On Sat, Mar 10, 2018 at 6:34 AM, Andy Rea <a...@azureussolutions.com> wrote: > I have an ARM CPU on a board that has 3 optional sub boards plugged into it, > all of which have 3 hardware rev bits connected to the CPU > > > > Rather than getting the CPU to do mmap type stuff or sys/class/gpio stuff to > read those versions in the kernel, is there a way for u-boot to push that > information ( even it's a U32 or a string ) into the kernel somewhere that > can be parsed? I tried some code in the board startup to create env vars to > append into the bootargs but they aren't evaluated each boot properly ( > boards are optional and revs can change ) so cat /proc/cmdlne stayed the > same value all the time > > > > Is there a better way to do this?
I've done something similar in the past by having u-boot manipulate the device-tree passed to the kernel with a few calls to fdt_setprop(). It's practical when you have a few tweaks to make. I've used it for telling the kernel to disable bits of hardware on prototype boards. For more substantial configurations you could use a FIT image[1]. I've also used this for having u-boot tell the kernel about plug-in boards. Ultimately we ended up switching to device-tree overlays once the kernel support caught up so that we could support hot-plugging boards. [1] - http://git.denx.de/?p=u-boot.git;a=blob_plain;f=doc/uImage.FIT/howto.txt;hb=HEAD _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
