I'm fairly new to Linux kernel development. It is certainly quite a bit different than the Windows kernel (I am a recovering Microsoft engineer). Can you provide advice on how to iterate effectively on updating modules that come with the Linux kernel?
Specifically, I am updating hid and bcm5974 to support the latest Macbook Pro (early 2015), and am using Ubuntu 15.04 (kernel 3.19). Would you recommend I test it out in a Virtual Machine? Are there ways to incrementally build instead of clean + build the whole tree? I'd love to be able to build just the affected modules but I can't find a good way to do that. The Makefiles are rather complicated.
Time to answer my own question. After doing a full build, incrementals are pretty straightforward given you're not editing headers that are consumed by other modules.
make modules SUBDIRS=drivers/input/mouse
Once I've installed the kernel from the full build, iterating on new module compilations is a breeze. sudo rmmod bcm5974. scp file from build desktop to Macbook Pro. sudo insmod bcm5974.
Related
I am new to buildroot. Using buildroot 2016.05, I have successfully built a target SD card for a MicroZed board with a Xilinx kernel, but it was missing some utilities that I wanted in the root file system. In particular, I wanted scp.
Looking through the buildroot documentation and web searches didn't yield the answer, but I was able to search the Config.in files in the package folders for "scp" and eventually determine that I could install either dropbear or openssh to get scp.
Other than the brute force way I searched Config.in files, is there an approach with buildroot to resolve a "which package produces binary XYZ" question?
A big part of building embedded Linux systems is understanding the components of Linux systems in general. How do you figure out what packages to install on your desktop/server Linux installation? In this way Buildroot isn't really any different. As a help we do sort packages in groups (E.G. Network applications in this case) and provide help text for each package, but you are really expected to know that 'scp' is part of the ssh package (openssh or dropbear).
What can sometimes be helpful is to check what package a program comes from on your desktop Linux installation - E.G. dpkg -S $(which scp) for this question in case you are using Debian/Ubuntu
I am new to yocto and developing drivers. I got source code (alter_driver.c and Makefile) for the drivers but I don't have any idea how to compile and get altera_driver.ko file, so that I can load that drivers and use them.
The version of yocto kernel is 3.0.32-yocto-standard which I got from terminal command uname -r.
Please help me in compiling the drivers. Thank you.
I suggest you read the Yocto Kernel Development Manual (the link is to current version: you should use the one for your Yocto release). If the only thing you have is a out-of-tree module, see part 2.5.2 which explains how to create a recipe for your driver.
The short version is: make a copy of the example recipe, add your sources in the files/-directory, modify the Makefile to build your sources... but read the manual, it's pretty good.
Also, the Kernel Lab may be useful: it mostly talks about working with a full kernel but also covers an out-of-tree module example (lab 4).
I am using ubuntu, but the question is for linux in general.
I installed a module/driver by compiling my linux kernel and install the new compiled kernel. It works fine.
In order to make this driver work in another machine without installing the new kernel, I copy the .ko file to the new machine under /lib/modules/<version>/... and then run sudo depmod -a. Then run sudo modprobe <drivername>. The module can be loaded without a problem. but the device is not working well with this .ko module.
The two machines are not identical to hardwares, BUT they are identical to kernel version and ubuntu release version. Normally, copying .ko file should work for the same linux release and the same kernel.
More information about the driver. it's a hid pen tablet driver. All patch files:
one .c file in drivers/hid/
add one line in drivers/hid/Makefile
add a few lines to drivers/hid/usbhid/Kconfig
add a few lines to drivers/hid/hid-ids.h
add a few lines to drivers/hid/usbhid/hid-quirks.c's hid_blacklist struct before { 0, 0 }
That's all.
I even tried to copy the entire drivers/hid/ directory includig all the .ko files from the first machine to the second one. but no luck. The pen tablet can be recognized in the second machine, I am able to do mouse left click event with the pen, but the pen can not move the cursor.
Hopefully, I provided enough details. My goal is to only install the module to identical linux release (kernel) without reinstalling the kernel. I am not sure how to achieve that or if it's possible.
Thanks a lot.
PS:
The dmesg output in 1st machine which works: http://paste.ubuntu.com/6419301/
The dmesg output in 2nd machine: http://paste.ubuntu.com/6419302/
In 1st machine, before plugging in the tablet, lsmod doesn't show the module. after plugging in, the module can be loaded automatically. I can see lsmod shows the module.
In 2nd mahcine, the module can not be loaded automatically by plugging in the device. I have to do sudo modprobe <module> manually.
Since I will have to install the module to many machines in my company, it's easier to install the module without reinstalling the kernel. I tried to install the kernel .deb packages which built in the 1st machine to the 2nd machine, it works fine in 2nd machine. but I don't feel good to reinstall the kernel to many machines. Thanks.
It seems the kernel you built isn't a 1:1 match. Also, generally there's no need to compile a new kernel.
The simplest way to deal with an out-of-tree driver deployment is to use DKMS.
What you need to provide is just a dkms.conf file specifying the package name, version, and driver names and destinations (within /lib/modules/{kernel}).
In the following examples, things within braces need to be replaced with the real thing, e.g. if version is 1.0.0, then {version} with 1.0.0, obviously.
Example dkms.conf:
PACKAGE_NAME="{mydriver}"
PACKAGE_VERSION="{version}"
BUILT_MODULE_NAME[0]="{mydriver}"
BUILT_MODULE_LOCATION[0]="/{mycompany?}"
AUTOINSTALL="yes"
Then you just need to install the sources to /usr/src/{mydriver}-{version}, and run dkms:
dkms add -m {mydriver} -v {version}
dkms build -m {mydriver} -v {version}
dkms install -m {mydriver} -v {version}
You should take a look at what other people have done in this area, there's a great deal of automation you can apply to testing and release processes. Bluecherry's solo6x10 out-of-tree version provides some useful make targets (disclosure: I'm the one who wrote that).
Also, you definitely want to build and distribute packages, you can use solo6x10/debian as a template, and you can read about repositories in the Debian wiki.
You can add the module to /etc/modules so it's loaded at boot time.
These are not installed on Android 4.2.1 by default, so is it possible to cross-compile the source for e.g. GNU grep or find and have it run on Android? ( Preferably without having to root the device or installing some app off PLAY e.g. busybox.) Are there any missing dependencies that will prevent this? I am developing on Ubuntu 10.0.04
Strange. I have them on /system/xbin/*. Maybe more luck with busybox. busybox find busybox grep Not sure if busybox is installed by default on Android 4.2 tho, but it's a pretty common binary.
This is not a complete answer because I haven't tried building grep or find. However, in general it is quite possible to build GNU utilities for Android. To do this, the best option is:
Download the Android native development kit
Build an Android standalone toolchain by referring to docs/STANDALONE-TOOLCHAIN.html in the NDK
Simply build the relevant GNU utility using the normal ./configure && make mechanism.
You'll then need to copy the resulting binaries onto your Android device, which you can do using adb push. You may need to arrange to put them into /data/ somewhere because /mnt/sdcard is often marked non-executable.
Missing dependencies
The main problem you'll find during the actual builds is that Android does not use the standard GNU libc (glibc). Instead, it uses its own, called Bionic. This does miss certain important APIs - for example, wide character string support.
I've found for some GNU utilities this is OK and they can be compiled with minimal source code changes.
However, if you run into trouble, you're probably better off using other versions of these utilities which are typically designed for more flexibility in terms of the underlying libc. Specifically, the previous advice about using busybox is excellent. If you don't wish to install it from the Android market, you can find the source code here.
I am using beaglebone, that contains Angstrom distribution. In that there is no build directory, so I have downloaded the kernel source from kernel.org, but the size of that is too much for my SD card (~430 MB). So I thought of removing some unwanted files or directories.
Which directories are not necessary to build a kernel module? And is there any other method to get those files only?
You can cross-compile kernel on your PC - it would be faster and much more comfortable.
All you have to do is to get cross-compiler. As i remember there were some prepared for beagleboard so you can try to use them. Of course you can build it by yourself - there are tools such as crosstool-ng or buildroot, which can help you a lot.