Hi,

I am working on a platform where loadable module is not an option(for security reason). When the kernel boots, if I look into /dev, I assume it shows all the device that are compiled as part of the kernel. My question is, how to I add a device to the kernel? For example, gpio driver source code is available in the /linux/driver/gpio directly. What do I need to do so it will be compiled as part of the kernel and, when the kernel boots, I will see a gpio device in /dev?

Thank you!
Wei Xu

Your assumption about the /dev directory is incorrect. A /dev node may exist when there is no driver or device, and a kernel driver may exist with no /dev/entry. The relationship between a driver in the kernel and an entry in /dev depends on the specific driver, the config file options chosen, and the code that runs after the kernel boots. The options are in .config in the kernel source root directory, and may also be copied to a file in /boot where the kernel is installed. One of the relevant options is CONFIG_DEVTMPFS, but there are others. It also depends on whether you run udev or MAKEDEV or something else to populate /dev. There are brief descriptions of the options in the Kconfig files in the kernel source and in Documentation/devices.txt.