device-tree

I am looking for a tool which can graphically represent the hardware device tree used in linux kernel. I am trying to understand linux kernel for particular arm chipset. It would be a really useful tool to have. TheCodeArtist You can try the Component inspector tool. It is part of QorIQ Configuration Suite which is a plugin for Eclipse. Download here . (Requires registration. Free to download.) Personally as i am on the cmd-line most of the time, and quite addicted to vi , i find its built-in code folding capabilities are somewhat sufficient as long as the dts is properly indented. Setup hot

The following is an excerpt from DTS file. linux/arch/powerpc/boot/dts/[board_name].dts memory { device_type = "memory"; reg = <0x00000000 0x40000000>; // 1GB at 0 }; The embedded device has 1 GB of memory. 0x40000000=1073741824 in decimal. The only way i get 1 GB is when i calculate 1073741824 as bytes. Which means 1073741824 bytes = 1GB. So does this mean 0x00000000 points to a byte of data in RAM? In other words, every byte in RAM has an address. Why is that so? What do we read a block of 8 bits? Why not a word? TL;DR : RAM accesses are NOT in byte sized chunks even though each byte is

I want to define a SPI device with usermode access, as explained for example in http://linux-sunxi.org/SPIdev Following these examples, I added in the devicetree this : &ecspi1 { .... other stuff ... mydev@0 { compatible = "spidev"; spi-max-frequency = <5000000>; reg = <2>; /*chipselect*/ }; }; The platform is i.MX6. ecspi1 seems to be their SPI controller. Then I indeed get /dev/spi0.2 and /sys/class/spidev/spidev0.2 But in kernel trace there's a WARNING saying this: spidev spi0.2: buggy DT: spidev listed directly in DT So how else the spidev should be described? What is the right syntax?

What is the difference between device tree and ATAGs? Also, are ATAGs a must and does the kernel expect them at a fixed address, or does it expect them in r0-r3? A device tree describes everything about the hardware which the kernel uses to select which drivers to load, where all the MMIO interfaces are, etc... at runtime. ATAGs just describes stuff like where to find an initrd and kernel parameters, memory, etc... - everything else about the machine is hard coded into the kernel. The preferred method now is to use device trees instead of ATAGs. One of the advantages include the fact that