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Kernel Module Compilation Query
by Doug Wilson May 8, 2014

May 8, 2014

Hi, I had a quick query on the module compilation. I get an error at Building modules, stage 2. MODPOST 1 modules LD [M] /root/code/modules/module.ko ld: no input files I could not find much info about this. The Makefile and code are very basic, just does a print. Thanks, Doug

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Linux DMA API Questions
by Mj Embd May 7, 2014

May 7, 2014

Following the text at https://www.kernel.org/doc/Documentation/DMA-API.txt a few inlined questions Part Ia - Using large dma-coherent buffers ------------------------------------------ void * dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t flag) Consistent memory is memory for which a write by either the device or the processor can immediately be read by the processor or device without having to worry about caching effects. (You may however need to make sure to flush the processor's write buffers before telling devices to read that memory.) Q1. Is it safe to assume that the area allocated is cacheable ? As the last line state that flushing is required Q1a. Does this API allocate memory from lower 16MB which is considered DMA safe. dma_addr_t dma_map_single(struct device *dev, void *cpu_addr, size_t size, enum dma_data_direction direction) Maps a piece of processor virtual memory so it can be accessed by the device and returns the physical handle of the memory. The direction for both api's may be converted freely by casting. However the dma_ API uses a strongly typed enumerator for its direction: DMA_NONE no direction (used for debugging) DMA_TO_DEVICE data is going from the memory to the device DMA_FROM_DEVICE data is coming from the device to the memory DMA_BIDIRECTIONAL direction isn't known Q2. Does the DMA_XXX options direct change of Page Attributes for the VA=>PA mapping. Say DMA_TO_DEVICE would mark the area as non-cacheable ? -- -mj

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Questions for a Kingston DT5000 driver
by Joel Holdsworth May 7, 2014

May 7, 2014

Hi Folks, I've just joined this ML, and I'm hoping someone can give me some advice. I've been experimenting with Kingston DT5000 hardware encrypted usb pen drives, and I'm hoping to write a driver. The DT5000 drives are probably most useful in corporate settings, where sensitive need to be protected. They might also be useful for machines that have sensitive information that must be left unattended. They also have excellent tamper evident characteristics. The device is a composite device containing an ejectable mass storage device, and a read only virtual cdrom. The cdrom contains windows software which autoruns and pops up a dialog that prompts the user to give the password, this is then conded and sent to the device via USB vendor control packets. I've got quite far hacking around with the device with pyusb and usbmon, and now I'm trying to gather information for a driver, so I have a few questions: First, via a series of messages the host PC uses Elliptic Curve Diffie Helman to establish a shared secret with the DT5000. The shared secret is then used to encrypt the password hash. I couldn't find any elliptic curve code in the kernel. Is this correct? Perhaps there are patent concerns? are there any plans to add it in? For a device like this, how would the user space interface look? Would one just make a sysfs file into which the the password plaintext is written? Or is it more normal to enter it via some userspace application that hashes and encrypts the password with the shared secret. Does dm_crypt, or IPSEC stuff offer a pattern to follow here? Or are there any very simple examples of password locking devices? I'm trying to figure out where the crypto work should be done. If the kernel did all the crypto, I guess the password interface would be very simple. If the task is split with user space then this is going to expose all this password hand-shake protocol to userspace - not such a slick interface I would say. Also, the device contains a few user programmable fields: For example the owner's name, address, and a hint for the password etc. These things are read-only when the device is locked, but become writable when the device is unlocked. I suppose this information would be communicated via sysfs. Is the pattern generally to have a separate file for each one? Also are there any general comments that I should take on board as I embark on this? Thanks for your help Best Regards Joel Holdsworth

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Freezing issue with Preempt-RT on OpenWRT MIPS
by Rob Connolly May 7, 2014

May 7, 2014

Hi All, I have already asked this question on the linux-rt-users mailing list and received no response, so I thought I' try here instead. I am attempting to use the rt patch set on an OpenWRT MIPS based system (ar71xx). I'm having some issues loading/using certain kernel modules, specifically for ethernet and USB support. The symptoms I am experiencing are: 1. The system will freeze completely after loading the usb modules (manually with insmod). Specifically this is after loading ehci_platform. The system appears to detect the hardware and then lock up, it is then rebooted by the watchdog a few seconds later. See below: root@OpenWrt:/# insmod /lib/modules/3.10.32/nls_base.ko root@OpenWrt:/# insmod /lib/modules/3.10.32/nls_base.procd: - root@OpenWrt:/# insmod /lib/modules/3.10.32/usb-common.ko root@OpenWrt:/# insmod /lib/modules/3.10.32/usbcore.ko [ 51.150000] usbcore: registered new interface driver usbfs [ 51.160000] usbcore: registered new interface driver hub [ 51.160000] usbcore: registered new device driver usb root@OpenWrt:/# insmod /lib/modules/3.10.32/ehci-hcd.ko [ 58.850000] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver root@OpenWrt:/# insmod /lib/modules/3.10.32/ohci-hcd.ko [ 65.730000] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver root@OpenWrt:/# insmod /lib/modules/3.10.32/ehci-platform.ko [ 77.830000] ehci-platform: EHCI generic platform driver [ 77.830000] ehci-platform ehci-platform: EHCI Host Controller [ 77.840000] ehci-platform ehci-platform: new USB bus registered, assigned bus number 1 [ 77.850000] ehci-platform ehci-platform: irq 3, io mem 0x1b000000 [ 77.880000] ehci-platform ehci-platform: USB 2.0 started, EHCI 1.00 [ 77.880000] hub 1-0:1.0: USB hub found [ 77.910000] hub 1-0:1.0: 1 port detected <lock up and reboot> 2. The second issue is similar but occurs when using the ethernet. I have the atheros ethernet drivers built into the kernel and can boot to a console with the interface disabled. I can even bring the interface up with ifconfig. However, the system freezes (as above) upon sending or receiving the first network packet. Investigating further and having read up on some of the debug options. I have turned on LOCKUP_DETECTOR and BOOTPARAM_SOFTLOCKUP_PANIC. Unfortunately I can't turn on the hard lockup detector since the hardware doesn't have a nmi watchdog. I also compiled in debugging symbols and enabled DEBUG_BUGVERBOSE in order to get a call trace. Here is the output of the kernel panic for the USB case above: [ 104.060000] BUG: soft lockup - CPU#0 stuck for 22s! [insmod:1053] [ 104.060000] Modules linked in: ehci_platform(+) ohci_hcd ehci_hcd usbcore usb_common nls_base pps_gpio_poll pps_core ath9k ath9k_common ath9k_hw ath mac80211 cfg80211 compat [ 104.060000] CPU: 0 PID: 1053 Comm: insmod Not tainted 3.10.32-rt31 #1 [ 104.060000] task: 87a1d420 ti: 87044000 task.ti: 87044000 [ 104.060000] $ 0 : 00000000 0000006e 10000000 00000000 [ 104.060000] $ 4 : 00000000 013fffff 00000002 87a1d420 [ 104.060000] $ 8 : 00000001 00000004 00000010 3120706f [ 104.060000] $12 : 00000000 87b88124 00000000 3d2b7573 [ 104.060000] $16 : f0000000 10000000 8725b800 0000000a [ 104.060000] $20 : 87813a00 00000001 00000002 00000064 [ 104.060000] $24 : 00000010 8007142c [ 104.060000] $28 : 87044000 87045850 00000001 80060890 [ 104.060000] Hi : 00000011 [ 104.060000] Lo : 00000001 [ 104.060000] epc : 80068144 preempt_schedule_irq+0x40/0x80 [ 104.060000] Not tainted [ 104.060000] ra : 80060890 need_resched+0x28/0x30 [ 104.060000] Status: 1100dc03 KERNEL EXL IE [ 104.060000] Cause : 40808800 [ 104.060000] PrId : 0001974c (MIPS 74Kc) [ 104.060000] Kernel panic - not syncing: softlockup: hung tasks [ 104.060000] CPU: 0 PID: 1053 Comm: insmod Not tainted 3.10.32-rt31 #1 [ 104.060000] Stack : 00000000 00000000 00000000 00000000 80392e72 00000039 87a1d5e4 00000068 [ 104.060000] 802df1c0 80333d1b 0000041d 80392624 87a1d5e4 00000068 ffffffff 042c227f [ 104.060000] 00000068 8007a288 00000000 80077834 00000000 00000040 802e0be8 870455b4 [ 104.060000] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 104.060000] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 87045540 [ 104.060000] ... [ 104.060000] Call Trace: [ 104.060000] [<8006e94c>] show_stack+0x48/0x70 [ 104.060000] [<8007764c>] panic+0xcc/0x20c [ 104.060000] [<800b6110>] watchdog_timer_fn+0x16c/0x19c [ 104.060000] [<8009995c>] __run_hrtimer.isra.26+0x80/0x104 [ 104.060000] [<8009a33c>] hrtimer_interrupt+0x204/0x494 [ 104.060000] [<80070770>] c0_compare_interrupt+0x4c/0x5c [ 104.060000] [<800b69a8>] handle_irq_event_percpu+0x74/0x1e8 [ 104.060000] [<800b96e4>] handle_percpu_irq+0x54/0x84 [ 104.060000] [<800b62c0>] generic_handle_irq+0x28/0x44 [ 104.060000] [<8006be28>] do_IRQ+0x1c/0x2c [ 104.060000] [<80060820>] ret_from_irq+0x0/0x4 [ 104.060000] [<80068144>] preempt_schedule_irq+0x40/0x80 [ 104.060000] [<80060890>] need_resched+0x28/0x30 [ 104.060000] From what I can tell it looks like it gets stuck in preempt_schedule_irq, but I'm not sure why need_resched should be below that in the call stack. Does anyone have any idea what might be going on here or any experience with similar issues which may help? Any help appreciated. Regards, Rob Connolly ########################################################################################### This communication, including any attachments, is confidential. If you are not the intended recipient, you should not read it - please contact me immediately, destroy it, and do not copy or use any part of this communication or disclose anything about it. ###########################################################################################

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LKML: Dropped mail fanout?
by David Matlack May 6, 2014

May 6, 2014

Hey fellow kernelnewbies. I sent a patch series to LKML last night from my work email address. I'm also subscribed to LKML from my personal email address (this one)... but I haven't received the patches on my personal account yet. The patch series is here: https://lkml.org/lkml/2014/5/6/1. So it was delivered to LKML. But maybe the fanout failed. The messages are _not_ in my spam or trash folders. I don't think they were delivered at all. If anyone would be willing to give a Yes/No if they received the patches on LKML that would be a big help for debugging this. Also, if anyone has any other tips let me know :) Thanks! --David

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Developing a Linux driver using a USB sniffer
by Luca Ellero May 6, 2014

May 6, 2014

Hi all, can someone please tell me if it is legal to develop an USB driver analysing the USB protocol with a USB sniffer? Can this driver be made public under GPL? Thanks Regards Luca Ellero

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Linux Device Driver
by Saurabh Jain May 6, 2014

May 6, 2014

Hello everyone! I am new to Linux Kernel . i studied a about CFS and processes a little bit. I want to write Device Drivers for Linux Kernel . Can any body tell me from where i should start? I completely new to this field , i do not know how to start and from where to start? Any recommended book ?

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Query on improving ADV driver 7180
by sanchayan maity May 6, 2014

May 6, 2014

Hello, I am currently using ADV7180 as a video decoder and using to view any one of the four video channel inputs. The driver is here: http://lxr.free-electrons.com/source/drivers/media/video/adv7180.c?v=3.0 The details for the decoder are here: http://www.analog.com/en/audiovideo-products/video-decoders/adv7180/product… I am trying to display two or four channels simultaneously in different windows. The problem is that even with two windows the frame rate is not acceptable. I am using the below code with OpenCV for rendering to multiple windows. ioctl call is use to switch between the multiple channels. #include "opencv2/objdetect/objdetect.hpp" #include "opencv2/highgui/highgui.hpp" #include "opencv2/imgproc/imgproc.hpp" #include <linux/videodev2.h> #include "i2c-dev.h" #include <fcntl.h> #include <iostream> #include <stdio.h> #include <errno.h> #include <unistd.h> #include <sys/ioctl.h> #include <string.h> #include <pthread.h> #include <queue> #include <X11/Xlib.h> #include <X11/Xutil.h> #define MAX4586_I2C_ADDR 0x37 #define RENDER_DELAY 80 #define SWITCH_DELAY 60 using namespace std; using namespace cv; queue<Mat> window1Queue; queue<Mat> window2Queue; pthread_t render1Thread; pthread_t render2Thread; void *renderToWindow1(void *arg) { while (true) { if(!window1Queue.empty()) { imshow("Window 1", window1Queue.front()); window1Queue.pop(); } usleep(RENDER_DELAY); } } void *renderToWindow2(void *arg) { while (true) { if(!window2Queue.empty()) { imshow("Window 2", window2Queue.front()); window2Queue.pop(); } usleep(RENDER_DELAY); } } /** @function main */ int main(int argc, const char** argv) { int fd, retVal; int counter = 1, maxChannel = 0; VideoCapture capture; Mat frame; fd = open("/dev/video0", O_RDWR); if (fd < 0) { perror("Failed to open\n"); return -1; } try { // Surround the OpenCV call by a try/catch block so we can give a useful error message! capture.open(0); /*------------------------------------------------------------*/ capture.set(CV_CAP_PROP_FRAME_WIDTH, 320); capture.set(CV_CAP_PROP_FRAME_HEIGHT, 240); /*------------------------------------------------------------*/ } catch (cv::Exception &e) { } if (!capture.isOpened()) { cerr << "ERROR: Could not access the camera!" << endl; exit(1); } pthread_create(&render1Thread, NULL, renderToWindow1, NULL); pthread_create(&render2Thread, NULL, renderToWindow2, NULL); while(true) { switch(counter) { case 1: maxChannel = 0; if (ioctl(fd, VIDIOC_S_INPUT, &maxChannel) < 0) { perror("1. Failed ioctl\n"); } counter = 3; capture >> frame; if(!frame.empty()) { window1Queue.push(frame); } break; case 2: break; case 3: maxChannel = 2; if (ioctl(fd, VIDIOC_S_INPUT, &maxChannel) < 0) { perror("2. Failed ioctl\n"); } counter = 1; capture >> frame; if(!frame.empty()) { window2Queue.push(frame); } break; case 4: break; default: counter = 1; break; } waitKey(SWITCH_DELAY); } return 0; } I am suspecting that the ioctl call, is one thing which take some time here, due to the copy required from user space to kernel space. Can the timing be improved with a mmap implementation in the driver, removing the implicit copy from user space to kernel space, giving me a decent frame rate for multi window rendering? The waitKey(SWITCH_DELAY) provides a delay without which the frames glitch badly and usleep(RENDER_DELAY) provides the necessary delay for rendering to the window. Thanks & Regards, Sanchayan Maity.

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Linux Suspend to Disk
by Ashwin Jha May 5, 2014

May 5, 2014

How does a freshly booted kernel, understand, that already a hibernated image of the same OS, exists, in the HDD? PS: I am trying to develop a new feature, which will allow multi-hibernation in Linux. Regards, Ashwin

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Extend the makefile to generate documentation with doxygen
by Saket Sinha May 5, 2014

May 5, 2014

Hi, I have implemented a project which includes *.c files with the functions, and *.h with the declarations of them and a Makefile to compile it. Now I want to make it generate the documentation of doxygen inside the makefile. Any help would be appreciated. Regards, Saket Sinha

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