May 2014 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

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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[Eudyptula Challenge] Not receiving tasks.
by Lucas Tanure May 5, 2014

May 5, 2014

Hi, I sent my task two over two days ago and didn't receive the task 03. I already sent 6 times the task 02 answer, but I got nothing instead. I used mutt, and a python script. The first time that I sent was two days ago. Has Eudyptula Challenge died ? Is down for a few days ? Thanks a Lot. -- Lucas Tanure The Python script tanure@archNote email $ cat sender.py #!/usr/bin/python3 from smtplib import SMTP from itertools import chain from errno import ECONNREFUSED from mimetypes import guess_type from subprocess import Popen, PIPE from email.mime.base import MIMEBase from email.mime.text import MIMEText from socket import error as SocketError from email.mime.multipart import MIMEMultipart from os.path import abspath, basename, expanduser import getpass # Define ID id_eudyptula = '[404ba4c8fd16]' # Define email addresses to use addr_to = 'little(a)eudyptula-challenge.org' addr_from = 'tanure(a)linux.com' # Define SMTP email server details smtp_server = SMTP("smtp.gmail.com",587) smtp_user = 'ltanure(a)gmail.com' smtp_pass = getpass.getpass() def get_mimetype(filename): content_type, encoding = guess_type(filename) if content_type is None or encoding is not None: content_type = "application/octet-stream" return content_type.split("/", 1) def mimify_file(filename): filename = abspath(expanduser(filename)) basefilename = basename(filename) msg = MIMEBase(*get_mimetype(filename)) msg.set_payload(open(filename, "r").read()) msg.add_header("Content-Disposition", "attachment", filename=basefilename) #encode_base64(msg) return msg def send_email(subject, text, files): # Prepare Message msg = MIMEMultipart() msg.preamble = subject msg.add_header("From", addr_from) msg.add_header("Subject", id_eudyptula + ' ' + subject) msg.add_header("To",addr_to) # Attach the main text msg.attach(MIMEText(text)) # Attach any files [msg.attach(mimify_file(filename)) for filename in files] # Contact local SMTP server and send Message try: smtp_server.ehlo() smtp_server.starttls() smtp_server.ehlo() smtp_server.login(smtp_user, smtp_pass) smtp_server.sendmail(addr_from, addr_to, msg.as_string()) smtp_server.quit() except SocketError as e: print(e) if __name__ == "__main__": text = open('text','r').read() send_email("Task 02 of the Eudyptula Challenge",text,['.config','dmesg'])

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Eudyptula Challenge
by Narendra Joshi May 5, 2014

May 5, 2014

Will the Eudyptula Challenge be always around? I want to do the challenge problems but I am busy these days. So I want to start doing them some time later. Will I be able to? -- narendra

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RE: Identifying neighbors within the LAN
by Hettiarachchige Hasitha Shan May 5, 2014

May 5, 2014

Dear Sir, > Step 1: When making security decisions, you probably don't need a list > of *all* neighbors - you only need an answer to "is *this* neighbor known or > not". And that would be a different API. If I am to get the information of known neighbors, which API should use in my kernel module. I searched this on Google for hours and that did not do any good. I am a novice at this, a reference/ example would be really great to point me in the right direction. Thank you very much sir, Best Regards, H. Hasitha Shan P.S. Thank you Mr. Valdis for pointing me that I should always reply beck to the kernennewbies mailing list. > To: hh_shan(a)live.com > CC: kernelnewbies(a)kernelnewbies.org > Subject: Re: Identifying neighbors within the LAN > From: Valdis.Kletnieks(a)vt.edu > Date: Sat, 3 May 2014 19:10:18 -0400 > > On Sat, 03 May 2014 11:01:19 -0700, Hettiarachchige Hasitha Shan said: > > > In the concept, it is required to obtain the list of neighbors within the > > LAN. I did some research online and I found out that I can obtain IPv4/ IPv6 > > neighbors by typing > > in "ip -4 neigh show" or "ip -6 neigh show" in the terminal where this > > feature is implemented by the module neighbour. > > > > My query is , If I am to obtain these information programatically through > > my kernel module, which methods should I call. > > Step 0: Figure out why a packet security module even *cares* what neighbors > are known. Why do you care if a neighbor is known or not? First, figure out > under what conditions a neighbor becomes known. What security decisions are you > planning to make based on "IPv4 address is in ARP table"? Whether an address > is in the ARP table is orthogonal to whether you should trust the host or not. > A trusted host can fail to be in the neighbor table simply because the ARP > entry has aged out. Or an untrusted host can be *in* your ARP table....) > > Step 1: When making security decisions, you probably don't need a list > of *all* neighbors - you only need an answer to "is *this* neighbor known or > not". And that would be a different API. > > (For bonus points, consider the case of a trusted host that has a longer > ARP table timeout than yours - then you can receive a packet from the host > without them ARP'ing for you first, but you still don't have a ARP entry > for them.

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confuse about generic_file_read_iter
by Jimmy Li May 5, 2014

May 5, 2014

Hello everyone, I'm trying to figure out how asyncchronous I/O implemented, but I'm confusing about the generic_file_read_iter in mm/filemap.c. major file systems use this function as read_iter for it's file_operations structure(eg, ext3). And it's called by syscall io_submit(fs/aio.c:1359): sys_io_submit -> do_io_submit -> io_submit_one -> aio_run_iocb The point I'm confusing is generic_file_read_iter seems do noting about asyncchronous I/O at all, as I see what generic_file_read_iter does: if opened with O_DIRECT flush pages; call direct_IO; else call do_generic_file_read(); Actually, I think it's syncchronous. It's that means file systems using generic_file_read_iter does not support aio(such as ext3)? I also tried `git log fs/aio.c`. I found retry-based AIO is removed at commit 41003a7bcfed1255032e1e7c7b487e505b22e298(Tue May 7 16:18:25 2013) Could anyone tell me how does linux AIO implement now? I'm working on linux-next(20140502) thanks.

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about the paing mode
by RS May 5, 2014

May 5, 2014

Hello I build my kernel with "CONFIG_HIGHMEM4G=y" option to disable the PAE, choose the 32-bit paging mode. In the runtime, the CR4 value is 0x0000 06D0, (bit 5 is 0, PAE=0, disabled). When I execute the code below: void *ret = kmalloc(sizeof(something), GFP_KERNEL); pte_t *pte = lookup_address(ret, &level); // int level the level value is 2(PG_LEVEL_2M), not the 1(PG_LEVEL_4K). So I think the kernel has used 2 kinds of pages, 4MB size page and 4KB size page. Is that right ? Thanks, HeChuan

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