Re: [PATCH 08/19] parisc: define DPS root partition type UUID

[Vincent Mailhol <mailhol@kernel.org>]

On 15/06/2026 at 22:27, Helge Deller wrote:
> On 6/15/26 22:02, James Bottomley wrote:
>> On Mon, 2026-06-15 at 18:09 +0200, Vincent Mailhol wrote:
>>> DPS [1] assigns GPT partition type UUIDs to operating system
>>> partitions. Root partitions use architecture-specific type UUIDs so
>>> the OS can discover the intended root filesystem without relying on a
>>> root=  cmdline option.
>>>
>>> Define DPS_ROOT_PARTITION_TYPE_UUID in asm/dps_root.h for parisc and
>>> select ARCH_HAS_DPS_ROOT_PARTITION_TYPE_UUID.
> 
> Vincent, first of all thank you for at least trying to including parisc
> (and other
> niche Linux ports) in the specification! (whatever the outcome is!)

You are welcome. My personal interest is only x86_64 at the moment, but
at least I tried to make it useful to the broader community!

>>> [1] The Discoverable Partitions Specification (DPS)
>>> Link:
>>> https://uapi-group.org/specifications/specs/
>>> discoverable_partitions_specification/
>>
>> How are you planning to make this work for parisc?  Some systems have a
>> PALO boot partition (fdisk type 0xf0) but the more modern way is to
>> place palo inside a hidden ext4 inode in /boot.  The way parisc IODC
>> works is very similar to the way MSDOS boots with the palo location
>> table in the first block so I theorize that would probably work for gpt
>> partitions as well ... I'm just not sure anyone has tested it.
>>
>> However, to get this to work with PALO for auto discovery, you'd need
>> palo patches to recognize the DPS UUID and no-one seems to have
>> submitted anything to palo for this.
> 
> Maybe it's not necessary that palo does this job?
> palo could stay as is and load kernel and the initrd.
> Then the kernel (or the scripts in initrd) could try to find the root
> partition on it's own (and handle GPT discs).
> 
> I even once started porting grub to parisc (which is currently on hold
> because I'm busy with other stuff). If I ever finish it, having such a
> mechanism/constant already in place is IMHO beneficial.

You can see my answer to Alexander on the cover letter. This was an
oversight. parisc does not have CONFIG_EFI to begin with, so the feature
is just dead code there.

I will remove parisc (and all other architectures which do not have a
CONFIG_EFI) in v2. If someone wants to implement EFI support those
architectures, only then, we can revisit this DPS topic for these
architectures.


Yours sincerely,
Vincent Mailhol