request_mem_region tells the kernel that your driver is going to use this range of I/O addresses, which will prevent other drivers to make any overlapping call to the same region through request_mem_region. This mechanism does not do any kind of mapping, it’s a pure reservation mechanism, which relies on the fact that all kernel device … Read more
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
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
On the Boundary Devices kernel, and maybe others, you can use cat /sys/kernel/debug/gpio to get a list of the mapped gpios, their states, and name given when it was allocated. You can grep the kernel source for the name and find out what module grabbed it. root@nitrogen6x:/opt# cat /sys/kernel/debug/gpio GPIOs 0-31, platform/209c000.gpio, 209c000.gpio: gpio-2 (flexcan-trx-stby … 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
-ERESTARTSYS is connected to the concept of a restartable system call. A restartable system call is one that can be transparently re-executed by the kernel when there is some interruption. For instance the user space process which is sleeping in a system call can get a signal, execute a handler, and then when the handler … Read more
Actually you missed a buzzword “USB sniffing“. 😉 Here are a few tutorials on USB sniffing on Linux, to get you started. Official Wireshark wiki for USB monitoring biot.com/blog/usb-sniffing-on-linux (InternetArchive) tjworld.net/wiki/Linux/Ubuntu/USBmonitoring Essentially you use the usbmon Linux kernel module to capture the USB-packets and Wireshark as a front-end to display and analyse the captured USB … Read more
From those three factors that you have listed only the first one is actually correct. As for the rest — not really. It is possible for a user space code to perform DMA operations — no problem with that. There are many hardware appliance companies who employ this technique in their products. It is also … Read more
If the module .ko file is really under /lib/modules/4.3.3-5-default/extra/ and 4.3.3-5-default is indeed your current kernel version, then the problem may simply be that you need to run depmod to re-create the module dependency list. Run: sudo depmod and try again to modprobe the module.