January 2017 - kernelnewbies@kernelnewbies.org

where is __percpu_seg initialized?
by 落痕 March 28, 2018

March 28, 2018

Hi all: I knew the kernel implement the per-cpu variable via __percpu_seg. For example on x86 architecture, it's defined as: #ifdef CONFIG_X86_64 #define __percpu_seg gs #define __percpu_mov_op movq #else #define __percpu_seg fs #define __percpu_mov_op movl #endif But I'm curious where __percpu_seg is initialized?? I fail to find the relative code. Thanks.

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How to handle Hotplug with UIO userspace driver
by Mandeep Sandhu Sept. 28, 2017

Sept. 28, 2017

Hi All, We're working on a custom PCIe based hardware, which can be hotplugged into the system. We're using the UIO approach of having a minimal kernel driver which basically handles the interrupt and provides a mmap of the device memory to userspace and userspace driver which mmap's the provided memory and manages the device. We're using systemd and udev rules to spawn off a user process whenever the hardware is plugged into the system. Now my question is, how can we gracefully inform the userspace process if someone pulls out the hardware (sitting on a PCI slot). Even with full hotplug support, there can always be a case of "surprise removal", where someone yanks the board without going through the whole "attention button" routine. While the kernel driver has no problem with hot-removal, I see that if I "unregister" our UIO driver in response to the removal, then the mapping for the hardware's physical memory would become "invalid" (done by UIO on unregsiter). This could possibly cause the user-space process to crash due to illegal memory access. Is there a "standard" way to handle this scenario, i.e for hotpluggable hardware using UIO? Basically, we'd want to "unregister" the UIO device only after the userspace process is informed of the removal so that it could unmap/close the device and exit gracefully. We could try doing it using some systemd trick, where we put a dependency on one of the UIO created files (/dev/uioX), so that when the file is destroyed, systemd could kill/shutdown the process. Although, there's no guarantee that the userspace process won't try to access the mmaped space during that interval, so this isn't a reliable solution either. Any hints, thoughts? Thanks., -mandeep

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What are need to makes humidifier?
by 윤영석 April 1, 2017

April 1, 2017

Hi, I want to make own humidifier. What sensor need when making humidifier?? humidity indicator (detecting humidity), ultrasonic waves maker?? Please shares your wisdom to me. Thanks. Best regards.

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should include/uapi include header files *unused* in kernel space?
by Robert P. J. Day Feb. 4, 2017

Feb. 4, 2017

was perusing the UAPI content in the kernel source, prepping for a course i'm teaching tomorrow, and just noticed there is a header file: $ find . -name mtd-user.h ./include/uapi/mtd/mtd-user.h $ which appears to be *entirely* unreferenced in the entire kernel code base (outside of the Kbuild file that refers to it): $ grep -r 'mtd-user.h' * include/uapi/mtd/Kbuild:header-y += mtd-user.h $ does this make any sense? am i missing something here? i would have thought that if a header file includes content that is wholly used exclusively in user space, it would be part of a package like "mtd-devel", or something like that. is this just for convenience to keep all the mtd stuff in the same place? rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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Send/receive ATA cmds from a linux kernel module
by Siddhartha Baral Feb. 2, 2017

Feb. 2, 2017

Hi All, I am trying to write a linux kernel module which can send/receive ATA SMART cmds to a HDD. The kernel module will take a set of actions based on the responses it receives from the HDD. I went through the ATA smart cmds spec and the "smartctl" user space code which sends the ATA cmds from user space via SG_IO ioctl cmd. I am not able to figure out how to open /dev/sda from kernel and achieve similar functionalities line "smartctl" tool from a kernel module. 1. Can someone point me to any sample code which tries to send ATA smart cmds from a kernel module instead of user space via ioctl? 2. Seems like I need to use some exported API from SG driver or libata. is this the right direction? 3. Please feel free to suggest how can I achieve this. Thanks, Sid

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Re: How do you generate the config file?
by Abel Jan. 31, 2017

Jan. 31, 2017

I've posted a mail with the screenshot (waiting for moderation) when I try to boot from make defconfig built kernel. Basically the kernel doesn't boot because "Missing modules (cat /proc/modules; ls /dev " it says...It's the same screen that appeared when I tried using make oldconfig pressing enter for default values. I tried using make localmodconfig but It again asks for many config params that I don't know anything about. Saludos, * Abel.* On 30 January 2017 at 01:11, Abel <akronix5(a)gmail.com> wrote: > Hi. > > I just built using make defconfig and it, again, doesn't boot. Instead it > displays the error that I've described before (sorry I forgot to attach the > screenshot, I attach it here). > > As I already stated, neither /boot/${uname -r} nor make oldconfig work for > me, they both show the screen above. > > Saludos, > > * Abel.* > > On 30 January 2017 at 01:08, Guru Das S <gurooodas(a)gmail.com> wrote: > >> On 29 January 2017 at 15:32, 慕冬亮 <mudongliangabcd(a)gmail.com> wrote: >> > Hello, >> > If you want to reuse the config of current kernel, you can use >> > `make oldconfig` to generate config file. >> > >> > -- >> > My best regards to you. >> > >> > No System Is Safe! >> > Dongliang Mu >> > >> > 2017-01-29 18:24 GMT-05:00 Ozgur Karatas <mueddib(a)goosey.org>: >> >> >> >> Hello, >> >> >> >> you can get .config files in two ways, firstly get the existing >> .config file >> >> and compile to kernel. >> >> >> >> $ cp /boot/config-x.x.x /bla/linux/.config >> >> >> >> Second, use the generate command: >> >> >> >> $ make defconfig >> >> >> >> Regards, >> >> >> >> ~Ozgur >> >> >> >> 30.01.2017, 01:18, "Abel" <akronix5(a)gmail.com>: >> >> >> >> Hi! >> >> >> >> Where do you get the config file from? or do you generate it yourself? >> >> >> >> I'm using xUbuntu 16.04 in a VM inside VMWare, following the >> instructions >> >> described in kernelnewbies wiki. (By the way, the download links to >> the iso >> >> images of Ubuntu don't work for me) >> >> >> >> If I copy the latest config file in /boot, kernel 4.4.0, it starts to >> ask me >> >> many config parameters that I don't know what to answer. I tried to >> press >> >> always <enter> to set up the default parameters, but after compiling I >> get >> >> an error trying to boot from that kernel (see atachment). >> >> >> >> I tried with make menuconfig and that seems to work, but it takes too >> long >> >> because it builds and includes many many drivers modules. >> >> Yeah, I know I could navigate through the ncurses window and select the >> >> stuff I want and deselect what I don't want, but I'd rather prefer >> just a >> >> simple config file that builds and works and don't waste time in >> >> understanding all the stuff that it's in there. >> >> >> >> So, isn't there a way to get a simple config file just to develop >> kernel >> >> stuff for an Ubuntu image? >> >> I've even gone to the kernel ppa sources for Ubuntu: >> >> http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.9.5/; but it only >> provides >> >> a patch using the debian config files (which don't come from git >> sources of >> >> course). >> >> >> >> I just want a config file, copy it to the kernel root code and compile. >> >> >> >> Greetings, >> >> >> >> Abel >> >> >> >> >> >> _______________________________________________ >> >> Kernelnewbies mailing list >> >> Kernelnewbies(a)kernelnewbies.org >> >> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> >> >> > >> > _______________________________________________ >> > Kernelnewbies mailing list >> > Kernelnewbies(a)kernelnewbies.org >> > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> >> Hi Abel, >> >> To add to what Ozgur said, you may first copy the existing .config >> file that comes along with your Linux distribution to your kernel >> tree, and then use: >> >> $ make localmodconfig >> >> instead of defconfig. A quick Google search should tell you the >> differences between the two - and from what I've read, localmodconfig >> is preferred to defconfig. >> >> Hope this helps. >> >> >> Guru Das Srinagesh. >> > >

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spi - real protocols
by Ran Shalit Jan. 30, 2017

Jan. 30, 2017

Hello, As I understand word length in spi, defines the cs active time. It therefore seems that linux driver suits when dealing with simple spi protocols which keeps word size constant. How can we deal with spi protocols which use different spi size as part of protocol. for example cs need to be active for sending spi word - 9 bits, and then reading spi - 8 bit word (only after write+read spi changes values back to non active), How can we implement that ? Do we need to set bits_per_word size for the sending and then another bits_per_word for the receiving ? Regards, Ran

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How do you generate the config file?
by Abel Jan. 30, 2017

Jan. 30, 2017

Hi! Where do you get the config file from? or do you generate it yourself? I'm using xUbuntu 16.04 in a VM inside VMWare, following the instructions described in kernelnewbies wiki <https://kernelnewbies.org/OutreachyfirstpatchAlt?action=show&redirect=OPWfi…>. (By the way, the download links to the iso images of Ubuntu don't work for me) If I copy the latest config file in /boot, kernel 4.4.0, it starts to ask me many config parameters that I don't know what to answer. I tried to press always <enter> to set up the default parameters, but after compiling I get an error trying to boot from that kernel (see atachment). I tried with make menuconfig and that seems to work, but it takes too long because it builds and includes many many drivers modules. Yeah, I know I could navigate through the ncurses window and select the stuff I want and deselect what I don't want, but I'd rather prefer just a simple config file that builds and works and don't waste time in understanding all the stuff that it's in there. So, isn't there a way to get a simple config file just to develop kernel stuff for an Ubuntu image? I've even gone to the kernel ppa sources for Ubuntu: http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.9.5/; but it only provides a patch using the debian config files (which don't come from git sources of course). I just want a config file, copy it to the kernel root code and compile. *Greetings,* * Abel.*

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Build error
by Amit Kumar Jan. 29, 2017

Jan. 29, 2017

Hi, For last several days when I build arm64/defconfig even against next-20170125, I get the following error. arch/arm64/crypto/crc32-arm64.c:1:0: error: unknown feature modifier ‘crc’ /* ^ make[1]: *** [arch/arm64/crypto/crc32-arm64.o] Error 1 make: *** [arch/arm64/crypto] Error 2 Regards, Amit Kumar

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Kernel device driver activates either touchpad or keyboard but not both
by tsopdump tsopdump Jan. 27, 2017

Jan. 27, 2017

Hi, I have a Bluetooth Sony MSG-MR5U remote that has a full keyboard and a touchpad. The keyboard works fine in Linux but the touchpad isn't recognized. I've edited the hid-sony module to enable the touchpad but I've run into a problem where the keyboard stops working when I enable the touchpad. More specifically, if I call input_mt_init_slots with the INPUT_MT_POINTER flag, the touchpad works but the keyboard stops working. If I don't pass this flag, the keyboard works but the touchpad doesn't. Only one device entry is created and after passing INPUT_MT_POINTER to input_mt_init_slots, /proc/bus/input/devices shows I: Bus=0005 Vendor=0609 Product=0368 Version=0111 N: Name="SONY NSG-MR5-U" P: Phys=00:1a:7d:da:71:0a S: Sysfs=/devices/pci0000:00/0000:00:0b.0/usb2/2-5/2-5:1.0/bluetooth/hci0/hci0:70/0005:0609:0368.0007/input/input12 U: Uniq=00:01:90:d2:1b:7b H: Handlers=sysrq kbd mouse1 event7 B: PROP=5 B: EV=10001f B: KEY=3007f 0 0 483ffff17aff32d bf54444600002420 10001 1130f938b17c007 ffff7bfad9415fff febeffdfffefffff fffffffffffffffe B: REL=40 B: ABS=2738f0100000003 B: MSC=10 Do I have to allocate a new device entry using input_allocate_device so the touchpad is using a separate device from the keyboard or is there a way to activate both the touchpad and the keyboard using a single device? BTW, I'm working with the 4.10.0-rc3+ kernel. Thanks, Todd

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