On 05/23/2018 08:25 AM, Geert Uytterhoeven wrote: > Hi Marek, > > On Wed, May 23, 2018 at 12:01 AM, Marek Vasut <marek.vasut@xxxxxxxxx> wrote: >> On 05/22/2018 04:43 PM, Geert Uytterhoeven wrote: >>> On Tue, May 22, 2018 at 2:02 PM, Marek Vasut <marek.vasut@xxxxxxxxx> wrote: >>>> Drop the MTD partitioning from DT, since it does not describe HW >>>> and to give way to a more flexible kernel command line partition >>>> passing. >>>> >>>> To retain the original partitioning, assure you have enabled >>>> CONFIG_MTD_CMDLINE_PARTS in your kernel config and add the >>>> following to your kernel command line: >>>> >>>> mtdparts=spi0.0:256k@0(loader),4096k(user),-(flash) >>> >>> I think the "@0" can be dropped, as it's optional? >>> 4m? >> >> My take on this is that the loader is actually at offset 0x0 of the MTD >> device and we explicitly state that in the mtdparts to anchor the first >> partition within the MTD device and all the other partitions are at >> offset +(sum of the sizes of all partitions listed before the current >> one) relative to that first partition. > > Where is this explicitly states for the first partition? > >> Removing the @0 feels fragile at best and it seems to depend on the >> current behavior of the code. > > Better, it also depends on the documented behavior: > > Documentation/admin-guide/kernel-parameters.txt refers to > drivers/mtd/cmdlinepart.c, which states: > > * <offset> := standard linux memsize > * if omitted the part will immediately follow the previous part > * or 0 if the first part > > None of the examples listed there or under the MTD_CMDLINE_PARTS Kconfig > help text, or in a defconfig bundled with the kernel, use @0 for the first > partition. I think this is exceptionally fragile and dangerous to depend on this, but so be it. -- Best regards, Marek Vasut
