linux-device-driver

Recently, i began developing a driver of an embedded device running linux. Until now i have only read about linux internals. Having no prior experience in driver devlopment, i am finding it a tad difficult to land my first step. I have downloaded the kernel source-code (v2.6.32). I have read (skimped) Linux Device Drivers (3e) I read a few related posts here on StackOverflow. I understand that linux has a "monolithic" approach. I have built kernel (included existing driver in menuconfig etc.) I know the basics of kconfig and makefile files so that should not be a problem. Can someone describe

There is so many structures in the Linux wireless driver mac80211. Things like struct net_device , struct ieee80211_hw , struct ieee80211_vif and struct ieee80211_local and so on. So many structures that I don't understand what information they contain and when them were initialized. How can I learn about them and the whole architecture of wireless drivers? eyalsh You may want to check out Johannes Berg's (mac80211 maintainer) slides here: http://wireless.kernel.org/en/developers/Documentation/mac80211?action=AttachFile&do=get&target=mac80211.pdf They may be somewhat outdated but should give

I know how to make loadable kernel modules in Linux. But i want that loadable kernel module to be a part of the kernel , and after booting that driver should automatically load, like most of the other general driver. How to do that? There are two ways to do for your query 1) building your module as statically compiled along with kernel (your source code should reside in kernel tree ),so while building build it static which come as a part of kernel, so when kernel boots your module will be loaded. 2)Same as above but while building build as dynamic loadable module so that wheneever required you

I am using YOCTO project SUMO release to Build Linux kernel for my embedded board. I want to customize the features of my board. They told me to edit the device tree file. My question is what is the path of this DT file ? And when i modify it, I must rebuild all the kernel using Bitbake ? Thanks. Create the following tree in your layer meta-custom: recipes-kernel/ └── linux ├── linux-at91 │ ├── 0001-my-custom-dt.patch └── linux-at91_%.bbappend In linux-at91_%.bbappend , put FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" SRC_URI += "file://0001-my-custom-dt.patch" To generate 0001-my-custom-dt

I have two modules A, B. A has a function f() that is globally acessible, i.e. the f() symbol is exported. B may want to call f() occasionally. But B should only call f() if module A is loaded. What is the best way for B to tell if A is loaded? Part b to this question is there is a way to check if f() is exported? I'm not sure which method is more effecient. I assume you load module B first, then optionally module A. My strategy would be to have A register a set of functions with B when A first initializes. B keeps a statically allocated function pointer (or a pointer to a struct full of

I am trying to write a program that will be installed on a Linux MCU (Raspberry Pi) that will read serial data coming to it from yet another MCU (something homegrown that I will build myself). I have researched how to do this and think I have the "big picture" but still missing a few things. For one, I need to enable the kernel module and give myself access to the device: sudo modprobe spi_bcm2708 sudo chown `id -u`.`id -g` /dev/spidev0.* From there I can use this famous C file to test the SPI connection. So now the connection is there, but I still need to read serial data from it. According

I want to define a SPI device with usermode access, as explained for example in http://linux-sunxi.org/SPIdev Following these examples, I added in the devicetree this : &ecspi1 { .... other stuff ... mydev@0 { compatible = "spidev"; spi-max-frequency = <5000000>; reg = <2>; /*chipselect*/ }; }; The platform is i.MX6. ecspi1 seems to be their SPI controller. Then I indeed get /dev/spi0.2 and /sys/class/spidev/spidev0.2 But in kernel trace there's a WARNING saying this: spidev spi0.2: buggy DT: spidev listed directly in DT So how else the spidev should be described? What is the right syntax?

I need the sequence of modules/drivers that are invoked|initialized|probed during the kernl boot. Can you please let me know if any flash command-line option available to get this sequence ? Passing the option "initcall_debug" on the kernel command line will cause timing information to be printed to the console for each init routine of built-in drivers. The initcalls are used to initialize statically linked kernel drivers and subsystems and contribute a significant amount of time to the Linux boot process. (Loadable modules are not available until after the root filesystem has been mounted.)