utilize > oarent device (MFD dev) for pretty much all devm releasing. I wonder if > this is safe? What happens if one tries to remove the RK808 clk module? > > I guess the clk deregistration and cleanups are not ran as parent device > stays there, right? But is the clk module and clk module code still > unload? So won't clk operation pointers registered to clk core become > invalid? > > I guess I don't have any HW to test this mnyself. And as the driver has > been there since 2014 - well, chances are the driver does work and I > just don't get it =) > > So can someone please shed some light on this? Is this a bug or am I > just plain wrong? > > Br, > Matti Vaittinen ----- End forwarded message ----- -- Matti Vaittinen ROHM Semiconductors ~~~ "I don't think so," said Rene Descartes. Just then, he vanished ~~~

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MMU related code
by Carter Cheng Oct. 29, 2018

Oct. 29, 2018

Hi, Where do I find the code in the kernel related to the MMU and resolving memory addresses? I am trying to understand what the implications are if code like this has bugs and the impact on the various functions that return chunks of memory for use via pointers (either as pages or kmalloc chunks) etc. Regards, Carter

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Testing the performance impact of kernel modifications
by Carter Cheng Oct. 23, 2018

Oct. 23, 2018

Hi, I was wondering what are some good ways to assess the performance impact of kernel modifications. Are there some papers in the literature where this is done? Does one need to differentiate between CPU bound and different types of I/O bound processes etc? Regards, Carter.

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Boot all yes config kernel with QEMU
by Tobin C. Harding Oct. 23, 2018

Oct. 23, 2018

Hi, I'd like to build and boot an allyesconfig kernel with QEMU. Building is no problem but when I try to boot it I get problems because the host system does not support features requested by the VM. How does one go about testing an allyesconfig kernel? Back story: I'm trying to set up some CI infrastructure to run scripts/leaking_addresses.pl against the various stable kernels. thanks, Tobin.

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Modify a file content from block layer
by jitendra kumar khasdev Oct. 22, 2018

Oct. 22, 2018

Hi All, Is there any way, by which I could write/update the sectors of a file (which already exist or created in user space) from the block layer interfaces? --- Jitendra

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