On 07/22/2018 12:23 AM, Olof Johansson wrote: [...] >>>>> You end up with user space tools trying to parse the kernel command >>>>> line to figure out what's on the flash, and other really bad habits. >>>>> :( >>>> >>>> You should just read /proc/mtd , see >>>> http://www.linux-mtd.infradead.org/doc/general.html >>> >>> Sure, I know that but not everybody does, and they do it in bad ways >>> if given the opportunity. >> >> That's what the documentation is for. I assume whoever is using MTD is >> also capable of reading the documentation and thus avoiding such basic >> mistakes. > > Why read the docs when the information obviously is there when you grep it? To do things correctly of course. > I'm agreeing with you -- I've just seen it done wrong so many times. > Making it harder to make mistakes is always a good thing. If you follow this argument through, you could say we should start plucking out random files from /proc because someone might cluelessly misuse them. This might lead to a system that's hard to misuse indeed, but likely also quite useless. >>>>> I'd strongly advice you to keep this in the board files, unless you >>>>> have an actual real motivation for changing it. This patch does not >>>>> provide one. >>>> >>>> Partitioning is not hardware description, it should not be in DT. >>> >>> Read my reply again. It's part of _platform_ description, and belongs in DT. >> >> I can repartition the flash whichever way I want for my purposes, just >> like I can repartition a harddrive. We don't have harddrive partitioning >> in the DT, why should we have flash partitioning there ? How do those >> differ ? > > A drive can be auto-probed. We have partition tables on the disk that > self-describes the contents. > > That doesn't exist on flashes, at least not usually. This is really > unfortunate, I wish we could change _that_ instead of argue here. Technically it does. Consider the fact that those flashes have between 4-64 MiB in size and sector size of 256 kiB . If you waste one sector on the 4 MiB flash for some sort of partition table, you waste 1/16th of the flash, which is a lot. The bootloader needs to know the flash layout and it must be in sync with the kernel, so there has to be some sort of communication channel between those two. I don't want to add handler for every possible bootloader that can be used on those platforms into the kernel though. > If you repartition your disk, you need to change the command line > arguments to the kernel too. It's definitely not an argument to > keeping it on the command line instead. How so ? /dev/sdxy remains /dev/sdxy . Sure, you can use UUID and change it, but that's a specific case. > Also, you now have a dependencies between hardware description, probe > order and stable naming in the kernel, and the command line. With DT, > you have it all in one place, right next to the flash part. It doesn't > matter what name it gets probed at, and nobody needs to know the > mapping to get it right. In this case it doesn't matter either, since you have only one flash device. -- Best regards, Marek Vasut
