linux-device-driver

I have been trying to write a simple device driver, in which I am suppossed to get the Vendor ID and Product ID programmatically. Having gone through almost all the necessary header files, I have come to a conclusion that I can access the vendor ID, product ID, and manufacturer details of the USB device through a structure: struct usb_device{} which has a member struct usb_device_descriptor{} . This nested structure has idVendor, idProduct and iManufacturer and some other members. But somehow, for some reason I am unable to access these members, so when I do a dmesg after inserting my module,

I am attempting to develop Linux device drivers and as my first attempt I am trying to develop a char device driver that has the following file options, struct file_operations fops{ .open=open_fun, .release=release_fun, .write=write_fun, .read=read_fun, }; When I load the driver using insmod , I see that /proc/devices lists the driver under char devices but I can't find it in /dev . A Google search suggested use of mknod to create a deivce in /dev and associate it with the driver's major and minor. However, an attempt to do so resulted in "Permission denied" error even when done as a super

I was trying to capture keyboard events. e.g. I want to drill down a keylogger from the scratch. After 2 hours of fighting I found the following neel@pc1$ ls -l /dev/input/by-id lrwxrwxrwx 1 root root 9 2010-05-05 21:33 usb-Plus_More_Enterprise_LTD._USB-compliant_keyboard-event-kbd -> ../event1 lrwxrwxrwx 1 root root 9 2010-05-05 21:33 usb-Plus_More_Enterprise_LTD._USB-compliant_keyboard-event-mouse -> ../event2 lrwxrwxrwx 1 root root 9 2010-05-05 21:33 usb-Plus_More_Enterprise_LTD._USB-compliant_keyboard-mouse -> ../mouse1 But when I tried to neel@pc1$ sudo cat /dev/input/usb-Plus_More

i am writing a device driver on linux-2.6.26. I want to have a dma buffer mapped into userspace for sending data from driver to userspace application. Please suggest some good tutorial on it. Thanks Here is what I have used, in brief... get_user_pages to pin the user page(s) and give you an array of struct page * pointers. dma_map_page on each struct page * to get the DMA address (aka. "I/O address") for the page. This also creates an IOMMU mapping (if needed on your platform). Now tell your device to perform the DMA into the memory using those DMA addresses. Obviously they can be non

What is the difference between arm-eabi, gnueabi and gnueabi-hf cross compilers. I am kind of finding it difficult to choose the compilers. Is there a native compiler for arm? I'm not completely sure: the eabi stands for the compilation of code which will run on bare metal arm core. the gnueabi stands for the compilation of code for linux For the gnueabi/gnueabi-hf part, I found an answer here . gcc-arm-linux-gnueabi is the cross-toolchain package for the armel architecture. This toolchain implies the EABI generated by gcc's -mfloat-abi=soft or -mfloat-abi=softfp options. gcc-arm-linux

In drivers I often see these three types of init functions being used. module_init() core_initcall() early_initcall() Under what circumstances should I use them? Also, are there any other ways of init? They determine the initialization order of built-in modules. Drivers will use device_initcall (or module_init ; see below) most of the time. Early initialization ( early_initcall ) is normally used by architecture-specific code to initialize hardware subsystems (power management, DMAs, etc.) before any real driver gets initialized. Technical stuff for understanding below Look at init/main.c .