On 2017-11-17, Karsten Merker wrote: > On Thu, Nov 16, 2017 at 07:54:42PM -0400, Joey Hess wrote: >> A utility in flash-kernel would be much nicer than needing to puzzle out dd >> commands from README.Debian files and hope you got it right. I'm currently >> having to embed those dd commands inside propellor; they're also embedded >> inside debian-installer (build/boot/arm/u-boot-image-config).
I've definitely thought about providing such a utility in u-boot-tools that at least handles a limited set of boards, and replace part of the image generation code in debian-installer. This could also be used to create independently bootable images. > Among the points of this discussion were: > > - On some devices u-boot isn't stored on an SD card but on an > onboard SPI flash chip with a rather limited number of write > cycles (in the area of ~1000) and no defects management. > Unconditionally writing u-boot on every invocation of > flash-kernel (which includes everything that modifies the > initrd) would have the potential to kill these devices in > comparatively short time. We could leave those devices as unsupported... > - Knowing the device type one is running on isn't necessarily > enough. Several supported devices are available in different > hardware configuration variants that influence where the u-boot > image can get written to (SD card, onboard eMMC, onboard raw > NAND, SPI flash, and combinations thereof). Once Linux is > running, there is no way to determine where the u-boot that > brought the system up was loaded from. Flash-kernel pulls the > system type from a /proc entry, but that doesn't provide the > information whether the current device e.g. has the SPI flash > for u-boot populated or not, and if yes, whether it has > actually been used for booting the system, so flash-kernel > cannot decide without user-interaction where to write the > u-boot image. Maybe not in an automated fashion, but specifying something like: u-boot-install --board=Cubietruck --device=/dev/mmcblk0 Or even with limited autodetection: u-boot-install --board=auto --device=foo.img u-boot-install --board=auto --device=/dev/mmcblk2 This could at least simplify the process of looking up the exact offsets and so on, and fail if it can't safely determine what to do. And --force might be an option as well. This could also be called by debian-installer, instead of maintaining it's own list of offsets... What's been hard is figuring out if this should be in u-boot-tools or part of flash-kernel. Obviously, flash-kernel has the database of boards based on /proc/device-tree/model, but u-boot is where the information such as supported boot media and device offsets generally comes from, as it sometimes changes changes between different versions of u-boot, and I hate updating things in multiple places. After having thought about it more while of writing this email, I think it should be in u-boot-tools, and *optionally* use the flash-kernel database to autodetect the appropriate device. Autodetection might require another field or two in the flash-kernel database... Doing this would also make me want to split the flash-kernel database out into a separate package from the boot script/kernel+initrd copying parts of flash-kernel; there is now the u-boot-menu package which can be used to generate an extlinux style menu instead of flash-kernel's boot scripts, and with u-boot EFI emulation, grub-efi can be used as well in some cases. live well, vagrant
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