[parted-devel] Partition tables and ARM booting

[Danny Milosavljevic]

Hi,

On Tue, 12 Dec 2017 09:04:35 -0500
Phil Susi <psusi at ubuntu.com> wrote:

> On 12/9/2017 12:07 AM, Danny Milosavljevic wrote:
> > And a minimal simple API would be
> > 
> > * gpt_limit_partition_count_by_sector which would do something
> > similar to what gpt_get_max_supported_partition_count already does
> > (!).  gpt_get_max_supported_partition_count already contains the
> > calculation needed, although the sector number is hard-coded to 34
> > there.
> > 
> > struct _PedDiskOps would have also to be extended in order to export
> > those (just limit_partition_count_by_sector would be enough, too).  
> 
> There is the rub: PedDiskOps represents generic partition table
> operations.  This is entirely specific to gpt, so does not fit there.

Is it? The Allwinner bootloader loads the boot code from a fixed sector number on the disk.  It doesn't know anything about GPT.

> Is this sector well known and standard or does it vary?  If it is well
> known then perhaps a partition table flag "arm-boot" could be used to
> trigger the GPT reduction?

Yeah, lots of Allwinner boards use this sector number.  But other ARM vendors use other sector numbers.  The API above is supposed to provide a means of saying "I need these sectors for lowlevel stuff, don't use them for either partitions or partition tables".