Detecting GPT-capability on SPARC machines in debian-installer
Since GRUB2 is now improving on SPARC support, we should start looking into the changes
necessary to use GRUB2 instead of SILO for new installations.
Newer SPARC machines starting from the T4 support GPT partition tables. In debian-installer,
partman-partitioning detects the architecture and subarch type to determine which types
of partition tables are supported .
This script calls archdetect from the src:hw-detect package  which uses functions
from libdebian-installer to determine the architecture and subarch. On x86, the presence
of EFI support is used to determine whether GPT is to be used . And the availability
of EFI itself is detected by checking whether the EFI filesystem (efivarfs) is present .
For sparc and sparc64, there is currently no subarch detectection at all  and thus,
the disk-label.sh script  hard-wires sparc and sparc64 to Sun partition tables.
So, the question now is what the best approach would be to let debian-installer use
GPT on sparc64 machines where it's supported. The simplest solution would certainly
be to just run "prtconf -pv | grep -c gpt" from busybox in the disk-label.sh script
and then enable GPT conditionally. But this isn't necessarily the cleanest solution.
>  https://anonscm.debian.org/cgit/d-i/partman-partitioning.git/tree/lib/disk-label.sh
>  https://packages.qa.debian.org/h/hw-detect.html
>  https://anonscm.debian.org/cgit/d-i/libdebian-installer.git/tree/src/system/subarch-x86-linux.c#n273
>  https://anonscm.debian.org/cgit/d-i/libdebian-installer.git/tree/src/system/efi.c
>  https://anonscm.debian.org/cgit/d-i/libdebian-installer.git/tree/src/system/subarch-sparc-linux.c
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer - firstname.lastname@example.org
`. `' Freie Universitaet Berlin - email@example.com
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913