October 2022 - kernelnewbies@kernelnewbies.org

Source code organization
by Billie Alsup (balsup) April 23, 2024

April 23, 2024

I have a set of drivers that I would like to upstream. These are primarily MFD style drivers supporting Cisco-8000 FPGAs. The devices can be instantiated through multiple top level drivers, which provide the access mechanism for the MFD driver. For example, an FPGA can be accessed via PCI, or via i2c, or via SLPC, or via P2PM (a point-to-point interface). We currently build these drivers out of tree, under a single directory drivers/cisco. I note that existing drivers are spread out across the kernel tree, sometimes by bus (pci, i2c), sometimes by function (gpio, net/mdio, spi), and sometimes under the generic mfd. I would like to start the upstream review process for our drivers, but first want to get recommendations on the source code layout. Is it permissible to keep a top level directory such as drivers/cisco to organize our code? It is not only the source code that is affected, but also provides a central place for Kconfig entries. Our FPGAs have multiple logical blocks, each of which is handled by a different MFD driver, e.g. i2c controllers, gpio controllers, spi controllers, mdio controllers. There can be multiple instances of each block as well (so multiple MFD devices are instantiated for each driver). And of course, there can be multiple FPGAs in a system, each with different combinations of logical blocks. The drivers themselves are pretty specific to our FPGAs, thus it makes sense to use Kconfig to select a hardware platform to automatically select the set of MFD drivers (and top level bus drivers) that would apply. Would a source layout putting all the code under drivers/cisco be acceptable in this case, or do I need to move things around and spread out the Kconfig entries across directories? I note that a single drivers/cisco would simplify any related modifications to MAINTAINERS as well.

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How is the size of init ram disk determined when initramfs is used?
by Chan Kim Jan. 2, 2023

Jan. 2, 2023

Hello all, I'm using initramfs.cpio.gz for initial file system image. I embed it in the kernel Image file. After linux boots, when I'm in the shell, I can create files. But I'm curious how much the file system can grow. I remember somewhere reading that the initramdisk is made and the initramfs archive is extracted in the ramdisk. Then how is the ramdisk size determined? During the build usig Kconfig variable, or does it dynamically grow? Thanks in advance. Chan Kim

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question about boot_params global variables
by shiyu chou Nov. 20, 2022

Nov. 20, 2022

Hello all: In arch x86 directory I found two global variables with the same name(master branch): 1.arch/x86/boot/main.c near line 18: struct boot_params boot_params __attribute__((aligned(16))); 2.arch/x86/kernel/setup.c near line 75: struct boot_params boot_params; Is that wrong to define two global variables with the same name? And when use extern to reference the variable,which one did it reference?

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kernel compile message
by Anatoly Pugachev Nov. 2, 2022

Nov. 2, 2022

Hello! Doing kernel testing, occasionally I started to get messages: mator@ttip:~/linux-2.6$ make -j olddefconfig; nice make -j20 && nice make -j20 modules # # configuration written to .config # SYNC include/config/auto.conf.cmd make[1]: /bin/sh: Bad address UPD include/generated/compile.h UPD include/config/kernel.release UPD include/generated/utsrelease.h It is not always "bad address" is shown, next time i run "make olddefconfig" it does not shows, but sometimes it shows... How do i debug this ? Thanks

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Vendor driver vs Kernel, which one gets priority?
by Do Hak Yong Oct. 20, 2022

Oct. 20, 2022

Hello kernel experts, I have a few questions about the priority of kernel drivers and third party drivers. If I install a third party vendor driver, which has the same module name as kernel provides, for example, Qlogic driver has the same module name as third party driver(qla2xxx). The questions are: Q1. Which driver has higher priority and which driver will be used? will there any be problems? Q2. How to control which driver the os will use? Q3. What if the updated kernel installed and provied higher driver version than third party? Which one will be used then? I think third party drivers have more precedence that kernel drivers refer to below Red Hat KB, but I'm not sure which one will be used when the kernel has updated. https://access.redhat.com/solutions/176213 Your advice will be much appriciated. Thank you Best regards, hakyong

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Re: work one webcam out of two webcam connect to xhci controller for 2 usb3.0 ports
by jim.cromie＠gmail.com Oct. 19, 2022

Oct. 19, 2022

Let's keep this on the list. I'm sure I don't have Silver Bullet answers. On Tue, Oct 18, 2022, 11:15 AM Malatesh <malatesh10(a)gmail.com> wrote: > Hi. > Thank you for the interest you have shown. > > > - both cameras work one at a time ? > [A]: No. I am using one by one and not at one time both cameras > - does order of plugin affect which one blanks ? > [A]: First plugged camera will give blank and second plugged will work > This certainly suggests two cameras are on or plugged in at the same time. that contradicts your first answer - are they both the same camera model ? > [A]: No one is logitech and another is microsoft > - can you borrow a 3rd camera ? > [A]: Third camera works > I think you need to retest and permute all combinations or at least some of them. I suspect your application doesn't know what to do with two cameras why don't you try another app and see if it works. Cheese is the one on my desktop > Actual Error: > When I click camera preview with two camera connected, one is giving error > some time with "xhci_configure_reset_endpoint:4543 Error to set dequeue > ptr for endpoint 3, 81, err 18, 0". > This is because "ep status is 0 and *Endpoint is disabled".* > > Full Log: > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011861> set halted 1 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011890> real interrupt > (status=0x00000008) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011897> event[77] = 32 > (0x0000000000000000 0x0c000000 0x02038000) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011901> trb 0x0 status c > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011904> slot=2 epno=3 > stream=0 remainder=0 status=12, td_event 0x0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011907> stream_id=0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011910> > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011940> trb halted 1, running > 0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011943> > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011944> Ep(129) No:129 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011946> Ep ID(129to3):3 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011949> dev 2, ep address 81 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011952> xfer > 0xfffffe003198f148, 0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011954> ep 81 is not started > yet > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011957> ------> epno:3, Oct > 18 16:35:42 WT544810D076E1 kernel: <3645.011861> set halted 1 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011890> real interrupt > (status=0x00000008) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011897> event[77] = 32 > (0x0000000000000000 0x0c000000 0x02038000) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011901> trb 0x0 status c > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011904> slot=2 epno=3 > stream=0 remainder=0 status=12, td_event 0x0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011907> stream_id=0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011910> > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011940> trb halted 1, running > 0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011943> > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011944> Ep(129) No:129 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011946> Ep ID(129to3):3 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011949> dev 2, ep address 81 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011952> xfer > 0xfffffe003198f148, 0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011954> ep 81 is not started > yet > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011957> ------> epno:3, > *epstatus:0* device:2, ep_address 81 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011960> ----> *Endpoint is > disabled* > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011962> > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011965> command[5] = 16 > (0x0000000009891001, 0x00000000, 0x02034000) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012003> real interrupt > (status=0x00000008) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012010> event[78] = 33 > (0x0000000100fffdd0 0x13000000 0x02008400) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012013> Received command event > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012042> trb 13000000, 2008400 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012046> src 16, > (0x0000000009891001, 0x00000000, 0x02034000) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012051> -----> Set dequeue > ptr for EP No:3, EP Addr:81, EP Status:0, EP Error:18 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012057> [ERROR] - > xhci_configure_reset_endpoint:4543 Error to set dequeue ptr for endpoint > 3, 81, err 18, 0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012061> ---> kick_ep 1 called: > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012064> endpoint is not > running 3, 81, 18 device:2, ep_address 81 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011960> ---->* Endpoint is > disabled* > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011962> > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.011965> command[5] = 16 > (0x0000000009891001, 0x00000000, 0x02034000) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012003> real interrupt > (status=0x00000008) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012010> event[78] = 33 > (0x0000000100fffdd0 0x13000000 0x02008400) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012013> Received command event > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012042> trb 13000000, 2008400 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012046> src 16, > (0x0000000009891001, 0x00000000, 0x02034000) > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012051> -----> Set dequeue > ptr for EP No:3, EP Addr:81, EP Status:0, EP Error:18 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012057> [ERROR] - > xhci_configure_reset_endpoint:4543 Error to set dequeue ptr for endpoint > 3, 81, err 18, 0 > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012061> ---> kick_ep 1 called: > > Oct 18 16:35:42 WT544810D076E1 kernel: <3645.012064> endpoint is not > running 3, 81, 18 > > > > > > > Regards, > Malatesh > > > On Thu, Oct 13, 2022 at 8:45 PM <jim.cromie(a)gmail.com> wrote: > >> On Wed, Oct 12, 2022 at 11:21 AM Malatesh <malatesh10(a)gmail.com> wrote: >> > >> > Hi Team, >> > >> > Good Morning/Afternoon/Evening. >> > >> > I connect two usb webcameras and one mouse, one keyboard to xhci >> controller, which has 4 usb v3.x ports. >> > Here, keyboard and mouse works fine without any issue. >> > But out of two cameras, only one camera works( I mean when I click >> preview only one camera show and one camera show blank ) >> > >> >> lemme ask some obvious questions: >> - both cameras work one at a time ? >> - does order of plugin affect which one blanks ? >> - are they both the same camera model ? >> - can you borrow a 3rd camera ? >> >

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How to refer to a code snippet in email?
by Drake Talley Oct. 17, 2022

Oct. 17, 2022

There is ample documentation for how to include a patch file, commits, or diff in emails, but I haven't been able to discern what is the preferred way to refer to code snippets as line ranges in a file for a given revision. Is this just not that common so it isn't done? Or is there a general approach to just pasting in a hunk of source code and manually stating the file/line numbers? Curious both as to what's possible in an email-driven git workflow and how things are done here. Thanks! Drake

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olddefconfig vs. menuconfig (just open, save file and close)
by Richard Oct. 15, 2022

Oct. 15, 2022

Hi all, When you have an existing .config and just open `make menuconfig` say close and save the file you end up with a working (for compilation) .config file. As you do when you use make olddefconfig. In a recent (arm) project I have noticed that the .config files produced in the two cases differ (when starting from the same base .config). In general menuconfig adds more options (lines) than olddefconfig. What is the difference between the two cases? When should I use olddefconfig, when should I use the menuconfig approach? Thanks, -- Richard

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Mutex midpath question (mutex-design.rst , CONFIG_MUTEX_SPIN_ON_OWNER)
by Richard Oct. 15, 2022

Oct. 15, 2022

Hi all, I have a question regarding understanding mutex-design.rst. It is about the feature that mutexes also have spinlocks for the case where the current lock is occupied but by a task that is runnning and might end soon (optimistic spinning). The top of the file says: > > In its most basic form it also includes a > wait-queue and a spinlock that serializes access to it. Furthermore, > CONFIG_MUTEX_SPIN_ON_OWNER=y systems use a spinner MCS lock (->osq), described > below in (ii). What is not fully clear for me here is: is the optimistic spinning always accessible and MCS is just an optimisation. Or is optimistic spinning only accessible with CONFIG_MUTEX_SPIN_ON_OWNER. The mentioning of the first spinlock in the first sentence confuses me. Thanks, -- Richard

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Faster, incremental depmod when adding modules?
by Ian Pilcher Oct. 13, 2022

Oct. 13, 2022

When installing 1 or more out-of-tree modules within /lib/modules/$UNAME, is it possible to run depmod in an incremental fashion - adding symbols from the new modules to modules.dep[.bin] without re-scanning all of the other modules from that kernel version? I've tried specifying the new module files, but that seems to create a completely new modules.dep containing *only* the symbols from the new modules (which obviously isn't very useful). -- ======================================================================== Google Where SkyNet meets Idiocracy ========================================================================

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