Hello Simon, On 29.11.23 20:44, Simon Glass wrote: > Hi Ahmad, > > On Wed, 29 Nov 2023 at 12:33, Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote: >> >> On 29.11.23 20:27, Simon Glass wrote: >>> On Wed, 29 Nov 2023 at 12:15, Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote: >>>> On 29.11.23 20:02, Simon Glass wrote: >>>>> On Wed, 29 Nov 2023 at 11:59, Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote: >>>>>> The specification says that this is the root U-Boot compatible, >>>>>> which I presume to mean the top-level compatible, which makes sense to me. >>>>>> >>>>>> The code here though adds all compatible strings from the device tree though, >>>>>> is this intended? >>>>> >>>>> Yes, since it saves needing to read in each DT just to get the >>>>> compatible stringlist. >>>> >>>> The spec reads as if only one string (root) is supposed to be in the list. >>>> The script adds all compatibles though. This is not really useful as a bootloader >>>> that's compatible with e.g. fsl,imx8mm would just take the first device tree >>>> with that SoC, which is most likely to be wrong. It would be better to just >>>> specify the top-level compatible, so the bootloader fails instead of taking >>>> the first DT it finds. >>> >>> We do need to have a list, since we have to support different board revs, etc. >> >> Can you give me an example? The way I see it, a bootloader with >> compatible "vendor,board" and a FIT with configuration with compatibles: >> >> "vendor,board-rev-a", "vendor,board" >> "vendor,board-rev-b", "vendor,board" >> >> would just result in the bootloader booting the first configuration, even if >> the device is actually rev-b. > > You need to find the best match, not just any match. This is > documented in the function comment for fit_conf_find_compat(). In my above example, both configuration are equally good. Can you give me an example where it makes sense to have multiple compatibles automatically extracted from the device tree compatible? The way I see it having more than one compatible here just has downsides. >> The configuration already has a compatible entry. What extra use is the compatible >> entry in the FDT node? > > It allows seeing the compatible stringlist without having to read the > FDT itself. I don't believe it is necessary though, so long as we are > scanning the configurations and not the FDT nodes. I think it's better to drop this if it has no use. Cheers, Ahmad > > Regards, > Simon > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
