October 2016 - kernelnewbies@kernelnewbies.org

Re: kernel loglevel
by Wenda Ni Oct. 17, 2016

Oct. 17, 2016

Thank you so much, Thibaut. I have spotted the source-code logic in include/linux/prink.h Cheers, Wenda Ni, Ph.D. On Mon, Oct 17, 2016 at 7:41 PM, Thibaut SAUTEREAU < thibaut.sautereau(a)telecom-sudparis.eu> wrote: > On Mon, Oct 17, 2016 at 07:17:32PM -0400, Wenda Ni wrote: >> Dear all, >> >> I am working on a kernel module that incorporate both pr_debug and >> pr_warn. I would like to see pr_debug messages from dmesg. >> >> What I followed is to specify kernel parameter by saying "loglevel=7". >> This can be seen confirmed from /proc/cmdline. But still, I donot get >> pr_debug level messages either from dmesg or from /var/log/messages. I >> also tried echo 7 > /proc/sys/kernel/printk. It does not return what I >> expect, either. >> >> Let me know what I am missing. Thank you very much in advance. >> >> Cheers, >> >> Wenda Ni, Ph.D. >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies(a)kernelnewbies.org >> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > Hello Wenda, > > I encountered the same issue a while ago. > As stated here: http://elinux.org/Debugging_by_printing > pr_debug is replaced with an empty statement unless the kernel is compiled > with DEBUG. So if you just want to play with printing kernel debug logs, > just define the DEBUG macro in your module source file for testing. > > I also observed that without a new line character at the end of the string > passed to pr_debug, I could not find the log line in dmesg output. Not sure > where this comes from. > > -- > Thibaut SAUTEREAU

1 0

Re: SocketCAN Driver
by Augusto Fraga Giachero Oct. 17, 2016

Oct. 17, 2016

Thank you, I'll study it! Em 17 de out de 2016 10:25 AM, "Daniel." <danielhilst(a)gmail.com> escreveu: > > If you're dealing with network drivers you will want to know about socket buffs: http://www.linuxjournal.com/article/1312 > LDD3 has a chapter for network drivers too: http://www.makelinux.net/ldd3/chp-17 > > > Regards :) > > 2016-10-17 10:22 GMT-02:00 Daniel. <danielhilst(a)gmail.com>: >> >> CAN drivers can be found here; http://lxr.free-electrons.com/source/drivers/net/can/ >> >> The device driver interface is at dev.c >> >> AFAIK the only other files referencing to can outside of drivers/ folder is http://lxr.free-electrons.com/source/include/uapi/linux/if_ether.h#L120 >> You may want to look at docs too: https://www.kernel.org/doc/Documentation/networking/can.txt >> Regards, >> >> 2016-10-17 9:05 GMT-02:00 Augusto Fraga Giachero <augustofg96(a)gmail.com>: >>> >>> I've been reading the source code for the ECI driver and discovered that >>> it only applies to PCI devices, the IXXAT CAN-to-USB Compact (V1.0) is >>> accessed through libusb, so please, ignore the ECI Kernel module that >>> I've attached in the last email. >>> >>> Thanks! >>> >>> On 17-10-2016 08:43, Augusto Fraga Giachero wrote: >>> > Hello! >>> > >>> > >>> > I recently started a project that uses the CAN serial protocol using >>> > microcontrollers. I've got an IXXAT CAN-to-USB Compact (V1.0) adapter to >>> > help debugging the CAN bus. The manufacturer of this adapter provides >>> > the kernel driver and and userspace libraries for Linux, but it uses a >>> > custom API (ECI) instead of SocketCAN (and I really need to use >>> > SocketCAN). The manufacturer also provides a SocketCAN driver but only >>> > for the CAN-to-USB Compact (V2.0), so it doesn't with what I have. >>> > >>> > >>> > I'm thinking in modifying the the SocketCAN driver to support the V1.0 >>> > adapter, but I don't have any experience in kernel driver development. >>> > I've a solid C knowledge and a lot of experience in firmware development >>> > for microcontrollers. Can someone show me where to find relevant >>> > information regarding SocketCAN, USB drivers development? I don't know >>> > if this challenge is above my skills. >>> > >>> > >>> > I've attached both drivers and a patch for the usb-to-can_v2_socketcan >>> > that substitutes the "netdev->trans_start =" deference to >>> > "netif_trans_update(netdev);", so you can compile for kernels newer than >>> > 4.4. >>> > >>> > >>> > >>> > Thanks! >>> > >>> > >>> >>> >>> _______________________________________________ >>> Kernelnewbies mailing list >>> Kernelnewbies(a)kernelnewbies.org <Kernelnewbies(a)kernelnewbies.org> >>> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies <https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies> >> >> >> >> >> -- *>> "Do or do not. There is no try"* *>> ** Yoda Master* > > > > > -- *> "Do or do not. There is no try"* *> ** Yoda Master*

1 0

SocketCAN Driver
by Augusto Fraga Giachero Oct. 17, 2016

Oct. 17, 2016

Hello! I recently started a project that uses the CAN serial protocol using microcontrollers. I've got an IXXAT CAN-to-USB Compact (V1.0) adapter to help debugging the CAN bus. The manufacturer of this adapter provides the kernel driver and and userspace libraries for Linux, but it uses a custom API (ECI) instead of SocketCAN (and I really need to use SocketCAN). The manufacturer also provides a SocketCAN driver but only for the CAN-to-USB Compact (V2.0), so it doesn't with what I have. I'm thinking in modifying the the SocketCAN driver to support the V1.0 adapter, but I don't have any experience in kernel driver development. I've a solid C knowledge and a lot of experience in firmware development for microcontrollers. Can someone show me where to find relevant information regarding SocketCAN, USB drivers development? I don't know if this challenge is above my skills. I've attached both drivers and a patch for the usb-to-can_v2_socketcan that substitutes the "netdev->trans_start =" deference to "netif_trans_update(netdev);", so you can compile for kernels newer than 4.4. Thanks!

2 3

is it accurate to describe /dev/watchdog as "legacy"?
by Robert P. J. Day Oct. 15, 2016

Oct. 15, 2016

poking around the watchdog code, and in drivers/watchdog/watchdog_dev.c, i see the snippet: /* * watchdog_cdev_register: register watchdog character device * @wdd: watchdog device * @devno: character device number * * Register a watchdog character device including handling the legacy ^^^^^^ * /dev/watchdog node. /dev/watchdog is actually a miscdevice and * thus we set it up like that. */ now, my normal understanding of the word "legacy" is of something that, while it may still function (possibly because of the need for backward compatibility), it typically refers to something that is, strictly speaking, *unnecessary*. that is, while one could continue to interact with the watchdog through the ostensibly "legacy" /dev/watchdog special file, there is a newer mechanism that makes it superfluous. in this case, i can see the sysfs structure that you can now select for working with the watchdog; however, in that same file, it *appears* that almost all of that sysfs structure is for *querying* watchdog information, not for making changes to it. IOW, as i read it (and i could be wrong), while one could extend the standard watchdog API with sysfs structure, it is still *necessary* to continue using /dev/watchdog for some things. am i reading this correctly? because if i am, then the word "legacy" should not really apply to /dev/watchdog, should it? rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

1 0

ARM v7 based SoC showing random behaviour with kernel and uboot
by AYAN KUMAR HALDER Oct. 15, 2016

Oct. 15, 2016

Hi, This query is about a random behaviour observed on on 2 out of 35 ARM v7 based chipsets. The intention here is to ask about the further diagnostic approach that should be done to root cause the malfunction observed only on 2 chipsets (Rest 33 chipsets are working fine consistently). All the 35 chipsets have the same SoC architecture. When the chipsets boot up (from uboot), I see that intermittently (1 out of 3 boots), the boot up halts/resets(sometimes) at uboot (while accessing some registers from ddr controller) or at kernel. The behaviour changes with temperature (some times seen prominently at lower temperatures like -5) or with logs (adding more console logs causes the occurence of this issue to diminish) or even by removing some external peripheral (i2c) access during bootup or by adding instructions like memory barriers/cache flush (which causes the occurence of the issue to diminish). I need some guidance/pointers to debug such issues further. Please note that we are observing such issues on silicon (SoC) and we do not have the fpga model available (for chipscope debugging). I need to give a concrete explanation for the malfunction observed on the 2 chipsets. In case if this is an inappropriate forum, I would humbly request to let me the know the appropriate forum to ask such queries. Regards, Ayan Kumar Halder

1 0

iptables-translate command not found
by Gargi Sharma Oct. 14, 2016

Oct. 14, 2016

Hi! I am looking to translate iptable rules to nftables and when I run the command sudo iptables-translate I get , command not found. The path for iptables command is /sbin/iptables. The other commands related to iptables that are available are: iptables-save iptables-restore ip6tables How do I install iptables-translate? From what I have understood from looking around is that iptables-translate comes with the iptables package. Thanks! Gargi

2 1

Getting started with Development
by Ganesh Oct. 12, 2016

Oct. 12, 2016

Hello, I am interested in memory management unit of KVM. On KVM's website it is mentioned that, try LRU (currently FIFO) and analyse the performance. I want to do it as a final year B. Tech project ;but I have time limitation of 4-5 months. I have basic background of operating system and little bit about virtualization. I am eager to do this ;but I want to know that, 1. how much time does it take for new developer to implement thing like LRU? 2. Is it doable within 4-5 months? If it is NOT doable within 4-5 months then, Is their any project related to kernel development which I can do it within 4-5 months? I assure that, I will give my best Thanks !!! Regards, Ganesh

2 1

Custom ASOC codec driver
by Christian N Oct. 11, 2016

Oct. 11, 2016

Hi All I'm implementing a driver for TEF663x, and link (machine driver) to iMX6 (kernel 4.x) I understand ALSA and ASOC layers and architecture. I have good knowledge about both chipset (soc and codec). Nevertheless I am really confused with asoc structures, wich fields are mandatory and some links between platform, machine and codec. 1-Why teh followin controls are duplicated? When muste ia have to use each one? struct snd_soc_component_driver{ .... /* Default control and setup, added after probe() is run */ const struct snd_kcontrol_new *controls; unsigned int num_controls; const struct snd_soc_dapm_widget *dapm_widgets; unsigned int num_dapm_widgets; const struct snd_soc_dapm_route *dapm_routes; unsigned int num_dapm_routes; .... } but this struct is included in snd_soc_codec_driver, which one has his own widgets, routes and kcontrols struct snd_soc_codec_driver { ..... struct snd_soc_component_driver component_driver; /* Default control and setup, added after probe() is run */ const struct snd_kcontrol_new *controls; int num_controls; const struct snd_soc_dapm_widget *dapm_widgets; int num_dapm_widgets; const struct snd_soc_dapm_route *dapm_routes; int num_dapm_routes; .... } 2-In kernel/Documentation/sound/alsa/soc/platform.txt, states "The platform drivers only target the SoC CPU and must have no board specific code", but several CODEC drivers have struct snd_soc_platform_driver defined Is it an specifications missleading, or bad codec implementation? 3-Is there any document/guide to implement asoc driver, or ASOC is under development, and the mess should be organized I was looking for information at http://processors.wiki.ti.com/index.php/Sitara_Linux_Audio_DAC_Example kernel/Documentation/sound/alsa/soc ALSA home page (of curse writing alsa driver) http://blog.csdn.net/sepnic/article/category/778492 Several kernel source files (each manufacturer have his own way :( ) Thanks ind advance

1 0

userspace app receive SIGSEGV, but not is crash, why?
by Lucha Chen Oct. 11, 2016

Oct. 11, 2016

Dear All, userspace app receive SIGSEGV, but not crash, why? The mtk kernel log is : <4>[67330.976640] -(6)[25390:ndroid.systemui][25390:ndroid.systemui] sig 11 to [25390:ndroid.systemui] stat=R Thanks Lucha

2 1

Error reading /dev/mem
by Paddie O'Brien Oct. 10, 2016

Oct. 10, 2016

Hi, I have a system call that maps virtual to physical addresses. I have disabled CONFIG_STRICT_DEVMEM and am reading from /dev/mem to verify that the contents of the syscall-returned physical address match the contents of the virtual address. It works fine up to a point. Reading beyond byte 935321597 in /dev/mem throws a "bad address" error. Not sure it's relevant but I'm running on virtual box and specifying 1GB of RAM. Tried with 2GB of RAM and hit the same problem. Any idea why I can't read beyond the above point? Thanks.

3 4