Bug#931852: [armel/marvell] cmdline mtd partition map without effect

[Chris Laif <chris.laif@googlemail.com>]

On Sat, Jul 13, 2019 at 11:37 PM Ben Hutchings <ben@decadent.org.uk> wrote:
> On Thu, 2019-07-11 at 15:11 +0200, Chris Laif wrote:
> > Package: debian-installer
> > Version: 20190702
> >
> > I'm using the current Buster kernel/initrd on my Seagate Blackarmor NAS.
> >
> > The mtd partition map ('mtdparts' cmdline variable) has no effect
> > (even with 'cmdline' module loaded):
> [...]
>
> What if you replace "mtdparts=" with "cmdlineparts.mtdparts="?
>

With "cmdlineparts.mtdparts" it does not work:

~ # cat /proc/cmdline
console=ttyS0,115200
cmdlineparts.mtdparts=orion_nand:0xa0000@0x0(uboot),0x010000@0xa0000(env),0x500000@0xc0000(uimage),0x1a40000@0x5c0000(rootfs)
~ # cat /proc/mtd
dev:    size   erasesize  name
mtd0: 02000000 00004000 "orion_nand"
~ #

With "cmdlinepart.mtdparts" (without trailing "s", equal to the name
of the kernel-module) it works!:

~ # cat /proc/cmdline
console=ttyS0,115200
cmdlinepart.mtdparts=orion_nand:0xa0000@0x0(uboot),0x010000@0xa0000(env),0x500000@0xc0000(uimage),0x1a40000@0x5c0000(rootfs)
~ # cat /proc/mtd
dev:    size   erasesize  name
mtd0: 000a0000 00004000 "uboot"
mtd1: 00010000 00004000 "env"
mtd2: 00500000 00004000 "uimage"
mtd3: 01a40000 00004000 "rootfs"
~ #

This seems to break backwards compatibility for a lot of devices
(Google shows lots of hits for "mtdparts=" and only a handful for
"cmdlinepart.mtdparts", so I think nobody is using the latter).

I wonder what's the best way to have a both Stretch and Buster
compatible cmdline. A quick test shows that "cmdlinepart.mtdparts"
works with Stretch, too (even Stretch does not have a seperate
"cmdlinepart" module). Do you have any recommendations?

Thanks,
Chris