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is there any more to having a single interrupt drive multiple handlers than IRQF_SHARED?
by Robert P. J. Day Oct. 26, 2017

Oct. 26, 2017

colleague just asked how he can use a single interrupt line to trigger more than one interrupt handler, and i just said, "well, IRQF_SHARED." i'm not sure if there's any more to this problem, but am i off-base in suggesting that that is pretty much what IRQF_SHARED is designed for? now, i do realize that it can be used along with a unique dev_id values to isolate a *particular* handler amongst a group of handlers, but if one simply wants to trigger *all* handlers registered for that interrupt, is there anything about that that's tricky? it seems pretty straightforward, but i'm going back to review my interrupt handlers this evening. rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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Re: Updating LDD3
by Ozgur Oct. 25, 2017

Oct. 25, 2017

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Re: Xilinx clock wizard driver
by Elias Kouskoumvekakis Oct. 25, 2017

Oct. 25, 2017

>From a quick look the driver reads / writes the clock wizard IP core's registers and uses device tree bindings to access that part of AXI4 mapped memory. All this implies that you need an hard/soft cpu core inside the FPGA that will run Linux and this driver. The clock wizard IP core will need to be properly instantiated and mapped on the hard / soft cpu's AXI4 interconnect so that the driver can access its registers. To test the driver I suggest that you buy the cheapest Zynq board that you can find and just build a simple block design in Vivado. The cpu on the FPGA that will run Linux will be the Zynq PS hard cpu core and thus you just need to create a simple block design with the Zynq PS and the clocking wizard IP core. Of-course actually running this involves the preparation of ROM that will contain your FPGA bitsteam with your design and the bootable image of the kernel, i.e you must be familiar with the whole Vivado/SDK flow for embedded designs. Xilinx provides a lot of documentation material on these, it's just a matter of time to read through them and follow the relative simple steps. An alternative is the Zynq Book which covers all these in a very simple fashion that I don't really like but it could be of use by someone inexperienced with FPGAs and particularly the Zynq FPGA devices. http://www.zynqbook.com And for Zynq development boards I recommend the Parallella board which can be bought for ~$125-$250 or the SnickerDoodle board for ~$145-$195. The former is a bit old and besides the FPGA it contains a parallel chip called Epiphany to experiment with parallel programming alongside the Zynq FPGA. The latter is more recent and has a lot of I/O pins if you need them. https://www.parallella.org/buy/ https://www.crowdsupply.com/krtkl/snickerdoodle Elias

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Re: Kernelnewbies Digest, Vol 83, Issue 20
by yash omer Oct. 24, 2017

Oct. 24, 2017

Hello On github There are all the sample Of lddr3 for kernel 4.xx and above Get Outlook for iOS<https://aka.ms/o0ukef> ________________________________ From: kernelnewbies-bounces(a)kernelnewbies.org <kernelnewbies-bounces(a)kernelnewbies.org> on behalf of kernelnewbies-request(a)kernelnewbies.org <kernelnewbies-request(a)kernelnewbies.org> Sent: Tuesday, October 24, 2017 9:30:02 PM To: kernelnewbies(a)kernelnewbies.org Subject: Kernelnewbies Digest, Vol 83, Issue 20 Send Kernelnewbies mailing list submissions to kernelnewbies(a)kernelnewbies.org To subscribe or unsubscribe via the World Wide Web, visit https://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: Updating LDD3 (Daniel.) 2. Re: Updating LDD3 (Liam Ryan) ---------------------------------------------------------------------- Message: 1 Date: Tue, 24 Oct 2017 10:49:34 -0200 From: "Daniel." <danielhilst(a)gmail.com> Subject: Re: Updating LDD3 To: Ozgur <okaratas(a)yandex.com> Cc: kernelnewbies <kernelnewbies(a)kernelnewbies.org> Message-ID: <CAF3SDA4psKGR1zzx11v1jVPgDMkQVretJb5gCnBHZvEs-GT%2BFA(a)mail.gmail.com> Content-Type: text/plain; charset="utf-8" You're welcome! On Oct 24, 2017 10:38 AM, "Ozgur" <okaratas(a)yandex.com> wrote: > > Hello, > > 24.10.2017, 15:31, "Daniel." <danielhilst(a)gmail.com>: > > Here it is https://github.com/martinezjavier/ldd3 > > Regards > > > oh, it's very good, nice. > Thank you > > Ozgur > > > > On Oct 24, 2017 9:58 AM, "Ozgur" <okaratas(a)yandex.com> wrote: > > Hello Daniel, > > 24.10.2017, 14:50, "Daniel." <danielhilst(a)gmail.com>: > > There is a repo at github with all the samples don't? > > > > I think that no, I not seen before on github. > > Regards > > Ozgur > > > > On Oct 24, 2017 9:06 AM, "Ozgur" <okaratas(a)yandex.com> wrote: > > Hello Ryan, > > 24.10.2017, 13:58, "Liam Ryan" <liamryandev(a)gmail.com>: > > I'm currently working through the Linux Device Drivers 3rd edition > > (https://lwn.net/Kernel/LDD3/) and much of the code is outdated. > > > > Right now I'm going through chapter 3 and rewriting the scull.c sample > > code so that it will compile with 4.14.x > > > > I'm wondering about the Creative Commons license on the LDD3 book. I > believe I would be able to annotate or alter the pdf files and re-publish > them once I respect the license, however I'm wondering if this would be > considered bad form? I assume there's a reason somebody else has not done > this to date? > > I think you can update and re-publish the example code and don't break the > original comment lines. > At least I think this. > > > Obviously as a kernel newbie I'm not best positioned to do this work but > > I'm happy to make a start and publish to a wiki or similar in a few > > months once I've gone through everything. > > > > Thanks, > > Liam > > Regards > > Ozgur > >

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Updating LDD3
by Liam Ryan Oct. 24, 2017

Oct. 24, 2017

I'm currently working through the Linux Device Drivers 3rd edition (https://lwn.net/Kernel/LDD3/) and much of the code is outdated. Right now I'm going through chapter 3 and rewriting the scull.c sample code so that it will compile with 4.14.x I'm wondering about the Creative Commons license on the LDD3 book. I believe I would be able to annotate or alter the pdf files and re-publish them once I respect the license, however I'm wondering if this would be considered bad form? I assume there's a reason somebody else has not done this to date? Obviously as a kernel newbie I'm not best positioned to do this work but I'm happy to make a start and publish to a wiki or similar in a few months once I've gone through everything. Thanks, Liam

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atomic test and set
by Tobin C. Harding Oct. 22, 2017

Oct. 22, 2017

Hi, Do we have an atomic test and set function in the kernel. I have tried const int KEY_FLAG_BIT = 1; ... static siphash_key_t ptr_secret __read_mostly; static unsigned long have_key = 0; if (test_and_set_bit(KEY_FLAG_BIT, &have_key)) get_random_bytes(&ptr_secret, sizeof(ptr_secret)); But that doesn't work. I looked in include/linux/atomic.h and thought about using static atomic_t have_key = ATOMIC_INIT(0); if (atomic_xchg(&have_key, 1) == 0) get_random_bytes(&ptr_secret, sizeof(ptr_secret)); This works. My question is; does this code LOAD the value at have_key and STORE the argument on every call? Or does it LOAD the value, check if it is the same as the argument, and STORE _only_ if it is different? (Is this whole discussion just premature optimization?) I cannot grok the macros in atomic.h, they seem circular. Here is the macro definitions in call chain order starting with atomic_xchg() #define atomic_xchg(...) \ __atomic_op_fence(atomic_xchg, __VA_ARGS__) #define __atomic_op_fence(op, args...) \ ({ \ typeof(op##_relaxed(args)) __ret; \ smp_mb__before_atomic(); \ __ret = op##_relaxed(args); \ smp_mb__after_atomic(); \ __ret; \ }) #define atomic_xchg_release(...) \ __atomic_op_release(atomic_xchg, __VA_ARGS__) #define __atomic_op_release(op, args...) \ ({ \ smp_mb__before_atomic(); \ op##_relaxed(args); \ }) #define atomic_xchg_relaxed atomic_xchg thanks, Tobin.

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ZRAM setup and configuration
by russel phillipe Oct. 20, 2017

Oct. 20, 2017

I am trying to setup ZRAM on ubuntu 4.4 kernel. I can load and create zram based swap devices fine as you can see below. # apt-get install zram-config cat /proc/swaps Filename Type Size Used Priority /dev/sda3 partition 16638972 0 -1 /dev/zram0 partition 2036816 0 5 /dev/zram1 partition 2036816 0 5 /dev/zram2 partition 2036816 0 5 How can I make it work. I tried running memtester and load it with stress stress --vm-bytes $(awk '/MemFree/{printf "%d\n", $2 * 0.9;}' < /proc/meminfo)k --vm-keep -m 1 It does not look like it is being used. I notice that 'used' count in /proc/swaps does not bump at all. I even tried 'vmstat 1 100 ' while running stress and memtester and did not see any change in SO and SI. What am I missing? Thanks Russel

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A question on vma_address()
by Perr Zhang Oct. 17, 2017

Oct. 17, 2017

I am reading codes on reverse mapping. The code of vma_address() was last changed at 2017-02-24 17:46:55 -0800 The link of the commit is: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?… The definition of vma_address(): http://elixir.free-electrons.com/linux/latest/source/mm/internal.h#L343 The code of vma_address() looks like this: ------------------------------------------------------------------------------------ static inline unsigned long __vma_address(struct page *page, struct vm_area_struct *vma) { pgoff_t pgoff = page_to_pgoff(page); return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); } static inline unsigned long vma_address(struct page *page, struct vm_area_struct *vma) { unsigned long start, end; start = __vma_address(page, vma); ... return max(start, vma->vm_start); } ------------------------------------------------------------------------------------ This function is only called by rmap_walk_file() and rmap_walk_anon() which ensure the page used by vma_address() is in an anon_vma or in an address_space. Why should we use the function max() on 'start' and 'vma->vm_start'? Could the 'start' be less than 'vma->vm_start'? If it is so, isn't it wrong to just return vma->vm_start but report an error?

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architecture conditional
by Tobin C. Harding Oct. 16, 2017

Oct. 16, 2017

What is the correct way to write code that is conditionally compiled depending on 32/64 bit? I found CONFIG_X86_64 CONFIG_64BIT Do we still support other word sizes? thanks, Tobin.

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kernel - Regarding tools/testing/ktests or selftests
by Pintu Kumar Oct. 12, 2017

Oct. 12, 2017

Hi All, Is anybody familiar with ktests of selftests framework under: tool/testing/ ? I have some queries. 1) What is the difference between ktests and selftests ? How to choose ? 2) How to invoke a test under ktests? For example: I have some user space C program, that tests some kernel driver IOCTL calls. I have a Makefile to build 2 executable for the tests. I invoke those executable from a bash shell script and execute all the tests. How can I do it automatically from ktests ? 3) Similarly, how can I do it using selftests? Using selftests looks much better option for me. But the problem is I have some sub directories to execute the tests. Example: Under, tools/testing/selftests , I have created 2 sub folders. selftests/folders/folder1/ My test setup is under: folder1 How to invoke selftests, for folder1 ? If anybody have added new tests under ktests of selftests, please provide some reference. Thanks, Pintu

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