May 2018 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

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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develoment workflow: how to avoid duplicate work ?
by Hugo Lefeuvre June 6, 2018

June 6, 2018

Hi, I've started to take a look at TODO entries in the staging drivers subtree and found some issues in pi433 I'd like to work on. Before starting to prepare my patch, I tried to check the LKML and the bug tracker to make sure nobody was working on the same issues as me (this driver seems to be pretty actively developed), but couldn't find anything helpful. No mailing list, nobody coordinating, only single patches without relationship. Did I miss something ? Is there a specific place where I can coordinate with the rest of the kernel dev community and make people aware I'm working on this particular issue ? (apart from the bug tracker, which doesn't seem to be very active when it comes to the staging subtree) Thanks ! Regards, Hugo -- Hugo Lefeuvre (hle) | www.owl.eu.com 4096/ 9C4F C8BF A4B0 8FC5 48EB 56B8 1962 765B B9A8 BACA

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Is there mailist about LSM
by Alexander Ivanov May 31, 2018

May 31, 2018

Hi All, What would be right place to ask questions about LSM?

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detecting i2c bus dynamically
by Rupesh Kumar May 30, 2018

May 30, 2018

Based on the daughter cards attached on to the main board, My set-up will have variable number of i2c adapters. I want to write driver for the client on one of the (variable) i2c adapter. I know the exact number for this adapter can be obtained using "i2cdetect -l" from command line. However, I want to know, Is there any method to detect the number of this (variable) i2c adapter inside a kernel module?

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Will RT patches be merged in main line?
by Daniel. May 29, 2018

May 29, 2018

Hi everybody. Does the RT patches have been merged in the main line? or, They will be merged at all? I found the RT wiki at https://wiki.linuxfoundation.org/realtime/documentation/technical_details/s… but can't find if the patches were merged. Also I have some questions about RT benefits/drawbacks: The main benefit of RT kernel is that decreases the latency right? I read that it make all parts of the kernel preemptive, is this right? Why aren't these parts preemptive in the main line? What is the impact of making these parts preemptive? My general concept is that RT kernel has decreased latency, but increased overhead, ... is this right? Regards, -- “If you're going to try, go all the way. Otherwise, don't even start. ..." Charles Bukowski

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Skb data ready callback crashing
by david preetham May 28, 2018

May 28, 2018

sk_data_ready callback crashing, I have used in kmalloc with GFP_ATOMIC inside callback but crashing with __might_sleep. [ 57.916454 / 05-28 10:23:43.705][0] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP [ 57.916464 / 05-28 10:23:43.705][0] Modules linked in: texfat(POE) [ 57.916483 / 05-28 10:23:43.705][0] CPU: 0 PID: 2066 Comm: Binder:2048_1 Tainted: P W OE 4.4.63 #143 [ 57.916492 / 05-28 10:23:43.705][0] Hardware name: Qualcomm Technologies, Inc. MSM8998 v2.1 MTP (DT) [ 57.916502 / 05-28 10:23:43.705][0] task: ffffffedc2554c80 ti: ffffffedc9708000 task.ti: ffffffedc9708000 [ 57.916521 / 05-28 10:23:43.705][0] PC is at ___might_sleep+0x134/0x144 [ 57.916530 / 05-28 10:23:43.705][0] LR is at ___might_sleep+0xf8/0x144 [ 57.916538 / 05-28 10:23:43.705][0] pc : [<ffffff8447ed2dcc>] lr : [<ffffff8447ed2d90>] pstate: 60400145 [ 57.917126 / 05-28 10:23:43.705][0] Call trace: [ 57.917136 / 05-28 10:23:43.705][0] Exception stack(0xffffffedfdb4e080 to 0xffffffedfdb4e1b0) [ 57.917147 / 05-28 10:23:43.705][0] e080: ffffffedc9708000 0000008000000000 00000000832ac000 ffffff8447ed2dcc [ 57.917157 / 05-28 10:23:43.705][0] e0a0: 0000000000000006 0000000000000000 ffffffedfdb4e0d0 ffffff8447f09260 [ 57.917167 / 05-28 10:23:43.705][0] e0c0: 0000000000000000 ffffff844a810000 ffffffedfdb4e170 ffffff8447f09454 [ 57.917178 / 05-28 10:23:43.705][0] e0e0: ffffff8447f0940c ffffff84497712ab 000000000000053a 0000000000000000 [ 57.917190 / 05-28 10:23:43.705][0] e100: ffffffedebec1590 ffffff844868d0bc 000000000000000c ffffff84498a21b7 [ 57.917200 / 05-28 10:23:43.705][0] e120: 0000000000000140 0000000057ac6e9d 0000000000000102 0000000000000000 [ 57.917211 / 05-28 10:23:43.705][0] e140: 0000000000000000 ffffff8008180000 000000000000006a ffffff844a83a9b8 [ 57.917221 / 05-28 10:23:43.705][0] e160: ffffff84480efd38 372e33343a33323a 69205d305b5d3530 63696d6f74615f6e [ 57.917231 / 05-28 10:23:43.705][0] e180: 69202c31203a2928 617369645f737172 203a292864656c62 0000000000000000 [ 57.917241 / 05-28 10:23:43.705][0] e1a0: ffffff8447ffb7b4 0000007f9da5e58c [ 57.917251 / 05-28 10:23:43.705][0] [<ffffff8447ed2dcc>] ___might_sleep+0x134/0x144 [ 57.917261 / 05-28 10:23:43.705][0] [<ffffff8447ed2e58>] __might_sleep+0x7c/0x8c [ 57.917275 / 05-28 10:23:43.705][0] [<ffffff8447fda74c>] kmem_cache_alloc_trace+0x60/0x25c [ 57.917289 / 05-28 10:23:43.705][0] [<ffffff844868d0bc>] mausb_sock_data_ready+0x394/0x57c [ 57.917303 / 05-28 10:23:43.705][0] [<ffffff8448fa79ec>] tcp_data_queue+0x55c/0xba8 [ 57.917312 / 05-28 10:23:43.705][0] [<ffffff8448fa8338>] tcp_rcv_established+0x300/0x6d8 [ 57.917325 / 05-28 10:23:43.705][0] [<ffffff8448fb11b0>] tcp_v4_do_rcv+0xf4/0x1f8 [ 57.917337 / 05-28 10:23:43.705][0] [<ffffff8448fb3c64>] tcp_v4_rcv+0x8a4/0xf38 [ 57.917349 / 05-28 10:23:43.705][0] [<ffffff8448f8e358>] ip_local_deliver_finish+0x118/0x224 [ 57.917359 / 05-28 10:23:43.705][0] [<ffffff8448f8e8e4>] ip_local_deliver+0xcc/0xe0 [ 57.917369 / 05-28 10:23:43.705][0] [<ffffff8448f8e698>] ip_rcv_finish+0x234/0x29c [ 57.917380 / 05-28 10:23:43.705][0] [<ffffff8448f8ebe8>] ip_rcv+0x2f0/0x390 [ 57.975786 / 05-28 10:23:43.765][0] Kernel panic - not syncing: Fatal exception in interrupt code: static void sock_data_ready(struct sock *sk) { skb_buff_rcv.skb_data = kmalloc(packet_length, GFP_ATOMIC);// allocating memory and copying skb data }

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Report on Linux kernel version 4.16
by Cornelius Vanderbilt May 27, 2018

May 27, 2018

Hey, This is addressed to the moderators of kernelnewbies.org or anybody associated with it.I would like to say the current state of affair on the website (kernelnewbies.org) isnot very nice.When linux kernel version 4.16 was released you were supposed to publish a detailed report about all the changes it had and post it here - www.https://kernelnewbies.org/LinuxVersions - like the way you have done for all the other versions.But upto today you havenet posted anything.Its good to conclude that report is dead.But donot be supised that there are people who actually read this reports and find them informative.Would it be worthwhile waiting for the report? thanks

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md and queue write_cache
by Jerome Charaoui May 25, 2018

May 25, 2018

Hello, I recently created a raid1 md volume using two Intel DC P3700 NVMe devices. I noticed that although both NVMe devices report not needing cache flushes (/sys/block/nvme*/queue/write_cache contains "write through"), the md volume created by linking them reports the opposite: /sys/block/md1/queue/write_cache contains "write back". I'm wondering if this is by design or simply a bug. My ultimate goal is to use this device to externally place the journal of an ext4 filesystem sitting on another big, slow, md device. AIUI, unless md itself requires cache flushes for it own ends, I'll be able to mount this filesystem with write barriers disabled and safely gain a significant performance improvement in write speeds. Thanks, -- Jerome

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searching for a missing driver
by Hugo Lefeuvre May 24, 2018

May 24, 2018

Hi, I've been reading documentation about linux drivers development for quite a while now, but never did anything really useful of it. Lack of time, but most importantly lack of projects to apply this knowledge. Now I've got some spare time ahead of me, and it seems to be the right moment to start a kernel driver project. ... but I don't know exactly what kind of device driver I want to write, and what kind of device I want to work on. I think I could have fun working on usb drivers, expecially after reading this blog post[0], but I don't know if it's the best for a first driver project. Is there a place where I can find a list of devices missing kernel drivers ? Can you recommend me a type of device I should opt for, given that this is going to be my first driver project ? A specific device ? Having to reverse engineer stuff isn't much of a problem for me, as long as it doesn't get too far into the "black magic" land. ;) Also, if you have any kind of advices for people starting their first driver project, I'd be glad to hear them. Thanks ! Cheers, Hugo [0] http://matthias.vallentin.net/blog/2007/04/writing-a-linux-kernel-driver-fo… -- Hugo Lefeuvre (hle) | www.owl.eu.com 4096/ 9C4F C8BF A4B0 8FC5 48EB 56B8 1962 765B B9A8 BACA

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Please add new user to Wiki editors list
by Alexey Brodkin May 23, 2018

May 23, 2018

Hello, As one of sub-maintainers of Linux port for ARC architecture I'd like to be able to add information about ARC-related changes in Linux kernel changelogs (https://kernelnewbies.org/LinuxVersions) Could you please add my username AlexeyBrodkin to the EditorsGroup? -Alexey P.S. If of any interest (sorta to confirm I'm not a bot these are my contributions in the kernel development so far: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/?qt=…)

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