The driver is called MultiMedia card driver for PXA, and it requires Direct Memory Access: we will therefore need to select MMC, MMC_PXA, DMADEVICES and PXA_DMA. Second, we need to add SD cards support for the mainstone board, that belongs to the PXA family. The mainstone default configuration is fairly minimal, and we will need to add a few options to support these two boot modes.įirst, we need to add initrd support by activating the BLK_DEV_INITRD configuration option. We will see how we can create an initrd in the subsequent paragraphs.
Initrd is primarily intended to be a bootstrap in RAM that allows the Kernel to get access to the ‘real’ rootfs, but we can also use it to simply boot the Kernel without providing a rootfs. Where additional modules are loaded from initrd. Where the kernel comes up with a minimum set of compiled-in drivers, and Initrd is mainly designed to allow system startup to occur in two phases, To a directory and can be subsequently unmounted. The previous root (from initrd) is then moved
Afterwards, a new root file system can be mountedįrom a different device. This RAM disk can then be mounted as the root file system and programsĬan be run from it. Initrd provides the capability to load a RAM disk by the boot loader. In this article, I will illustrate two boot modes: a stand-alone Kernel with a RAM initrd, and a Kernel that boots on a root filesystem on an SD card. The Linux Kernel is very versatile in the way it boots, and it can be frankly overwhelming if you consider all options. You need to specify the architecture to tell the Kernel where it should look for existing configurations (here arch/arm/configs) $ make -C linux/linux-4.7.5 ARCH =arm mainstone_defconfig O =linux/build
Qemu system arm exit install#
Morin for developping crosstool-ngįirst, we need to fetch and install the tool. More namedropping: kudos to my friend Yann E. Generating a toolchain used to be quite painful, but since the awesome crosstool-ng tool has been made available, this is a piece of cake. Most of the time, the board manufacturer will have provided the toolchain as part of the BSP (Board Support Package). To generate the binaries for our embedded target, we need a toolchain, which is a set of tools targeting the corresponding processor architecture. He is _very_knowledgeable on the Kernel and also very nice. The only reason I chose this platform is because the maintainer of this board is Robert Jarzmik, who has been sitting next to me in the Open space for the last year. I will use in this tutorial an old Intel ARM platform, the Mainstone. Versatileab ARM Versatile/AB (ARM926EJ-S )
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