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| - | ===== Lab 04 - Linux kernel development ===== | ||
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| - | ===== Objectives ===== | ||
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| - | * Learn Linux kernel development basics; | ||
| - | * Build your own Linux kernel module; | ||
| - | * Understand userspace device types; | ||
| - | * Use MMIO to communicate with the IMX UART peripheral! | ||
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| - | ===== Contents ===== | ||
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| - | {{page>:ass:laboratoare:04:tasks:nav&nofooter&noeditbutton}} | ||
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| - | ===== Lecture ===== | ||
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| - | No lecture available :( | ||
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| - | ===== Tasks ===== | ||
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| - | Let's build a Linux kernel module and load in onto our board! | ||
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| - | ==== 00. Preparation ==== | ||
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| - | First, you need to have the Linux source code for the same version of the kernel you're running your board on. | ||
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| - | You can check the version by running ''uname -a'' on the imx8 device (we will use ''v6.4'' in our example). | ||
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| - | Check your linux source code using ''git status'' to see if you're running the same one: | ||
| - | <code> | ||
| - | # git status | ||
| - | HEAD detached at v6.4 | ||
| - | </code> | ||
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| - | If you need to recompile the kernel, check out the desired tag. | ||
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| - | **Next (optional)**, it's going to be useful to have ssh installed inside the rootfs. | ||
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| - | Use buildroot's ''menuconfig'' to install ''PACKAGE_OPENSSH'' (all of them). | ||
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| - | In either case (kernel / buildroot recompilation), you will need to regenerate the [[:ass:laboratoare:02#task_d_-_fit_image|linux.itb image]] with your new binaries. | ||
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| - | ==== 01. Your first kernel module? ==== | ||
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| - | [[https://www.kernel.org/doc/html/latest/kbuild/modules.html|Read some of this]] and create your external module's makefile. | ||
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| - | <note warning> | ||
| - | **DO NOT FORGET** TO ADD ''ARCH=arm64'' to the kbuild make invocation! | ||
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| - | If you don't do so, the kernel's ''.config'' will be reset and you'll probably need to recompile the kernel if you do anything more on the kernel tree. | ||
| - | </note> | ||
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| - | TODO | ||
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| - | ==== 02. Making a simple character device ==== | ||
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| - | [[https://www.google.com/search?q=linux+kernel+character+device+example|Google]] for some inspiration on Linux kernel sample character device modules. | ||
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| - | Next: build it! | ||
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| - | Upload it onto your board and test it using ''insmod''! | ||
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| - | TODO | ||
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| - | ==== 03. Writing to a serial device (UART) ==== | ||
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| - | Download & read the [[https://drive.google.com/file/d/1_hOAcGqI9MfIomBiNO6H0EVqqU5Kj7yQ/view|i.MX8M's Reference Manual]], chapter **16.2**. | ||
| - | //Ahem// not all of it, check the memory map / register definition for ''UTXD'' and ''UTS''. | ||
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| - | Next, we will enhance our character device to print the using IMX UART peripheral using a simple MMIO interface. | ||
| - | Useful resources for mapping, reading & writing IO memory: https://www.kernel.org/doc/html/latest/driver-api/device-io.html | ||
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| - | TODO | ||
