On 05/22/18 13:01, Rob Herring wrote: > On Mon, May 21, 2018 at 09:57:54AM +0300, Tero Kristo wrote: >> On 17/04/18 17:49, Tony Lindgren wrote: >>> * Tero Kristo <t-kristo@xxxxxx> [180417 09:36]: >>>> In typical setup, you can boot a large number of different configs via: >>>> >>>> bootm 0x82000000#dra71-evm#nand#lcd-auo-g101evn01.0 >>>> >>>> ... assuming the configs were named like that, and assuming they would be >>>> compatible with each other. The am57xx-evm example provided is better, as >>>> you can chain the different cameras to the available evm configs. >>> >>> Why not just do it in the bootloader to put together the dtb? >>> >>> Then for external devices, you could just pass info on the >>> kernel cmdline with lcd=foo camera=bar if they cannot be >>> detected over I2C. >> >> (Added Linux ARM list to CC, this was not part of the original delivery.) >> >> Ok trying to resurrect this thread a bit. Is there any kind of consensus how >> things like this should be handled? Should we add the DT overlay files to >> kernel tree or not? > > IMO, yes. Agreed. > >> Should we add any kind of build infra to kernel tree, and at what level >> would this be? Just DT overlay file building support, and drop the FIT build >> support as was proposed in this RFC series or...? > > I think I mentioned this already, but I expect that this is going to > cause a number of conversions of dtsi + dtsi -> dtb into base dts and > overlay(s) dts files. In doing so, we still need to be able to build the > original, full dtb. > >> U-boot can obviously parse the base DTB + overlay DTB:s into a single DTB, >> but this is somewhat clumsy approach and is relatively error prone to get it >> right. > > Why? How is the kernel better? > >> Building the FIT image post kernel build would also be possible, but who >> would be doing this, is there any need to get this done in generic manner or >> shall we just add SoC vendor specific tools for this? > > I'll tell you up front, I'm not a fan of FIT image (nor uImage, > Android boot image, $bootloader image). If you want a collection of > files and some configuration data, use a filesystem and a text file. My gut feel is that using a filesystem and a text file is the easier way to create the boot info. But that also makes applying the overlay(s) during early Linux boot (at the point of FDT unflattening) impractical (can't access the file system without a driver, the driver depends on the devicetree, the devicetree depends upon the overlay). > > Rob > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
