March 2016 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

How to use OF-style driver w/o dtd (ARM s3c24xx rtc driver)
by Woody Wu March 7, 2016

March 7, 2016

Hi, As I understood from the source code (4.4.3), the Samsung RTC driver rtc-s3c.c is an OF or DT style driver. It means probably that I cannot use it by simply defining a platform device in my board file. Actually, I found out this after I did that and then didn't see the RTC drive's probe method got called as I expected. Then my question comes, how can I use the RTC driver to active the RTC device w/o involving the complexity of DTD loading at this moment? Since I cannot change the boot loader, so I have no an easier way to load DTD to the kernel as that usually suggested in the documents I googled. Can I use a statically defined device node in my board file? I only concern the RTC device at this moment, so I think this is the easiest way to go for my situation. Would someone please give out suggestions and even a simple how-to? Best Regards, -woody -- Life is the only flaw in an otherwise perfect nonexistence -- Schopenhauer woody public key at http://subkeys.pgp.net:11371 (narkewoody(a)gmail.com)

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How to use earlycon and earlyprintk on Samsung S3C24xx
by Woody Wu March 7, 2016

March 7, 2016

Hi, It seems, at least in 4.4.2 kernel, earlyprintk parameter supports something like 's3c24xx,<addr>'. But I dont know where to find out the addr value of the first uart port on my *s3c2416* based board. Can someone please tell me? Also, I desire to know if the earlycon parameter supports the Samsung S3C24xx uarts, if so, what should the value of the parameter look like? Thank in advance, -woody -- Life is the only flaw in an otherwise perfect nonexistence -- Schopenhauer woody public key at http://subkeys.pgp.net:11371 (narkewoody(a)gmail.com)

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stack pointer
by Nitin Varyani March 7, 2016

March 7, 2016

struct task_struct { volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */* void *stack;* atomic_t usage; unsigned int flags; /* per process flags, defined below */ unsigned int ptrace; What does the field void *stack indicate here? Is it the pointer to kernel stack of the process? Where is the stack pointer for the current process stored in linux?

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What does %P1 mean in gcc inline assembly?
by 张云 March 7, 2016

March 7, 2016

Hi In /arch/x86/boot/main.c (http://lxr.free-electrons.com/source/arch/x86/boot/main.c) , In the function init_heap, asm("leal %P1(%%esp),%0" 122 <http://lxr.free-electrons.com/source/arch/x86/boot/source/arch/x86/boot/mai…> : "=r" (stack_end) : "i" (-STACK_SIZE <http://lxr.free-electrons.com/source/arch/x86/boot/ident?i=STACK_SIZE>)); What does the ‘%P1’ mean in the inline assembly above ? Thanks !

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kexec not working
by Ronit Halder March 6, 2016

March 6, 2016

When I am doing normal load of kernel using kexec, it works. #kexec -l /boot/vmlinuz-4.3.0-crash+ --initrd=/boot/initramfs-4.3.0-crash+.img --append="root=/dev/mapper/fedora-root 1 irqpoll maxcpus=1 reset_devices" #kexec -e But, when I am doing load on panic using kexec, it isn't working. #kexec -p /boot/vmlinuz-4.3.0-crash+ --initrd=/boot/initramfs-4.3.0-crash+.img --append="root=/dev/mapper/fedora-root 1 irqpoll maxcpus=1 reset_devices" #echo "1" >/proc/sys/kernel/sysrq #echo c > /proc/sysrq-trigger What am I doing wrong?

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Re: Booting with SYSLINUX on Loopback Device: Kernel Panic - Where to Start?
by Patrick March 5, 2016

March 5, 2016

On Fri, Mar 4, 2016 at 3:56 PM, Kristof Provost <kristof(a)sigsegv.be> wrote: > > On 04 Mar 2016, at 23:50, Patrick <plafratt(a)gmail.com> wrote: > Thanks for the response. I had seen that StackOverflow post and done > that a couple of days ago. I was hoping there was another answer, since I > wouldn't be able to do that if I weren't using QEMU. > > If you weren’t using Qemu I’d point you at netconsole. The first step in > debugging panics is always to figure out what the panic is. > > When I looked at the output from QEMU a couple of days ago, the kernel was > saying that it couldn't find a device to mount with the root filesystem. So > I generated an initrd image on the host Linux system, and I used that on > the guest which got me to a BusyBox prompt. But this was totally a hack, > since I didn't even know if getting an initrd image was really the next > thing I needed to do. I was hoping someone might be able to point me to > something that might explain what to do to get the kernel to mount a device > with the root filesystem. > > You want to pass the ‘root=/dev/foo’ option to your kernel. Obviously > change /dev/foo into whatever device you’re booting from. > > Regards, > Kristof > Ok, thanks. I will try to look into netconsole. I had tried changing the "root" option. I had noticed that the QEMU output showed the kernel printing out this: [ 4.312088] VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6 [ 4.322029] Please append a correct "root=" boot option; here are the available partitions: [ 4.327850] 0100 65536 ram0 (driver?) [ 4.337399] 0101 65536 ram1 (driver?) [ 4.345170] 0102 65536 ram2 (driver?) [ 4.345691] 0103 65536 ram3 (driver?) [ 4.346251] 0104 65536 ram4 (driver?) [ 4.346825] 0105 65536 ram5 (driver?) [ 4.347442] 0106 65536 ram6 (driver?) [ 4.350055] 010a 65536 ram10 (driver?) [ 4.352624] 010b 65536 ram11 (driver?) [ 4.353597] 010c 65536 ram12 (driver?) [ 4.354517] 010d 65536 ram13 (driver?) [ 4.354977] 010e 65536 ram14 (driver?) [ 4.358393] 010f 65536 ram15 (driver?) [ 4.359420] 0b00 1048575 sr0 driver: sr [ 4.360499] 0800 102400 sda driver: sd [ 4.367898] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) I hadn't noticed "sda" before. So I tried pointing root at this. Then I got this: [ 4.375721] List of all partitions: [ 4.383491] 0100 65536 ram0 (driver?) [ 4.386418] 0101 65536 ram1 (driver?) [ 4.388736] 0102 65536 ram2 (driver?) [ 4.390931] 0103 65536 ram3 (driver?) [ 4.391266] 0104 65536 ram4 (driver?) [ 4.391726] 0105 65536 ram5 (driver?) [ 4.392812] 0106 65536 ram6 (driver?) [ 4.393340] 0107 65536 ram7 (driver?) [ 4.393932] 0108 65536 ram8 (driver?) [ 4.394906] 0109 65536 ram9 (driver?) [ 4.396283] 010a 65536 ram10 (driver?) [ 4.399212] 010b 65536 ram11 (driver?) [ 4.400067] 010c 65536 ram12 (driver?) [ 4.401832] 010d 65536 ram13 (driver?) [ 4.402775] 010e 65536 ram14 (driver?) [ 4.403572] 010f 65536 ram15 (driver?) [ 4.404046] 0800 102400 sda driver: sd [ 4.412148] 0b00 1048575 sr0 driver: sr [ 4.413323] No filesystem could mount root, tried: ext3 ext2 ext4 vfat fuseblk [ 4.415310] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(8,0) So, I think maybe now the kernel is missing some things it needs on /dev/sda. Right now, I don't think there is anything on it other than the bootloader. Do you happen to know where I can find what the kernel needs to proceed? Thanks, Patrick >

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What is the role of LIST_POISON1 and LIST_POISON2?
by Navy Cheng March 4, 2016

March 4, 2016

Hi, When I read the code of list_del(), I find LIST_POISON1 and LIST_POISON2: static inline void list_del(struct list_head *entry) { __list_del(entry->prev, entry->next); entry->next = LIST_POISON1; entry->prev = LIST_POISON2; } Why not set entry->next and entry->prev to NULL ? Thank you!

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Re: Kernelnewbies Digest, Vol 64, Issue 4
by Vishwas Srivastava March 4, 2016

March 4, 2016

On Thu, Mar 3, 2016 at 10:07 PM, <kernelnewbies-request(a)kernelnewbies.org> wrote: > Send Kernelnewbies mailing list submissions to > kernelnewbies(a)kernelnewbies.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > or, via email, send a message with subject or body 'help' to > kernelnewbies-request(a)kernelnewbies.org > > You can reach the person managing the list at > kernelnewbies-owner(a)kernelnewbies.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Kernelnewbies digest..." > > > Today's Topics: > > 1. Re: Submitting patches to non-staging (Christoph Lameter) > 2. Re: Submitting patches to non-staging (Pratyush Patel) > 3. Fw: new important message (bear.yogi(a)gmx.de) > 4. Re: where is disk block access in kernel ? (Mulyadi Santosa) > 5. Re: where is disk block access in kernel ? > (Valdis.Kletnieks(a)vt.edu) > 6. remote system call (Nitin Varyani) > 7. Re: remote system call (Mulyadi Santosa) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 2 Mar 2016 13:45:54 -0600 (CST) > From: Christoph Lameter <cl(a)linux.com> > Subject: Re: Submitting patches to non-staging > To: Pratyush Patel <pratyushpatel.1995(a)gmail.com> > Cc: kernelnewbies(a)kernelnewbies.org > Message-ID: <alpine.DEB.2.20.1603021344420.3497(a)east.gentwo.org> > Content-Type: text/plain; charset=US-ASCII > > On Tue, 1 Mar 2016, Pratyush Patel wrote: > > > I will be pursuing my undergraduate thesis research in the field of > > real-time (operating) systems and as such, I expect to be closely > > involved with the timer and interrupt subsystems in Linux (as well as > > other areas, but to a lesser degree). I am also hoping to work with > > the hrtimer subsystem, and while going through the latest code > > (4.5-rc6) of the same, I found a very minor code-level change that > > could be incorporated (redundant #ifdef). Would such a change in a > > core kernel file be acceptable coming from a beginner? Or should I aim > > for the staging drivers first? > > Dont worry about staging. There is no staing for interrupts and timers. Go > direct and post to the relevant maintainers and lkml > > > I very much look forward to contributing my first patch! > > love to see it. > > > > > ------------------------------ > > Message: 2 > Date: Thu, 3 Mar 2016 07:20:18 +0530 > From: Pratyush Patel <pratyushpatel.1995(a)gmail.com> > Subject: Re: Submitting patches to non-staging > To: Christoph Lameter <cl(a)linux.com> > Cc: kernelnewbies <kernelnewbies(a)kernelnewbies.org> > Message-ID: > <CAAnMKKbXAKUDHXx7Mf-npnM1BRWVbNoA= > BcZFB-xu5r6Ay46dA(a)mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > On Thu, Mar 3, 2016 at 1:15 AM, Christoph Lameter <cl(a)linux.com> wrote: > > On Tue, 1 Mar 2016, Pratyush Patel wrote: > > > >> I will be pursuing my undergraduate thesis research in the field of > >> real-time (operating) systems and as such, I expect to be closely > >> involved with the timer and interrupt subsystems in Linux (as well as > >> other areas, but to a lesser degree). I am also hoping to work with > >> the hrtimer subsystem, and while going through the latest code > >> (4.5-rc6) of the same, I found a very minor code-level change that > >> could be incorporated (redundant #ifdef). Would such a change in a > >> core kernel file be acceptable coming from a beginner? Or should I aim > >> for the staging drivers first? > > > > Dont worry about staging. There is no staing for interrupts and timers. > Go > > direct and post to the relevant maintainers and lkml > > > >> I very much look forward to contributing my first patch! > > > > love to see it. > > > > Here's the archive link: > http://comments.gmane.org/gmane.linux.kernel/2165466 > > Please do let me know in case I did something wrongly. > > Awaiting for it to be accepted! > > It seems to be a valid change and should be accepted in the kernel. > You may probably change the commit message something like.. " removing nested macro definition (CONFIG_SMP)" if you want. good luck -- Vishwas > > ------------------------------ > > Message: 3 > Date: Thu, 3 Mar 2016 05:37:11 +0300 > From: <bear.yogi(a)gmx.de> > Subject: Fw: new important message > To: "kernelnewbies" <kernelnewbies(a)kernelnewbies.org>, "leo kirotawa" > <kirotawa(a)gmail.com>, "lifelong0811" <lifelong0811(a)126.com>, > "lind.lampe(a)gmx.de" <lind.lampe(a)gmx.de>, "linux-api" > <linux-api(a)vger.kernel.org> > Message-ID: <0000073edf2f%2453e14ef2%246fb257ae%24(a)gmx.de> > Content-Type: text/plain; charset="us-ascii" > > Hello! > > > > New message, please read <http://majorinvesting.com/longer.php?drpr> > > > > bear.yogi(a)gmx.de > >

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Add Wiki Edit Permissions
by Roberto Caballero March 4, 2016

March 4, 2016

Hi, Would you be able to add me to the wiki edit list? Let me know if you need any specific info. -- Roberto Caballero Electrical Engineer Embedded System Specialist (647) 234 - 0179

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where is disk block access in kernel ?
by Ran Shalit March 3, 2016

March 3, 2016

Hello, I would like to monitor the write access to disk blocks (so that I can monitor the block index in some bitmap) I think this must be done in kernel (userspace have no such information) I have tried to search in kernel but did not found where is the API to access disk blocks. There is libata-core.c , but I can't find such routines there, and neither any documentation. Is there any idea ? Regards, Ran

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