September 2021 - kernelnewbies@kernelnewbies.org

Re: MTD: How to get actual image size from MTD partition
by Pintu Agarwal Nov. 12, 2021

Nov. 12, 2021

On Thu, 29 Jul 2021 at 17:33, Ezequiel Garcia <ezequiel(a)vanguardiasur.com.ar> wrote: > > On Thu, 29 Jul 2021 at 08:45, Richard Weinberger <richard(a)nod.at> wrote: > > > > Ezequiel, > > > > ----- Ursprüngliche Mail ----- > > > [snip] > > > > > > Ouch, so surprised that after all these years someone is doing squashfs/mtdblock > > > instead of using ubiblock :-) > > > > > > Can we patch either Kconfig or add some warn_once on mtdblock > > > usage, suggesting to use ubiblock instead? > > > > a hint in Kconfig makes IMHO sense. Do you want to send a patch? > > A warning is too much since on some tiny embedded system with NOR flash mtdblock is still > > a good choice. > > ubiblock is mostly useful for NAND flash. > > > > > I remember there was still some use case(s) for mtdblock but I can't remember > > > now what was it, perhaps we should document the expectations? > > > (Is that for JFFS2 to mount?) > > > > a long time ago mount didn't accept character devices, so you had to pass mtdblockX to mount > > JFFS2. > > This limitation is gone. > > > > OK, let me try to cook a patch for you. > Dear Eze and Richard, First of all, thank you so much for all your replies so far. Sorry, I have limited knowledge about NAND, MTD, UBI layers, but my current work involves all these so I am here. But I will surely share this information to our internal team about using ubiblock instead of mtdblock. However, I still fail to understand the problem and consequences of using mtdblock for rootfs instead of ubiblock. Last time, for my squashfs test, when I tried to replace the command line with ubiblock, I could not see any difference. How to visibly see the difference so that I can easily understand and explain the difference internally? Or, is there a document available somewhere to highlight the difference between the two? BTW, we have few raw nand partitions and few ubi volumes [including rootfs(squashfs), data(ubifs, rw)] So, I guess we should use ubiblock for all ubi volumes? Regarding Kconfig, I have few opinions. Yes, adding more description in Kconfig is a good choice. But I see that most of the time these kernel config options remains (as default) and platform developers never cares about the description. So, how to better create awareness among them, not to make these mistakes? One option is to capture these details as part of Kernel documentation. Right now when I search I could not find anything. Another option is to add a few (critical) warnings in kernel bootup logs to give some hint to the developer that there is probably something wrong. This will directly be visible to all and some developers will not like to ignore it. Or, maybe adding both options is also good. Thanks, Pintu

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Re: Kernel 4.14: Using dm-verity with squashfs rootfs - mounting issue
by Pintu Agarwal Oct. 29, 2021

Oct. 29, 2021

On Mon, 30 Aug 2021 at 22:25, Thomas Petazzoni <thomas.petazzoni(a)bootlin.com> wrote: > > Hello, > > On Mon, 30 Aug 2021 21:55:19 +0530 > Pintu Agarwal <pintu.ping(a)gmail.com> wrote: > > > Sorry for coming back to this again.. > > Unfortunately, none of the options is working for us with squashfs > > (bootloader, initramfs). > > initramfs have different kinds of challenges because of the partition > > size issue. > > So, our preferred option is still the bootloader command line approach.. > > > > Is there a proven and working solution of dm-verity with squashfs ? > > If yes, please share some references. > > > > The current problem with squashfs is that we could not append the > > verity-metadata to squashfs, so we store it on a separate volume and > > access it. > > Here, it definitely worked to append the hash tree to the squashfs > image and store them in the same partition. > > > By specifying it like : /dev/mtdblock53 > > > > Then we get the error like this: > > { > > [ 4.950276] device-mapper: init: attempting early device configuration. > > [ 4.957577] device-mapper: init: adding target '0 95384 verity 1 > > /dev/ubiblock0_0 /dev/mtdblock53 4096 4096 11923 8 sha256 > > 16da5e4bbc706e5d90511d2a3dae373b5d878f9aebd522cd614a4faaace6baa3 > > aee087a5be3b982978c923f566a94613496b417f2af592639bc80d141e34dfe7 10 > > restart_on_corruption ignore_zero_blocks use_fec_from_device > > /dev/mtdblock53 fec_roots 2 fec_blocks 12026 fec_start 12026' > > [ 4.975283] device-mapper: verity: sha256 using implementation > > "sha256-generic" > > [ 4.998728] device-mapper: init: dm-0 is ready > > Could you show the full kernel command line ? Shared below > > Do you see any other problem here with dm-verity cmdline or with squashfs ? > > > > Is squashfs ever proved to be working with dm-verity on higher kernel version ? > > Currently our kernel version is 4.14. > > I confirm we used squashfs on dm-verity successfully. For sure on 4.19, > perhaps on older kernels as well. ohh that means we already have a working reference. If possible can you share the details, even 4.19 or higher will be also a good reference. > > Or, another option is to use the new concept from 5.1 kernel that is: > > dm-mod.create = ? > How are you doing it today without dm-mod.create ? I think in 4.14 we don't have dm-mod.create right ? > Again, please give your complete kernel command line. > Here is our kernel command line: [ 0.000000] Kernel command line: ro rootwait console=ttyMSM0,115200,n8 .... verity="95384 11923 16da5e4bbc706e5d90511d2a3dae373b5d878f9aebd522cd614a4faaace6baa3 12026 " rootfstype=squashfs ubi.mtd=40,0,30 ubi.block=0,0 root=/dev/dm-0 .... init=/sbin/init root=/dev/dm-0 dm="rootfs none ro,0 95384 verity 1 /dev/ubiblock0_0 /dev/mtdblock53 4096 4096 11923 8 sha256 16da5e4bbc706e5d90511d2a3dae373b5d878f9aebd522cd614a4faaace6baa3 aee087a5be3b982978c923f566a94613496b417f2af592639bc80d141e34dfe7 10 restart_on_corruption ignore_zero_blocks use_fec_from_device /dev/mtdblock53 fec_roots 2 fec_blocks 12026 fec_start 12026" ... Do you see any issue here ? Can you share your command line for squashfs to compare ? Thank you, Pintu

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ALSA kernel projects - for academic purposes
by Muni Sekhar Oct. 1, 2021

Oct. 1, 2021

Hi all, What small projects would you suggest to a novice with the ALSA kernel. The aim is to develop a familiarity with the ALSA kernel source code, and also to submit it for academic purposes. -- Thanks, Sekhar

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Can register addresses conversion go through iommu too? probably not..
by ckim＠etri.re.kr Oct. 1, 2021

Oct. 1, 2021

Hello all, I know when a device does dma to memory, we use functions like dma_alloc_coherent to allocate a memory region for the dma and we get the kernel virtual address and device virtual address at the same time. The iommu hardware converts the device virtual address to physical address reducing the processing time. I have a question (to make sure my understanding is correct). To use registers in the device driver, we use ioremap function to get the kernel virtual address for the device registers. If the OS is running in virtualized environment (a hypervisor under it), this kernel virtual address should go under conversion twice 1. virtual to physical by OS (this physical is not actually physical, an intermediate physical?) 2. intermediate physical to real physical I thought these two conversions are done by kernel or hypervisor software because iommu is for address translation for the addresses that the device "uses(or generates)", not for the kernel to access the device itself. Is my understanding correct? Any help will be appreciated. Thank you! Chan Kim

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does dma_alloc_coherent setup iommu page table?
by ckim＠etri.re.kr Sept. 29, 2021

Sept. 29, 2021

Hello all, When the driver calls dma_alloc_coherent for a device, and if the device uses iommu, is the table entry for the iommu setup for the dma_handle? Seeing the struct device has something related to iommu, I guess so.. Any help appreciated. Thanks! Chan Kim

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List of all available kernel modules per version
by Leon Gross Sept. 26, 2021

Sept. 26, 2021

Hi everyone, If got more of a general question: Is there a way to list all the standard kernel modules that are included in a specific kernel version? And I don't meant the currently running modules I could get via lsmod but I mean all the modules that are supported by a specific kernel version. Or can I even derive these myself from the source tree, without even compiling the kernel (that would be very helpful)? Thanks a lot in advance!

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how to avoid CPU watchdog error during debug
by ckim＠etri.re.kr Sept. 25, 2021

Sept. 25, 2021

Hello, While debugging a kernel module, I get this error and the OS crashes. [39068.833652] rcu: INFO: rcu_sched self-detected stall on CPU [39068.834739] watchdog: BUG: soft lockup - CPU#3 stuck for 164s! [systemd-journal:399] [39068.834854] watchdog: BUG: soft lockup - CPU#0 stuck for 164s! [test_axpu_app:2896] This seems because I stopped the processor for debugging. How can I avoid this watchdog error during debug? Any help will be appreciated. Thanks! Chan Kim

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Re: Device doesnt show up on Ble Scanner - gatt-service example in tools folder as per Documentation(doc)
by Raul Piper Sept. 25, 2021

Sept. 25, 2021

On Tue, Aug 31, 2021 at 12:08 PM Luiz Augusto von Dentz <luiz.dentz(a)gmail.com> wrote: > > Hi Raul, > Hello Luiz, > On Mon, Aug 30, 2021 at 11:32 PM Raul Piper <raulpblooper(a)gmail.com> wrote: > > > > Any inputs on this? > > Did you remember to advertise? I mean those only services but it > doesn't necessarily advertise which is something perhaps could be > updated on those samples so they become visible on the scanners. > Isnt ./gatt-service supposed to advertise as well? I cross built and rant ./advtest with -h and it gave not much information : ./advtest --h advtest - Advertising testing Usage: advtest [options] and when I ran ./advtest it gave : At least 2 controllers are required what other input does it take ? hci0?hci1? when i try to run ./advtest -hci0 it gave : Invalid command line parameters i tried to find bt controllers on my board and it gave : hcitool dev Devices : It gave nothing. Any idea how to proceed ?I suspect I need to enable the hci controller or something? But it is strange that ./gatt-service did not throw any error and registered the services without any error?shouldn't these examples check for the ble controller first before proceeding further? > > On Sun, Aug 29, 2021 at 11:42 PM Raul Piper <raulpblooper(a)gmail.com> wrote: > > > > > > Hello, > > > I tried cross compiling the bluez and ported it to my linux platform.I > > > think i have done it correctly as I am able to launch the gatt-service > > > example successfully but i am not able to view it on the Smartphone > > > app - blescanner or light blue. > > > > > > Below are the logs : > > > =============================================== > > > ./gatt-service > > > gatt-service unique name: :1.18 > > > Registered service: /service1 > > > Registered service: /service2 > > > Registered service: /service3 > > > Get Primary: True > > > Get UUID: 00001802-0000-1000-8000-00805f9b34fb > > > Exist Includes: 00001802-0000-1000-8000-00805f9b34fb > > > Get Includes: 00001802-0000-1000-8000-00805f9b34fb > > > Includes path: /service3 > > > Get Includes: /service2 > > > Characteristic(00002a06-0000-1000-8000-00805f9b34fb): Get("Value") > > > Descriptor(8260c653-1a54-426b-9e36-e84c238bc669): Get("Value") > > > Get Primary: True > > > Get UUID: A00C > > > Exist Includes: A00C > > > Characteristic(00002c07-0000-1000-8000-00805f9b34fb): Get("Value") > > > Descriptor(FFFF): Get("Value") > > > Get Primary: True > > > Get UUID: A00D > > > Exist Includes: A00D > > > Characteristic(00002b06-0000-1000-8000-00805f9b34fb): Get("Value") > > > Descriptor(0260c653-1a54-426b-9e36-e84c238bc669): Get("Value") > > > > > > > > > > > > I also tried to run the python example inside test/example-gatt-server > > > but again I am not able to view the device name. > > > > > > Below are the logs : > > > ======================================= > > > python3 example-gatt-server > > > example-gatt-server:395: PyGIDeprecationWarning: GObject.timeout_add > > > is deprecated; use GLib.timeout_add instead > > > GObject.timeout_add(5000, self.drain_battery) > > > example-gatt-server:652: PyGIDeprecationWarning: GObject.MainLoop is > > > deprecated; use GLib.MainLoop instead > > > mainloop = GObject.MainLoop() > > > Registering GATT application... > > > GetManagedObjects > > > GATT application registered > > > > > > I even opened the btmon on a different tab but still I am not able to > > > see anything on that. > > > Is there any other application we have to run? > > > Has any one ran it successfully and able to view/connect and see all > > > the 3 services it is advertising. > > > > > > Please advise / ask for any further information , I will provide. > > > > > > Thanks in advance ! > > > > > > Regards, > > > R > > > > -- > Luiz Augusto von Dentz

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where can I find the explanations for pin-ctrl or #clock-cells in the dts file? (device tree)
by ckim＠etri.re.kr Sept. 25, 2021

Sept. 25, 2021

Hi I've downloaded device tree spec from https://www.devicetree.org/specifications/ but it doesn't tell me anything about #clock-cells or pin-ctrl properties. (the spec is the newst 2020 version) Isnt there any full specification somewhere? Thanks, Chan Kim

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Accessing a pdev or its members
by Drew Abbott Sept. 25, 2021

Sept. 25, 2021

Hello all, A third party driver has a probe function foo_probe(struct platform_device) that ends up allocating and initializing a list of various device structs: struct device *dev = &pdev->dev; struct ucsi_dev *udev; udev = devm_kzalloc(dev, sizeof(*udev), GFP_KERNEL); /* initialize udev to important data */ platform_set_drvdata(pdev, udev); I have my own driver that I would like to use to access the *udev that is created when the other device is probed. How would I access a pdev? Or is there a way I can add a function to this driver to expose a *udev? I can't seem to get to it without having a pointer to the pdev, the udev, or some other device struct related to the hardware. Thanks for the help, Drew

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