August 2019 - kernelnewbies@kernelnewbies.org

How to make /dev/ttyACM0 (and friends) exclusive?
by Jeffrey Walton Oct. 11, 2020

Oct. 11, 2020

Hi Everyone, I'm trying to trackdown a problem using my dialup modem. I have a program that opens the modem and watches caller id's. It flashes the hook when a telemarketer calls. It works well until... When another program opens the modem then my program starts reading intermittent responses intended for the other program. I cannot seem to open the device in exclusive mode. The current open is (I also tried with O_EXCL): int modem = open(device_path, O_RDWR | O_NOCTTY | O_SYNC); I'm not sure if it because udev configures the device incorrectly or the kernel driver is configured incorrectly. Or maybe it is impossible to do. Does anyone know how I can make the device exclusive? Thanks in advance.

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[OSSNA] Intro to kernel hacking tutorial
by Tobin C. Harding Sept. 4, 2019

Sept. 4, 2019

Hi, I am doing a tutorial at OSSNA in San Diego on getting into kernel hacking. I'm only a couple of years deep into kernel hacking so I wanted to reach out to those more experienced than myself (and those less experienced). Is there any thing that you would really like to see covered in this tutorial? If you are a grey beard is there anything that you have been lamenting us newbies not knowing/doing? If you are a newbie is there anything that you are struggling with that you really want to learn? Current format/content: the tutorial will attempt to bridge the gap in the learning process between the 'first patch' page on kernelnewbies.org wiki and being 'comfortable' patching the kernel via LKML. Outcome will (hopefully) be a small patch set into drivers/staging/. (Don't worry Greg only one group got to this stage last time, you won't get flooded with patches :) Thanks, Tobin.

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Re: GPIO Driver for Skylake-Y PCH
by Andy Shevchenko Aug. 29, 2019

Aug. 29, 2019

On Thu, Aug 29, 2019 at 01:49:55PM +0200, Valentin Vidić wrote: > On Thu, Aug 29, 2019 at 01:49:31PM +0300, Andy Shevchenko wrote: > > This actually should be done other way around, i.e. enabling ACPI WDAT table > > will get you watchdog and this is *highly* recommended way. > > If I understand correctly you are suggesting to try the wdat_wdt driver instead? Yes. That driver should be in use assuming properly crafted firmware. > > Discussion about iTCO_wdt problem with Intel NUC is here but no solution so far: > > https://www.spinics.net/lists/linux-watchdog/msg16232.html > https://www.spinics.net/lists/linux-i2c/msg41504.html > > # modprobe i2c_i801 > [40450.070587] i801_smbus 0000:00:1f.4: SPD Write Disable is set > [40450.070652] i801_smbus 0000:00:1f.4: SMBus using PCI interrupt > [40450.072919] iTCO_vendor_support: vendor-support=0 > [40450.073485] iTCO_wdt: Intel TCO WatchDog Timer Driver v1.11 > [40450.073546] iTCO_wdt iTCO_wdt: can't request region for resource [mem 0x00c5fffc-0x00c5ffff] > [40450.073578] iTCO_wdt: probe of iTCO_wdt failed with error -16 -- With Best Regards, Andy Shevchenko

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Re: GPIO Driver for Skylake-Y PCH
by Alexander Ivanov Aug. 29, 2019

Aug. 29, 2019

On Thu, 29 Aug 2019 00:47 -07:00, Valentin Vidić <vvidic(a)valentin-vidic.from.hr> wrote: > On Wed, Aug 28, 2019 at 02:04:44PM -0700, Alexander Ivanov wrote: > > It took me (or rather the vendor) to update the firmware and enable INT344B > > controller. After update, the system enumerates gpio controller > > How did you get them to update the firmware? I have a similar problem > with iTCO_wdt on Intel NUC not being enabled. > We have quite big account with them and paid support service, otherwise it would be virtually impossible :/

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Re: GPIO Driver for Skylake-Y PCH
by Andy Shevchenko Aug. 29, 2019

Aug. 29, 2019

On Thu, Aug 29, 2019 at 09:47:42AM +0200, Valentin Vidić wrote: > On Wed, Aug 28, 2019 at 02:04:44PM -0700, Alexander Ivanov wrote: > > It took me (or rather the vendor) to update the firmware and enable INT344B > > controller. After update, the system enumerates gpio controller > > How did you get them to update the firmware? I have a similar problem > with iTCO_wdt on Intel NUC not being enabled. This actually should be done other way around, i.e. enabling ACPI WDAT table will get you watchdog and this is *highly* recommended way. -- With Best Regards, Andy Shevchenko

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GPIO Driver for Skylake-Y PCH
by Alexander Ivanov Aug. 29, 2019

Aug. 29, 2019

Hi, I have a hardware platform with Skylake i7-6500 CPU and Skylake-Y PCH southbridge, running 4.8.5 kernel fc25. The platform has 12 GPIO pins, however, none are available. gpio-pch driver does not support D31:F2 device that manages GPIO. Am I missing something here? Cheers, --Alex

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Why some user space programs write to writable pages of other processes?
by Lev Olshvang Aug. 26, 2019

Aug. 26, 2019

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KernelProjects still alive?
by Ivan D Aug. 22, 2019

Aug. 22, 2019

Hi all, I'd like to do some kernel development (driver, non-trivial feature, etc.). I'm fairly experienced overall and wrote proprietary kernel modules at my job, so not interested in newbie/janitor stuff. KernelProjects looked like a perfect place for this, but it seems long abandoned. Is there a substitute, or may be someone can pinpoint me at something to work on in particular? Could be support for old but still possible-to-buy hardware, or anything non-trivial really. I've worked mostly with ARM if that matters, including fairly low level things. Thanks, Ivan

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How to handle page allocation when memory exceeds a local node
by Won-Kyo Choe Aug. 22, 2019

Aug. 22, 2019

Suppose that there are two nodes and each node has 16GiB memory size. When a process needs pages from the kernel, I understand that __alloc_pages_nodemask() will do allocation for the process. In the function, I noticed that if there is no available page on a zone (or a node) while it loops for_next_zone_zonelist_nodemask() (a macro in get_page_from_freelist()), the kernel would try to reclaim reclaimable page from the zone. This loops will continue until the kernel gets a free page. This means that the kernel would try to find a page from the remote node if there is no free page in the local node. My question is that when the kernel starts to allocate a page from the remote node due to no enough memory in the local node, does the kernel always check there is a reclaimable page from the local node? In other words, does the kernel always start to find a page from the very first entry (which would be the local node and the first zone) in the loop? In my perspective, if the kernel starts to allocate in the remote node, I think the scheduler should move the process to the remote node and it will allocate a page in the remote node at first in the loop (in the process view, the node would be the local now since it is moved). Would the scheduler do that? Regards, WK Choe

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kernel selftest - gup_benchmark: getting "ioctl: Invalid argument"
by Probir Roy Aug. 16, 2019

Aug. 16, 2019

Hi, I am testing Linux 4.19.60. I build the kernel with CONFIG_GUP_BENCHMARK. However, during gup_benchmark self-test, I am getting "ioctl: Invalid argument". Any idea what could be the problem? Probir

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