@ -28,7 +28,7 @@ First of all, let's see how to get, build, and run the Linux kernel. You can run
* Run the Linux kernel on a virtual machine;
* Run the Linux kernel on real hardware.
I'll provide descriptions for both methods. Before we start doing anything with the Linux kernel, we need to get it. There are a couple of ways how to do it. It depends on your purpose. If you just want to update the current version of the Linux kernel on your computer, you can use the instructions specific for your Linux [distro](https://en.wikipedia.org/wiki/Linux_distribution).
I'll provide descriptions for both methods. Before we start doing anything with the Linux kernel, we need to get it. There are a couple of ways to do this depending on your purpose. If you just want to update the current version of the Linux kernel on your computer, you can use the instructions specific to your Linux [distro](https://en.wikipedia.org/wiki/Linux_distribution).
In the first case you just need to download new version of the Linux kernel with the [package manager](https://en.wikipedia.org/wiki/Package_manager). For example, to upgrade the version of the Linux kernel to `4.1` for [Ubuntu (Vivid Vervet)](http://releases.ubuntu.com/15.04/), you will just need to execute the following commands:
One is of you fork (`origin`) and the second is for the main repository (`upstream`).
One is of your fork (`origin`) and the second is for the main repository (`upstream`).
Now that we have a local copy of the Linux kernel source code, we need to configure and build it. The Linux kernel can be configured in different ways. The simplest way is to just copy the configuration file of the already installed kernel that is located in the `/boot` directory:
@ -110,11 +110,11 @@ The `defconfig` argument generates the default kernel configuration file for the
$ make ARCH=arm64 defconfig
```
The `allnoconfig`, `allyesconfig` and `allmodconfig` arguments allow you to generate a new configuration file where all options will be disabled, enabled and enabled as modules respectively. The `nconfig` command line arguments that provides `ncurses` based program with menu to configure Linux kernel:
The `allnoconfig`, `allyesconfig` and `allmodconfig` arguments allow you to generate a new configuration file where all options will be disabled, enabled, and enabled as modules respectively. The `nconfig` command line arguments that provides `ncurses` based program with menu to configure Linux kernel:
And even `randconfig` to generate random Linux kernel configuration file. I will not write how to configure the Linux kernel, which options to enable and what not, because it makes no sense to do so for two reasons: First of all I do not know your hardware and second, if you know your hardware, the only remaining task is to find out how to use programs for kernel configuration, and all of them are pretty simple to use.
And even `randconfig` to generate random Linux kernel configuration file. I will not write about how to configure the Linux kernel or which options to enable because it makes no sense to do so for two reasons: First of all I do not know your hardware and second, if you know your hardware, the only remaining task is to find out how to use programs for kernel configuration, and all of them are pretty simple to use.
OK, we now have the source code of the Linux kernel and configured it. The next step is the compilation of the Linux kernel. The simplest way to compile Linux kernel is to just execute:
@ -293,7 +293,7 @@ $ git pull upstream master
After this my local repository with the Linux kernel source code is synced with the [mainline](https://github.com/torvalds/linux) repository. Now we can make some changes in the source code. As I already wrote, I have no advice for you where you can start and what `TODO` in the Linux kernel. But the best place for newbies is `staging` tree. In other words the set of drivers from the [drivers/staging](https://github.com/torvalds/linux/tree/master/drivers/staging). The maintainer of the `staging` tree is [Greg Kroah-Hartman](https://en.wikipedia.org/wiki/Greg_Kroah-Hartman) and the `staging` tree is that place where your trivial patch can be accepted. Let's look on a simple example that describes how to generate patch, check it and send to the [Linux kernel mail listing](https://lkml.org/).
If we will look on the driver for the [Digi International EPCA PCI](https://github.com/torvalds/linux/tree/master/drivers/staging/dgap) based devices, we will see the `dgap_sindex` function on line 295:
If we will look in the driver for the [Digi International EPCA PCI](https://github.com/torvalds/linux/tree/master/drivers/staging/dgap) based devices, we will see the `dgap_sindex` function on line 295:
This function looks for a match of any character in the group, and returns that position. During research of source code of the Linux kernel, I have noted that [lib/string.c](https://github.com/torvalds/linux/blob/master/lib/string.c#L473) source code file contains implementation of the `strpbrk` function that does the same that`dgap_sinidex`. It is not a good idea to use a custom implementation of a function that already exists. So we can remove the `dgap_sindex` function from the [drivers/staging/dgap/dgap.c](https://github.com/torvalds/linux/blob/master/drivers/staging/dgap/dgap.c) source code file and use the `strpbrk` instead.
This function looks for a match of any character in the group and returns that position. During research of source code of the Linux kernel, I have noted that the [lib/string.c](https://github.com/torvalds/linux/blob/master/lib/string.c#L473) source code file contains the implementation of the `strpbrk` function that does the same thing as`dgap_sinidex`. It is not a good idea to use a custom implementation of a function that already exists, so we can remove the `dgap_sindex` function from the [drivers/staging/dgap/dgap.c](https://github.com/torvalds/linux/blob/master/drivers/staging/dgap/dgap.c) source code file and use the `strpbrk` instead.
First of all let's create new `git` branch based on the current master that synced with the Linux kernel mainline repo:
0xAX
9 years ago