August 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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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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ASoC/ALSA Out of Memory Issue
by Alex Roberts Sept. 10, 2021

Sept. 10, 2021

Hello, I am developing a dummy codec to interface with an 8-channel, 24-bit ADC. I've got it working on an NXP imx8m through the fsl_sai driver on kernel 5.4.85. I can capture all 8 channels at varying sample rates using arecord, and I've verified correct data capture via opening the resulting .wav file in Audacity. The problem I am having is that occasionally, upon starting arecord - after a fresh power cycle - I get an out of memory error. Other times I get an out of memory after a non-deterministic period of capture. Starting capture again also reports out of memory, but if I wait several minutes and start capture it will start recording again. A power cycle usually helps, but as stated earlier, not 100% of the time. I'm trying to track down where the oom error is coming from, but haven't had much luck. My colleague tried running arecord with valgrind to check for memory leaks and nothing of note was observed. My suspicion is there's something going on with allocated memory for DMA, like fragmentation starts to happen and it can't get a contiguous region for operation. Reserving a larger pool - either via device tree or kernel cmdline arguments in the bootoader - did not seem to help. Another thought is that it's a boundary/alignment issue due to the 24-bit data, and the error is the result of trying to allocate a chunk of memory for DMA that doesn't align. I'm very new to ALSA dev with some exposure to kernel dev in general, so please correct me if I'm wrong or completely mis-understanding something. Any suggestions on where I should / how I can debug this memory error? Thanks, Alex. PS: Previously sent this to just alsa-devel mailing list on 7/21, but never saw it show up in the archives. Here is more info since then: The goal is 8-channel, 96k sampling rate. I've reduced sampling rate and still have the issue. Reducing down to 4-channels helps, but haven't tested long term enough to evaluate by how much. Narrowed it down to device_prep_dma_cyclic(..) returning NULL within dmaengine_prep_dma_cyclic(..)..... still tracing through source to learn exactly what is going on.

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Kernel bug tracker
by Adverg Ebashinskii Sept. 6, 2021

Sept. 6, 2021

Hello. I’m a kernel newbie and try to get involved into the Kernel development. So I’d like to start with small bug fixes related to any subsystem (fs is preferred since I familiar with it the most) or something like that. Is there some kernel bug tracker where anybody could pick a bug to fix and then send patches? -- Regards, Adverg Ebashinskii

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how do you find the subsystem of a file?
by daniel watson Sept. 1, 2021

Sept. 1, 2021

i wrote a patch that got rejected because it did not apply cleanly to the tree of greg kh https://lkml.org/lkml/2021/8/18/304 the file i modified is drivers/staging/rtl8723bs/include/rtl8192c_recv.h get_maintainer.pl gave me the list of emails to send the patch to, and i used it for that purpose. the file Documentation/process/submitting-patches.rst says to see the T: entry for the subsystem in MAINTAINERS to find the right tree to base the patch on. i tried searching through MAINTAINERS and found that there are a few subsystems that start with RTL8*. greg kh is listed a few times in MAINTAINERS, so i'm not able to find the exact tree to start with by looking for the maintainer. is there a systematic way of finding the subsystem, given a file? in addition, how do i know what branch to use? the T: entries have a repo, but not a branch name. thanks! :wq, danny

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MODULE_SUPPORTED_DEVICE macro existed in the Kernel 5.9.16, but got removed
by Adverg Ebashinskii Sept. 1, 2021

Sept. 1, 2021

I recently tried to compile my driver developed for the Kernel 5.9.16 using the latest upstream version checked out from git and figured out that there is no more MODULE_SUPPORTED_DEVICE macro. Could you please give a hint where to look at for the information on why it was removed? -- Regards, Adverg Ebashinskii

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Device doesnt show up on Ble Scanner - gatt-service example in tools folder as per Documentation(doc)
by Raul Piper Aug. 31, 2021

Aug. 31, 2021

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

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how to properly use BUILD_BUG_ON_MSG ?
by jim.cromie＠gmail.com Aug. 30, 2021

Aug. 30, 2021

so I got this macro which depends upon config choices to work, Id like to have alt-config versions which throw some obvious error. like this: #elif (defined(CONFIG_DYNAMIC_DEBUG_CORE) && !defined(DYNAMIC_DEBUG_MODULE)) #define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, var, bitmap_desc, ...) \ BUILD_BUG_ON_MSG(1, "you need -DDYNAMIC_DEBUG_MODULE in compile") #else ... is that more or less the expected usage ? the error messages seem less clear than Id like, leading me to suspect poor usage, or a better way to do it. /home/jimc/projects/lx/wk-next/include/linux/compiler_types.h:310:11: error: expected identifier or ‘(’ before ‘while’ 310 | } while (0) | ^~~~~ /home/jimc/projects/lx/wk-next/include/linux/compiler_types.h:316:9: note: in expansion of macro ‘__compiletime_assert’ 316 | __compiletime_assert(condition, msg, prefix, suffix) | ^~~~~~~~~~~~~~~~~~~~ /home/jimc/projects/lx/wk-next/include/linux/compiler_types.h:328:9: note: in expansion of macro ‘_compiletime_assert’ 328 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^~~~~~~~~~~~~~~~~~~ /home/jimc/projects/lx/wk-next/include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’ 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) | ^~~~~~~~~~~~~~~~~~ /home/jimc/projects/lx/wk-next/include/linux/dynamic_debug.h:283:9: note: in expansion of macro ‘BUILD_BUG_ON_MSG’ 283 | BUILD_BUG_ON_MSG(1, "you need -DDYNAMIC_DEBUG_MODULE in compile") | ^~~~~~~~~~~~~~~~ /home/jimc/projects/lx/wk-next/drivers/gpu/drm/drm_print.c:60:1: note: in expansion of macro ‘DEFINE_DYNAMIC_DEBUG_CATEGORIES’ 60 | DEFINE_DYNAMIC_DEBUG_CATEGORIES(debug, __drm_debug, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #if defined(CONFIG_DYNAMIC_DEBUG) || \ (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE)) /** * DEFINE_DYNAMIC_DEBUG_CATEGORIES() - bitmap control of categorized prdbgs * @fsname: parameter basename under /sys * @var: C-identifier holding bitmap * @_desc: string summarizing the controls provided * @...: list of struct dyndbg_bitdesc initializations * * Intended for modules with substantial use of "categorized" prdbgs * (those with some systematic prefix in the format string), this lets * modules (using dyndbg) control those prdbg groups according to * their prefixes, and map them to bits 0-N of a sysfs control point. * The @bits... identifies the prefixes to be used by dyndbg to * select and alter those categorized prdbgs, order defines bitpos. */ #define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, _var, _desc, ...) \ MODULE_PARM_DESC(fsname, _desc); \ static struct dyndbg_bitmap_param ddcats_##_var = \ { .bits = &_var, .map = { __VA_ARGS__, { .prefix = NULL }}}; \ module_param_cb(fsname, &param_ops_dyndbg, &ddcats_##_var, 0644) #define _DD_cat_(pfx) { .prefix = pfx, .help = "help for " pfx } #define _DD_cat_help_(pfx) "\t " pfx "\t- help for " pfx "\n" extern const struct kernel_param_ops param_ops_dyndbg; #elif (defined(CONFIG_DYNAMIC_DEBUG_CORE) && !defined(DYNAMIC_DEBUG_MODULE)) #define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, var, bitmap_desc, ...) \ BUILD_BUG_ON_MSG(1, "you need -DDYNAMIC_DEBUG_MODULE in compile") #else #define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, var, bitmap_desc, ...) \ BUILD_BUG_ON_MSG(1, "DYNAMIC_DEBUG support required to use this macro: " #var) #define _DD_cat_(pfx) #define _DD_cat_help_(pfx) #endif #endif

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