Lots of type casts are going to just “work well”. However, this is not very strict. Nothing stops you from casting a u32 to a u32 * and dereference it, but this is not following the kernel API and is prone to errors. __iomem is a cookie used by Sparse, a tool used to find … Read more
Kernel Makefiles are part of the kbuild system, documented in various places on the web, for example http://lwn.net/Articles/21835/. The relevant excerpt is here: — 3.1 Goal definitions Goal definitions are the main part (heart) of the kbuild Makefile. These lines define the files to be built, any special compilation options, and any subdirectories to be … Read more
The Linux kernel maps most of the virtual address space that belongs to the kernel to perform 1:1 mapping with an offset of the first part of physical memory. (slightly less then for 1Gb for 32bit x86, can be different for other processors or configurations). For example, for kernel code on x86 address 0xc00000001 is … Read more
Re-enumerating the PCIe bus/tree via echo 1 > /sys/bus/pci/rescan is the correct solution. We are using it the same way as you described it. We are using echo 1 > $pcidevice/remove to disconnect the driver from the device and to detach the device from the tree. The driver (xillybus) is not unloaded, just disconnected. A … Read more
It adds some type checking. With your version, this compiles fine (without warning): struct foo { int bar; }; …. float a; struct foo *var = container_of(&a, foo, bar); With the kernel version, the compiler reports: warning: initialization from incompatible pointer type Good explanation of how the macro works: container_of by Greg Kroah-Hartman.
This is an out-of-sequence array initialization by index. It’s like writing actions[Start] = do_start; actions[Collect] = do_collect; except that you can do it as a static initializer.
This is not a Device Tree syntax issue, you just have to pre-process the .dts file with the C preprocessor, cpp, in order to obtain a file that can be digested by the Device Tree Compiler as is. In your specific case, assuming your current directory would be the kernel root directory, you would have … Read more
Docker uses the host operating system kernel, there is no custom or additional kernel inside the container. All containers running on the machine are sharing this “host” kernel. See for more information this question on SuperUser.
A crash course in kernel mode in one stack overflow answer Good questions! (Interview questions?) What happens (in detail) when a thread makes a system call by raising interrupt 80? The int $80 operation is vaguely like a function call. The CPU “takes a trap” and restarts at a known address in kernel mode, typically … Read more
Built-in drivers wont be loaded, hence built-in. Their initialization functions are called and the drivers are activated when kernel sets up itself. These init functions are called in init/main.c::do_initcalls(). All init calls are classified in levels, which are defined in initcall_levels and include/linux/init.h These levels are actuall symbols defined in linker script (arch/*/kernel/vmlinux.lds.*). At kernel … Read more